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Water treatment

The document discusses various types of sedimentation tanks and filters used in water treatment. It describes quiescent sedimentation tanks, continuous sedimentation tanks including horizontal and vertical flow types. It also discusses the process of sedimentation with coagulation including methods of coagulant feeding, mixing and flocculation. Slow sand filters and rapid sand filters are described and compared. Pressure filters are also introduced. The document covers various steps in water treatment like disinfection using chlorination and water softening methods.

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Overview of quiescent and continuous sedimentation tanks including horizontal, vertical, and circular designs.

Details on sedimentation processes involving coagulation, mixing methods, flocculation, and sedimentation mechanisms.

Classification of filters including slow sand filter, rapid sand filter, and pressure filter with efficiency metrics.

Explanation of disinfection methods, particularly chlorination, chlorine demand, and factors affecting chlorine efficiency.

Techniques for removing hardness in water such as boiling, lime addition, and procedures for demineralization.

Methods for aeration, removal of contaminants like iron and manganese, and the use of bio sand filters.

Overview of water transportation to treatment plants, storage reservoirs, and distribution systems.

Classification of various pipe materials suitable for water supply systems, including their advantages and disadvantages.

Steps involved in laying pipes, including site preparation, joining, and testing procedures.

Various types of valves used in water supply systems for controlling flow, releasing air, and other functions.

Steps in planning gravity water supply projects, including need identification, budget preparation, and surveys.

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1 TYPES OF SEDIMENTATION TANKS 1. Quiescent or fill and draw type:  Rectangular in plan.  Water is filled, allowed for retention period of 30 to 60 hrs (normally 24 hrs) then clear water is drawn from outlet  Empty the tank and cleaning of sediment is done.  Needs more detention period, labours and supervision,  More than one tanks  Not used nowadays.
2 2. Continuous type: A. Horizontal Flow Type (a) Rectangular tanks with longitudinal flow
3 (b) Circular with radial flow i. Circular with central feed ii. Circular with peripheral feed
4 B. Vertical Flow Type
5 Surface loading or surface overflow rate (SOR) of sedimentation tank:
6 PROCESS OF SEDIMENTATION WITH COAGULATION 1. Feeding the coagulant Dry feeding Wet Fedding 2. Mixing of coagulant a. Mixing basin with baffle walls b. Mixing basin with mechanical means c. Mixing channels d. Hydraulic jump method e. Compressed air method f. Centrifugal pumping method 3. Flocculation 4. Sedimentation
7 a. Mixing basin with baffle walls i. Horizontal or round end type:
8 ii. Vertical or over and under type
9 b. Mixing basin with mechanical means
10 3. Flocculation
11
12 4. Sedimentation
13 FILTER AND THEIR CLASSIFICATION 1. Slow sand filter (SSF)
14 a. Enclosure tank:  depth = 2.5 – 3.5 m  surface area = 10 – 2000 m2  filtration rate = 100 – 200 lph/m2  cross slope = 1 in 100 – 1 in 200 towards central drain b. Filter media: • sand layer = 90 – 110 cm thick • effective size (D10) = 0.25 – 0.35 mm (0.3 mm is common) • coefficient of uniformity (Cu) = 3 – 5. c. Base material: • 30 to 75 cm thick gravel • four layers of each about 15 cm • 3 – 6 mm, 6 – 20 mm, 20 – 40 mm and 40 – 65 mm from the top e. Appurtenances: vertical air pipes, depth controlling devices,head loss measuring device, rate maintaining devices etc
15 d. Under drainage system: Efficiency of SSF:  98 – 99% bacteria removal  removes turbidity up to 50 ppm  Only 20 – 25 % of color removal  not so efficient in removal of colloidal matters
16 2. Rapid sand filter (RSF)
17 a. Enclosure tank:  depth = 2.5 – 3.5 m  surface area = 10 – 50 m2  filtration rate = 3000 – 6000 lph/m2  Length width ratio = 1.25 – 1.35 b. Filter media:  sand layer = 60- 90 cm thick  effective size (D10) = 0.35 – 0.60 mm  coefficient of uniformity (Cu) = 1.3-1.7. c. Base material: • 45 to 60 cm thick gravel • four layers of each about 15 cm • 2 – 6 mm, 6 – 12 mm, 12 – 20 mm and 20 – 50 mm from the top
18 d. Under drainage system:
19 e. Appurtenances: Wash water trough, air compressor, rate control device, head loss indicators meters, valves etc Efficiency of RSF:  35-40 ppm turbidity removal  removes colour below 3 ppm  Less efficient in iron and manganese removal  not efficient in odour removal  Less efficient in bacteria removal (Only 80 – 90 %)
20 3. Pressure filter (PF) water is passed under pressure of 3 – 7 kg/cm2 through pumping  Rate of filtration of PF is 6000 – 15000 lit/hr/m2 of filter area  low efficient than RSF for the removal of color, turbidity and bacterial load  can be used for small colonies, industry and swimming pools etc.
Difference between 21 Criteria Slow sand filter Rapid sand filter Filtration rate LPH/M2 100 – 200 3000-6000 Filter Media :sand layer (cm) 90 – 110 60-90 effective size (D10) mm 0.25 – 0.35 0.35-0.6 coefficient of uniformity (Cu) 3 – 5. 1.3-1.7 Efficiency bacteria removal 98 – 99% Less efficient (Only 80 – 90 %)
22 DISINFECTION  To kill pathogens  Chemicals called disinfectants Characteristics of a good disinfectants: 1.Should be able to destroy all harmful bacteria economically within the contact time and in the wide range of temperature and pH values. 2.It should not render the water toxic or impart colour and odour. 3.It should be easily available at reasonable cost. 4.It should be safe to handle and method of application should be simple. 5.It should persist in residual concentrations as safeguard recontamination.
23 Methods of disinfection: Chlorination • When Chlorine is used Cl2 + H2O ↔ HOCl + H+ + Cl – [Called Hydrolysis reaction occurs at 49 - 212°C] The HOCl further dissociates (ionizes) as follows HOCl ↔ H+ + OCl – [Called Ionization reaction] HOCl and OCl – penetrate cell walls and reacts with the enzyme system in the cell of micro-organism and results death of micro- organism
24 FORMS OF APPLICATION OF CHLORINE (a) Bleaching powder CaOCl2 ↔ Ca++ + 2 OCl – H+ + OCl – ↔ HOCl – this process is called hypochlorination (b) Chloramines H2O + Cl2↔ HOCl + H++ Cl – NH3 + HOCl ↔ NH2Cl (monochloramine) + H2O NH2Cl + HOCl ↔ NHCl2 (dichloramine) + H2O NHCl2 + HOCl ↔ NCl3 (trichloramine) + H2O (c) Chlorine gas or liquid chlorine (d) Chlorinedioxide 2NaClO2 + Cl2 ↔ 2NaCl + 2 ClO2↑
25 CHLORINE DEMAND AND DOSE (a) Chlorine demand Chlorine demand = Total amount of chlorine added – Amount of residual chlorine required after a specified contact period Reaction for combined available chlorine: Cl2 + H2O ↔ HOCl + H++ Cl – NH3 + HOCl ↔ NH2Cl (monochloramine) + H2O NH2Cl + HOCl ↔ NHCl2 (dichloramine) + H2O NHCl2 + HOCl ↔ NCl3 (trichloramine) + H2O (b) Chlorine dose Quantity of chlorine required to be added to water to leave 0.2 mg/l or ppm of freely available residual chlorine after 10 minutes of contact period
26 FORMS OF CHLORINATION 1. Plain chlorination or simple chlorination: To raw water 2. Pre-chlorination: Before treatment 3. Post chlorination: After treatment 4. Double or multiple chlorination: Two or more point 5. Super chlorination: Application beyond break point 6. De-chlorination Removing chlorine 7. Break point chlorination or free residual chlorination:
27 7. Break point chlorination or free residual chlorination:
28 FACTORS AFFECTING BACTERIAL EFFICIENCY OF CHLORINE 1.Turbidity: low efficient 2.Presence of metallic compound: Efficiency is decreased. 3.Ammonia compound: Efficiency is decreased 4.pH value of water: If pH is high in water, efficiency is low 5. Temperature: If temperature decreased, efficiency decreased. 6.Time of contact: time of contact should be at least 30 minutes. 7.Type, condition and concentration of micro-organism: Efficiency low if the favorable condition for bacteria is available and concentration of bacteria is high.
29 WATER SOFTENING • Process of removing hardness • Purpose: To remove Hardness A. Removal of temporary hardness: (a) Boiling: It is costlier and not used in public water supply. Ca(HCO3)2 CaCO3↓ + CO2↑ + H2O Mg(HCO3)2 MgCO3↓ + CO2 ↑+ H2O (b) Adding lime: Ca(HCO3)2 + Ca(OH)2 → 2CaCO3↓ + 2H2O Mg(HCO3)2 + Ca(OH)2 → CaCO3↓ + MgCO3↓ + 2H2O
30 A. Removal of permanent hardness: a. Lime soda process: CO2 + Ca(OH)2 = CaCO3↓ + H2O Ca(HCO3)2 + Ca(OH)2 = 2CaCO3↓ + 2H2O Mg(HCO3)2 + Ca(OH)2 = CaCO3↓ + MgCO3 + 2H2O MgCO3 + Ca(OH)2 = Mg(OH)2↓ + CaCO3↓ MgSO4 + Ca(OH)2 = Mg(OH)2↓ + CaSO4 CaSO4 + Na2CO3 = CaCO3↓ + Na2SO4 MgCl2 + Ca(OH)2 = Mg(OH)2↓ + CaCl2 CaCl2 + Na2CO3 = CaCO3↓ + 2NaCl MgCl2 + Na2CO3 = MgCO3 + 2NaCl           +      →           + 2NaCl SONa 2NaHCO Z Mg Ca Cl SO )(HCO Mg Ca ZNa 42 3 2 4 23 2 b. Permutit Process:
31 b. Permutit Process:
32 C. Demineralization or deionization process: Regeneration of zeolite: 22 Cl Mg Ca ZNa2NaClZ Mg Ca       +→+                + +      →           + 2HCl SOH 2COO2H R Mg Ca Cl SO )(HCO Mg Ca RH 42 22 2 4 23 2 Regeneration of hydrogen exchanger:                 +→+           2 4 2 42 2 Cl/Cl SO 2Na Mg Ca RH HCl SOH R Na Mg Ca
33 MISCELLANEOUS TREATMENT A. Aeration: (A) Aeration (B) Removal of iron and manganese (C) Removal of colour odour and taste Purpose of aeration: 1. To make water fresh by absorbing oxygen from air. 2. To release dissolved gases (CO2, H2S etc) to atmosphere. 3. To remove bad taste and odour. 4. To reduce corrosiveness of water. 5. To precipitate Fe and Mn to some extent by oxidizing. 6. To kill harmful bacteria to some extent. 7. To mix mixing chemicals to water.
34
35 Methods of aeration: Free fall or gravity aerators:
36
37 Methods of aeration: Free fall or gravity aerators: Mechanical aerators:
38 Free fall or gravity aerators:
39
40
41 B. Removal of iron and manganese: Effect: i. Produce taste, odour and brown red colour. ii.Stains on clothes, corrosion and clogging of pipes by accumulation of precipates. iii.Causes difficult in various industrial process. Purpose: Removal of iron and manganese Methods: (a) By aeration (b) By adding lime (c) Passing over manganese zeolite
42 (a) By aeration: In this case aeration is done before sedimentation. Fe: 4Fe + O2 + 10 H2O → 4Fe(OH)3 ↓ + 8H Fe(HCO3)2 : Fe(HCO3)2 + 2H2O → FeO + 2CO2 + 3H2O 4FeO + O2 → 2Fe2O3 Fe2O3 + 3H2O → 2Fe(OH)3 ↓ Mn: 6Mn + 3O2 + 6H2O → 6MnO2 ↓ + 12H
43 C. Removal of colour, odour, taste: Purpose: Removal of colour, odour and taste Methods: (a) By aeration (b) By activated carbon treatment • Activated carbon is manufactured by heating saw dust, paper mill waste etc. at 500°C in a closed vessel in controlled condition of burning at 800°C. • readily available in market in powder or granular form • absorbs organic matters and removes colour, odour and taste. (c) Using copper sulphate: in swimming pools
SODIS method is very easy to apply: A transparent PET bottle is cleaned with soap. Then, the bottle is filled with water and placed in full sunlight for at least 6 hours. The water has then been disinfected and can be drunk.
Membrane Filtration 45
46 Reverse Osmosis
47
48
BIO SAND FILTER • (BSF) is a point-of-use water treatment system adapted from traditional slow sand filters. • Bio sand filters remove pathogens and suspended solids from water using biological and physical processes that take place in a sand column covered with a bio film. • BSFs have been shown to remove heavy metals, turbidity, bacteria, viruses and protozoa. • BSFs also reduce discoloration, odor and unpleasant taste. • Studies have shown a correlation between use of BSFs and a decrease in occurrence of diarrhea because of their effectiveness, ease of use, and lack of recurring costs, bio sand filters are often considered appropriate technology in developing countries.
How Well Does the Bio sand Filter Work? • Water naturally contains many living things. Some are harmless and others can make people sick. Living things that cause disease are also known as pathogens. They are sometimes called other names, such as microorganisms, microbes or bugs, depending on the local language and country. • There are four different categories of pathogens that are : bacteria, viruses, protozoa and helminths. • Turbid water looks cloudy, dirty or muddy and is caused by sand, silt and clay that are floating in the water. Drinking turbid water will not make people sick by itself. • However, viruses, parasites and some bacteria can sometimes attach themselves to the suspended solids in water. • This means that turbid water usually has more pathogens so drinking it increases the chances of becoming sick
56 CHAPTER 7: INTRODUCTION TO CONVEYANCE • Transportation of water to treatment plant or reservoir or distribution through conduits. • Transmission: Source – TP – Reservoir • Distribution: Reservoir – Users Tap • Conduits: A. Gravity: Open channel flow Canals, aqueducts, tunnels B. Pressure Pipes, pressure tunnels, pressure aqueducts etc.
57 PIPE, PIPE MATERIALS AND PIPE TYPES Pipe: • Circular conduit where fluid flows under pressure • Designed to carry external and internal loads Requirement of good pipe: • Withstand external, internal and temperature stresses • Smooth for minimum frictional losses • Durable • Light • Noncorrosive • Cheap • Easy joint
58 Pipe types as per materials:
59 (a) Cast Iron (CI) Pipe: • Manufactured by sand molding or centrifugal method • Standard 1.8 m length but up to 3m for smaller diameter • 50 mm to 1.2 m dia. Advantages: Easy to join, can withstand high pressure, resistance to corrosion, long life (> 100 yrs), durable, strong and moderate in cost, joined by flanged or Spigot and socket joint, low maintenance cost. Disadvantages: Brittle and very heavy so difficult to transport and may be expensive. Suitability: Suitable for distribution system.
60 (b) Wrought Iron (WI) Pipe: • Manufactured by rolling the flat plates of metal to proper diameter and welding to the edges Advantages: Strong, light weight, can withstand high pressure (400 m) and cheaper than CI pipes Disadvantages: It can’t withstand external load and when there is no water inside, liable to corrosion and costly to maintain. It is costlier than CI pipes Suitability: Occasionally used for main lines where pressure is high
61 (c) Steel Pipe: • Manufactured by WI or mild steel which are galvanized by providing a protective coating of zinc on inner and outer surface Advantages: It is cheap, light, easy in handling and transport, easy in joining with screwed socket joints and 20 years of life, resistant to corrosion when exposed to atmosphere Disadvantages: may get corroded by acidic and alkaline waters and liable to incrustation. Suitability: main lines where pressure is high and when pipe is exposure in open atmosphere
62 (d) Galvanized iron (GI) pipes: • Manufactured similar as WI pipes • 15,20,25,32,40,50,63,75,90,110,125,150, 200 mm inner dia Advantages: Light in weight, easy in transport, handling, cutting, threading, working, joining, and gives neat appearance, joined couplings or screwed socket joint. Disadvantages: Costly, corrosive and less durable than CI pipes Suitability: Inside plumbing in buildings but not used nowadays due to high cost.
63 (e) Concrete (GI) pipes: • Made of cement concrete (precast or cast in site) Advantages: Withstand 150 m head of water, resist corrosion and life is above 75 years, maintenance cost is low, least thermal expansion, can be laid under water and resist normal traffic load Disadvantages: Precast type is heavy to handle and transport, concrete pipes can’t resist high pressure and difficult to repair, it may be affected by acids and alkali and salty waters, difficult to join and liable to leak due to porosity Suitability: Where water does not flow under pressure (i.e. sewerage system)
64 (f) Asbestos cement (AC) pipes: • Made of mixture of cement and asbestos fibers Advantages: not affected by salt water and corrosive materials, smooth, light so easy in handling Disadvantages: Affected by alkali and acid and also brittle so costlier in transport. Suitability: Small size distribution pipes
65 (g) Wooden pipes: • made of wood by making channels or boring at center and used in ancient times • not used in water supply nowadays (h) Vitrified clay Pipes: • made of vitrified clay so has smooth surface • not used in water supply nowadays (i) Lead and copper Pipes: • Copper pipe is made of copper and can resist corrosion even if water contains some acids and expensive so not used in water supply nowadays • Leads are soluble in water so lead pipe causes lead poisoning hence it is not used in water supply nowadays.
66 (f) Plastic Pipes: • Made of Plastic and common in nowadays • it is corrosion resistant, light in weight and economical Advantages: Light, cheap, available in longer length, electrical insulation, corrosion free, life correspond to GI Disadvantages: Less resistant to hot water, may impart smell to water, can be easily cut. Suitability: All water sypply systems
67 Types: 1. Low density polyethylene (LDPE) pipes: Used in electrical wiring 2. High density polyethylene (HDPE)pipes 3. Polyvinyl chloride (PVC) pipes: 4. Unplastisized Polyvinyl chloride (UPVC) pipes: 5. Poly Propylene Random (PPR) Pipes: Plastic Pipes
68 LAYING OF PIPES 1.Preparation of detailed maps: 2.Locating proposed alignment of pipeline on the ground: 3.Location of pipes with respect to ground surface during laying 4.Excavation of trench: 5.Dewatering of trench: 6.Lowering the Pipes: 7.Joining pipes: 8.Testing of pipes: 9.Back filling and disinfection before first use:
69
70 PIPE JOINTS
71
72
73
74
75 CHAPTER 8: VALVES AND FITTINGS (a) Sluice or gate or cutoff valve (b) Reflux or check or non-return valve (c) Safety or pressure relief valve (d) Air valve or air relief valve (e) Drain or scour or blow off valve : Ordinary sluice valve to remove silt deposit (f) Butterfly valve and globe valve Devices used to control the flow of water, regulate pressures, release air, prevent back flow etc
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77
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79 FIRE HYDRANT:  Devices used for tapping water from mains for the fire extinguishing, street washing, watering gardens, flushing sewer lines etc.  Provided at all road junctions & every 100 – 300 m apart.  For tapping water, the hose is connected to the hydrant and if necessary the engine is used to increase head.  It should be cheap, easily connectable & detachable to the hose pipe and able to give sufficient water. It may be of post type or flush type.
80
81 FITTINGS
82
83
84 CHAPTER 9: PLANNING OF GRAVITY WATER SUPPLY • Need identification of scheme • After need identification, mass meeting is called, prioritize is done and then scheme acquisition form is filled up and submitted to VDC, DDC and divisional district water supply office • With feasibility study report the schemes are forwarded from divisional office thru regional office to department of water supply and sewerage (DWSS) • After obtaining scheme acquisition form list from all 75 districts , budget ceiling is prepared for forthcoming fiscal year by DWSS and forward to ministry of concern. • The ministry approves ceiling consulting with National planning commission then distributed to DWSS and district offices for implementation
85 • After obtaining approved budget ceiling, detailed survey is carried out. • Detail survey  horizontal and vertical control and  questionnaire • Analysis based on detail survey, the design, drawing, estimating and costing is done and final report is prepared. • Water Users Committee (WUS) is formed and trained in agreement with WUC or implementation agency • After agreement, construction is carried out and it is handover to the WUC. • WUC are responsible for regular maintenance.

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Water treatment

  • 1.
    1 TYPES OF SEDIMENTATIONTANKS 1. Quiescent or fill and draw type:  Rectangular in plan.  Water is filled, allowed for retention period of 30 to 60 hrs (normally 24 hrs) then clear water is drawn from outlet  Empty the tank and cleaning of sediment is done.  Needs more detention period, labours and supervision,  More than one tanks  Not used nowadays.
  • 2.
    2 2. Continuous type: A.Horizontal Flow Type (a) Rectangular tanks with longitudinal flow
  • 3.
    3 (b) Circular withradial flow i. Circular with central feed ii. Circular with peripheral feed
  • 4.
  • 5.
    5 Surface loading orsurface overflow rate (SOR) of sedimentation tank:
  • 6.
    6 PROCESS OF SEDIMENTATIONWITH COAGULATION 1. Feeding the coagulant Dry feeding Wet Fedding 2. Mixing of coagulant a. Mixing basin with baffle walls b. Mixing basin with mechanical means c. Mixing channels d. Hydraulic jump method e. Compressed air method f. Centrifugal pumping method 3. Flocculation 4. Sedimentation
  • 7.
    7 a. Mixing basinwith baffle walls i. Horizontal or round end type:
  • 8.
    8 ii. Vertical orover and under type
  • 9.
    9 b. Mixing basinwith mechanical means
  • 10.
  • 11.
  • 12.
  • 13.
    13 FILTER AND THEIRCLASSIFICATION 1. Slow sand filter (SSF)
  • 14.
    14 a. Enclosure tank: depth = 2.5 – 3.5 m  surface area = 10 – 2000 m2  filtration rate = 100 – 200 lph/m2  cross slope = 1 in 100 – 1 in 200 towards central drain b. Filter media: • sand layer = 90 – 110 cm thick • effective size (D10) = 0.25 – 0.35 mm (0.3 mm is common) • coefficient of uniformity (Cu) = 3 – 5. c. Base material: • 30 to 75 cm thick gravel • four layers of each about 15 cm • 3 – 6 mm, 6 – 20 mm, 20 – 40 mm and 40 – 65 mm from the top e. Appurtenances: vertical air pipes, depth controlling devices,head loss measuring device, rate maintaining devices etc
  • 15.
    15 d. Under drainagesystem: Efficiency of SSF:  98 – 99% bacteria removal  removes turbidity up to 50 ppm  Only 20 – 25 % of color removal  not so efficient in removal of colloidal matters
  • 16.
    16 2. Rapid sandfilter (RSF)
  • 17.
    17 a. Enclosure tank: depth = 2.5 – 3.5 m  surface area = 10 – 50 m2  filtration rate = 3000 – 6000 lph/m2  Length width ratio = 1.25 – 1.35 b. Filter media:  sand layer = 60- 90 cm thick  effective size (D10) = 0.35 – 0.60 mm  coefficient of uniformity (Cu) = 1.3-1.7. c. Base material: • 45 to 60 cm thick gravel • four layers of each about 15 cm • 2 – 6 mm, 6 – 12 mm, 12 – 20 mm and 20 – 50 mm from the top
  • 18.
  • 19.
    19 e. Appurtenances: Wash watertrough, air compressor, rate control device, head loss indicators meters, valves etc Efficiency of RSF:  35-40 ppm turbidity removal  removes colour below 3 ppm  Less efficient in iron and manganese removal  not efficient in odour removal  Less efficient in bacteria removal (Only 80 – 90 %)
  • 20.
    20 3. Pressure filter(PF) water is passed under pressure of 3 – 7 kg/cm2 through pumping  Rate of filtration of PF is 6000 – 15000 lit/hr/m2 of filter area  low efficient than RSF for the removal of color, turbidity and bacterial load  can be used for small colonies, industry and swimming pools etc.
  • 21.
    Difference between 21 Criteria Slowsand filter Rapid sand filter Filtration rate LPH/M2 100 – 200 3000-6000 Filter Media :sand layer (cm) 90 – 110 60-90 effective size (D10) mm 0.25 – 0.35 0.35-0.6 coefficient of uniformity (Cu) 3 – 5. 1.3-1.7 Efficiency bacteria removal 98 – 99% Less efficient (Only 80 – 90 %)
  • 22.
    22 DISINFECTION  To killpathogens  Chemicals called disinfectants Characteristics of a good disinfectants: 1.Should be able to destroy all harmful bacteria economically within the contact time and in the wide range of temperature and pH values. 2.It should not render the water toxic or impart colour and odour. 3.It should be easily available at reasonable cost. 4.It should be safe to handle and method of application should be simple. 5.It should persist in residual concentrations as safeguard recontamination.
  • 23.
    23 Methods of disinfection:Chlorination • When Chlorine is used Cl2 + H2O ↔ HOCl + H+ + Cl – [Called Hydrolysis reaction occurs at 49 - 212°C] The HOCl further dissociates (ionizes) as follows HOCl ↔ H+ + OCl – [Called Ionization reaction] HOCl and OCl – penetrate cell walls and reacts with the enzyme system in the cell of micro-organism and results death of micro- organism
  • 24.
    24 FORMS OF APPLICATIONOF CHLORINE (a) Bleaching powder CaOCl2 ↔ Ca++ + 2 OCl – H+ + OCl – ↔ HOCl – this process is called hypochlorination (b) Chloramines H2O + Cl2↔ HOCl + H++ Cl – NH3 + HOCl ↔ NH2Cl (monochloramine) + H2O NH2Cl + HOCl ↔ NHCl2 (dichloramine) + H2O NHCl2 + HOCl ↔ NCl3 (trichloramine) + H2O (c) Chlorine gas or liquid chlorine (d) Chlorinedioxide 2NaClO2 + Cl2 ↔ 2NaCl + 2 ClO2↑
  • 25.
    25 CHLORINE DEMAND ANDDOSE (a) Chlorine demand Chlorine demand = Total amount of chlorine added – Amount of residual chlorine required after a specified contact period Reaction for combined available chlorine: Cl2 + H2O ↔ HOCl + H++ Cl – NH3 + HOCl ↔ NH2Cl (monochloramine) + H2O NH2Cl + HOCl ↔ NHCl2 (dichloramine) + H2O NHCl2 + HOCl ↔ NCl3 (trichloramine) + H2O (b) Chlorine dose Quantity of chlorine required to be added to water to leave 0.2 mg/l or ppm of freely available residual chlorine after 10 minutes of contact period
  • 26.
    26 FORMS OF CHLORINATION 1.Plain chlorination or simple chlorination: To raw water 2. Pre-chlorination: Before treatment 3. Post chlorination: After treatment 4. Double or multiple chlorination: Two or more point 5. Super chlorination: Application beyond break point 6. De-chlorination Removing chlorine 7. Break point chlorination or free residual chlorination:
  • 27.
    27 7. Break pointchlorination or free residual chlorination:
  • 28.
    28 FACTORS AFFECTING BACTERIALEFFICIENCY OF CHLORINE 1.Turbidity: low efficient 2.Presence of metallic compound: Efficiency is decreased. 3.Ammonia compound: Efficiency is decreased 4.pH value of water: If pH is high in water, efficiency is low 5. Temperature: If temperature decreased, efficiency decreased. 6.Time of contact: time of contact should be at least 30 minutes. 7.Type, condition and concentration of micro-organism: Efficiency low if the favorable condition for bacteria is available and concentration of bacteria is high.
  • 29.
    29 WATER SOFTENING • Processof removing hardness • Purpose: To remove Hardness A. Removal of temporary hardness: (a) Boiling: It is costlier and not used in public water supply. Ca(HCO3)2 CaCO3↓ + CO2↑ + H2O Mg(HCO3)2 MgCO3↓ + CO2 ↑+ H2O (b) Adding lime: Ca(HCO3)2 + Ca(OH)2 → 2CaCO3↓ + 2H2O Mg(HCO3)2 + Ca(OH)2 → CaCO3↓ + MgCO3↓ + 2H2O
  • 30.
    30 A. Removal ofpermanent hardness: a. Lime soda process: CO2 + Ca(OH)2 = CaCO3↓ + H2O Ca(HCO3)2 + Ca(OH)2 = 2CaCO3↓ + 2H2O Mg(HCO3)2 + Ca(OH)2 = CaCO3↓ + MgCO3 + 2H2O MgCO3 + Ca(OH)2 = Mg(OH)2↓ + CaCO3↓ MgSO4 + Ca(OH)2 = Mg(OH)2↓ + CaSO4 CaSO4 + Na2CO3 = CaCO3↓ + Na2SO4 MgCl2 + Ca(OH)2 = Mg(OH)2↓ + CaCl2 CaCl2 + Na2CO3 = CaCO3↓ + 2NaCl MgCl2 + Na2CO3 = MgCO3 + 2NaCl           +      →           + 2NaCl SONa 2NaHCO Z Mg Ca Cl SO )(HCO Mg Ca ZNa 42 3 2 4 23 2 b. Permutit Process:
  • 31.
  • 32.
    32 C. Demineralization ordeionization process: Regeneration of zeolite: 22 Cl Mg Ca ZNa2NaClZ Mg Ca       +→+                + +      →           + 2HCl SOH 2COO2H R Mg Ca Cl SO )(HCO Mg Ca RH 42 22 2 4 23 2 Regeneration of hydrogen exchanger:                 +→+           2 4 2 42 2 Cl/Cl SO 2Na Mg Ca RH HCl SOH R Na Mg Ca
  • 33.
    33 MISCELLANEOUS TREATMENT A. Aeration: (A)Aeration (B) Removal of iron and manganese (C) Removal of colour odour and taste Purpose of aeration: 1. To make water fresh by absorbing oxygen from air. 2. To release dissolved gases (CO2, H2S etc) to atmosphere. 3. To remove bad taste and odour. 4. To reduce corrosiveness of water. 5. To precipitate Fe and Mn to some extent by oxidizing. 6. To kill harmful bacteria to some extent. 7. To mix mixing chemicals to water.
  • 34.
  • 35.
    35 Methods of aeration: Freefall or gravity aerators:
  • 36.
  • 37.
    37 Methods of aeration: Freefall or gravity aerators: Mechanical aerators:
  • 38.
    38 Free fall orgravity aerators:
  • 39.
  • 40.
  • 41.
    41 B. Removal ofiron and manganese: Effect: i. Produce taste, odour and brown red colour. ii.Stains on clothes, corrosion and clogging of pipes by accumulation of precipates. iii.Causes difficult in various industrial process. Purpose: Removal of iron and manganese Methods: (a) By aeration (b) By adding lime (c) Passing over manganese zeolite
  • 42.
    42 (a) By aeration:In this case aeration is done before sedimentation. Fe: 4Fe + O2 + 10 H2O → 4Fe(OH)3 ↓ + 8H Fe(HCO3)2 : Fe(HCO3)2 + 2H2O → FeO + 2CO2 + 3H2O 4FeO + O2 → 2Fe2O3 Fe2O3 + 3H2O → 2Fe(OH)3 ↓ Mn: 6Mn + 3O2 + 6H2O → 6MnO2 ↓ + 12H
  • 43.
    43 C. Removal ofcolour, odour, taste: Purpose: Removal of colour, odour and taste Methods: (a) By aeration (b) By activated carbon treatment • Activated carbon is manufactured by heating saw dust, paper mill waste etc. at 500°C in a closed vessel in controlled condition of burning at 800°C. • readily available in market in powder or granular form • absorbs organic matters and removes colour, odour and taste. (c) Using copper sulphate: in swimming pools
  • 44.
    SODIS method isvery easy to apply: A transparent PET bottle is cleaned with soap. Then, the bottle is filled with water and placed in full sunlight for at least 6 hours. The water has then been disinfected and can be drunk.
  • 45.
  • 46.
  • 47.
  • 48.
  • 49.
    BIO SAND FILTER •(BSF) is a point-of-use water treatment system adapted from traditional slow sand filters. • Bio sand filters remove pathogens and suspended solids from water using biological and physical processes that take place in a sand column covered with a bio film. • BSFs have been shown to remove heavy metals, turbidity, bacteria, viruses and protozoa. • BSFs also reduce discoloration, odor and unpleasant taste. • Studies have shown a correlation between use of BSFs and a decrease in occurrence of diarrhea because of their effectiveness, ease of use, and lack of recurring costs, bio sand filters are often considered appropriate technology in developing countries.
  • 55.
    How Well Doesthe Bio sand Filter Work? • Water naturally contains many living things. Some are harmless and others can make people sick. Living things that cause disease are also known as pathogens. They are sometimes called other names, such as microorganisms, microbes or bugs, depending on the local language and country. • There are four different categories of pathogens that are : bacteria, viruses, protozoa and helminths. • Turbid water looks cloudy, dirty or muddy and is caused by sand, silt and clay that are floating in the water. Drinking turbid water will not make people sick by itself. • However, viruses, parasites and some bacteria can sometimes attach themselves to the suspended solids in water. • This means that turbid water usually has more pathogens so drinking it increases the chances of becoming sick
  • 56.
    56 CHAPTER 7: INTRODUCTIONTO CONVEYANCE • Transportation of water to treatment plant or reservoir or distribution through conduits. • Transmission: Source – TP – Reservoir • Distribution: Reservoir – Users Tap • Conduits: A. Gravity: Open channel flow Canals, aqueducts, tunnels B. Pressure Pipes, pressure tunnels, pressure aqueducts etc.
  • 57.
    57 PIPE, PIPE MATERIALSAND PIPE TYPES Pipe: • Circular conduit where fluid flows under pressure • Designed to carry external and internal loads Requirement of good pipe: • Withstand external, internal and temperature stresses • Smooth for minimum frictional losses • Durable • Light • Noncorrosive • Cheap • Easy joint
  • 58.
    58 Pipe types asper materials:
  • 59.
    59 (a) Cast Iron(CI) Pipe: • Manufactured by sand molding or centrifugal method • Standard 1.8 m length but up to 3m for smaller diameter • 50 mm to 1.2 m dia. Advantages: Easy to join, can withstand high pressure, resistance to corrosion, long life (> 100 yrs), durable, strong and moderate in cost, joined by flanged or Spigot and socket joint, low maintenance cost. Disadvantages: Brittle and very heavy so difficult to transport and may be expensive. Suitability: Suitable for distribution system.
  • 60.
    60 (b) Wrought Iron(WI) Pipe: • Manufactured by rolling the flat plates of metal to proper diameter and welding to the edges Advantages: Strong, light weight, can withstand high pressure (400 m) and cheaper than CI pipes Disadvantages: It can’t withstand external load and when there is no water inside, liable to corrosion and costly to maintain. It is costlier than CI pipes Suitability: Occasionally used for main lines where pressure is high
  • 61.
    61 (c) Steel Pipe: •Manufactured by WI or mild steel which are galvanized by providing a protective coating of zinc on inner and outer surface Advantages: It is cheap, light, easy in handling and transport, easy in joining with screwed socket joints and 20 years of life, resistant to corrosion when exposed to atmosphere Disadvantages: may get corroded by acidic and alkaline waters and liable to incrustation. Suitability: main lines where pressure is high and when pipe is exposure in open atmosphere
  • 62.
    62 (d) Galvanized iron(GI) pipes: • Manufactured similar as WI pipes • 15,20,25,32,40,50,63,75,90,110,125,150, 200 mm inner dia Advantages: Light in weight, easy in transport, handling, cutting, threading, working, joining, and gives neat appearance, joined couplings or screwed socket joint. Disadvantages: Costly, corrosive and less durable than CI pipes Suitability: Inside plumbing in buildings but not used nowadays due to high cost.
  • 63.
    63 (e) Concrete (GI)pipes: • Made of cement concrete (precast or cast in site) Advantages: Withstand 150 m head of water, resist corrosion and life is above 75 years, maintenance cost is low, least thermal expansion, can be laid under water and resist normal traffic load Disadvantages: Precast type is heavy to handle and transport, concrete pipes can’t resist high pressure and difficult to repair, it may be affected by acids and alkali and salty waters, difficult to join and liable to leak due to porosity Suitability: Where water does not flow under pressure (i.e. sewerage system)
  • 64.
    64 (f) Asbestos cement(AC) pipes: • Made of mixture of cement and asbestos fibers Advantages: not affected by salt water and corrosive materials, smooth, light so easy in handling Disadvantages: Affected by alkali and acid and also brittle so costlier in transport. Suitability: Small size distribution pipes
  • 65.
    65 (g) Wooden pipes: •made of wood by making channels or boring at center and used in ancient times • not used in water supply nowadays (h) Vitrified clay Pipes: • made of vitrified clay so has smooth surface • not used in water supply nowadays (i) Lead and copper Pipes: • Copper pipe is made of copper and can resist corrosion even if water contains some acids and expensive so not used in water supply nowadays • Leads are soluble in water so lead pipe causes lead poisoning hence it is not used in water supply nowadays.
  • 66.
    66 (f) Plastic Pipes: •Made of Plastic and common in nowadays • it is corrosion resistant, light in weight and economical Advantages: Light, cheap, available in longer length, electrical insulation, corrosion free, life correspond to GI Disadvantages: Less resistant to hot water, may impart smell to water, can be easily cut. Suitability: All water sypply systems
  • 67.
    67 Types: 1. Low densitypolyethylene (LDPE) pipes: Used in electrical wiring 2. High density polyethylene (HDPE)pipes 3. Polyvinyl chloride (PVC) pipes: 4. Unplastisized Polyvinyl chloride (UPVC) pipes: 5. Poly Propylene Random (PPR) Pipes: Plastic Pipes
  • 68.
    68 LAYING OF PIPES 1.Preparationof detailed maps: 2.Locating proposed alignment of pipeline on the ground: 3.Location of pipes with respect to ground surface during laying 4.Excavation of trench: 5.Dewatering of trench: 6.Lowering the Pipes: 7.Joining pipes: 8.Testing of pipes: 9.Back filling and disinfection before first use:
  • 69.
  • 70.
  • 71.
  • 72.
  • 73.
  • 74.
  • 75.
    75 CHAPTER 8: VALVESAND FITTINGS (a) Sluice or gate or cutoff valve (b) Reflux or check or non-return valve (c) Safety or pressure relief valve (d) Air valve or air relief valve (e) Drain or scour or blow off valve : Ordinary sluice valve to remove silt deposit (f) Butterfly valve and globe valve Devices used to control the flow of water, regulate pressures, release air, prevent back flow etc
  • 76.
  • 77.
  • 78.
  • 79.
    79 FIRE HYDRANT:  Devicesused for tapping water from mains for the fire extinguishing, street washing, watering gardens, flushing sewer lines etc.  Provided at all road junctions & every 100 – 300 m apart.  For tapping water, the hose is connected to the hydrant and if necessary the engine is used to increase head.  It should be cheap, easily connectable & detachable to the hose pipe and able to give sufficient water. It may be of post type or flush type.
  • 80.
  • 81.
  • 82.
  • 83.
  • 84.
    84 CHAPTER 9: PLANNINGOF GRAVITY WATER SUPPLY • Need identification of scheme • After need identification, mass meeting is called, prioritize is done and then scheme acquisition form is filled up and submitted to VDC, DDC and divisional district water supply office • With feasibility study report the schemes are forwarded from divisional office thru regional office to department of water supply and sewerage (DWSS) • After obtaining scheme acquisition form list from all 75 districts , budget ceiling is prepared for forthcoming fiscal year by DWSS and forward to ministry of concern. • The ministry approves ceiling consulting with National planning commission then distributed to DWSS and district offices for implementation
  • 85.
    85 • After obtainingapproved budget ceiling, detailed survey is carried out. • Detail survey  horizontal and vertical control and  questionnaire • Analysis based on detail survey, the design, drawing, estimating and costing is done and final report is prepared. • Water Users Committee (WUS) is formed and trained in agreement with WUC or implementation agency • After agreement, construction is carried out and it is handover to the WUC. • WUC are responsible for regular maintenance.