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Global Pollution and Environmental Monitoring 1st
Edition H.V. Jadhav Digital Instant Download
Author(s): H.V. Jadhav; S.H. Purohit
ISBN(s): 9789350435137, 9350435136
Edition: 1
File Details: PDF, 21.50 MB
Year: 2008
Language: english

Global Pollution
and
Environmental
Monitoring
Principal H.V. Jadhav
M.Sc., FIGGE
Dr. S.H. Purohit
M.Sc., Ph.D., LLM, FIGGE
Imt
GfIimalayaGpublishingGflouse
MUMBAl. NEW DELHI • NAGPUR • BANGALORE • HYDERABAD • CHENNAI • PUNE • LUCKNOW • AHMEDABAD • ERNAKULAt.I

©Authors
No part of this book shall be reproduced, reprinted or translated for any purpose whatsoever without prior
permission of the publisher in writing.
Published by
Branch Offices:
New Delhi
Nagpur
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Hyderabad
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Pune
Lucknow
ISBN : 978-81-84880-16-8
First Edition: 2008
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Contents
1. Environmental Awareness 1
2. Sampling Procedures 3
3. Water 12
4. Physical Examination of Water 27
5. Chemical Examination of Water 30
6. Physico-Chemical Analysis of Water 33
7. Soil Analysis 61
8. Instrumental Methods in Environmental Monitoring 118
9. Radioactive Pollution 141
10. Thermal Pollution 150
11. Noise Pollution 155
12. Micro-Organisms - Environmental Impact, 164
Morphology and Enzymatic Activity
13. Micro-biological Analysis 177
14. Water Microbiology - Selected Tests 197
15. Industrial Microbiology 220
16. Soil Microbiology 222
17. Biological Analysis 224
18. Bacteriological Examination of Air 237
19. Air Pollution Monitoring 239
20. Estimation of Carbon Dioxide 258
21. Humidity and Dew Points 260
22. Environmental Laws - D.M.P.lE.T.A/INTERNET 262
23. Standard References for Environmental Monitoring 284
24. Appendix 1, 2, 3, 4, 5, 6, 7 306
- References 315

"This page is Intentionally Left Blank"

1
ENVIRONMENTAL AWARENESS
Introduction
Environmental awareness has to begin with the knowledge of the surroundings. The
surroundings include our home, our workplace, all the people and growing plants, that live.
around us. It also includes the air we breath, the water we drink, the food we consume.
Nature has been very kind to us so far, in providing enough to the growing population.
In the past few years there has been growing concern over the state of environment.
The quality of our surrounding has declined due to exposure to industrial wastes and harmful
chemicals. There is loss of Bio-diversity, changes in the climatic conditions, 'Green House'
effect, depletion of ozone layer and recent happenings of Tsunamis. There is a threat to the
life support system, and an increased risks for environmental accidents.
The U.N. conferences have the focus on arresting this degradation, due to increase in
pollution; by creating awareness through education, utilizing proper management principles
on the line of conservation and strictly enforcing the environmental laws that look after the
monitoring aspects of pollution control.
In order"to control or monitor the pollutants present in the surroundings, i.e., air, water
and soil, nature and qualities of pollutants were required to be identified. Their toxic effects
and permissible limits needed to be ascertained. Fortunately, science has made enough
progress in this direction. There are highly sophisticated and dependable instrumentations
and techniques in use. These monitoring technologies are very reliable, accurate and less
time consuming, compared with classical methods. There are sampling procedures and
instruments available to carry out these operations. The pollution concentration can be
accurately quantified at trace levels as parts per million (ppm) or even parts per billion (ppb).
The global concern for 'Green Technology' means pollution free environment. This has
been made possible by adopting new methodology. These procedures aim at reducing the
waste, recycling the waste or conducting some treatment on the waste matter before it is
ready for disposal. The entire technology is to become Eco-friendly.
After the UN conference in 1972, our government has introduced twenty important
legislations on Environmental Protection. Our Constitution under Article 21, gave us
.Fundamental Freedoms' including right to life. But after introduction of Article 48 and 51 g,
right to healthy life has been provided. The first talks about duty of the state towards creating
proper environment and the second explains the duty of every citizen in India to protect the
environment.
It is worth remembering that the target in improvement must be the socio-economic
position and society; for the laws have limitation in bringing about changes without active

2 Global Pollution and Environmental Monitoring
participation and support of people. The first step in this direction, is to bring awareness by
incorporating as a syllabus for schools, colleges and universities. We are lucky, that with the
order of the Supreme Court of India in 2004, this has been made compulsory.
a a 0

z
SAMPLING PROCEDURES
Introduction
The analyst must take all reasonable precautions while taking samples of air, water or
soil. It is necessary to take into consideration the safety aspects while dealing with harmful
or poisonous materials. The procedures for sampling must be meticulously followed so also
its preservation before analysis. There are statistical approaches and correct methodology.
Proper care is also required during handling so that specific components of mixture are not
lost or destroyed. The entire analysis is dependent on 'analytical sample'; hence the material
collected must be true representative of the original bulk material. Sampling procedures
depend on objectives of analysis and accessibility of sites. The size, number and location of
portions of sample also influence the final result of analysis.
Theory of Bul~ Material
The bulk is described as one that does not contain discrete, identifiable or constant
units. This is dependent on number, size and site or location of the sample collection.
Standard equation is as follows:
2 A B
s = WN =N
where
Objective of Sampling
s-variance
A-constant of homogeneity
B-constant of segregation
N-number of samples
W-weight of sample
The objective of sampling is to collect a portion of material small enough in volume to
be transported conveniently and handled in the laboratory while still accurately representing
the material being sampled. This objective implies that the relative proportions or
concentrations of all pertinent components will be same in the samples in the material being
sampled and that the sample will be handled in such a way that no significant changes in
composition occur before the tests are made.

General Precautions
(1) Before filling, rinse sample bottle two or three times with the water being collected,
unless the bottle contains a preservative or dechlorinating agent.
(2) Depending upon the determinations to be performed, fill container (most organic
determination) or leave the space for aeration mixing etc. (microbiological analysis).
(3) Special precautions are necessary for sample containing organic compounds and trace
metals. Because many constituents may be totally or partially lost if proper sampling
and preservation procedures are not followed.
(4) Important factors affecting the results are:
(a) Presence of suspended matter or turbidity, the method chosen for its removal.
(b) Physical and chemical changes brought about by storage or aeration.
(5) Do not use the same sample for chemical, bacteriological and microscopic examination
because methods of collecting and handling are different.
Procedure for Collection of Sa:m.ples
(A) Chain of Custody Procedure
It is essential to ensure sample integrity from collection to data reporting. This includes
the ability to trace possession and handling of the sample from the time of collection through
analysis and final deposition. This is referred to as chain of custody and is important in the
event of litigation involving the result. Where litigation is not involved chain-of-custody
procedures are useful for routine control of sample flow.
(i) Sample· Labels
Use label to prevent sample misidentification: Gummed paper labels or tags generally
are adequate. Include at least the following information:
Sample Number
Name of collector
Date and time of collection
And place of collection
(ii) Sample Seal
Use sample seals to detect unauthorized tampering with samples up to the time of
analysis. Although seal in such a way that it is necessary to break it to open the sample
container. Affix seal to container before sample leaves custody of sampling personnel.
(iii) Field Logbook
Record all information pertinent to a field surveyor sampling in a bound logbook. As a
minimum include the following in the logbook: Location of sampling point, name and address
of field contact; procedure of material being sampled and address etc.
(iv) Chain of Custody Record
Fill out a chain-of-custody record to accompany each sample or group of samples.
The record includes the following information: Sample number, Signature of collector, date,
time and address of collection, sampling type, signature of persons involved in the chain of
possession and inclusive dates of possession.

Sampling Procedures 5
(v) Sample Analysis Request Sheet
The sample analysis request sheet accompanies sample to the laboratory. The collector
completes the field portion of such a form that includes most of required information noted in
the logbook. The laboratory portion of such a form is to be completed by laboratory, personnel
and includes: Name of person receiving the sample, date of sample receipt and determinations
to be performed.
(vi) Sample Delivery to Laboratory
Deliver sample to laboratory as soon as possible as practicable. Accompany sample
with chain of custody record and sample analysis request sheet.
(vii) Receipt and Logging of Sample
In the laboratory, the sample custodian receives the sample and inspects its condit.ions
and seal, reconciles label information and seals against the chain-of-custody record, assigns
a laboratory number logs samples in the laboratory logbook and stores it in a secured
storage room until it is assigned to an analyst.
(viii) Assignment of Sample for Analysis
--
The laboratory supervisor usually assigns the sample for analysis. Once in laboratory
the supervisor is analyst and responsible for the care and custody.
(8) Sampling Method
(i) Manual Sampling
Manual sampling involve no equipment but may be unduly costly and time-consuming
for routine or large-scale sampling programs.
(ii) Automatic Sampling
Automatic samples can eliminate human error in manual sampling, can reduce the
labour cost, may provide more frequent sampling, and are used increasingly. Be sure the
automatic sampler does not contaminate sample.
(C) Sample Containers
The type of sample container used is of utmost importance. Containers typically are
made of plastic or glass; but one material may be preferred over another for diff8lent kinds
of samples.
(D) Number of Samples
If an overall standard deviation is known, the required number of samples may be
established by the following relationship:
N > (T * S/U)2
Where
N =Number of samples
S = Overall standard deviation
U = Acceptable level of uncertainty
T =Student-to-statistic for a given confidence level

(E) Quantity
Collect a 2-L sample for most physical.and chemical analysis. For certain determinations,
Larger samples may be necessary.
{F) Safety Consideration
Because sample constituents can be toxic, take adequate precautions during sampling
and sample handling.
(1) Precautions may be limited to wearing gloves or may include coverS3l1, aprons.
(2) Always wear eye protection when toxic vapours present.
(3) Always wash han~s thoroughly before handling food.
(4) If flammable organic compounds are present, take adequate precautions to
prohibit smoking near samples.
(5) Keep sparks, flames and excessive heat sources away from samples and
sampling locations.
Sample Preservation
(A) General
Regardless of the sample nature, complete stability for every constituent never can be
achieved. At best preservation techniques only retard chemical and biological changes that
inevitably continue after sample collection.
(B) Sample Storage Before Analysis
(i) Nature of Sample Changes
(a) Certain cautions are subject to loss by adsorption on or ion exchange with, the
walls of glass containers. These includes aluminum, cadmium, copper chromium,
iron, lead, manganese, etc.
(b) Temperature changes quickly; pH may change Significantly in a matter of minutes;
dissolved gas (oxygen, CO2) may be lost. Determine temp, pH and D.O. in the
field.
(c) Microbiological activity may be responsible for changes in the nitrate-nitrite-
ammonia content, for decreases in phenol concentration and in BOD, or for
reducing sulfate .to sulfide.
(d) Biological changes taking place in a sample may change the oxidation state of
some constituents. The well-known nitrogen and phosphorous cycles are example
of biological influence on sample composition.
(e) Zero head space is important in preservation of samples with volatile organic.
Avoid loss of volatile material by collecting sample in a completely filled container.
Achieve this by overfilling bottle before capping or sealing.
(ii) Time Interval BIW Collection and Analysis
(I) (a) In general, the shorter the time that elapse between collection of a sample
and its analysis, the more reliable will be the analytical result.
(b) For certain physical values, immediate analysis in the field is required.

(II) It is impossible to state exactly how much elapsed time may be allowed between
collection of sample and analysis; this depends upon:
(a) Character of sample.
(b) The analysis to be made.
{c} Conditions of storage.
(III) Changes caused by growth of micro-organism are greatly retarded by keeping
the sample in the dark and at a low temperature.
(IV) When the interval between sample collection and analysis is large enough to
produce change in either the concentration or physical state of the constituents
to be measured.
(C) Preservation Techniques
(i) To minimize the potential for volatization or bio-degradation between sampling
and analysis, keep sample as cool as possible without freezing.
(ii) Preferably pack sample in crushed or cube ice before shipment.
(a) Avoid using dry ice because it will freeze samples and may cause glass
container to break.
(b) Dry ice also may effect a pH change in sample.
(iii) Use Chemical Preservatives only when they are shown not to interfere with the
analysis being made. When they are used, add them to the sample bottle initially
so that all sample positions are preserved as soon as collected. No single
method of preservation is entirely satisfactory. Because a preservation method
for one determination may interfere with another one. Samples for multiple
determination may need to be split and preserved separately.
Clearly it is impossible to prescribe absolute rules for preventing all possible changes,
but to a large degree of the dependability of an analytical determination rest on the experience
and good judgement of the person collecting the sample.
Conclusions
• The main purpose of collecting and examining environment samples is to assess their
quality from the point of view of safety and environmental protection.
• Samples are taken from different sources, so as to truly represent all the characteristics
at the time and place of collection.
• Volumetric analysis is suitable for testing acidity, alkalinity, chlorides, hardness and
dissolved oxygen.
• Colour comparison procedure is adopted for measuring parameters like turbidity, pH,
residual chlorine, iron, sulphate, fluorides.
• Various instruments are available for directly measuring turbidity, conductivity, pH,
dissolved oxygen etc.
Sampling is a process of obtaining a reasonable amount of material that has all the
essential properties of the bulk material.
The procedure depends on nature of the test material, accuracy required, cost of the
product involved, the cost of the analysis and the cost of sampling. If a drug is required to be
manufactured, high degree of purity of raw material is desirable, however, for chalk sticks
similar degree of care is not required.

Sampling includes three stages:
(I) Identification of Bulk material.
(II) Collection of Gross sample.
(III) Reducing it to Lab sample.
Since many substances are present at only very low levels in environmental media, it
is often necessary to pre-concentrate them in some manner prior to chemical analysis. This
may be achieved in a wide variety of ways, dependent upon the type of sample and the
nature of the analysis.
The latest techniques for analysis of metals are of sufficient sensitivity for direct assay
of many metals in natural waters. Where older instrumentation is employed, or for elements
present at a very low abundance, a pre-concentration may be required. Where little chance
of sample contamination exists, the crudest form of pre-concentration, simple evaporation to
a smaller volume by heating, may be effective and has commonly been employed with fresh
waters. Alternatively, a metal-chelating reagent (e.g., ammonium pyrolidine dithiocarbamate-
APDC) may be added and the complexed metal extracted into a small volume of organic
solvent (e.g., methyl isobutyl ketone-MIBK). The metals are thus preconcentrated by an
amount equal to the ratio of volume of water sample and organic solvent, and indeed the use
of organic solvents with flame atomic absorption spectrometry gives a further enhancement
in sensitivity relative to analysis of aqueous samples. In other cases the metal is extracted
from the organic solvent into an acid medium, which is then analysed.
Metal Species Occurring in Natural Water in Relation to Size Associati.on
Typical size
range (nm)
<1
1-10
10-100
100-1000
>1000
Metal
species
free metal ions
inorganic ion pairs,
inorganic complexes, low
molecular weight organic
complexes
high molecular weight
organic complexes
adsorbed onto inorganic
colloids (or complexion
by surface-adsorbed
humic); associated with detritus
adsorbed onto living cells;
associated with mineral
solids and precipitates
Example
Pb2+, Cu2+
CdCll-
Pb-fulvates
Cu-humates
CO-Mn02
Pb-FeOOH
Cd-clay
2PbC03Pb(OHh
Phase state
dissolved
dissolved
colloidal
colloidal
particulate
Organic compounds in both air and water may be pre-concentrated by passage of the
sample through a porous organic polymer or resin where the analyte is adsorbed. Thus
hydrocarbons in street air are commonly collected upon a porous polymer such as Tenax,
from which they may be displaced by heating for a subsequent chemical analysis.
There are two ways of sampling:
(I) Random, i.e., without any bias. This depends on the homogenity of sample.
(II) Non-Random or systematic sampling.

This eliminates bias or prejudice. It also, requires a prior list of items in the bulk.
The three states of the sample, i.e., gas, liquid and solid, all require different treatment.
For comparatively it is easier to sample gaseous products (air) than solids (soil). In general,
the gases are sampled based on their property of expansion, displacement and flushing. The
liquids are sampled based on their homogenity as well as their fluidity and the solids are
sampled with the help of different types of instruments depending on the nature of the solid
material. They could be grounded, pulvarised, powdered, conned and simply divided physically.
The soil samples in this category are required to be homogeneous. Distribution of
pollutants in soil may not be vertical with depth but can be sidewise (spatial). There are two
strategies, (one), which is expensive, require to take all care separately and analyse, whereas
the (second), more time consuming, where all samples can be combined and mixed to
provide single bulk. Obviously, contamination in soil samples may give misleading results.
The equipment used for sampling and storage must be cleaned with acid, EDTA and ultra
pure water. Soil samples are relatively stable. For preparing for analysis this sample is
completely dissolved in acid mixture containing hydrofluoric acid and oxidant. Aqua regia or
a mixture hydro-chloric acid and nitric acid. Use of Hydrofluoric acid is also recommended.
Fusion mix like alkaline Borax can be used.
For air samples there are two basic methods suggested. Grab sampling and continuous
sampling. In this the vapours are removed from the air. For a certain fixed time, followed by
concentration using new instrumentation. The collection efficiency in this is nearly 100%.
Types of Santple Collection for Water
(A) Grab or Catch Sample
A sample collected at a particular time and place can represent only the composition
of source at that time and place. However, when the source is known to be fairly constant in
composition over a considerable period of time or over substantial distance in all direction,
then the sample may be said to represent a longer time period or a large volume or both
than the specific points at which it was collected. In such circumstances, some sources may
be represented quite well be single grab samples, e.g., some water supplies, some surface
water and rarely some waster water streams.
(B) Composite Sample
In most cases, the term "Composite Sample" refers to a mixture of grab samples
collected at the same sampling point at different times. Time-composite samples are most
useful for observing average concentration. As an alternate to the separate analysis of a
large number of samples, followed by computations of average and total result, composite
samples represent a substantial saving in laboratory effort and expense. For these purposes
a composite sample representing a 4-hr period is considered standard for most determinations.
(C) Integrated Samples
For certain purposes, the information required is provided best by analysing mixtures
of grab samples collected from different points simultaneously or as nearly so as possible
are integrated samples. An example of the need for such sampling occur in a river or stream
that varies in composition across its width and depth. To evaluate average composition or
total loading, use a mixture of sample representing various points in the cross-section in
proportion to their relative flow. .

10
Sampling
Global Pol/ution and Environmental Monitoring
(A) Samples for Physical and Chemical Examination
Samples for physical and chemical examination should be collected in clean glass
stoppered bottle made of neutral glass of capacity not less than 2 Itr. Stoppered glass bottle
technically known as "Winchester Quart bottles" are suitable. Before collecting the sample
rinse the bottle well three times with water filling it each time about 30%. Then fill it with the
water, tie the stopper tightly down with a piece of cloth over it and seal the string.
(B) Sample for Bacteriological Examination
(a) Sample for bacteriological examination should be collected in clean sterilized bottle
made of neutral glass of capacity 200-250 ml. and provided with a ground stopper having an
overlapping rim. The sampling bottle should not be opened until the moment at which it is
required for filling.
(b) Be very careful so that nothing except the water to be analysed comes in contact
with inside of the bottle or the cap.
(c) The outside of the tap .or faucet at the sample point should be inspected, and if
found leaking around the handle a different point must be chosen because the water might
turn down outside of the tap and enter the bottle causing contamination.
(d) Clean and dry the outside of the trap or faucet with sterile papers before taking the
sample.
(e) Allow the water to run for at least one-half of minute before collecting the sample.
(f) While filling the bottle, the bottle must be held properly so that no water which
contacts the hand enter into the bottle.
(g) The sample must be handed over immediately to laboratory otherwise extra bacteria
may develop, thus giving wrong result.
Collecting the Sample From
(A) A Tap (Distribution System)
(a) When the sample is to be taken from a tap in regular use, the tap should be
opened fully and the water run to waste at least 2 minutes in order to flush the interior of the
nozzle and discharge the stagnant water in the service pipe.
(b) In the case of samples to be collected from taps which are not in regular use the
tap should be sterilized by heating it. Then the tap should be cooled by allowing the water to
run to waste before the sample is collected.
(B) From Well
Collect samples from wells only after the well has been pumped sufficiently to insure
that samples represent the ground water source. Sometimes it will be necessary to pump at
a specified rate to achieve a characteristics draw down, if this determines the zone from
which the well is supplied. Record pumping rate and draw down.
(C) River or Stream
When samples are collected from a river or stream. observed result may vary with
depth, stream flow and distance from shore and from one shore to another.

Sampling Procedures 1 1
(a) If equipment is available take an "Integrated sample" from top to bottom in the
middle of the stream or from side to side at mid depth, in such a way that the sample is
integrated according to flow.
(b) If only a grab sample can be collected, take it in the middle of the stream and at
mid-depth.
(0) Lake & Reservoirs
Lake and reservoirs are subject to considerable variations from normal causes such
as seasonal stratification, rainfall, run-fall, run off and wind. Choose location, depth and
frequency of sampling depending upon local conditions and the purpose of the investigation.
Avoid surface scum.
(Use only representative sample for examination. The great variety of conditions under
which collection must be made make it impossible to prescribe a fixed procedure).
Soil Satnpling
A representative homogeneous soil sample is essential pre-requisite of any analysis.
Distribution of pollutants not only change vertically with depth but also increase side ways
horizontally. There are two strategies to act upon (firstly), a number of cores may be taken
and analysed separately. (Secondly), all the samples can be combined and thoroughly mixed
to provide a single bulk sample. The first is costly and time consuming. The second method,
however, is followed with variations in concentration. The equipments of sampling soil must
be cleaned with acid, EDTA and finally with Ultrapure water.
Particular care must be taken for storage of samples when air dried, these are relatively
stable. For purpose of extraction the extract solution should be acidised before storage.
Sampling sites, depth and method to be used for the collection of soil sample, should
be decided by keeping in mind the purpose of study and parameters in question. For
characterisation in general, a few random samples from the study area to the depth of about
15 cm, may be sufficient. For the study of soil profiles, samples at this depth may be
needed.
Using spade and shovel, surface soil samples may be obtained. The samples near the
root of a large tree must be avoided. Over and near civil construction sites can be avoided.
Special borer samples are required to get the samples from deeper profiles.
The ones collected must be retained in polythene bags and must be brought to the
laboratory without delay. This is because the parameters such as redrox potential, nitrogen
phosphorus content etc. must be analysed immediately. Alternatively the sample can be
stored after drying at 40°C.
000

3
WATER
Introduction
Human civilisation reveals that water supply and civilisation are almost synonymous.
Water is the most vital resource for all kinds of life on this earth. But this resource is now
adversely affected both qualitatively and quantitatively by all kinds of human activities on
land, in air or in water.
About 97% of the earth's water supply is in the ocean, which is unfit for human
consumption and other uses because of its high salt content. Of the remaining 3%, 2% is
locked in the polar ice caps and only 1% is available as fresh water in rivers, lakes, streams,.
etc.
Sources of Water Supply
(a) Rain water (b) Surface water in the form of : (i) stream, river, brooks, (ii) Upland
surface water (c) Underground water:
(i) Shallow well water
(ii) Deep well water
(iii) Springs
(iv) Artesian well water.
(a) Rain water: Rain water during its passage towards ground absorbs nitrogen,
oxygen, carbon dioxide, volatile acids, Ammonia Fumes, Micro-organism and dust particles
with it. Rain water is generally free from mineral matter. Due to absorption of carbon dioxide
it becomes slightly acidic in nature.
(b) Surface water: Rain water when falls on ground, it carries vegetable matter which
in turn converts into humic acid in due course. Water also carries the excreta of human and
animals. This addition is dangerous as it may contain pathogenic micro-organism. Surface
water may also contain algae, soil bacteria, fungi, molluccas, sponges and polyzoa. Surface
water near industrial area, village, cities may also carry obnoxious minerals and poisonous
materials.
(c) Underground water: Sub-soil water is suspicious as it contains inorganic or organic
impurities. There is also possibility of heavy populations of micro-organisms which enters
from sewage water. The well water becomes hard due to presence of carbonates, chlorides,
sulphates, etc.) of calcium, magnesium and sodium.
There are many sources for the. water supply and each has its own type of
contamination. Examination of water is essential to confirm purity, potability and
wholesomeness. It is essential also for safeguard of the public health.

Water 13
Water Quality Parall1.eters
The water quality parameters are roughly classified into the three categories: (I) Physical
(II) Chemical (III) Biological. Following table represents the important water quality parameters:
Table 3.1
Physical Chemical Biological
Temperature Dissolved Oxygen Pathogenic
Colour Biological Oxygen Bacteria
Odour Demand Coli Forms
Conductivity Chemical Oxygen and other
Solids Demand Bacteria
pH, Acidity Algae
Turbidity Alkalinity,
Foam and Froath Ammonia, Nitrates, Viruses
Nitrites, Phosphates,
Sulphates, Chlorides,
Silica, Hardness,
Calcium, Magnesium,
Heavy Metals,
Sodium, Potassium
Detergents, Pesticides
Pure water is one which is colourless, free from turbidity and abnormal tests and
smell. Wholesome water is that water which is free from pathogenic organism and may
contain chemical within permissible limits. Following table represents the drinking water
standards:
Water Quality Standards in India
Parameter
pH
Total hardness
Turbidity
Chlorides (as CI)
Cyanide (as CN)
PAH
Fluoride (as F)
Nitrate (as N03)
Phenols
Sulphate (as S04)
Manganese
Mercury
Iron
Copper
Cadmium
Standard (Revised 1975)
6.3 - 9.2
600 ppm
25 ppm
1000 ppm
0.05 ppm
0.2 ppm
1.5 ppm
45 ppm
2 ppm
400 ppm
0.5 ppm
0.001 ppm
1 ppm
1.5 ppm
0.01 ppm

14
Selenium
Chromium
Lead
Arsenic
Zinc
Magnesium
0.01 ppm
0.05 ppm
0.1 ppm
0.05 ppm
15 ppm
150 ppm
Table 3.2 : Drinking Water Standards
World Health Ministry of Works
Organisation and Housing
Characteristics Highest Maximum Acceptable Cause of
Desirable Permissible Rejection
PHYSICQ-CHEMICAL
Turbidity, JTU 5.0 25.00 2.5 10.00
Taste and odour Nothing Disagreeable Nothing Disagreeable
Colour (Pt. scale) 5.00 50.00 5.00 25.00
pH 7.0-8.5 6.5-9.2 7.0-8.5 6.5-9.2
Total solids 500.0 1500.0 500.0 1500.0
Total hardness (as
CaC03 100.0 500.0 200.0 600.0
Magnesium 30.0 150.0 30.0 150.0
Iron (Fe) 0.1 1.0 0.1 1.0
Manganese '0.05 0.5 0.05 0.5
Copper 0.05 1.0 0.05 1.5
Chloride 200.0 600.0 200.0 1000.0
Sulphates (as S04) 200.0 400.0 200.0 400.0
Phenolic substances 0.001 0.002 0.001 0.002
Fluoride* 1.0 1.5 1.0 1.5
Nitrate 45.0 45.0 45.0 45.0
Zinc 5.0 15.0 5.0 15.0
Mineral Oil 0.01 0.30 0.01 0.30
Anionic detergents (as MBAS) 0.2 1.0 0.2 1.0
Arsenic 0.05 0.05 0.05
Hexavalent Chromium 0.01 0.05 0.05 .
Cyanide 0.05 0.05 0.05
Lead 0.10 0.10 0.10
Selenium 0.01 0.01 0.01
Cadmium 0.01 0.01 0.01
Mercury 0.001 0.001 0.001
PCB (ug/1) 0.2 0.2 0.2
Gross Alta-activity (PCil1) 3.0 3.0 3.0
Gross Beta-activity (PCi/1) 30.0 30.0 30.0

Water
Bacteriological
15
A.
B.
W.H.O.
Water entering distribution system. If disinfected
coliform count in any sample of 100 ml
should be zero.
Water in the distribution System: (Ideally all
samples taken from the distribution system
including consumers premises should be free
from coliform organisms.)
Since in practice it is not always possible
hence following standards:
(i) throughout any year, 95% of the sample
examined should not have any coliform
organisms.
(ii) E. Coli count in 100 ml of any sample should
be zero.
(iii) Coliform organisms not more than 10 per
100 ml shall be present in any sample.
(iv) Coliform organisms should not be detectable
in 100 ml of any two consecutive samples.
All the values are in mg/L otherwise stated.
Ministry of Works and Housing Coliform count in
any sample of 100 ml should be zero.
Water in the distribution system:
shall satisfy all the three criteria indicated
below:
(i) E. Coli count in 100 ml of any sample should
be zero.
(ii) Coliform organisms not more than 10 per 100
ml shall be present in any sample
(iii) Coliform organisms should not be detectable in
100 ml of any two consecutive samples or
more than 50% of the samples collected for
the year.
The acceptable Fluoride concentration varies as a function of ambient temperature.
Water Santpling and its Exantination
Water samples are usually collected and examined properly keeping the following
objectives:
Objectives:
(1) To keep the reql.lired degree of purity.
(2) To note the SUitability of a source of water for human beings and animals.
(3) To confirm the best source of water supply by comparative water analysis.
(4)' To find out the suitability of the water for domestic water supply, tannery, wool
washing and for slaughter house.
(5) To check pollution in river water and investigate its sources.
(6) To record the changes in the quality of water in wells and rivers during rainy
season or drought.
(7) To study the- effect of water on metals, e.g., reservoirs or pipes used for
distribution of water.
(8) To determine the efficiency of purifiers or softners.
(9) To find out the variations in the characteristics of water of various levels of the
deep well.

1 6 Global Pollution and Environmental Monitoring
(10) To detect the source of infection during outbreak of certain diseases, e.g., cholera,
dysentry, dyphtheria, Anthrex, Blackquarter, foot and mouth disease and
rinderpest.
(11) To find out the suitability of water for the use of patients of certain diseases,
e.g., rheumatism and kidney disorders.
(12) To detect any leakage in the mains, subsoil, sewage water escaping from the
main.
Selection of Sampling Sites
Sampling sites are important to understand the quality of water. The selection of
actual sampling location in water body depends upon the character of the water system or
body. In a lake or wide river many sampling sites should be selected at various corners. If
the lake is stratified, three vertical samples at one site (surface, middle and bottom) shall be
required. In shallow ponds only surface and bottom samples are required. In organically
polluted river at least one location should be selected above the outfall of the wastes and
remaining four sites should be selected downstream, representing the zone of recent pollution
saprobic zone, recovery zone and clean water.
STRING---t,.
4(-'k'--METAL RING
CATGUT --.g...~
n----RUBBER BAND
---RUBBER
,,It':_~---RUBBER CORK
t----f-+-- LONG TUBE·
t-411---H--SHORT TUBE
SAMPUNG BOmE
LEAD CASE
Fig. 3.1
Sampling Site Selection for Organic Polluted River
If the river is polluted by inorganic pollutants then one site above and one below the
point of discharge is considered for collection of water samples.
Water samples must be collected by proper care by avoiding any external contamination
- there should not be any error. The following factors must be considered during the
collection of the samples.
(i) The collected sample should be a representative one.
(ii) It should be collected at different times and frequencies.
(iii) The variations in rate of flow over a period of sampling must be taken into
account.
(iv) The objective and character of the laboratory analysis to be done.
(v) The use to be made from the result of analysis.

Water 17
Selection of Containers
When the sample is to be analysed for organic content, green, or amber coloured
bottle should be used. Dark coloured bottles are used for re~idual chlorine estimation.
Polythene bottles are used for analysis of radioactive substances, corning glass ware is
good for the collection of samples for bacteriological examination.
Bottle should be cleaned by good quality of detergent and clean water. Rinsing of the
bottle with concentrated sulphuric acid and then with distilled water several times is necessary.
Stopper should be cleaned thoroughly by the same manner. Polythene bottles should be
cleaned by distilled water or may be boiled in distilled water. The glass bottles are sterilized
of 15 1b pressure in autoclave for 30 minutes or at 150°C in hot air over for 2 hours.
Samples should be directly collected in the bottle without the help of funnel or tube,
the bottle should be rinsed with water to be sampled.
Types of Safl1.ples
(1) Composite Sample: Sample taken from different zones and at different depth (vertically
and horizontally) and then mixed together.
(2) Grab Sample: Sample taken at random from ponds and lakes.
(3) Representative Sample : Samples are taken at different times and at different
frequencies. The frequency of samples depends on the population using the sample
and the purpose for which water is to be used.
(4) Integrated Sample: Samples taken of regular hourly interval and all are pooled together
and then a portion of it is taken for the examination.
Safl1.ple Collection Procedure
(i) River and Streams: In river and stream, the sample should be collected at a point
which practically represents the condition of the stream, points near the banks should be
avoided. Middle zone or mid-depth is the proper place for collecting the sample, composite
or integrated sample may be taken in such cases.
(ii) Lakes and Ponds: Water sample should be collected from sufficient depth. Bank
should be avoided. For sampling sufficient time is given to settle the disturbed clay or sand
particles at the bottom so that clean water can be collected, sampling bottle should be held
at the bottom.
The bottle along with stopper is taken into the water in inverted position upto the depth
one to two feet below the surface of water. Then the mouth of bottle is raised in slanting
position and stopper is removed, so that air comes out and water easily enters in the bottle.
It is allowed to fill up to three-fourth capacity. The bottle is then closed and taken out.
(iii) Sample Col/ection from Deep Well: A glass bottle is taken which is properly fitted
with rubber stopper. Rubber stopper is provided with two holes (Fig. 3.2). In one hole long
glass tube is fixed and in another hole short glass tube. The two tubes are connected with a
rubber tube of their outer ends. Due to this, assembly becomes air tight and water in the
well. The rubber tube is tied by means of string. The other end is tied to a metal ring. A
strong sting is also tied over the other end so as to hang the bottle for immersing into the
well water.
The neck of the bottle is tied with rubber band. The rubber band is passed through the
metal ring. A metallic case (madi up of lead) is placed over the bottle, such bottle is lowered
into the well up to the required depth. A strong jerk is given to string which pulls the

connecting rubber tube. By this air comes out and water enters into the bottle. When the
bubbles stop on the water surface the bottle is pulled out and fitted with stopper.
(iv) Shallow well samples: The sample bottle is fixed properly to a metal sand. The
bottle is sealed by a string. Another string is used to secure the stand. The stand along with
the bottle is allowed to dip in well. When the bottle reaches about 7-8 feet deep from surface
of water, a jerk is given to the string which holds the stopper of the bottle. Stopper is
removed from bottle and air bubbles come out allowing water to enter in the bottle. Total
disappearance of bubbles indicates that bottle is filled with water. The bottle is taken out
from the well and it is sealed.
Fig. 3.2
Flow Measuretnent
Number of methods are available to measure the flow in stream and waste water
carrying pipes.
(i) Bucket Method: This method is applicable when the waste water is. coming from
the pipe or sewer. A bucket is easily used to fill the water from the pipe, time is recorded by
stop watch.
Litre in bucket x 60
Flow (~n litres/min) = T' . S d
Ime In econ s
(ii) Surface Float Method: A Float (any piece of plastic, wood etc.) is thrown on water
surface. The time required for a float to travel a known distance is observed and average
velocity is obtained by
d
V=t
d is the distance, t is the time. The factor 1.2 indicates· that surface velocities are
normally about 1.2 times heavier.

Water
Sample Handling and Preservation
After accur~te sampling the bottles are properly labelled as under:
(1) Submitted for Physical I Chemical
(2)
(3)
(4)
(5)
(6)
Submitted by
Source of sample
Place of Sample
Sample taken in presence of
Signature of Authority
Bacteriological examination.
Name of authority and address.
Surface/Well/Tap/Effluent pit.
Location address.
Signature and name of the person
with address.
Appointed /
19
It is essential to protect the water sample from changes in composition and deterioration.
Parameters like pH, D.O., temperature, must be recorded quickly.
The following table represents the preservation technics for various parameters (Table
3.3). Preservation is essential to control the hydrolysis, biological reduction and complex
formation, volatility etc. It is always suggested that analysis must be undertaken within 4
hours for same parameters and 24 hours for other, from time of collection and it must be
completed, within a week.
Table 3.3: Water Sample Preservation
Parameter Mini sample Container Preservation
size, ml
2 3 4
pH 100 Polythene Measure with 0-4 hrs.
DO 100 Polythene
COD 500 Polythene Add H2
S04 to pH 2; refrigerate
Nitrogen Ammonia 500 Polythene Analyze as soon as possible;
add 0.8 ml conc. H2S04/L
Nitrate + Nitrite 500 Polythene Add 40 mg HgCI2/L and
refrigerate
Cyanide 500 Polythene Add NaOH to pH 12 and
25 ml of 2% ascorbic acid and
refrigerate .
Sulphide 500 Polythene Add 1 ml. of 2N Zn (CH3 COOh
and 2 ml of 1M NaOH; stir and
refrigerate
Phosphate 500 Polythene/glass A.dd 40 mg HaCI2/L and refrigerate
Phenol 500 Polythene/glass Acidify with H3
P04 to pH 4.0 and add
Ig CUS04' 5H2
0 per L to inhibit
bi0gegradation
Tannin and lignin '500 Polythene/glass Analyze as soon as possible.
Chromium, arsenic, 500 Glass/Polythene Add 5 ml conc. HN03Land
lead, zinc, mercury refrigerate
E. Coli/total bacteria 100 GICjss bottle Sterilize the bottles in autoclave
/acteno-mycetis at 121°C at 15 Ib/inch2pressure for
15 minutes. Collect the sample in

20
Microplankton/algae
and other biological
organisms
500
Glass bottie
sterilized bottle and refrigerate
immediately
Add 5 ml formali~ per 100 ml sample
and refrigerate immediately
Characteristics of Potable Water
(1) It should be colourless, odourless and tasteless.
(2) It should be free from turbidity and other suspended impurities.
(3) It should be free from germs, bacteria and other pathogenic organisms.
(4) It should not contain toxic dissolved impurities, such as heavy metals, pesticides,
etc.
(5) It should have a pH in the range 7-8.5.
(6) It should be moderately soft, having hardness preferably in the range 50-100
ppm. Its hardness should not be above 150 ppm.
(7) It should be aesthetically pleasant.
(8) It should not be corrosive to the pipelines and should not cause any incrustations
in the pipes.
(9) It should not stain clothes.
Table 3.4 gives the WHO (World Health Organization) standards for drinking (Potable)
water.
Thble 3.4 : Standards (maximum permissible limits) for drinking water as
recommended by World Health Organisation (WHO)
Parameters
pH
BOD
COD
Arsenic
Calcium
Cadmium
Chromium
Ammonia
Copper
Iron
Lead
Mercury
Magnesium
Manganese
Chloride
Cyanide
Nitrate + Nitrite
Polyaromatic hydrocarbons (PAH)
Selenium
Level WHO Standard
6.5 - 9.2
6
10
0.05 ppm
100 ppm
0.01 ppm
0.05 ppm
0.5 ppm
1.5 ppm
1.0 ppm
0.1 ppm
0.001 ppm
150 ppm
0.5 ppm
250 ppm
0.05 ppm
45 ppm
0.2 ppm
0.01 ppm

Water 21
Treatment of Water for Municipal Purposes
The mun'icipal water supply for drinking and other domestic uses should be colourless,
odourless, free from suspended impurities, free from germs, bacteria and other pathogenic
organisms and should not contain harmful dissolved impurities. Therefore, the raw or impure
water obtained by municipalities from sources such as rivers, lakes, wells, tube wells, etc.
has to be properly treated before supplying for the domestic purpose. The various steps
involved in the treatment are as follows:
(1) Aeration: The raw water is first aerated by bubbling compressed air. This
removes bad odours, CO2, etc.} and also removes iron and manganese by
precipitating them as their respective hydroxides.
(2) Settling: The water is then allowed to stand in large settting tanks. At this
stage, some of the heavier impurities present in water settle down by gravity.
Also, the bacteria present are partially eliminated due to the UV radiation from
sun light.
(3) Coagulation: The suspended impurities present are then removed by coagulation
using lime, soda ash and aluminium sulphate (or ferric alum) as the case may
be. The suspended impurities are trapped by the resulting precipitate of AI(OH3)
and settle down at the bottom, thereby bringing about partial clarification of the
water. Also, the negatively charged colloidal impurities are neutralized by the
trivalent aluminium cation, followed by agglomeration and settling down by gravity.
(4) Filtration: The partially clarified water is then passed through sand gravity
filters. These comprise of rectangular tanks which contain (a) a top layer (about
1 meter thick) of fine sand (b) a middle layer (0.3 - 0.5 meter thick) of coarse
sand, and (c) a bottom layer (0.3 - 0.5 meter thick) of graded gravel. A series of
porous drains are provided at the bottom of the gravel layer through which
filtered water is collected. The slimy surface layer comprising of finely divided
clay, algae, bacteria, etc. formed on the filter bed acts as an effective filtering
medium which filters the finely divided residue, suspended matter and bacteria.
The filters are backwashed periodically to remove the precipitated matter from
the surface, so as to ensure efficient filtration. Activated carbon may be used for
filtration, if the water contains odours.
(5) Chlorination: The filtered water is sterilized by chlorination (by adding chlorine
pr bleaching powder) to destroy the pathogenic micro-organisms. The water is
now pumped to overhead tanks for subsequent domestic distribution.
Sewage Treatment
The wastewater from bathrooms, kitchens, lavatories, etc., is called Domestic Sewage.
The wastes disposed from factories, laundries, laboratories, business houses, schools,
hospitals, etc., also results in Sewage. The spent water from the community as a whole is
called Sanitary Sewage.
,
Sewage contains
(a) Organic impurities (e.g., Urea (from urine) proteinaceous matters, detergents,
biodegradable faeces, animal wastes, fats, carbohydrates, etc.)
(b) Inorganic impurities (e.g., nitrates, phosphates, detergents, surfactants, trace
metals, other anions and cations).

(c) Saprophytic bacteria which are harmless and feed upon organic matter.
(d) Pathogenic bacteria such as
(i) Vibrio cholerae (which cause cholera)
(ii) Shigelia dysenteria (which causes bacillary dysentery)
(iij) Salmonella typhi (which cause typhoid)
(e) Industrial wastes, wherever applicable
From the point of view of public health, sewage has to be properly treated.
Objectives of Sewage Treatment
(i) Stabilization: This is the process which involves breaking down of organic
matt~r with the help of bacteria into simple substances that do not decompose
further. Stabilization can be accomplished with the help of aerobic or anaerobic
bacteria.
(ii) To render the sewage inoffensive and devoid of its nuisance value.
(iii) To prevent contamination of water supplies, thereby protecting aquatic life.
Sewage Treatment Methods
The extent of sewage treatment required mostly depends on the following two
characteristics :
(1) The content of suspended solids.
(2) The biological oxygen demand (BOD) of the sewage.
The following major treatment methods are generally employed :
(1) .preliminary treatment: In this treatment, gross solids (e.g., large floating and
suspended solid matter, grit, oil and grease) are removed by passing through
screens, skimming tanks and grit chambers.
(2)
(3)
Primary treatment : This step is meant to remove the remaining suspended
settleable solids, reduce the strength of the waste and to facilitate subsequent
secondary treatment. The processes employed include sedimentation, mechanical
flocculation and chemical coagulation. After this treatment, about 60% of the
suspended solids, 30% COD, 35% BOD, 10% Phosphorous and 20% total
nitrogen, are generally reduced.
Secondary treatment: In this treatment step, the dissolved and colloidal organic
matter present Iii the sewage is removed by biological processes involving bacteria
and other micro-organisms. These processes may be aerobic or anaerobic.
They pring about the following sequential changes :
(a) Coagulation and flocculation of colloidal matter.
(b) Oxidation of dissolved organic matter to CO2,
(c) Degradation of nitrogenous organic matter to ammonia, which is t~n
converted into nitrite and eventually to nitrate.
(d) Reduction of BOD.
The effluent from primary sedimentation tanks is first subjected to aerobic oxidation in
systems such as aerated lagoons, trickling filters, activated sludge units, oxidation ditches or
oxidation ponds. Then the sludge obtained in this aerobic processes, together with that
obtained in the primary sedimentation tanks, is subjected to anaerobic digestion in the
sludge digesters.

Water 23
The sludge from the digester which contains 90 to 93% water, is de-watered in drying
beds, filter presses or vacuum filters. The de-watered sludge, after chlorination, can be sent
for ultimate disposal. The options available for ultimate disposal include dumping in land-
fills, incineration, dumping at selected sites in sea, or utilizing as a low-grade fertilizer after
composting depending upon the local conditions.
After secondary treatment, about 90% reduction in COD, 90% reduction in BOD, 30%
reduction in phosphorous, and 50% reduction in total nitrogen, could be generally achieved.
(4) Tertiary treatment: This is the final treatment meant for "polishing' the effluents
from the secondary treatment processes, to improve its quality further. The main
objectives of tertiary treatment processes are :
(a) Removal of fine suspended solids
(b) Removal of dissolved inorganic solids
(c) Removal of final traces of organics, as desired
(d) Removal of bacteria
(e) Decrease the load of nitrogen and phosphorous in the effluents
(f) Further purification of wastewater to enable its reuse.
The various processes employed in tertiary treatment include:
(1) Precipitation: Calcium compounds in the effluent from secondary treatment as
calcium phosphate by adding lime.
(2) Nitrogen Stripping: Nitrogen is present in the effluent for secondary treatment
in the form of ammonia, nitrites and nitrates. Ammonia is toxic to aquatic biota.
Nitrogen compounds enhance eutrophication. Ammonia in the effluenUs removed
by trickling the effluent from the top of a baffle tower while it meets the air
coming upwards.
(3) Chlorination: The residual micro-organisms in the effluent are removed by
chlorination before it is discharged.
(4) Adsorption: The undesirable tastes and odours are removed by adsorption on
activated charcoal.
(5) Coagulation and filtration : The residual solids in the effluent are coagulated
and removed by filtration.
(6) Desalination: The residual dissolved inorganic impurities may be removed by
ion-exchange, reverse osmosis or electrodialysis.
(7) Oxidation ponds : Bacteria, particularly of faecal origin, can be removed by
retaining the effluents from the secondary biological treatment plants in maturation
ponds or lagoons for specific time periods. The final effluent which has very low
BOD and very low suspended solids may be chlorinated before final disposal.
(8) Anaerobic digestion: Using digesters, septic tanks, Imhoff's tanks.
For large towns, a combination of aerobic and anaerobic treatment followed by irrigation
may be ideal. The bio-gas produced in the anaerobic treatment can be used as domestic
fuel.
Bhawalker Earthworm Research Institute (BERI), Pune developed a process in which
the waste water is passed through a vermifilter formed by enclosing earthworms and worm-
casts which harbour cocoons and a variety of microflora in a specially developed medium.
The impurities in the waste-water are converted into worm casts (Le., earthworm excreta)

24 Global Pol/ution and Environmental Monitoring
which have strong absorption properties. After repeated filtration, clear water is obtained.
The worm casts accumulated in the vermifilter may be harvested periodically for use as a
fertilizer.
Eutrophication
Enrichment of a water body by nutrients is called "eutrophication." The word
eutrophication originated from two greek words - 'eu' = good or well, and "trophes" = food.
Eutrophication thus means "well-fed" or "nutrient-rich", The enrichment of a water body with
respect to nutrients may take place because of natural sources (e.g., decomposition of plant
and animal remains) or by anthropogenic sources (e.g., man-made sources like domestic,
industrial or modern agricultural practices).
A newly formed waterbody possesses a very low concentration of plant nutrients and
hence little plant life grown in such water. Low primary production limits animal communities
too. The nutrient content in it slowly increases due to surface run-offs, windborn dust and
organic debris, excreta and exudates of animals which use the water. Bacteria and blue
green algae fix atmospheric nitrogen. Phosphates present in the rocks and detritus at the
bottom are solubilized by the micmbial activity. Thus the nutrient status of the water body
gradually increases. At this stage, a moderate population of plants, animals and microbes
now develops in the system, which further increases with increasing nutrient enrichment with
passage of time. Eventually, dense population of plants, phytoplanktons and animals appears.
At this stage, the aquatic system becomes highly productive in terms of fish, etc.
On the basis of nutrient status and productivity, anaquatic systems may be classified
into the following three types:
(i) Oligotrophic: Water with poor nutrient status and productivity.
(ii) Masotrophic : Water with moderate nutrient status and productivity.
(iii) Eutrophic: Water with rich nutrient status and high productivity.
Oligotrophic waters gradually turns into mesotrophic and finally to eutrophic waters.
Further ageing causes over-abundance of nutrients which leads to profuse growth of rooted
and floating green plants and the water body loses its aesthetic and economic value. Organic
debris and silt settles at the bottom. The water becomes useless. The boundaries of the
water body turn into a marsh with only a small shallow pond in the middle. Organic debris
and silt finally fill the depression and what was once a lake now converts into a dry land.
The accelerated or cultural eutrophication of several waterbodies is caused by human
activity. Large quantities of mineral nutrients and organic matter are added to the waterbodies
in the form of sewage effluents, organic wastes, agricultural run-offs, excreta and exudates
of animals and humans, etc. These provide plenty of phosphates, nitrates (mostly from
fertilizers applied to agricultural lands, domestic sewage, etc.) which lead to exuberant growth
of algae and other water plants. A rich microbial and animal population also develops. If
water from such a waterbody is to be used for domestic or industrial purposes, expensive
cleaning operations will be required. The process of natural eutrophication which is generally
very slow, thus gets accelerated. Silt and organic debris accumulates at the bottom and the
system turns into a shallow muddy pond, then to a marsh and finally into a dry land. Thus a
waterbody which could have been useful as a reservoir of fresh water and could have helped
the growth of fish, etc., for hundreds of years becomes totally useless within a span of a few
years only.

Water 25
Lake Washington and lake Mendota have undergone rapid eutrophication due to
anthropological activities. Similarly, the recreational value of lakes in Kashmir is reduced.
Nainital lake is undergoing accelerated eutrophication due to loading with sewage.
Undesirable Effects of Eutrophication
(1) Dense population of Planktonic algae develops rapidly in eutrophic waters. The water
turns green. Such waters are useless' for human use because it is very difficult and
expensive to remove the micro'scopic green plants. In due course of time, the entire
mass of planktonic algae may die abrupty. The decaying organic matter causes bad
tastes and odours. Further, the toxic chemicals released are fatal for fish, birds and
other aquatic animals which causes stinking and repulsive smell.
The decay and death of dense algae lead to biodegradation, cause sudden depletion
of oxygen in the water, thereby destroying fish habitats and other desirable aquatic
species.
(2) The inability of the water body to replenish the oxygen results in suffocation and death
of several aquatic organism.
(3) The layer of slime produced restrict the penetration of light and prevent atmospheric
regeneration of water.
(4) The decaying algae, fish, Planktons and other organisms cause foul smell.
(5) Anaerobic bacteria, e.g., Clostridium botulinum flourishing in such environment
generated toxins which are fatal to livestock, birds, etc.
(6) Pathogenic microbes, bacteria, viruses, protozoa which flourish under the prevailing
anaerobic conditions may result in causing water-borne diseases such as diarrhoea,
dysentery, typhoid, viral hepatitis, etc.
(7) On depletion of oxygen level and on exhausting nitrate oxygen, sulphates are reduced
as a last resort to yield hydrogen sulphide which results in bad smell and putrified
taste of water.
(8) Growth of very long filamentous weeds reduce the stream velocity and also trap solid
particles along with them. In our country, Dal lake, Loktak lake, Hussain Sagar, etc.,
are choked due to aquatic weeds thus affecting aesthetics, productivity of fish, and
utility of aquatic flora and recreational value.
(9) Over fertilization results in over production of algae and diatoms which leads to clogging
of filters in water treatment plants, retard water flow and affects water quality.
(10) High population densities of hydrilla, potamogeton, myriphllum, ceratophyllus and other
macrophytes render the water body unsuitable for any useful purpose.
(11) During eutrophication, growth of very large populations of tubicid worms and midge
chironomous plumosus, etc., occur, thereby causing aesthetic and economic problems
for maintaining the waterbodies.
(12) Prolonged eutrophic conditions lead to "dystrophic" conditions when bog flora and
large quantities of humic acid are produced while drastically reducing Plankton
productivity.
(13) The filamentous algae are washed into beaches during storms and piled up. The
rotting and stinking piles of organic matter render the beaches unsuitable for recreational
uses such as swimming, boating and fishing.

26 Global Pollution and Environmental, Monitoring
Steps to Control Eutrophication
(1) Effective wastewater treatment and removal of nutrients like nitrogen and phosphorous
before discharging the sewerage into waterbodies.
(2) Controlling the recyeling of nutrients through harvest.
(3) Effective disposal of organic matter as sludge.
(4) Removal of the algal blooms by dredging.
(5) Developing phosphate-free detergents for domestic use.
(6) Adopting effective physico-hemical methods for removal of dissolved nutrients such as
nitrogen and phosphorous compounds.
(7) Overcoming the temptation of over-fertilization.
(8) Controlling entrophication by applying algicides such as copper sulphate, chlorine, etc.
on susceptible surface waterbodies.
DOD

4
PHYSICAL EXAMINATION OF WATER
Introduction
Physical Examination is the quick test and can be performed in the field to test the
quality of water. Unpleasant or water with dirty smell is not liked by human beings and
animals. Colourful water indicate the presence of organic matter and the presence of
microorganisms. Turbidity of water is due to the presence of inorganic salts in water. Such
water is not accepted by animals. Water sample is examined for physical parameter as per
following manner.
Colour
Pure water has pale blue-green tint in large volume. Colour of the water is examined in
a Nessler Cylinder. Test artificial light. Colour should be confirmed from one foot depth.
Examine 100 ml of water sample and compare with distilled water, water sample is examined
by viewing vertically downward.
Greenish colour of water is due to the unicellular algal flora. Yellow colour is due to the
presence of organic matter or iron. Greenish yellow colour is due to presence of vegetations
in water. It is advisable to filter or centrifuge the water sample to decide the colour property.
Nature and colour density can be measured by Lovibondis Nessleriser. Hazen colour
standards matched with Lovinbond Glasses and disc containing nine colour standards values
are from 5 to O. Colour of the water provides the guideline regarding acceptance or non-
acceptance of water.
Taste and Odour
Taste and odour of the water is due to the presence of organic matter. The odour of
water is usually related with taste. In case of fishy taste the odour is also fishy.
Odours of water are caused by living and decaying aquatic organisms. Dissolution of
gases like hydrogen sulphide, ammonia, chlorine etc. are also responsible for odour. Many
algae also provide taste and odours to water sample. Discharge of chemical effluent into
water also imparts taste and odours to water. Water sample with unpleasant taste and odour
is rejected on aesthetic ground. Some colours and odours are found to be toxic. Water
sample is examined for odour parameter as per the following method. Take 100 ml of water
in stoppered conical flask. Sample is shaken for five minutes and then stopper is removed. It
is smelled quickly to get good results. The odour test is also performed by warming the
sample to about 40°C and then smelling and comparing with the smell of distilled water.
Chlorinated water with phenoltraces gives very strong chloraphenol odour, water weeds such
as chara, rotten hay and strew after decaying imparts fishy odour to water. Decomposition of

~ewage and its contamination with well water imparts odour of hydrogen sulphide. Fungi
browing on decaying vegetable matter will give a musty odour. Many fnorganic chemicals are
also responsible to impart characteristic tastes. NaGI salt imparts salty taste to water.
MnCI2, MgCI2, MgS04, impart bitter tastes. Pleasant or palatable taste waters are
acceptable. Unpleasant or unpalatable water is not acceptable. Stagnant, peaty and polluted
waters are definitely unpalatable.
Turbidity
Turbidity in a water may be due to either inorganic matter or organic matter. Turbidity
indicates the pollution and such water never be used for drinking purposes. Turbidity in
water is also caused by phytoplankton and other microscopic organism. Turbidity determina-
tion is possible by turbidometre. It works on the Tyndall effect. Here light is scattered by the
particles present in the water. Turbidity is measure in JTU. As per WHO, Turbidity for
drinking water must be always less than 5 JTU.
Under normal condition turbidity of water is confirmed by following method. 100 ml of
water sample taken in round bottom flask of 250 ml capacity. The sample is examined from
oversight keeping a white paper of its background. Such sample is now compared with same
amount of pure distilled water. Distilled water is normally of bright colour. Highly polluted
water is dull, opalescent and distinctly turbid. Appearance of filamenous structures, muscle
fibres indicates pollution.
Turbid water is unfit for domestic purposes, food and beverage industries. Turbidity in
water also retards the rate of photosynthesis in aquatic plants. Turbidity is removed by the
method of coagulation and then filtration.
Organic Matter
Presence of organic matter indicates the contamination of water with sewage water,
vegetations or carcase. Such addition in water favours the growth of microorganisms making
the water very dangerous. Seprophytic bacteria also grow In water containing organic matter.
Presence of organic matter is tested by undertaking 50 ml of sample of water in a conical
flask of 100 ml capacity and same amount of distilled water is taken in another flask. Both
the samples are shaken for 5 minutes. The formation of froth or bubbles are carefully
watched and compared with distilled water. The appearance of forth or bubbles if persists for
some time shows the presence of organic matter. In case of distilled water the minute
bubbles formed, break and disappear immediately.
Tentperature
Constant turbidity with organic matter and high temperature such as 22°C to 3rC
indicates serious pollution. Temperature should be recorded at the location where the sample
is taken. It should be taken at different depth. Temperature of deep source is always higher
than superficial water. To take proper temperature, sample bottle is placed in a thermos
flask having good insulation. Temperature is recorded as soon as the sample is taken out.
This indicates type and depth of source.
Reaction Acidic / Alkaline
This test is important so as to safeguard the life of human and animals. Under normal
conditions this test is performed by using red and blue litmus paper or pH papers. For
accurate measurements pH metres are available. Sample is taken in two test tubes. Test the

Physical Examination of Water 29
two samples with litmus papers. When red litmus paper turns blue, it shows alkaline reaction
and when blue litmus paper turns red, it shows acidic reaction. pH papers also indicate
mode of reaction. The pH of water should be 7 to 8.5, i.e., slightly alkaline side. Highly acidic
or alkaline water have action on water carrying pipes. It also provides abnormal taste of
water and makes the water hard.
DOD

5
'CHEMICAL EXAMINATION OF WATER
Introduction
Chemical examination is a preliminary test for deciding the quality of water and its
objective is to help the estimation of the quality parameters. Water containing toxic or
hazardous chemicals can be straightaway eliminated. This examination also indicates about
the pollution, particularly organic in nature. Such tests are carried out for the presence of
non-metallic and metallic inpurities or contaminations.
Non-Metallic hnpurities or Contantinations
(i) Chloride: In 5 ml of sample, a few drops of dilute silver nitrate solution is added. A
white precipitate of silver chloride indicates the presence of chlorides. Roughly estimation of
chloride can be done as, 10 ml of sample, add three drops of potassium chromate solution.
Titrate the sample against silver nitrate solution till the samle develops brick red colour. The
total content of chloride is given by the amount of AgN03 consumed by sample X100.
(ii) Sulphate: In 5 ml of sample, few drops of dilute hydrochloric acid are added and
then added 2N Barium chloride solution. A white precipitate of barium sulphate insoluble in
dilute nitric acid is the result. Regular use of water containing sulphate leads to diarrhoea in
human and scoor in animals. Maximum permissible level in case of drinking water is 250
ppm.
(iii) Nitrite: In 5 ml of water sample, a few drops of sulphanilic acid is added and
solution is well shaken. To this add few drops of alpha naphthaI amine solution. Solution is
well agitated and kept for one or two minutes. A pink colour is developed indicating the
presence of nitrite. Such water is unwholesome and dangerous.
(iv) Nitrate: In 5 ml. of water sample add few drops of sulphanilic acid and solution is
well shaken. Then add few drops of alpha naphthal amine solution. Agitate well. Then add a
pinch of zinc dust and keep it for 5 to 10 minutes. Development of pink colour indicates the
presence of nitrate in water. Excess of nitrate and excess of chloride indicate the sewage
pollution. Presence of nitrite and nitrate also indicate the sewage pollution. Nitrate M.P.L. is
1.5 ppm.
(v) Fluoride: In 5 ml of water sample, few drops of ferric chloride solution is added.
Formation of white crystalline precipitate indicates the presence of fluorides. Fluoride is a
potential toxin. Excess levels lead to dental dystrophy and constipation. M.P.L. is 1 ppm.
Ferric chloride reagent is prepared by dissolving 10 gm of Ferric chloride in 50 to 60 ml of
distilled water which makes the quantity 100 ml.

Chemical Examination of Water 31
(vi) Cyanide: In 5 ml of sample, add small amount of Ferrous sulphate. Boil the
mixture for one minute and add little amount of 2N hydrochloric acid (dilute) and wait.
Formation of blue precipitate indicates the presence of cyanide.
(vii) Ammonia: In 5 ml of water sample add few drops of Nessler's reagent. Formation
of brown or yellow or black colouration or precipitation indicates the presence of ammonia.
Nessler's reagent is prepared as,
(a) Dissolve 2.5 gm of HgCI2 and 2 grams of KI in 50 ml of distilled water.
(b) Dissolve 10 gm of NaOH in 50 ml of distilled water. Store these two solutions in
brown glass bottle and seal properly. Mix 1 + 1 Just before use. Maximum
permissible level, i.e., M.P.L. of free ammonia is 0.05 ppm and for albuminoid
ammonia it is 0.1 ppm.
(viii) Total Solids: Weigh the empty crucible of 100 ml capacity. 50 ml of water sample
is taken in crucible. Water is evaporated to dryness by using water bath. Residue is perfectly
dried by placing crucible in hot air over above 120°C. Crucible is allowed to cool and
weighed. If 50 ml of water sample used then:
Total solid in ppm.
Wt. of solid x 1000
=
50
Hard water is unfit for drinking purpose. Hard waters have been found responsible for
development of renal calculi, dyspesia and gastric disturbances.
Its M.P.L. is 500 to 1500 ppm.
Qualitative Estimation of Pb, As, Cu, Fe
(i) Lead: In 5 ml of water sample add few drops of potassium iodide. Formation of
bright yellow preCipitate indicates the presence of lead. Precipitate of lead iodide disappears
on boiling and reappears on cooling. Lead is cumulative poison. M.P.L. is 0.01 ppm.
(ii) Arsenic: To the sample (5 ml) add few gms zinc metal powder or zinc metal
granules and few ml. of concentrated sulphuric acid. A filter paper containing few crystals of
silver nitrate are placed over the tube. Silver nitrate crystals turn yellow and then black due
the liberation of arsine (ASH3) gas from arsenic. Arsenic is a cumulative poison. Excess
dose is intestinal irritant and nervous depressant. Drinking water should not contain even in
traces.
.(iii) Copper: In 5 ml of water sample add few drops of potassium ferro cyanide solution.
Chocolate red coloured preCipitate indicate the presence of copper. M.P.L. is 3 ppm.
(iv) Iron: In 5 ml of water sample add few drops of potassium ferrocyanide. Formation
of blue colour or precipitate indicate the presence of iron. M.P.L. is 0.3 ppm.
Reagent Required for Nitrites
(1) Sulphanilic Acid: Completely dissolve 1 gm of sulphanilic acid in 70 ml of hot
distilled water cool, add 20 ml of 12N Hydrochloric acid and then dilute the amount to 100 ml
with distilled water.
(2) Naphthylamine Hydrochloride Reagent: 0.60 gm of naphthylamine hydrochloride is
dissolved in distilled water. Acidify the solution by adding 1 ml of 12N hydrochloric acid.
Dilute the amount to 100 ml with distilled water. Store in a cool place. Filter before use.

Reagents Required for Iron and Copper
Dissolve 9 gms of potassium ferrocyanide salt in 100 ml of distilled water.
Reagent for Lead
Dissolve 10 gms of potassium iodide in 100 ml of distilled water.
Reagent Required for Chloride
(1) Silver Nitrate Solution: Dissolve 5 gms of Silver Nitrate in one litre of dis~illed water.
(2) Potassium Chromate Solution: 5 gm of Potassium Chromate is dissolved in 100 ml of
pure distilled water.
000
,.:

6
PHYSICO CHEMICAL ANALYSIS
OF WATER
Introduction
The significance of chemical analysis depends to a large extent on the sampling
programme. Samples should be collected as per the sampling procedure and preservation of
the sample is also equally important. Preservation is essential to protect water samples from
changes in composition and deterioration with aging due to various internal reactions. The
optimum sample holding time ranges from a zero for parameters like pH, temperature and
D.O., to one week for metals.
Santple Preservation
It is not possible to protect a sample from change in composition. However, various
additives and treatment techniques can be minimized sample deteriotion.
Table 6.1: Preservatives and Preservation Methods used with Water Samples
Preservation or Effect on Sample Type of Sample for which
Technique Used the Method is Employed
Nitric acid
Sulphuric acid
Sodium hydroxide
Mercuric chloride
Cooling (4°C)
Chemical reaction
Keeps metals in solution
Bactericide
Formation of sulfates with volatile bases
Formation of sodium salts with
volatile acids
Bactericide
Inhibition of bacteria, retention of volatile
material
Fix a particular constituent
Metal-containing samples.
Biodegradable samples including organic
carbon, COD, oil, and grease
Amides, ammonia
volatile organic acids, cyanides
Samples containing various forms of
nitrogen or phosphorus, some
biodegradable organics
Micro-organism; acidity; alkalinity; BAD,
organic C,P, and N; Colour; odour
Dissolved oxygen determined by the
Winkler method.

Technique - Methodology and Paratneters
(1) pH
It is the scale of acidity which defines the medium of the sample. pH is the negative
Log10 of the hydrogen ion concentration. pH measurement is possible due to litmus paper,
various pH papers. But the correct pH measurement is with pH meter.
Method
(1) Calibrate the pH meter with two standard buffer solutions of pH 4.0 and 9.2.
(2) Buffers of different pH values are prepared in the laboratory as per following
manner:
Dissolve 10.2 gms of potassium hydrogenphthalate in water to prepare one litre of
buffer solution. This buffer solution has pH 4 at room temperature. Dissolve 3.40 gms of
KH2P04 and 4.45 gms of Na2HP04.2H20 in distilled water and make the volume one litre.
This buffer has pH 7 at room temperature.
Dissolve 3.81 gms of Na2B407.1 OH20 in water to prepare one litre of buffer solution.
pH is 9.2 at room temperature.
(3) Rinse the combined electrode thoroughly with deionized or distilled water and
carefully wipe with filter or tissue paper.
(4) Dip the electrode into sample solution, swirl the solution and wait up to 1 minute for
constant reading.
This is essentially a Nernst concentration cell with potentials controlled by the activities
of W ions on either side of very thin glass membrane.
RT aH(sarT'4'le)
E = constant + -In -~~
nF aH(standard)
E = constant + 0.058 pH (at 20°C)
Ag/AgCI
Reference----+--~...
Electroode
KCI solution ---1--.-
Porous Plug _.--'J~~--,/ I~~=- HCI or buffer
-:.n Glass Membrane
Fig. 6.1 A combined glass/Ag-AgCI electrode
(2) Conductivity
Conductivity is measured by conductivity meter with dip-type cell. Conductivity is
measured in terms of specific conductance, i.e., K. The instrument and cell are calibrated by
using 0.0005 M KCI solution having conductivity 654~ Mho cm-1.

Physico Chemical Analysis of Water
Specific Conductance
1 A
K=-x-
R 1
35
Here R is the observed resistance of a column of electrolyte 1 cm long and cross
sectional area A cm2.
Note the temperature of the sample and find out the factor following table to convert
the values at 25°C.
Temp. °C. Factor Temp.oC. Factor Temp.oC. Factor
3 1.62 13 1.27 21 1.08
4 1.58 14 1.24 24 1.06
5 1.54 15 1.21 23 1.04
6 1.50 16 1.19 24 1.02
7 1.46 17 1.16 25 1.00
8 1.42 18 1.14 26 0.98
9 1.39 19 1.12 27 0.97
10 1.36 20 1.10 28 0.93
11 1.33 21 1.08 29 0.93
12 1.30 30 0.92
Conductivity=observed conductance x cell constant x temp. factor at 25°C.
(3) Total Solids (TS)
Total solids are determined as the residue left after evaporation of the unfiltered water
sample.
(i) Take a clean and dry evaporating dish of 100 ml capacity. Weigh it accurately. Let
the weight of dry crucible be "b" gm.
(ii) Now take 100 ml unfiltered sample of water in evaporating dish. Evaporate the
sample by placing dish on water bath or hot plate having temperature not more that 98°C.
(iii) After this residue redried at 105°C in an electric oven for one hour cool it and
weigh the dish. Let the Weight be "a" gm.
. (a-b)x106
Total solids Mg/L = -'------'--
v
Here a = Final weight of the dish in gram.
b = Initial weight of the dish in gram.
v = Volume of water sample taken in mililitre.
(4) Total Dissolved Solids (TDS)
Total Dissolved Solids are estimated as the residue left after the evaporation of the
filtered water sample.
(1) Take clean and dry evaporation dish of 100 ml capacity. Weigh it accurately. Let
the weight be "b" gm.
(2) Now take 100 ml of filtered sample of water in dish. Evaporate the sample by
placing the dish on water bath or hot plate having temperature not more than 98°C.

(3) Heat the residue at 105°C in an electric oven for one hour, cool the dish and weight
it. Let the weight be "a."
TDS Mg/L = (a -b)x10
6
v
Here a = Final weight of dish.
b = Initial weight of dish.
v = Volume of sample.
(5) Total Suspended Solids (TSS)
Determination of suspended solids is possible by taking the difference between the
total dissolved solids.
TSS = TS - TDS
(6) Acidity
Acidity signifies the presence of mineral acids present in the water. Acidity is determined
by titrating sample with strong base like NaOH using methyl orange or phenolphthalein as an
indicator. The titration method is suitable mainly for colourless samples.
Requirements
(1) Sodium hydroxide, O.05N: Prepare 0.1 N NaOH by dissolving 4.0 gm of NaOH in
distilled water and make the vOlume one litre.Now dilute 5 ml of 0.1 N NaOH to one litre with
distilled water.
(2) Methyl orange indication: Dissolve 0.5 gm of Methy orange in one IitrQ of distilled
water.
(3) Phenolphthalein indicator: Dissolve 0.05 gm of phenolphthalein in 50 ml of absolute
alcohol and then add 50 ml of distilled water.
Method
Now take 100 ml of sample in the titration flask and add 3 drops of methyl orange
indicator. If the solution turns yellow it indicates the absence of methyl orange acidity. If the
sample turns pink then titrate it with 0.05N NaOH. End point is pink to yellow. Let the reading
be A.
Now add few drops of the phenolphthalein indicator to the same sample and titrate
further with 0.05N NaOH until solution acquires pink colour. Let the reading be B.
Calculations
Methyl orange acidity
AxN of NaOH x 1000 x 50
mg/L as CaC03 = Volume of sample
Phenolphthalein acidity
BxN of NaOH x 1000 x 50
mg/L as CaC03 =
Total Acidity at pH 8.3
Volume of sample

Physico Chemical Analysis of Water 37
(AxB) x N of NaOH x 1000 x 50
mg/L as CaC03 =
Volume of sample
(7) Alkalinity
Total alkanity of water samples is measured in terms of volume of sample required to
neutralize the strong acid. Total alkanity is estimated by titrating the sample with strong acid
like HCI or H2S04 (pH 8.3) using phenolphthalein as indicator and further to pH between 4.2
to 5.4 with methyl orange. The alkalinity by using phenolphthalein indicator is called
phenolphthalein alkalinity and symbolically shown as PA. Alkalinity by using methyl orange is
called total alkalinity and represented as TA.
Requirements
(1) Phenolphthalein indicator: Dissolve 0.5 gm of indicator in 50 ml of absolute alcohol
and then add 50 ml of distilled water.
(2) Methyl orange: Dissolve 0.5 gm of indicator in 100 ml of distilled water.
(3) Sodium Carbonate solution O.1N: Dissolve 5.3 gms of a Na2C03 in distilled water
and make the volume to one litre.
(4) Hydrochloric acid 0.1N: Add 83.4 ml of 12N HCI in water and make quantity one
litre. It gives 1N HCI. Now.dilute it ten times to give 0.1N HCI (i.e., 10 to 100 or 100 to 1000
ml.) Now standardise it against sodium carbonate solution to know exact normality of HCI.
Method
(1) Take 100 ml of sample in the titration flask and add 3-4 drops of phenolphthalein
indicator.
(2) Solution turns pink. Titrate it against standard solution of HCI until the disappearance
of pink colour. Let the reading be A.
(3) Now add 3-4 drops of methyl orange indicator to the same sample and continue
the titration further to obtain yellow colour. Let the reading be B.
(If the solution remains colourless by adding phenolphthalein it indicates PA = O. In
such a case alkalinity is calculated by the use of methyl orange indicator.)
Calculation
Phenolphthalein alkalinity, i.e.,
PA as CaC03 mg/L =
Total Alkalinity, i.e.,
TA as CaC03 mg/L =
AxN of HCI x 1000 x 50
Volume of sample
BxN HCI x 1000 x 50
Volume of sample
Alkalinity is due to hydroxyl ions, carbonate ions or bicarbonate ions. The following
table provides the necessary information.

Result OH alkalinity C03 alkalinity
P=T T
P> 1/2 T 2P-T
-p = 1/2T a
P < ,1/2 T a
p=o a
Here P stands for phenolphthalein alkalinity
T =Total alkalinity
(8) Hardness
a
2(T-P)
2P
2P
a
HC03 alkalinity
a
a
a
T-2P
aT
Hardnes.s of water is not pollution parameter but indicates water quality. Hardness is
due to presence of Ca++ and Mg++ ions in water. It is measured in terms of CaC03 Mg/L.
Requirements
(1) Buffer solution: Dissolve 68 gms NH4CI in 540 ml of concentrated ammonia and
make the solution 1 litre with distilled water. This is called ammonia buffer with pH = 10.
(2) Eriochrome black indicator: (i) Mix 1 gm of eriochrome black T with 100 gm pure
NaCI and grind it properly. Use a pinch of indicator for each titration. (ii) 1 gm of eriochrome
black T is dissolved in 75 ml of teriethanol amine and then add 25 ml of ethyl alcohol. Shake
it well. Use 3 drops of indicator for each titration.
(3) EDTA solution O.01M: Dissolve 3.723 gm. of disodium salt of EDTA in distilled
water and make t~~olume to 1 litre with distilled water. Store in polyethylene bottle.
Method
(1) Take 50 ml of sample in a titration flask.
(2) Add 5 ml of buffer solution.
(3) Add in pinch of eriochrome black T indicator or 3 drops of liquid indicator, solution
acquires wine red colour.
(4) Titrate the contents against 0.01M EDTA solution. At the end point colour of the
solution changes from wine red sky blue.
Calculation
1 ml of 0.01M EDTA =1.0 mg CaC03
or
Volume of EDTA required x 1000
Hardness as CaC03 mg/L = ml of sample taken
(9) Dissolved Oxygen (DO)
Analysis of DO plays a key role in water pollution control activities and water treatment
process control. The manganese sulphate reacts with KOH or NaOH to form precipitate of
manganese hydroxide which turns brown due to presence of oxygen. In strong acidic medium,
Mn ions get reduced by iodide equivalent to the original concentration of oxygen in the
sample. The liberated iodine is titrated with thiosulphate by starch indicator. This is called
Winkler Method.

Physico Chemical Analysis of Water
1
Mn2+ + - O2 + 20H ~ Mn02 t + H20
2
Mn02 + 21- + 4H- ~ Mn2+ + 12 + 2H20
12 + s20l- ~ 21n
+ S40 6
2-
5 ml of 0.025M Na2S203 =1 mg - (D. 0.)
Interference of oxidents can be eliminated by adding NaH3.
Requirements
39
(1) Sodium thosulphate: Dissolve 24.82 gms of Na2S203. 5H20 in water and make the
volume to one litre with distilled water. This is 0.1 N Na2S203. 5H20 solution. Now 250 ml of
this is diluted to one litre with distilled water.
(2) Alkaline azide solution: 50 gm of NaOH +13.5 gms Nal and 1 gm NaN2 diluted to
one litre.
(3) Manganese sulphate solution 40%: Dissolve 80 gms of MnS04. 4H20 in 200 ml of
distilled water and filter.
(4) Starch indicator: Dissolve 1 gram of starch in 100 ml warm distilled water and add
few drops of formeldeyde solution as preservative.
(5) Conc.H2S04
(6) 40% KF (to mask Fe3+)
2 ml 36% MnS04 + 2 ml alkaline Iodide.
Method
(1) Take 100 ml of water sample in 250 ml bottle. Add 2 ml of 40% MnS04 and 2 ml of
alkaline iodide-azide solution.
(2) Shake the content well. Bottle contains brown coloured precipitate.
(3) Now add few ml of Conc. H2S04 to dissolve the precipitate.
(4) Now add drops of starch indicator. Content acquires dark blue colour.
(5) Titrate the content with sodium thiosulfate. End point disappearance of blue colour.
Let reading be A.
Calculation
AxO.025xax1000
DO mg/L = V
Here V is the volume of sample taken.
(10) Biochemical Oxygen Demand (BOD)
The degree of microbially mediated O2 consumption by organic pollutants in water is
k.nown as Biochemical Oxygen Demand. This parameter by the quantity of O2 utilised by
suitable aquatic micro-organism during 5 days' period.
Requirements
(1) Sodium sulphite O.025N: Dissolve 1.575 gms Na2S03 in distilled water and make
the volume to 1 litre.

4 0 Global Pollution and Environmental Monitoring
(2) Ferric Chloride: Dissolve 0.25 gm FeCI3,6H20 in distilled water and make to volume
to 1 litre.
(3) Calcium Chloride: Dissolve 27.5 gms of anhydrous CaCI2 in distilled water to
prepare one litre with water.
(4) Magnesium Sulphate: Dissolve 22.5 gms of MgS04,7H20 in distilled water and
make the volume to one litre with water.
Phosphate Buffer
Dissolve each 8.5 gms. of KH2P04, 21.75 gms of Na2HP04 and 1.7 gms of NH4CI and
make one litre volume with water.
Method
(1) Prepare aerated water in a glass container by bubbling the compressed air in
distilled water for about 30 minutes.
(2) Add 1 ml each of phosphate buffer, magnesium sulphate. calcium chloride and
ferric chloride for each litre of dilution water mix properly.
(3) Neutralize the sample to pH =7 by using 1N NaOH or 1N Hel or 1N H2S04
depending on the initial medium or pH.
(4) Here the DO in the sample is likely to be exhausted, it is therefore necessary to
prepare suitable dilution of the sample according to the expected BOD range. (Refer the
table).
(5) Made dilutions in a large container. Mix to contents thoroughly. Fill the contents in
2 BOD bottles.
(6) Keep one B.O.D. bottle in BOD incubetor at 20°C for 5 days and determine to DO
. level in other set immediately.
(7) Now determine the D.O. level of sample, immediately after the completion of 5
days incubation.
(8) Similarly for blank, take 2 BOD boUle for dilution of water. In one determine DO
level and in other incubate with sample to determine DO after 5 days.
o
4
10
20
40
100
200
400
1000
2000
Dilutions as per B.O.D. Range (A.P.H.A. reference)
Range of BOD Dilution %
6
12
20
60
120
300
6
1200
3000
6000
No dilution
50
20
10
5
2
0.5
0.2
0.1

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Fig. 3. Wing patterns contrasted.
The pattern of the first figure illustrates the wing of the common
blue-bottle; here "vein 4" does not run at all straight in the last part
of its course, but curiously bends very suddenly upwards at an angle
and meets the margin very near to "vein 3." In the wing of a large
blue-bottle it will be easy to recognise this plan.
The pattern of the second figure is rather similar, for the vein 4
likewise has a sudden bend upwards; it terminates practically
contiguous with vein 3 at the margin. This pattern is characteristic of
the "house-fly"; thus it will be easy for the reader to identify the
common house-fly by the close resemblance of its wing pattern to
that of the blue-bottle, with which it is classified in the family of the
Muscidæ.
In the pattern of the next figure the vein 4 runs comparatively
straight throughout and meets the margin at a spot intermediate
between the third and fifth veins; here all the main nerve-lines
diverge more evenly and terminate more equi-distantly apart; this
latter plan is the wing pattern which will suffice to identify the lesser
house-fly, but it is shared with all the Anthomyidæ, and more or less
with some others, which are very common outdoor flies.
The pattern of the lowest figure illustrates the wing of the
common blood-sucking stable-fly, Stomoxys calcitrans, which only
occasionally invades the house. Here the vein 4 is deflected upwards
towards the margin ending near the termination of the vein 3, but
the bend is a smoothly rounded curve and not a curiously abrupt
angle, as in the first and second figures.
If the reader will study the house-fly in captured specimens, he
will be able to observe that they slightly differ in their inconspicuous
colouration and markings.
The male of the lesser house-fly is sometimes more observable
than the male of the commoner house-fly, by reason of his being a
most indefatigable dancer with companions in mid air around any
central ornament, and also by reason of his possessing pale patches,

more or less yellowish grey, on the sides of the abdomen; but such
markings are also in some degree observable in other male flies,
being very conspicuously of a brighter yellow in the common small
outdoor raven-fly, M. corvina. The back of the thorax of the house-
fly is marked sometimes distinctly, sometimes indistinctly, with four
dark lines on an ash-grey background; the lesser house-fly has three
faintly darkish lines only. Quite a number of outdoor flies have
similar markings, but these often look like closely adjacent or
indistinct spots. The wing pattern is the readiest guide for
distinguishing the lesser house-fly, both male and female. The males
of the hairy (almost bristly) raven-fly also indulge in the dancing
habit, but still more so do those of the latrine-fly, Fannia scalaris,
which may be distinguished by its uniformly ashy-grey abdomen.
These common co-inhabitants of our dwellings vary in size
according to their nourishment when in the larval stage (maggots);
after the perfect insect emerges from the puparium, it swells out and
fattens, but does not grow in the real sense of the word. If 1000
house-flies will weigh an ounce, then it may be calculated that 1600
average specimens of the other kind will likewise weigh an ounce.
In representing that the house-fly exceeds the lesser house-fly in
numbers in the proportion of twenty or thirty to one, it must be
borne in mind that the occurrence of the latter varies widely—
casually according to the locality, and temporarily according to the
time of the year, being more commonly observed when and where
the other kind is scarce.
The lesser house-fly has summer broods at longer intervals than
has the common house-fly. Towards the end of the summer its last
brood hibernates in the puparium, and emerges as early as the end
of March or early in April, whilst the common house-fly is not usually
observable until a later date, although it is credited with more
generally braving the dangers of attempting to hibernate in the
imago stage. My attempts to test the capability of the house-fly by
aiding October and November flies to hibernate invariably terminated
in the creature's death long before springtime. However, it is very
apparent that under the shelter and encouragement of warm winter

environments in towns, amidst restaurants, bakeries, large hotels
and certain factories, as well as and even more than in mews, adult
flies of the latest autumn broods can, to some extent, survive mid-
winter with very little or no prolonged hibernation.

CHAPTER III
SOME OTHER FLIES AND THEIR DIVERSE HABITS
Just as the common "house-fly" and the "lesser house-fly" are
often in error regarded as the same species with an insignificantly
small difference of size, so the identity of each in turn may be
confused with several other species which are not uncommon, but
they are all normally outdoor flies.
The chief of these is the excessively common stable-fly, Stomoxys
calcitrans, whose generic and specific designations are well given,
for they mean "sharp-mouth," "kicking," the latter word denoting the
action of the tormented horse; it has a long, thin, stiff, skin-piercing,
shining black trunk, furnished with two lancets. It is an eager blood
sucker. In size and colour it rather resembles the house-fly, but
anyone who is keen sighted will recognise it at once by its bayonet-
like trunk, held projecting prominently in front of its head. It is much
addicted to basking outdoors on sunny walls, but on the approach of
darkness or of inclement weather it will occasionally seek shelter
indoors. Its wing pattern rather resembles that of the common
house-fly, as has been previously explained.
Round about dairy farms Hæmatobia stimulans, a fly slightly
smaller than the stable-fly, with a striped thorax and a blood-sucking
trunk, will often leave the cattle to assail humanity. A still smaller,
somewhat hairy, muscid type of fly, Lyperosia irritans, is also a
common aggressor of oxen throughout the summer.
Musca corvina, the raven-fly, is smaller than the house-fly; it has
very distinct dark markings; the abdomen of the female is

chequered, but that of the male has a black central stripe on a
yellowish abdomen. It frequents gardens, parks, and meadows. It is
much less prolific than the house-fly, with which it shares the sweat-
fly pestering habit.
Cyrtoneura simplex is a little smaller and more common than the
species last mentioned; its larvæ are bred in the dung of cows and
other animals which it very severely pesters. However, many species
of dung-bred flies do not in the least participate in the cattle-
pestering habit.
The Anthomyidæ are a family of about 250 small and medium
sized garden frequenting and country flies, mainly of flower and
honey seeking habits. Nevertheless, some are dung-frequenting;
none are blood-sucking, but several are cattle-pestering sweat-flies,
which, even more pertinaciously than the house-fly, will circle round
one's head and repeatedly buzz against one's face. Of these, the
small Hydrotœa irritans and Hy. dentipes are amongst the worst
offenders. A few of the Anthomyidæ are vegetarian garden pests;
the larvæ of the cabbage-fly, the root-fly, the onion-fly and the
celery-fly are, in some seasons, very destructive. The so-called
"turnip-fly" is a small striped beetle of the same genus, Phillotreta,
as the unstriped "flea-beetle" of the hop-fields. The larvæ of the
majority of the species of the family of Anthomyidæ are, more or
less, feeders on decadent vegetable matter, but some, like those of
the genus Fannia, are preferentially feeders on dung. The female of
the latrine fly, Fannia scalaris, so closely resembles the lesser house-
fly that only the expert with a magnifying glass, after a careful
examination, can tell which is which; the male differs from the male
of the lesser house-fly by being without the yellowish patches on the
abdomen.
There is a larger and less common muscid fly, with an ashy-grey
body, but with reddish legs, named by entomologists Muscina
stabulans, which not only in body colour, but also in the pestering
habit, resembles the house-fly; its Latin specific name is rather
objectionable as too suggestive of the common "stable-fly," which
name belongs to Stomoxys calcitrans above-mentioned; its larvæ

have been found in cow-dung, but they can also flourish on
vegetarian fare.
The common blue-bottle is now named Calliphora erythrocephala
(red-head), and it can be recognised by its reddish face and black
hairs for a beard, whilst the less common blue-bottle, named
Calliphora vomitoria, may be said to have a reddish beard upon a
black face; the latter has the blue colour more evenly distributed
over the abdomen, whereon the former has dark markings.
Polietes lardaria is a fly sometimes mistaken for the blue-bottle; its
specific name is rather too suggestive of resemblance in habit. It
may be recognised by its having four black stripes on the thorax, by
its large white squamæ, and its tesselated glaucous abdomen; its
wing pattern classifies it as belonging to the Anthomyidæ, whilst the
true blue-bottles belong to the Muscidæ, and the grey blow-flies to a
section (Sarcophagina) of the Tachinidæ.
There are some other outdoor flies which are not very dissimilar to
the common blue-bottle, but they are more soberly coloured,
ranging from bluish black to speckled and tinted greys; some of
these have a pattern on the shiny upper surface of the abdomen
which is conspicuously and beautifully chequered. Closely akin to
these latter is the large grey blow-fly, or flesh-fly, Sarcophaga
carnaria; it is much referred to in entomological books as of
marvellous fecundity. The female deposits not eggs in a few
hundreds, but already hatched maggots to the number of many
thousands. Amongst half-a-dozen rarer kinds of smaller grey blow-
flies the females differ in their striped markings, but their respective
males seem quite indistinguishable apart.
Notwithstanding the prodigious fecundity of the grey blow-fly, the
credit of being a practically useful scavenger of carrion must be
given only to the blue-bottle, which is of a more robust habit, and
which so promptly monopolises available matter that Sarcophaga
carnaria and her congeners are sometimes, perforce, compelled to
give their larvæ a mere vegetarian diet.

The yellow cow-dung fly, Scatophaga stercoraria, is inoffensive,
and one of the commonest flies observable in the course of a
country-side ramble. It and its congeners are distinct in habits and
appearance from any of the other flies above-mentioned. In this
species the male is larger than the rather more smooth and dull-
coloured female. Its body is furry but slender; it has small eyes and
head parts. In repose it holds its wings parallel close above the
abdomen, more like the "breeze-flies," or true "gad-flies," than the
ordinary muscid flies. Although its proboscis does not seem as
formidable as that of more insectivorous flies, yet it may sometimes
be observed pouncing upon some small fly, which it holds with its
powerful legs. This fly does not appear to be very predaceously
inclined; perhaps it is only "acting a part," like some other creatures,
including the amorous male of the common frog, which, failing to
secure a more natural and complacent "partner in the dance," will in
springtime seize upon and very persistently cling to an astonished
carp.
Amongst many flies with bodies favoured with a brilliant metallic
sheen, several species of green-bottle flies (Luciliæ) are notorious.
Of these latter L. Cæsar is the most common, but L. Sericata is by
far the worst in England, not uncommonly laying eggs upon sheep;
many are of a brilliant golden green, but some vary towards a
coppery green; all have red eyes and silvery faces. In summer-time
these flies seize every opportunity of depositing their eggs upon any
sores or skin wounds of animals; their larvæ normally feed on
carrion and dung. The green-bottle, like the blue-bottle flies, are
fond of both sweets and filth, but they do not pester wholesome
animals as do the sweat-flies.
Next to the Muscidæ the most often observed and easily
recognisable as a distinct family of flies are the Syrphidæ, which
include the "hover-flies," the drone-flies (often mistaken for the male
of the hive-bee), and a number of other very common flies of a
generally similar full-bodied shape, in most of which colour stripes
and bands more or less suggest a comparison with wasps. The
numerous species native to Great Britain are widely distributed, and,

excepting the rare and very hairy Merodon narcissi, of which the
larvæ feed on liliaceous bulbs, none is injurious and some are
beneficial. Nearly all the flies of this family frequent flowers. The
habit of many to hover for hours about a favoured spot, as if for
mere pleasure, is remarkable; but it is not generally recognised that
some of these hover-flies (of the genus Syrphus) are hawking for
winged aphides and other small insects, which they quickly suck dry
and drop whilst still on the wing. Many of the flower-frequenting
Syrphidæ are great devourers of pollen; all have strongly developed
suctorial mouth parts.
The larvæ of the various syrphid flies differ greatly in appearance
and habit; some are terrestrial; some aquatic; some semi-aquatic;
some feed on decadent vegetation; some on sewage and filth, and
some are insectivorous. Most useful to the horticulturist are those of
the genus Syrphus, which feed on green-fly and other aphides. The
most curious in shape are the "rat-tail" maggots of the common
drone-fly, Eristalis tenax (also others of allied genera), which can
extend their long tubular tails and breathe atmospheric air through
the same whilst lying under water. The larvæ of the genus Volucella
are found dwelling in the nests of bumble-bees and wasps; it is
rather uncertain how far they are commensal, or parasitic, or
devourers of dead matter. Some of the syrphid flies are single-
brooded, but some at least are double or treble-brooded in the year;
records are wanting about many, and which, if any other than the
common drone-fly, are multi-brooded. Anyhow, none appears to
breed in Great Britain as rapidly as do the house-fly, the blue-bottle,
and other muscid flies.
The larvæ of Conops flavipes are parasitic in the body of the adult
bumble-bee, and they pupate therein.
The small family of the Stratiomyidæ contains a few fairly common
species called soldier-flies; these are interesting as linking
Orthorrhapha with Cyclorrhapha; their larvæ are some aquatic (the
star-tailed maggots), others terrestrial, and some have hard shell-
like skins; but they are not so curiously like a creeping marine limpet

as are those belonging to the genus Microdon (of the Syrphidæ),
which are rare and wonderful dwellers in ants' nests.
There is a curiously shaped race of parasitic flies which cling to the
host like a louse, called Hippoboscidæ; these have more than the
usual provision of claws to their feet, both in the number (normally
two) and size of the claws. The forest or spider-fly attaches itself to
some part of the body out of reach of the horse's tongue. The ked,
tick, or sheep louse-fly has a similar mode of life, and, after selecting
its host, it becomes wingless. These flies, strange to say, nurse and
nourish their larvæ within the oviduct, and, when one might think
that they were laying their eggs, they are depositing pupæ or larvæ
just ready to pupate. There are some species of the family of the
louse-flies which infest birds.
The true gad-flies of the family of Tabanida were, and sometimes
still are called "blinden breeze-flies," and sometimes dun-flies; by a
very easy mistake the countryman's word "blinden" (blind) has got
changed by authors in books to "blinding," which is nonsense, and
misses a wonderful instance of old-folk knowledge; the females are
amongst the most inveterate blood-sucking flies, but the males are
mere idle loiterers in summer sunshine on flowers; the eggs are laid
on herbage in moist situations; the maggots and pupæ of many of
these species are said "to be found in the soil," and some, if not all
the larvæ, are predaceous, attacking worms and underground larvæ
of various insects. They are more or less midsummer flies and are
single-brooded. There are several largeish species (of the genera
Tabanus and Therioplectes) found in Great Britain, and they are
diversely distributed, being respectively woodland, moorland,
lowland, and highland inhabitants. The great ox-gad-fly is as large as
a bumble-bee, though more long than broad in body, but the term
gad-fly is often wrongly given to the worble-fly, which is really more
bee-like, being furry and rounder in body. The genus Hæmatopota
comprises three smaller sized extra vicious blood suckers, H.
pluvialis, rather common, H. italica, very local, and H. crassicornis,
darker in colour and with spotted and dark tinted wings. Several of
the large gad-flies have dull-tinted wings. They have large, shallow,

brightly shining and curiously banded compound eyes, but no
"ocelli"; they all seem to be at least semi-blind, and the females are
rather sluggish, except between the hours of 11 a.m. and 5 p.m. in
bright midsummer sunshine. The females hunt entirely by scent and
are easily captured when attacking human beings; they alight on
their victims with a stealthy silent approach. They appear unable to
discriminate between clothing and bare skin as suitable spots for
feeding. Amongst a band of mountaineering pedestrians, on a sunny
day, it was observable that there would be a dozen or more "blinden
breeze-flies" settling on the back of one, whilst the rest of the party
were only favoured now and then by one or two apiece. It was
apparently the smell of the "home-spun" coat which attracted; the
colour of the garment did not seem to be the cause of the selection.
Sunshine loving flies prefer white and pale colours. If a dog could
speak, he would explain the smell of some "finished" cloth, but, for
the sake of the fastidious, the secret is not here disclosed.
Very closely allied to the true breeze-flies in habit of life are the
species of the genus Chrysops, of which two only are often met with
in England, namely Ch. cœcutiens and Ch. relicta; these flies are
very keen blood suckers; they are smaller, slightly more slender and
brighter coloured than the commoner Tabanidæ; it is characteristic
of the genus Chrysops that the antennæ are quite twice the length
of the remarkably short horns of the majority of common full-bodied
flies; all the species possess beautiful golden glittering eyes (whence
the name Chrysops), and their wings are spotted and tinted.
One of the most horribly disgusting but serious facts connected
with flies is observable most conspicuously amongst the wondrous
family of the Œstrida. These pass the larval stage of life, not on, but
inside the bodies of living animals; and the perfect insect, strange to
say, is absolutely destitute of a mouth opening. Much
misrepresentation has been prevalent, based entirely upon surmise,
connecting "myiasis" in mankind, which is various but very rare, with
the common infliction of horses and horned cattle with Œstrid
maggots. Myiasis is the medical term given to all the various forms

of animal infliction by internal parasitic maggots, and this subject is
reserved for discussion in the next chapter.
The characteristics and natures of the very numerous tribes and
families of other kinds of flies will be found summarised in the
Appendix of this booklet.

CHAPTER IV
MYIASIS AND THE ŒSTRIDÆ
The family of the Œstridæ is the most curious and horrific of all
the different tribes of flies; it is very limited in species, of which five
or six are prevalent throughout Great Britain. The worst of these
could be almost exterminated with ease, but unfortunately mistaken
ideas have prevailed, and graziers commonly believe that though the
sheep's nostril fly is conspicuously harmful and dangerous, the
horse's bot-fly and its congeners are negligible as regards the
practical health of the host. The bot-fly and the worble-flies are all of
a largish size, only the sheep's nostril fly and Œstrus
hæmorrhoidalis, which latter infests the throat and rectum of the
horse, are of a medium size.
It has been known from very ancient times that man himself was
not exempt from some fly, which was imagined to resemble the
horse's bot-fly, and it has been wrongly surmised that many different
creatures and all ruminant animals were more or less subject to the
attacks, each one of its own kind, of œstrid fly. It is undeniable that
man is sometimes internally afflicted with dipterid larvæ, but it is
most certain that the fly to be incriminated is not a congener of the
horse's bot-fly.
An old illustrated French encyclopædic work gives coloured
pictures of the flies and larvæ of Œstrus bovis (the worble-fly of the
ox) and of Œstrus equi (the bot-fly of the horse), but only the larvæ
of a so-called Œstrus hominis is figured. Recently, however, new
attempts have been made to identify the species causing intestinal

myiasis, of which the larvæ are observable from time to time in the
course of post-mortem examinations and during anatomical study.
Of recent years it has been suggested that the lesser house-fly is
addicted to such a manner of breeding; then later that another
species of the same genus has been found to be the real culprit.
However, the peculiar larvæ of these last-mentioned flies do not in
the least resemble the fat round larvæ of the true bot-fly or of the
worble-fly, which are correctly represented in the above-mentioned
French work, nor the round and rather smooth maggots which were
observed in Westminster Hospital nearly fifty years ago, and at other
places from time to time both before and since, giving rise to much
wonder and discussion, and also to very incredible tales.
Another more credible surmise attributes the offence of human
intestinal myiasis to Muscina stabulans; if this be correct, the
infliction would be probably due to the subject having eaten
damaged and egg-laden plums or similar fruit, for M. stabulans is
credited with being normally, though not exclusively, fruitarian or
vegetarian.
If any one of the above suppositions be true, it does not exclude
any other one, amongst many explanatory surmises, from being
possible. Judging from the remarkable attractiveness of the odour of
humanity to the common house-fly, and from the fact of the
maggots possessing well developed tenter-hooks on their heads
(somewhat like those which the bot-fly maggots use for internal
attachment), it is just as likely, nay more likely, that this species (as
the writer stated for the information of the authorities of
Westminster Hospital nearly fifty years ago) is more than any other
capable of adopting such a life-cycle existence; these maggots would
mature after five or six days feeding and then emerge. If there were
a veritable "Œstrus hominis," however rare, the hairy and peculiar
female would be conspicuously observable, a persistent hoverer
about the person of her victim until she had attached eggs to his
body, from which the maggots would not emerge until after nine
months. Most of the tropical flies, which are said to similarly attack
humanity, may be rather compared to the green-bottle flies which

infest sheep, but the latest medical records and reports profess to
identify ten or twelve species of very different genera as having
myiasic capabilities.
The family of Œstrida has been fitly divided into three sections,
namely, the Gastrophilinæ (the larvæ living in the gullet, the
stomach, or the intestines), the Hypoderminæ (worble-flies), and the
Œstrinæ (nasal or nostril flies); all the species are hairy or furry, and
the gravid females fly slowly with loud buzzing, in a characteristic
attitude peculiar by the bending downwards of abdomen and tail,
with a much extruded ovipositor.
The sheep's nostril-fly, Œstrus ovis, has a chequered abdomen
and is less hairy than others; it is the type of the section to which
the generic term Cephalomyia is given in some books; species of this
section attack deer and other animals.
The section termed Hypoderminæ comprises the "worble" flies or
"marble" flies. One may imagine that the latter name indicates in the
mind of the cowherd the appearance of the round pustulent boils on
the hide of the suffering animal, and that the former name is a
corruption of "worm-hole," originating with the tanner, observant of
the deterioration of injured hides. A mixing of the terms worm-hole
and marble probably originated the name "warble." The maggots live
under the skin on the back of oxen, and breathe externally through
openings in the boil-like excrescences. The discoloured flesh of
infected oxen is called "flecked." Two species of worble-flies are
prevalent, one or the other, in many parts of England.
The third section, to which the sub-family termed Gastrophilina is
sometimes applied, comprises the "bot-fly," which commonly infects
the horse; it is the imperfect knowledge of this latter which has led
to erroneous surmises explanatory of the horribly disgusting fact of
human intestinal myiasis.
All the species of all the three sections are single-brooded.
Although the flies themselves can inflict no immediate pain, at their
mere sight all the animals out at grass on the farm are seized with
an instinctive terror, conspicuously greater than when attacked and

copiously bled by any "blinden" breeze flies, which, however, fly
more silently and settle on their victims very furtively. One can
understand the violent efforts of the horse to free himself from the
exceedingly painful bites of a newly attached forest-fly, but one can
only wonder at the frantic galloping of oxen and horses to and fro
when a non-biting œstrid fly buzzes about like a harmless fat bumble
bee and slowly approaches.
The females of all the worble-flies, the nostril-flies, and the bot-fly
are short-lived, appearing on the wing in August, possibly seen a few
days earlier. In the act of ovipositing they make themselves very
conspicuous; they lay their eggs whilst hovering in the air, their
extruded ovipositors attaching glutinous eggs to their victims. The
hatching of the eggs of the bot-fly is assisted by the habit of animals
to lick themselves and each other, when certainly their warm, moist
tongues will convey into their mouths the newly emerged bot-fly's
maggots, which many months later are to be found attached to the
internal lining of the unwilling host's stomach. When fully grown in
June, these maggots loosen their hold, are discharged with the
dung, and pupate in the soil.
No satisfactory account has yet been given as to the early stages
of the maggots of the worble-flies. The eggs, having been attached
to hairs on the host's hide in August, the prominent round pustulent
swellings, called worbles, wherein the maggots dwell, do not
become conspicuous until the following months of April and May. It
is a reasonable surmise that the obscure and long first-period of the
maggot's existence may more or less conform to that of some of
those flies which are also single-brooded but are predaceous or
parasitic on insects. The newly hatched maggot perhaps can crawl,
but does not feed until after several moults; at each moulting the
strange creature becomes smaller and smaller, but probably at the
same time is provided with a new head well suited for the purpose
of that period; firstly, with a burrowing or grappling head, and in due
time with a feeding suctorial mouth, and then only does practical
growth begin. No dipterid flies, at all events, known to be native to
Great Britain, possess skin-piercing ovipositors.

I have been astonished to read in current literature much about
œstrid flies which is not in agreement with my long course of
personal observation; for instance, one high authority (F. R. S.)
writes that œstrid "flies" appear from May until October, and hints
that their egg-laying aggressions upon their victims are not
conspicuously observable. I feel confident that the facts are quite
otherwise.
That the bot-flies normally (and a few others abnormally, but for
short periods only) pass a very long larval stage in the stomach and
alimentary canal of herbivorous animals is one of the greatest
marvels of insect life. All other growing creatures, which normally
breathe in free air, require a certain large amount of breathable
oxygen; and they would be stupefied or killed by a much smaller
percentage of carbonic dioxide and other fermentive gases of
digestion than undoubtedly exist in the strange abode wherein the
bot-fly maggots dwell during the entire period of their feeding
career. It has been stated that fly maggots artificially ingested into
the human system have emerged alive in a normal condition, but the
repulsive and objectionable experiment is not stated to have
procured well nourished and full grown normally pupating larvæ.
Some of the maggots of human intestinal myiasis are not perhaps
amenable to artificial culture up to the stage of final metamorphosis;
and they do not appear to have developed a breed or new species
with a distinct habit of life. All the credible accounts of human
intestinal myiasis point towards some fly which is plural-brooded,
and of which the larvæ develop rapidly and promptly quit the body
all at once; otherwise more than one infection must have occurred.
The tales of prolonged continuous breeding, with slow and
prodigiously copious emergings at intervals, should be altogether
discredited.
It is an amply warranted criticism to say that recently published
records by authorities, in an endeavour to comprise every reported
instance of myiasic infection, seem to countenance mere coarse
Gargantuan jokes. On the other hand, it is painful to read such a
"cock-and-bull" story as that of the doctor about his elderly lady

patient, up whose nostril a gravid female blue-bottle flew and
successfully performed the prolonged and delicate operation of
laying therein a large batch of eggs, in spite of all attempts to expel
the invader by violent sneezing. Day by day the said doctor observed
the terrible injury, and the symptoms accompanying the growth of
the feeding maggots, whilst the injection of a spoonful of paraffin
would have effected an instantaneous cure.

CHAPTER V
GENERAL LIFE HISTORY
Whereas the blue-bottle rarely enters the dwellings of mankind,
except gravid females led by the sense of smell in search of fish, or
flesh meat, and (less eagerly) sweets, both species of house-fly and
both sexes seem to delight in the mere odour of humanity; breeding
females will seek the larder and the dust-bin, but others will very
provokingly pervade all quarters. Although avoiding a dark or deeply
shaded room, the house-fly seems to like partial shade; it will be
content to remain indoors and to rejoice in a warm kitchen, even on
a hot summer's day, whilst all the other kinds of flies are enjoying
the outdoor sunshine. It may be said of nearly a dozen other
species, occasionally observable crawling on window panes, that
they are "outdoor" flies, and that their occurrence indoors is
accidental. In fact, they are mostly observed when trying to escape.
Next after human habitations, stables, cow-sheds and pig-sties are
the delight of the breeding female house-fly. Round about and in
these latter resorts she associates with an immense host of rather
small sized flies, and amongst a few others of equal size with the
skin-piercing and blood-sucking stable-fly; but many stablemen are
ignorant of the difference of the two kinds of flies and of the serious
suffering of their horses from the bites of the stable-fly. This
lamentable ignorance was shared by the joint authors of "Humble
Creatures," published in 1858, when Neo-Darwinism was in vogue,
and many books were published for popularising a knowledge of
common things and spreading an interest in nature-study; this

publication, which is still (1914) in print and very little revised, has
probably led some later would-be nature-study teachers to follow
suit in confusing the characteristics of the two species. Very often
the fly most numerously breeding in the manure heaps of the mews
will be Borborus equinus, or some other of the same family, which
are characterised by a very simple pattern of wing nervures and by
the absence of squamæ or scales behind the wings; also the ankle
joints of the feet are most peculiarly short and broad. B. equinus,
and a great host of other dung breeding flies of a still smaller size,
may be considered beneficial insects; they do not pester cattle, and
their larvæ make food more scarce for injurious flies.
The breeding habits of the blue-bottle are very conspicuous by
reason of its haste and boldness in taking possession of dead
animals. It is incapable of breeding in horse or cow dung, to which
latter the green-bottle fly often resorts.
The blue-bottle deposits her eggs, 500 or 600, preferably on dead
fish, or flesh, and sometimes on the sores or the flesh of wounded
animals, but both the house-flies preferably affect dung, carrion,
garbage, and all kinds of fermenting vegetable matter. It has been
commonly but not truly said that the principal breeding places of the
house-fly are the mews and the farmyards where manure is allowed
to accumulate; the house-fly has a preference for horse dung before
cow dung, which is preferred by some other kinds of flies; however,
near towns, the domestic dust-bins, heaps of market garbage, and
deposits of town refuse give rise to a worse plague of house-flies
than stables. All these flies deposit batches of white eggs, and are
careful to place them as much as possible in crevices and shielded
from exposure to strong light, or from draughts.
The two house-flies and the blue-bottle have similar larval stages,
but their larvæ, called maggots, differ. The larvæ avoid daylight and
cannot withstand dryness. As the larvæ feed, they have the power
of ejecting or excreting a juice, which dissolves the food before they
imbibe the material; their mouths are suctorial and are destitute of
teeth or biting jaws.

The larva of the house-fly is an eyeless and legless maggot, one
half inch long when full grown and extended; twelve cylindrical
segments may be counted in its body, or even thirteen if we
separately distinguish the small head segment, which may be
withdrawn, and but little observable; five or six rear segments are of
nearly equal stoutness when only half grown; afterwards counting
from the three stoutish rear segments, the others taper towards the
very small head. The middle and rear segments have pad-like bristly
processes underneath, which aid the maggots in creeping, in which
action they also make much use of the head segment's grappling
hook. The maggots feed voraciously, but they seem, like the larvæ
of the honey bee, to pass out very little anal excreta; some have
thought that, like what is said of bee larvæ, no excrement is
discharged until after the imago has emerged from the puparium;
but such conduct seems altogether incredible. In the bee-hive
doubtless the assiduous workers ever wash their babies clean and
lick up all matter, just like domestic cats and dogs, when nursing
their young.
The larva of the blue-bottle, called a gentle, is proportionately
larger but very similar, except that the rear segment possesses a
ring of tubercles, which may have some useful function in
connection with two breathing tracks, which have their orifices at
that part of the body.
The larva of the lesser house-fly is very peculiar; all its segments
have projecting tubercles; its whole body is rather louse-shaped,
having not cylindrical but somewhat flattened segments, of which
the middle are the broader, and those near the head and tail the
narrower.
The transformations in the case of the blue-bottle are typical of
the house-fly and others of closely related families and genera which
are many-brooded within the year; these creatures develop very
rapidly immediately after emerging from the egg. Some other kinds
of dipterid maggots, which are single-brooded, pass a very
prolonged and obscure early period of skin-shedding and non-
feeding, a preparatory sort of baby-hood metamorphosis; then at

last they begin to feed voraciously and to follow the general habits
of other maggots. Some maggots curiously refuse to feed except in
company; probably some are unable to feed on dung except where
other species are providing the necessary dissolving juice.
When the common maggots or gentles have ceased feeding, they
burrow into the ground or crawl away, often to a considerable
distance, apparently seeking a secluded, a more wholesomely clean,
and a dryer spot. During this migrating time, they are palatable food
for many birds, which would not eat them in their former food-
loaded or unscoured state. Indeed, it is doubtful whether either a
vulture or a raven could eat a fly-blown carcase without danger of
myiasic punishment. The skin of the larva whilst growing is
transparent, but, when about to pupate, it thickens and becomes an
opaque creamy white.
The most marvellous part of the metamorphosis of the blue-bottle
is concealed, when the gentle becomes the pupa; according to
Réaumur the embryonic fly develops most curiously inside the
puparium by a procedure not exactly like the change from the
caterpillar to the chrysalid in the case of the butterfly. After a pause
of a day or two, the front segments of the fully fed maggot contract,
so that the body assumes a barrel-like shape; the skin then hardens,
and turning a reddish brown it becomes a much contracted shell or
case called the puparium. However, the long slender maggot has
done something more than merely shrink and shape itself
conformably to the case; it has withdrawn its embryonic head, so
small as to be hardly distinguishable microscopically, together with
its embryonic legs, wings and thorax into its embryonic abdomen! As
the development proceeds, and the embryonic members of the
future perfect insect acquire their destined shape, the immensely
increased head and the thorax with its appendage members slowly
emerge, and the partly inverted integument of the abdomen rolls
back, disclosing the shape of a fly not before recognisable.
Other naturalists would have it believed that the true account of
the transformation is as follows,—when the maggot has shrunk and
freed its body inside its skin which forms the case or puparium, all

its pre-existing internal organs become absolutely dissolved; then
out of the fluid mass a new growth ensues, constituting the pupa
with its recognised shape. This account is the one represented in
most modern entomological books, and is based partly upon B. T.
Lowne's monographic work on the blow-fly.
The comparative embryologist of our day is inclined to be a hyper-
theorist, and so it seems that some have not remained content with
either of the above accounts; to them, apparently, the production of
the large and complex head of the imago out of a single small
anterior segment of the maggot requires a more recondite
explanation, and must be brought into harmony with analogous
facts. To this end some degree of linked support is found by the
investigations of microscopic anatomy, and it has been conjectured
that not one or two head segments, but five are lying blended and
embryonically hidden in the larvæ, all ready to bud forth. However,
for fear of wearying too much with the theories of advanced erudite
scientists, the following jeu d'esprit is presented, instead of a more
elaborate and sober attempt, to lure the unscientific lay reader to an
extreme hypothetical conception of the "essential unity" underlying
the apparent diversities of Nature within that vast domain of the
Kingdom of Fauna, which is obviously outside the later creation of a
vertebrate Animalia.

Fig. 5. Illustrating the debatable continuity of a
12-segmented structure throughout the metamorphosis.
The futurist's dogmatic CREDO of creative progress, "For him who
would meritoriously pass his histological examinations, and qualify as
a Professor and Doctor of Science, above all it is necessary that he
should acknowledge the unicellularity of the primæval OVUM (or
egg), whence proceeds the seventeen-segmented boneless
ANNELID (or worm), out of which there develops the quadrangular
articulated crustacean INSTAR (or shell-encased aurelian), which
metamorphosises into the winged IMAGO (the angelic? or diabolic?
fly); in the contemplation of this knowledge alone is there supreme
Darwinian Modernismal salvation and felicity." Amen.

In view of the prosaic illustration of transmutation, figure 5 above,
the futurist disciple will have to accept the seventeenness of
segmentation by something like faith without sight.
The quadrangularity of the crustacean stage is based upon the
idea that the wings bud out from the two upper corners, whilst the
legs develop from the lower corners of the transmuting instar.
Perchance the reader will desire information about the use of this
curious word "instar," which has not the honour of notice in Dr. Sir J.
Murray's New English Dictionary. One might well feel proud of the
opportunity of adding the smallest item to such a stupendous and
monumental work, but I fear I am only qualified to venture a fair
guess. Virgil, I believe, used this term in allusion to the legendary
wooden horse of the Greeks at their siege of Troy. Some time less
than one hundred years ago entomologists recognised that the
words aurelian, chrysalis, and pupa were none of them an inherently
fit term of general application to the stage of insect life to be
indicated. After many attempts, this latest proposed substitute
seems to be gaining favour.
The fly emerges after bursting apart the first four segments of the
puparium; this it does by a curious provision, whereby it can inflate
a chamber in its head in a queer, balloon-like fashion, making a bag-
like extrusion, which it uses as a punching and pushing machine.
After emerging from the ground, the fly withdraws the bag-like
extrusion and cleans itself. Its body soon grows fit and it becomes
very active, as long as daylight and warm weather favour it;
otherwise it seeks shelter and becomes quiescent; however, artificial
light and heat will awaken it to nocturnal activity. Sweets, carrion,
and filth are all attractive to the blue-bottle, but the house-fly and
the lesser house-fly also find extraordinary attraction in both man
and his dwelling.
Considering the superfluity of other flies, and the multitude of
other insects ever ready to do duty as devourers of carrion, garbage,
and filth, the scavenging services of the larvæ of the house-fly can
be well dispensed with.

In civilised communities cremation in a refuse destructor is the
only sanitary method of treating town refuse. The economic value of
the fly is very little, and consists merely in its food value for certain
birds.
In warm weather the scavenging capabilities of all the carrion and
filth feeding maggots are very remarkable, and there appears no
exaggeration in the statement by Linnæus, that the progeny of three
flesh flies can eat up the carcase of a horse sooner than it could be
devoured by a lion.
When a batch of eggs has matured in the abdomen of the female,
she is most careful in the location and manner of their disposal.
Guided by the sense of smell, she will not lay her eggs except in
contact with food, or in places securing her progeny access to their
intended food. By the use of her soft, slender ovipositor, which is
telescopically extensile and flexible, the eggs are deposited in
shaded and concealed situations.
The house-fly is credited with laying batches of eggs at intervals,
perhaps four or more times, and about 150 on the first occasion,
then 100, and less on subsequent occasions. Under favourable
circumstances the eggs may hatch within a few hours of their being
laid. The maggots of midsummer broods may be full grown and
pupate in six days, and the perfect insect may emerge from the
puparium in another ten days of warm weather, but in cold weather
the pupæ of autumnal broods may remain dormant for several
weeks, or even months. When nine or ten days old the mature fly
may begin to lay eggs; hence, with such a life-cycle, in a month of
very favourable weather the progeny of a single pair may number,
say, 500; in two months' time the number may become 250 times
500; and in three months' time many millions!

CHAPTER VI
THE STRUCTURE OF THE HOUSE-FLY
The house-fly has quite the typical insect form, inasmuch as there
are three well defined sections of body—the head, the chest or
thorax, and the abdomen; also it has three pairs of legs, each with
nine joints, of which five joints constitute what may be called the
foot. The twelve segments of the maggot are observable as twelve
rings in the puparium, but in the fly the three which form the thorax
look like one, whilst the eight which should theoretically exist in the
abdomen look like four or five, until the rings of the ovipositor are
counted.
The illustration on page 39 will make plain how the permanence of
the twelve-segment structure (conspicuous in the larval stage) has
been thought to persist throughout the life-cycle, but at the same
time will disclose how great is the change in the relative proportions
of these segments.
The prominent features of the hemispherical head are the two
large compound eyes and the proboscis or trunk-like mouth. The
antennæ or horns are very short appendages with three joints; small
plume-like projections, called arista, are attached to the third
segment; the horns hang down over a hollow in the middle of the
face, and are insignificant in size when compared with those of other
kinds of insects; but their structure viewed under the microscope is
intricate, and they may be efficient organs of sense perception,
probably in part auditory. The really unique feature is the retractile
and suctorial proboscis, which is often incorrectly regarded as the

tongue; it is normally held doubled up and withdrawn towards a
hollow under the head, whence it is from time to time extruded. The
structure of this member is characteristic of the entire tribe to which
the house-fly belongs; it is a fusion or combination of mouth parts,
which in other insects are used more or less separately for the
various functions of inspecting, biting, masticating, drinking and
swallowing. In the house-fly the proboscis is absolutely suctorial,
and is not provided with the lancets used by the blood-sucking flies
for piercing the skin. Two maxillary palpi are attached to the upper
or basal part of the proboscis, which is called the rostrum (a snout);
the lower part is called the haustellum (a pump), and it has at the
end a pair of soft cushion-like lobes or lips, which, when spread
apart, form a heart-shaped pad with an opening in the centre. The
maxillary palpi are used for feeling and probably smelling. Each
mouth-lobe has a main collecting central channel and thirty
subsidiary cross channels of a wonderfully complex character.
Imbibed fluids pass from the mouth-lobes to the gullet along a
passage in the haustellum and the rostrum.
As with many other flies and other insects, there are on the top of
the head very small simple and rather inconspicuous eyes called
ocelli, three in number, between the large and prominent compound
eyes, which latter are said to possess each four thousand facets. The
compound eyes of the male fly are proportionately larger than those
of the female; it is quite observable that they approach each other
more closely at the top of the head, a feature of sex differentiation
which is shared with bees, wasps, and many other insect creatures.
It is thought that a single brain image arises from the combined
views of the four thousand facets of the compound eyes blending
with the view conveyed through the "ocelli." However, it is a most
curious fact that it is the inconspicuous ocelli which are of supreme
importance visually. The compound eyes have doubtless some
special function, but throughout the insect world the size of
compound eyes is not a certain indication of keenness of sight. The
vision of the fly is good for distinguishing the movement of any
broad mass, but it is rather ineffective for observing a thin line, as

may be proved by slowly lowering a knife blade, with a steady hand,
when its body may be severed before the fly takes alarm. It is a
remarkable fact that the family of Tabanida (blood-sucking breeze
flies), which are destitute of "ocelli," are the dullest sighted of all
flies; in fact, at least semi-blind. Moses Harris observed that a blue-
bottle became practically blindfolded when its ocelli were covered
with an opaque pigment. Probably this is the case with other insects.
Bees, which require long distance sight for home returning, are well
provided with ocelli. Butterflies, however, without the use of ocelli
have a distinct faculty of daylight vision for a moderate distance. The
investigation of sight by blindfolding is very difficult in flies.
There are two cephalic ganglions, which are regarded as the
brain; these are situated in the upper part of the head close to the
neck. There are also ganglions in the thorax with connections
extending into the abdomen.
The thorax is mainly occupied with the powerful muscles which
actuate the attached wings, the legs, and the small appendages
called halteres or balancers, which are supposed to be obsolete hind
wings. There are three unequal segments in the thorax; the pair of
front legs belong to the first segment, the wings and the pair of
middle legs are attached to the second larger segment, whilst the
third is connected with the hind legs and the halteres.
The breathing apparatus of the fly is distributed in portions over
the head, thorax, and abdomen; it consists of a number of internal
air-sacks with membranous ducts ramifying everywhere; the largest
air-sacks are in the abdomen near the waist. There is a pair of
external spiracles to each segment of the body, and these lead to
the air-sacks.
The lines on the wings of the house-fly called nervures have
already been alluded to in Chapter II. These nervures are
strengthening ribs to the transparent tissues of the wings. The
tissues are double (top and bottom) enclosing the nervures, which
are so united to the connections called trachæ of the air-sacks, that
the newly emerged fly helps to extend its limp and crumpled wings
by a process of inflating the nervures.

The stomach is located partly in the thorax and partly in the
abdomen. A passage from the gullet passes through the neck into
the lower part of the thorax, where are the entrances to two long
capacious chambers, of which the upper one is the true stomach and
the lower one a store pouch, which latter may be likened to the
honey bag of the bee. The fly habitually regurgitates liquid food
stored in this pouch, and, somewhat after the manner of the cow
chewing the cud, passes the same back into the true stomach,
whence it proceeds onwards through the digestive track.
The abdomen holds all the other ordinary internal organs including
that which may be called the heart, and which lies above the
stomach; it consists of a long muscular tubular vessel with four
contractile chambers.
Although the organ called the brain is located in the head, and
although that called the heart is in the abdomen, yet some sense of
control over bodily motions curiously exists separately in the
ganglions of different parts of the body. This fact seems to make it
possible for one extremity of the body to continue performing a
pleasurable action (say, the head drinking honey) after the other
extremity has endured a painful catastrophe (say, amputation of the
abdomen). However, it may be fairly surmised that no creatures of a
lower grade than warm-blooded vertebrate animals feel pleasure and
pain in any way at least after the manner of mankind.
The most vital part of the fly is not the head but the thorax. A
severe squeeze on the thorax will effectually paralyse and kill the
creature. Muscular movements of different parts of the fly's body,
which continue after severance or other fatal injury, cannot be
regarded as visible proof of a slow death and prolonged sensibility.
Possessed of six legs, each with nine joints, the fly exercises a
unique capability of walking; the legs are moved three at a time, a
front and a hind leg on one side advancing simultaneously with the
middle leg on the other side; thus the fly proceeds most securely
always poised on three feet, which are so well furnished with pads,
claw-like hooks, and hairs, that it can walk over polished glass and
can even walk upside-down along comparatively smooth surfaces.

In comparison with the more heavily constructed wasp, with its
four wings, the house-fly, with its two wings, is the more alert and
active flier. The wasp is more robust than the fly and will be active in
weather too inclement for the latter; however, some of the frail and
slender gnats will brave cold temperatures impossible for the wasp.

CHAPTER VII
DISTRIBUTION AND CONCENTRATION OF FLIES
It might be supposed that a strongly developed house haunting
proclivity would not be consistent with a disposition to roam far
afield from the locality of birth. Many clever experiments have been
made with marked flies released and recaptured within measured
distances and times. After an immensity of pains taken, very little
profitable knowledge has been arrived at thereby. Little of what we
really want to know is indicated by such a fact as that, out of
hundreds or of thousands of marked flies released, one per cent was
recaptured at spots as remote as a mile within two or three days, or
by such a fact as that a large percentage should be observed to
remain within a more limited home circuit. The variable factors of
temperature, wind, sunshine and rain inevitably tend to discredit the
reliability of the observed results following any such experiments.
Close observations of the habits of the house-fly reveal the very
appurtenant fact that the movements of newly-hatched flies, for
their first six or seven days' active life, differ from those of a more
mature age, when the breeding instinct has grown strong. The latter
are disposed to locate themselves for the rest of their lives in and
about one attractive spot, and they are indisposed to fly high above
ground or to travel far, unless it be with the object of leaving an
unsatisfying locality and discovering a better place. However, the
younger flies seem to feel no such restrictive influence, for, as soon
as they have become fit and the weather suits, they show an
inclination to fly high and thus may travel to very remote places. It is

just the same with peacock, red admiral, and tortoise-shell
butterflies, which I have often reared and released for adding to the
interest and beauty of a flower garden. In sunny weather many or
most will soon wander never to return; those which have remained a
few days continue residence close round about, especially if nettles,
the food plant, grow in the neighbourhood.
It would be of great interest if we could discover how far a plague
of flies arising from unsanitory surroundings in one locality is liable
to spread to the injury of other localities.
On this subject nothing useful can be said other than can be safely
surmised from the known habits of the fly. The female has none of
the attachment of the honey-bee to its hive and community; she is
not moved by an instinct like that of the wandering bumble-bee in
spring to found a colony; she is indeed very solicitous about the
disposal of her eggs, but she is not impelled by any desire to place
successive deposits in one locality.
The lesser house-fly has proclivities similar to those of the
common house-fly, but probably she travels less far afield although a
little more inclined to outdoor life.
Very little is known about most of the common outdoor sweat-
flies. Some breed in dung, and may be many-brooded and otherwise
resemble the house-fly in prolific increase; others are more
consistently vegetarian in the larval stage and slower in
development; and some are possibly even single-brooded, like
certain foreign large sized flies which fortunately appear only for a
few weeks of summer weather, for they have a curious semi-blood-
sucking habit of feeding after or alongside the skin-piercing flies, and
their suctorial mouths are capable of further inflaming wounds and
carrying infection from one animal to another.
The robust blue-bottle very closely resembles the house-fly in an
inclination to spread the brood. Mature females, however, do
sometimes show a slight temporary kind of "homing" instinct; having
secured a cosy corner and a well sheltered retreat in a sunny wall,
the occupant will battle for its possession, buffeting new comers.

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