Environmental engg

Environmental Engineering
LAB EXPERIMENTS
From: Er. Love Sharma
Shri Mata Vaishno Devi University, Katra,
Jammu

DETERMINATION OF pH VALUE OF WATER
Overview: “pH stands for potential of Hydrogen” It is one of the basic water and wastewater characteristics.
It expresses the intensity of acid or alkaline conditions by indicating the hydrogen ion activity.
Apparatus :
 pH meter & Beaker
Procedure :
 In a clean dry 100 mL beaker take the water sample
and place it in a magnetic stirrer, insert the Teflon
coated stirring bar and stir well.
 Place the electrode in the beaker containing the water
sample and check for the reading in the pH meter.
 Take the electrode from the water sample, wash it with
distilled water and then wipe gently with soft tissue.
Technical Discussion:
 pH is one of the most important
controlling factors for treatment and
chemical analysis of water and
wastewater
 pH (6.5 to 8.5) has no direct effect on
health however a lower value below 4
will produce sour taste and higher
value above 8.5 a bitter taste.
 pH below 6.5 starts corrosion in pipes,
thereby releasing toxic metals such as
zinc, lead, cadmium & copper etc.,
According to BIS water for domestic
consumption should have pH between
6.5 to 8.5
pH S c a l e
 High pH induces the formation of trihalomethanes which are causing cancer in human
beings.

DETERMINATION OF HARDNESS IN WATER
Overview: Hard waters are generally considered to be those waters that require considerable
amounts of soap to produce foam or leather. The hardness of water varies considerably from place
to place. In general, surface water is softer than groundwater.
Procedure :
 Take 20 ml of the sample and add 2 ml of
ammonia buffer to the flask.
 Add 5 to 6 drops of EBT to the flask wine red
colour will be developed.
 Titrate it with standard EDTA solution which is
filled in the burette till the colour changes from
red to blue.
 For determination of non-carbonate hardness
the sample is to be boiled for 30 minutes.Technical Discussion:
 Hardness =
M2+ x 50
Equivalent weight of M2+
Where: M2+ = concentration of divalent metal
cation (mg/l) and 50 is the equivalent weight of
CaCO3.
 Hardness of water is important in determining
the suitability of water for domestic and
industrial uses.
 Determination of hardness serve as a basis for
routine control of softening process.
Chemicals Required:
 Eriochrome Black-T (EBT), Ammonium
chloride, Ammonium solution, EDTA
Apparatus :
 Burette, Pipette, Conical flask, measuring
jar
Degree of
Hardness
Grains per
Gallon (gpg)
(mg/L)
Soft < 1.0 < 17.0
Slightly Hard 1.0 - 3.5 17.1 – 60
Moderately Hard 3.5 - 7.0 60 – 120
Hard 7.0 - 10.5 120 – 180
Very Hard > 10.5 > 180

DETERMINATION OF TURBIDITY OF WATER
Overview: Turbidity is the technical term referring to the cloudiness of a solution and it is a
qualitative characteristic which is imparted by solid particles obstructing the transmittance of light
through a water sample. Turbidity often indicates the presence of dispersed and suspended solids
like clay, organic matter, silt, algae and other microorganisms.
Procedure :
 For testing the given water sample first the reagents are to be
prepared. Then the turbidity meter is required to be calibrated.
 To the sample cells, add sample water up to the horizontal
mark, wipe gently with soft tissue and place it in the turbidity
meter. Cover the sample cell with the light shield.
 Check for the reading in the turbidity meter. Wait until you get
a stable reading.
 Knowledge of the turbidity variation in raw water supplies
along with other information is useful to determine whether a
supply repairs Special treatment by chemical coagulation and
filtration before it may be used for a public water supply.
Apparatus :
 Turbidity Meter
Chemicals Required:
 Formazin Polymer standards
 Turbidity measurements help to gauge the amount of chemicals needed from day- today in the
operation of water treatment works.
 Turbidity measurements are useful to determine the optimum dosage of coagulants to treat the
domestic and Industrial wastes.

DETERMINATION OF BIOCHEMICAL OXYGEN DEMAND
Overview: The biochemical oxygen demand determination is a chemical procedure for determining the
amount of dissolved oxygen needed by aerobic organisms in a water body to break the organic materials
present in the given water sample at certain temperature over a specific period of time.
Procedure :
 Fill two BOD bottles with sample (or diluted sample)
 Determine initial DO (DOi) in one bottle immediately after
filling with sample.
 Keep the other bottle in dark at 20°C and after particular days
(usually 5-days) determine final DO (DOf) in the sample.
Dissolved oxygen (DO) is determined according to the
following procedure:
 Add 1 ml of manganous sulfate & alkaline potassium iodide
solution to the BOD bottle and mix it
 Allow the "precipitates" to settle halfway and mix again.
 Again allow the "precipitates" to settle halfway.
 Add 1 ml of concentrated sulfuric acid and allow the solution
to stand at least 5 minutes.
 Withdraw 100 mL of solution into an Erlenmeyer flask and
immediately add 0.025N sodium thiosulfate drop by drop from
a burette until the yellow color almost disappears.
 Add about 1 mL of starch solution and continue the addition of
the thiosulfate solution until the blue color just disappears.
Record the ml. of thiosulfate solution used.
Apparatus :
 BOD bottle and Beaker
 Measuring cylinder
 Dropper & Stirrer
Reagents:
 Manganous sulfate solution
 Alkaline potassium iodide
solution
 0.025N sodium thiosulfate
 Starch solution (indicator)
 Concentrated sulfuric acid.

 Dissolved oxygen, DO:
DO (mg/L) = (mL of 0.025N sodium thiosulfate added) x (Multiplying Factor)
 Biochemical Oxygen Demand:
The five-day BOD of a diluted sample: BOD5 = [DOi - DOf] × D.F.
Where:
Dilution factor (D.F.) =
(𝐕𝐨𝐥𝐮𝐦𝐞 𝐨𝐟 𝐰𝐚𝐬𝐭𝐞 𝐰𝐚𝐭𝐞𝐫+𝐕𝐨𝐥𝐮𝐦𝐞 𝐨𝐟 𝐝𝐢𝐥𝐮𝐭𝐢𝐨𝐧 𝐰𝐚𝐭𝐞𝐫)
𝐕𝐨𝐥𝐮𝐦𝐞 𝐨𝐟 𝐰𝐚𝐬𝐭𝐞 𝐰𝐚𝐭𝐞𝐫
 BOD is the principle test to give an
idea of the biodegradability of any
sample and strength of the waste.
 The amount of pollution can be easily
measured by it.
 Data from BOD tests are used for the
development of engineering criteria for
the design of wastewater treatment plants.
BOD Level
(mg/liter)
Water
Quality
1 - 2 Very Good
3 - 5 Fair
6 - 9 Poor
10 or more Very Poor
 BOD is important parameter to assess the pollution of surface waters and ground waters
where contamination occurred due to disposal of domestic and industrial effluents.
 Drinking water usually has a BOD of less than 1 mg/L. But, when BOD value reaches
5mg/L, the water is doubtful in purity.
 It is the only parameter, to give an idea of the biodegradability of any sample and self-
purification capacity of rivers and streams.

DETERMINATION OF CHEMICAL OXYGEN DEMAND
Overview: The chemical oxygen demand (COD) test allows measurement of oxygen demand of the
waste in terms of the total quantity of oxygen required for oxidation of the waste to carbon dioxide and
water. The test is based on the fact that all organic compounds, with a few exceptions, can be oxidized by
the action of strong oxidizing agents under acid conditions.
Procedure :
 Pipette 100 mL of the sample into a 250 mL
Erlenmeyer flask. Add 10 mL of diluted sulfuric acid
and 10 mL of standard KMn04 solution.
 Heat the flask in a boiling water bath for exactly 30
minutes.
 After 30 minutes in the water bath, add 10 mL of
standard ammonium oxalate [(NH4)2C2O4] solution into
the flask. The excess of reducing agent [(NH4)2C204]
now remaining in the flask is just equivalent to the
amount of the oxidizing agent (KMn04) used in the
oxidation of organic matter.
 The quantity of ammonium oxalate remaining in the
flask is now determined by titration with standard
potassium permanganate. Titrate the content of the flask
while hot with standard potassium permanganate to the
first pink coloration. Record the mL of potassium
permanganate used.
Apparatus :
 Beaker (250 mL)
 Dropper & Stirrer
Reagents:
 Diluted sulfuric acid solution
 Standard potassium permanganate
solution
 Standard Ammonium Oxalate solution

 COD (mg/L) =
mL of KMnO4
x 100
mL of sample used
 COD is often measured as a rapid indicator of organic pollutant in water; it is
normally measured in both municipal and industrial wastewater treatment plants and
gives an indication of the efficiency of the treatment process.
 One of the chief limitations of COD test is its inability to differentiate between
biodegradable and non-biodegradable organic matter.
COD (mg/L) Water Quality
0 - 5 Very clear water, used for drinking.
5 - 20 Fairly clean.
20 - 100
Unfit for drinking but can be used for washing and
agriculture
 The ratio of BOD to COD is greater than or equal to 0.8 indicates that the waste water
are highly amenable to biological treatment.

DETERMINATION OF CARBON DIOXIDE IN WATER
Overview: Carbon Dioxide is present in water in the form of a dissolved gas. Surface waters
normally contain less than 10 ppm free carbon dioxide, while some ground waters may easily
exceed that concentration.
Procedure :
 Take a 100 ml of sample in a beaker and add 10 drops of
Phenolphthalein indicator. If a pink color develops, no carbon
dioxide is present in the water sample.
 Add N/44 sodium hydroxide solution to the sample and stir
until a slight permanent pink color appears. Record ml of
sodium hydroxide used.
Apparatus :
 Beaker Beaker
 Measuring cylinder
 Dropper, Stirrer & Burette
Reagents:
 Standard N/44 Sodium
Hydroxide
 Phenolphthalein Indicator
Carbon dioxide (mg/L) = mL of N/44 NaOH used x M.F
Where;
M.F; Multiplying Factor
=
𝐍𝐨𝐫𝐦𝐚𝐥𝐢𝐭𝐲 𝐨𝐟 𝐍𝐚𝐎𝐇 𝐱 𝐞𝐪𝐮𝐢𝐯𝐚𝐥𝐞𝐧𝐭 𝐰𝐭𝐞𝐢𝐠𝐡𝐭 𝐨𝐟 𝐂𝐎𝟐 𝐱 𝟏𝟎𝟎𝟎
𝐦𝐋 𝐨𝐟 𝐬𝐚𝐦𝐩𝐥𝐞 𝐭𝐚𝐤𝐞𝐧
 When the oxygen concentration in waters containing
organic matter is reduced, the carbon dioxide
concentration rises.

DETERMINATION OF CARBON DIOXIDE IN WATER
Overview: Alkalinity is primarily a way of measuring the acid neutralizing capacity of water. In
other words, its ability to maintain a relatively constant pH.
Procedure :
 Take 50 ml sample and measure its initial pH value.
 If the sample pH is below 8.3, add several drops of
methyl orange indicator. If the color of the solution
turned yellow, titrate your sample with 0.02 N H2SO4
until the color changes to slightly orange ting. Record the
total volume of acid used for the titration.
 If pH of your sample is above 8.3, add several drops of
phenolphthalein indicator. If the color of the solution
turned pink, titrate your sample with 0.02 N H2SO4 or
HCl, until color changes from pink to clear (pH 8.3).
 Record the volume of acid used for the titration.
Apparatus :
 Burette with Burette stand
 Conical flask & Measuring cylinders
 Beakers, Dropper, Stirrer, etc.
Chemicals:
 Standard 0.02N sulphuric acid
 Phenolphthalein indicator
 Methyl orange indicator
Total Alkalinity (mg/L as CaCO3)
=Multiplying Factor (MF) x ml of 0.02N H2SO4
Where:
M.F =
𝐍𝐨𝐫𝐦𝐚𝐥𝐢𝐭𝐲 𝐨𝐟 H2SO4 𝐗 𝐞𝐪𝐮𝐢𝐯𝐚𝐥𝐞𝐧𝐭 𝐰𝐭𝐞𝐢𝐠𝐡𝐭 𝐨𝐟 𝐂𝐚𝐂𝐎𝟑 𝐗 𝟏𝟎𝟎𝟎
𝐦𝐋 𝐨𝐟 𝐬𝐚𝐦𝐩𝐥𝐞 𝐭𝐚𝐤𝐞𝐧
 Large amount of alkalinity
imparts bitter taste in water.

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