Distribution System

Pipes : mains, sub mains, branches and Laterals
Valves : For controlling flow

Hydrants: For releasing water during fire breakouts

Meters : For measuring discharges

Pumps : For lifting water

Service reservoir : For storing the treated water & stabilizing pressures.

Importance : It involves 40 to 70% of the total cost of W.S. scheme. .

Recommendations:  Pressure for single storey buildings is 7 m for two storey buildings is 12 in of water for three storey buildings is 17m of water

The fire hydrant’s pressure should not be less than 1 Kg/sq. cm.

Minimum pipe size: 100 mm

Systems of Distribution:

1. Gravity System
2. Direct Pumping System
3. Combined System or Dual System.

Gravity System: Water is distributed by gravity only, to the consumers points. It is suitable for situations where the source of water is located at a sufficiently higher level than the town. This system is economical and reliable since no pumping is involved at any stage. It needs a lake or storage reservoir as a source of supply located at a sufficient higher level.

Direct Pumping System: Treated water is directly pumped into the distribution pipes by

means of high lift pumps without scoring anywhere.

• Pumps should be capable of being operated at variable speeds to meet the maximum and minimum demand and maintain sufficient residual pressures at various points of consumption. This system is not commonly preferred.
• Advantage is that during fire accidents, large quantities of water at high pressures can be pumped to put off the fire.

Combined or dual systems : “Pumping with storage system” or “Direct- indirect system”. In this system, the treated water is pumped at constant rate into an elevated reservoir as well as directly into distribution system.

, Thus it is a combination of gravity system and direct pumping system. This is most widely adopted system in water supply schemes for its obvious advantages such as Pumps can be operated with uniform speed at their rated capacities.

1. It is a reliable system as there is always some reserve water in elevated tanks to augment the supply during peak demands,
2. In case of lire accidents large quantities of water can be drawn
3. It is an economic and efficient system

Lay out of Distribution systems.:

• Dead end or tree system
• Grid iron system or Reticulation or interlaced system.
• Circle or Ring system
• Radial system

 Dead end system:

A supply main starting from the service reservoir is laid along the main road. The submains are connected to the main in both the  directions along the other roads. Submains divide into several branch lines. Service connections are taken form these branches to the individual houses.

Suitability: For old towns and cities with irregular and unplanned development

Advantages: Quite simple design ; Lesser number of cutoff valves; Easier expansions Short pipe lengths are required Cheap and economical 

Limitations: Considerable area gets affected during repairs.

• Water stagnation at dead ends leads to pollution
• Water rate of supply cannot be increased in case of fire breakouts.
• less successful in maintaining satisfactory pressures in the remote pans.

Grid iron system : Mains. submains and branches arc interconnected with each other. Main line runs through the centre of the area.

Suitability: Suitable for well planned cities.

Advantages:

• Since water reaches from different directions, sizes of pipes get reduced.
• Very small area gets affected in case of repairs.
• Due to free circulation, water cannot be polluted.
• More water can be diverted in case of fire breakout.

Disadvantages:

• More lengths of pipes and larger number of valves
• Costlier
• Design is difficult.

Ring system: Main pipe is laid peripherally.

• Laying of mains peripherally increase the pressure at farthest points.
• Suitable for towns and cities having well planned roads.
• Advantages and disadvantages arc same as Grid iron system.

Radial system: The area is divided into small distribution zones and in the center of each zone a distribution reservoir is provided Water from these reservoirs is supplied through radially laid distribution pipes running towards the periphery of the zone.

• Ensures high pressure and efficient water distribution.
• Suitable for cities with radial roads.

Design of Distribution System:

For head loss calculation, Hazen-Williams formula is more commonly used

Breakdown storage: It is the storage required to be provided in a distribution reservoir to take care of emergencies which may arise due to failure of pumps, failure of electric supply, etc. For this storage a lump sum provision of about 25 % of the total storage capacity of the distribution

reservoir is provided.

Fire storage : A provision of fire storage in a distribution reservoir is required to be made to provide water for fire fighting purposes.

• 1 to 4 lit/per/day for normal Indian conditions.
• Total capacity of D.R Balancing storage+ Break down Storage + Fire storage

APPURTENANCES IN DISTRIBUTION SYSTEM

1. Valves 
2. Manholes
3. Fire hydrants 
4. Water meters

Valves: Valves are provided in the pipelines to control the flow of water, to isolate and drain sections for test, inspection, cleaning and repairs to regulate pressures and to release or admit air.

• Sluice Valves or Gate Valves: used to regulate the flow of water through the pipelines.
• Butterfly valves : used to regulate stop the flow especially in large Size conduits.
• Globe Valve: To regulate flow.These valves are normally used in pipes of small diameter and as water taps.
• Check Valve: Also known as reflux valve or non return valve . A Check valve allows water to flow in one direction only and the flow in the reverse direction is automatically slopped by it. The reflux valve is invariably placed in a pumping main so that if the pump thus or slops, water is prevented from flowing hack to the pump and thus pumping equipment is saved from possible damage.
• Air Valve or Air-relief Valves: The air valve helps to admit air into the pipe when the pipe is being emptied or when negative or vacuum pressure is created in the pipe. Air valve operates automatically while allowing air to escape from or to enter a pipe. The air valves arc usually located at summits and also at changes in grade to sleeper slopes.
• Scour valve  or Blow-off Valves or Drain Valves: Provided for completely emptying or draining of the pipe for removing sand or silt deposited in the pipe and for inspection, repair, etc Located at dead ends and depressions or low points in the pipeline
• Pressure-relief Valves: Also called overflow towers arc provided to keep the pressure ¡n a pipeline below a predetermined value, and thus protect it against the possible Thus these valves are often placed at low points where the pressures are high. Further a pressure relief valve is usually provided on the upstream side of a sluice valve so that the pipe lying on the upstream side of the valve is relieved of water hammer pressure resulting from the sudden closure of the sluice valve.

Manholes: provided at suitable intervals along the pipeline for inspection and repairs. Usually spaced 300 to 600 m apart on large Pipelines.

Their most useful positions are at summits and downstream of main valves.

Fire hydrants: Hydrant is an outlet provided in a pipeline for tapping water many for the purpose of fire fighting. Also be used for withdrawing water for certain other purposes such a sprinkling on roads, flushing  streets, etc.

Generally fire hydrants are placed at all important road junctions and al intervals not exceeding about 300 m.

Water meters: Installed in pipelines to measure the quantity of water flowing through them.

Types: 

• Inferential type meters or velocity meters: Used for large pipes.
• Displacement type meters: Used for small pipes and domestic connections.

Location of leaks: For locating leaks in water supply pipes following methods may be used

• By direct observations
• By using sounding rods
• By plotting hydraulic grade line
• By using waste

— detecting meters(Deacon’s meter)

Sounding rods: A metal rod is inserted into the ground at the suspected portion. If there is a teak in the pipe the sound of the water escaping through the leak can be heard by placing the ear against the rod, or by means of an amplifying device such as aqua phone or sonoscope

Miscellaneous Water Treatment

• WATER SOFTENING: 

Removal of hardness from water is known as Water softning.

Removal of Temporary Hardness:

1. by boiling
2. by adding lime

Removal of permanent hardness:

1. Lime Soda Process
2. Zeolite Process
3. Demineralization Process (or) Deionization Process):

Lime Soda Process: Lime (Ca(OH2) and Sodium carbonate [Na2CO3] (or soda ash) are used to removal permanant hardness from water.

Quick lime CaO, or hydrated lime Ca(OH)2 can be used for water softening.

Lime Soda Water Softening plant consists of the following units:

1. Feeding and mixing devices
2. Settling tank or settling basin
3. Recarbonation plant.
4. Filters

Recarbonation plant: Carbon dioxide CO2 gas is diffused through the effluent so that the insoluble calcium carbonate and magnesium hydroxide combine with carbon dioxide to again foms the soluble bicarbonates of calcium and magnesium

Advantages of Lime-Soda Process:

1. Economical
2. pH value increases arid corrosion of the distribution system decreases
3. he process is suitable for turbid, chalybeate and acidic waters for which zeolite process cannot be used
4. quantity of coagulant will be required for coagulation.
5. removal of iron and manganese to some extent.
6. here is likelihood of killing of pathogenic bacteria in this process.
7. Better for excessively hard waters.

 Disadvantages of lime-soda Process:

1. A large quantity of sludge is formed  in this process which needs to be disposed off by some suitable method
2. In this process recarbonation is required by Lime soda process water of zero hardness cannot be produced.

Zeolite Process: 

• Zeolite is a complex compound of aluminium. silica and soda
• Hard water is passed through a bed of ion exchange material or ion commonly known as Zeolite
• Calcium and magnesium are removed from water as these are substituted b sodium by ion- exchange process
• By Zeolite process the hardness of water is reduced almost to zero.

Advantages of Zeolite process:

1. Sludge is not formed and there is no problem of sludge disposal.
2. Does not require any skilled supervision.
3. His possible to reduce hardness of  water to zero. This is useful for softening of water to be used for boilers and certain textile industries.

Disadvantage or zeolite process:

Cannot be adopted for highly turbid water

Demineralization Process or Deionization process: It is similar to zeolite process with the difference that in demineralization process the metallic ions viz,calcium magnesiurn. etc. are exchanged for hydrogen ions. The ion exchanger is prepared with carbonaceous material or resin. The effluent obtained in the demineralization process is free from minerals and it has a quality almost equal to that of distilled water used for industries

Removal of  Colour, Odour and taste:

1. Aeration
2. Treatment by activated carbon
3. Use of Copper sulphate.

Aeration: it is a process in which water is brought in intimate contact with atmospheric air to promote exchange of gases between water and atmospheric air.

1. Carbon dioxide, hydrogen Sulphide and other volatile substances imparting taste and odour to water are easily expelled
2. Iron and manganese present in water are oxidized to certain extent by aeration.

Treament by activated  carbon: Activated carbon is used to remove colour, taste mid odour from water. It is available  granular as well as powder form.

Activated carbon is used to remove organic contaminants from water by the process of adsorption.in

adsorption high surface area is the prime consideration.

Activated carbon can be applied for treatment of water in two ways

• As filter media
• As fine powder feed

Use of copper sulphate:

• removal of colour ,odour & taste from water

Iron and manganese: often occur together in groundwater but manganese usually occurs in much lower concentrations than iron. Both iron and manganese are readily apparent in drinking water supplies. Both impart a strong metallic taste to the water and both cause staining.

Fluoridation and Defluoridation:

Fluoridation: Water fluoridation is the controlled addition of fluoride to a public water supply to reduce tooth decay. Fluoridated water contains fluoride at a level that is effective for preventing cavities; this can occur naturally or by adding fluoride.

Defluoridation: is a treatment used to remove fluoride from drinking water. The process of this technique is to remove fluoride, which is a highly toxic chemical, to prevent health issues and dental issues that contains in humans. It is suppose to help save the environment so people can drink safe water

DESALINIZATION OR DESELINATION:

Distillation: is a method of separating mixtures based on differences in their volatiles in a boiling liquid mixture. Distillation is a unit operation, or a physical separation process, and not a chemical reaction. Commercially, distillation has a number of applications.

Reverse osmosis: a process by which a solvent passes through a porous membrane in the direction opposite to that for natural osmosis when subjected to a hydrostatic pressure greater than the osmotic pressure

Electrodialysis (ED): is used to transport salt ions from one solution through ion-exchange membranes to another solution under the influence of an applied electric potential difference. This is done in a configuration called an electrodialysis cell.

Freezing: Temperature of saline water is gradually lowered until ice crystals are formed. These are free of salt and can be separated. The ice crystals when melted gives fresh water.

Demineralization: Salts are removed from water through the use o)’ ion exchangers.

Solar evaporation: Solar energy is utilized to convert saline water to fresh Water.

Procedure to calculate Chemicals requirement in lime-soda process:

Method-I: Approximate Procedure

This procedure is used when hardness is given as CaCo3

Calculate lime requirement based on Total hardness :

• Lime as CaO required (mg/I) = TH x 56/100
• Soda required (mg/I) = NHC x 106/100

Disinfection

Disinfection : It is the process of killing pathogenic bacteria.

Methods:

Boiling of water:

• Most effective method of disinfection of water
• Cannot be used for huge quantities of public water supplies
• Cannot take care of the future possible contaminations 
• Used only for Domestic purposes in emergencies

Treatment with excess limes :

• Effectively kills the bacteria, but cannot safe guard the future pollution.
• Enough lime is added to water to raise its pH value to 9.5 or more, thereby most of the bacteria will be killed.
• Recarbonaiton is necessary. The process of removal of excess lime before it is supplied to public is known as Recarbonation

Ozone :

• Ozone is a more powerful disinfectant than chlorine.
• Ozone is more costly than chlorine.
• Does not provide residual protection against recontamination.
• Cannot be stored.
• Used for disinfection of water on a small scale such as for swimming pool waters.

Iodine and Bromine pills:

• Compared lo chlorine , iodine provides longer lasting protection against pathogens and reduced offensive tastes and odours.
• Used for water supply for army troops, private plants, swimming pools.
• Cannot be used for public water supply us it is costly.

Ultra violet rays :

• Very costly technique and is an effective method for the disinfection of water
• No residual effect is available for protection against recontamination.
• Adopted for water supply installations of private Buildings, Institutions, Treatinsmall quantities of water in hospitals, dispensaries for surgical use. Swimming pools

Potassium Permanganate:

• For disinfecting well water supplies are generally contaminated with amounts of bacteria.
• Can remove 100 % organisms causing 
• It also oxidizes organic matter

Silver or EIectro-Katadyn 

• Removes algae also and takes care of future pollution. It is costly.

Chlorination :

• Universally adopted for public waters supplies because ¡us capable of providing residual disinfecting effects for long periods. it satisfies all the requirements of an ideal disinfectant.
• It takes care of any possible future contamination.(i.e it prevents recontamination) only disadvantage is it imparts bad taste.
• The addition of chlorine does not produce any significant change in the pH
• value of the natural waters
• Chlorination is not effective if the water is alkaline.

Action of chlorine: When chlorine is added to water, the following reaction takes place:

Hypochlorous acid (HOCl) and the hypochlorite ions (OCI) accomplish disinfection of water Thus Chlorine reacts with water to produce hypo chlorous acid (HOCI) and hypochlorite (OCI) which are together known as “free available chlorine.” HOCI is 80 to 100 times more powerful than OCI.

The free Cl2 reacts with compounds such as ammonia, proteins, amino acids and phenol that may generally be present in water to form Chloromines and Chloro derivatives which are called “Combined Chlorine”. It possesses some disinfecting properties but less effective compared to free available chlorine .Some free chlorine also exists along with combined available chlorine.

Free chlorine is about 25 times more powerful than combined chlorine.

These compounds either in free or combined form of chlorine, interfere with enzymes in the bacteria forming toxic chloro compounds and thus destroying the bacteria.

Residual chlorine = Chlorine dosage - Chlorine Demand

Chloramines:

• The Monochloramines and Dichloramines have got disinfecting properties
• The Trichloramine has not negligibal disinfecting property
• The relative distribution of chloramines depends on pH value
• If pH<4.4, only trychloramine exist 
• For pH : 4.4 to 5.5 ,only dichloramine exist 
• For pH : 5.5 to 8.4 , both mono and dichloramine exist 
• If pH > 8.4,only monochloramine exist 

M = Destruction of chlorine residual by reducing compounds(Fe, Mn, H2S)

N = Formation of chloro-organic compounds and chloramines

O = Destruction of chloramines and chloro organic compounds

P = Formation of free chlorine and presence of chloro-organic compounds not destroyed.

When chlorine is added to water, some of it is consumed in killing bacteria and oxidizing organic matter to form its compounds (Chloramines) and the remaining chlorine is available as residual chlorine. This is indicated by line Q. The fall of line R indicates oxidation of chloro-organic compounds and chloramines. indicated by bad odour and taste in water. Any further increase in chlorine dose beyond point B will appear as residual chlorine only and this i shown by line S.

Factors affecting bactericidal efficiency of chlorine:

1. Turbidity: Turbidity decreases the efficiency of chlorine as disinfectant.
2. Metallic compounds presence: Iron and manganese if present in water, they reduce the effectiveness of chlorine.
3. Ammonia Compounds: Reduces the efficiency
4. pH Value of water: Increased pH value reduces the effectiveness of chlorine as bactericide.
5. Temperature of water: At lower temperature, the efficiency will be less and hence requirement of residual chlorine will be more.
6. Contact Time: The killing of bacteria increases with increase of contact period.Viruses are more resistant than bacteria and hence require longer time of contact and higher doses of Cl2

Dosage:

The dose of chlorine which leaves a residual chlorine of about 0.2 mg/litre at the end of 10 minutes contact period is selected which gives the optimum dose of chlorine for the given water sample.

• Normal dosage 0.3 to 1.1 mgI 1
• Residual Chlorine 0.. I to 0.2 mg /1
• Chlorine dose must be generally increased during rainy season.
• Cl2 dosage = Cl2 demand - Cl2 residual

 Various forms of Chlorine:

1. As bleaching power or hypo chlorite
2. As chloramines
3. As chlorine gas or liquid chlorine
4. As chlorine dioxide gas

Bleaching powder.

The bleaching powder contains about 30 to 35 percent of available chlorine. Therefore, it can not be used for large public water supplies. This chlorination is known as hypochlorination.

Chloramines: Chloramines are the compounds formed by the reactions between ammonia and chlorine .chloramines do not cause bad taste and odour. Residual effects lasts for longer duration.

Chloramines are much weaker disinfectants as compared to free chlorine.

Chlorine gas or liquid chlorine: Chlorine in gaseous or liquid form is now-a-days

universally adopted(liquid chlorine) disinfectant for public water supplies. It is a powerful disinfectant and may remain in water as residual for sufficient time

No sludge is formed in its application, as may be formed by using hypochlorites or chloramines.

Chlorine dioxide: It has an oxidizing capacity 2 1/2 times that of chlorine. Further it is effective in the removal of tastes and odours, but due to its high cost of production it is not economical

Types of Chlorination :

Plain chlorination: Only chlorine treatment and no other treatment.

Helps to remove bacteria and colour from water and for also controls the growth of Algae. It is used in case of emergencies. when full fledged treatment cannot be given. Also adopted for clean water.

Prechlorination : Chlorine is added before raw water enters sedimentaion tanks. It helps in reducing the quantity of coagulants and to improve coagulation. It reduces taste and odour of water;

• controls the growth of algae .It reduces the bacterial load on filters
• It prevents putrefaction of sludge in settling tanks.

Post chlorination : This is the standard form of chlorination in which chlorine is added to water as it leaves filters and before it enters distribution system. The residual chlorine present in water is useful for its protection against contamination in the distribution system.

Residual 0.1 to 0.2 mg/l.

Double or multiple chlorination: ft consists of pre-chlorination and post chlorination. Adopted when raw water is highly contaminated and contains large amount of bacterial life

Break point chlorination (or free residual chlorination):

Break point chlorination gives an idea of chlorine to be added to water so as to ensure the desired amount of residual chlorine..

Advantages (or other actions) of Chlorine as disinfectant:

• It will remove taste and odour.
• It will have adequate bactericidal effect
• It will leave a desired chlorine residual
• It will remove manganese and iron.
• It will complete the oxidation of ammonia and other compounds. Organic matter.

Super chlorination :The application of chlorine to water beyond the stage of break point is known as super-chlorination. It is most commonly added at the end of filtration. Adopted whenever there is breakout of water borne diseases.

When super - chlorination  is practiced. it becomes necessary to remove the excess chlorine by any suitable method of dechlorination before water is supplied to the consumers

Dechlorination : Process of removing excess chlorine by dechlorinating agents. This is to avoid chlorinous taste from water. Chemicals used for dechlorination are:: sulphur dioxide, Sodium thiosulphate, sodium bio sulphate. Activated carbon, potassium permagnate ammonia.

Testing of chlorine Residuals:

1. Orthotolodine test
2. D. P. D test (Diethyl-p-Phenylene -Diamine)
3. Chlorotex test
4. Strach-lodide test

• The orthotolidine test is most commonly used to determine the amount of residual chlorine in water.
• The Strach-iodide test is more precise than the orthotolidine test, particularly when residual chlorine is greater than I p.p.m

KINETICS OF DISINFECTION:

Chick’s Law: The rate of kill of organisms is proportional to the number of organisms

remaining in water ai any time ‘t’.

 Increase in temperature results in a more rapid kill

Nt = N0e-kt

cn t= constant

k = Disinfection rate constant

C= concentration of disinfectant

n =dilution coefficient

Coagulation

Sedimentation Aided with coagulation

• To remove very fine suspended particles and colloidal particles.
• Certain chemicals called “Coagulants" are mixed with water which form a gelatinous precipitate called “floc’ which attracts the fine suspended particles.

Commonly used coagulants

1. Alum: A12 (S04)3. 18 H2O (Aluminum Sulphate). Also called filter alum.
2. Copperas (Ferrous Sulphate + lime)
3. Chlorinated Coppers (Ferric Sulphate)
4. Sodium Sulphate.

•  Iron salts arc used more frequently for treating sewage and alum is used for treating water.
• Detention time: 2 to 4 hours
• Overflow rate : 1000 to 1250 lit/hr /m of plan area.


• 
   
  

Floc Chamber:

• After mixing alum to the water in the mixing basin, it is gently stirred by paddles in the floe chamber to build up the floc.
• Detention time: 15 to 40 min.
• Depth of floc  chamber is half the depth of settling chamber,

Flocculation : Slow mixing technique which promotes agglomeration of particles

Coagulation : Mixing of coagulants  +Flocculation

Dosage: It depends on the amount of turbidity present in water.

• Average dosage for normal water is 14 mg/I.
• Optimum alum dosage my be determined by Jar Test.
• Alum functions effectively only when pH value lies between 6.5 & 8.5
• Iron salts can be used over a wide range of pH values.

• Addition of alum to water imparts permanent hardness and CO2 evolved causes corrosion
• Presence of alkalinity is necessary for the functioning of coagulants. If raw water is not alkaline, lime or soda ash is added to make water alkaline.

Advantages of alum as coagulant:

1. Reduces taste and odour apart from turbidity
2. The floc is effective
3.  It is cheap

Disadvantages of alum as coagulant:

1. Difficult to dewater the sludge formed 
2. It imparts permanant hardness 
3. CO2 causes corrosion

Quality of water

Pure water: It is a chemical compound (H₂O).

Potable Water: Water which is fit for drinking.

Palatable water: Water which is aesthetically looking good. Wholesome Water: Chemically may not be pure but doesn’t contain anything harmful to human beings.

Polluted Water: it contains undesirable substances rendering it unfit for drinking and domestic use.

Contaminated Water : It. contains pathogenic bacteria and unfit for drinking.

Mineral water: It contains useful minerals viz. Calcium. Magnesium and iron in required proportion.

CHARACTERISTICS OF WATER:

PHYSICAL CHARACTERISTICS

Turbidity :

• It is caused by suspended materials such as clay, silt or some other finally divided organic and inorganic matter. Turbidity is also due to presence of bacteria, algae, protozoa, fungi. Expressed in ppm (or mg/I)
• Standard unit is that which is produced by 1 mg. of finally divided silica (Fullers earth) in 1 liter of distilled water.
• Measured on ‘Silica Scale”
• Permissible limit for potable water 5 to 10 ppm
• Measured by: Turbidity meters

1. Jackson Turbid meter: Used to measure high turbidity (>25 p pm) -    (JTU)
2. Baylis Turbidity meter: precisely record even low turbidity values( of the order of 0 to 2 ppm.) BTU
3. Nephelometer : Commonly used for turbidity of range of 0 to 1 ppm-(NTU & FTU)—Fortmazin potymer is standard reference suspension. 

Turbidity Is the measure of resistance to the passage of light through water.

Colour:

• It is Caused by dissolved organic matters from decaying vegetation or some inorganic coloured soils, growth of algae, metallic ions (Fe and Mn).
• Measured by comparing the colour of water sample with other standard glass tubes (Nesslar tubes)
• Measured by Platinum Cobalt Method. (Measured on Platinum Cobalt Scale.)
• Permissible limit; 5 to 20 ppm.
• Measured by Tintometer..

Toste & Odour:

• Due to dissolved organic matter or inorganic salts, dissolved gases etc.
• Threshold number is the standard unit for measuring. .
• Taste is expressed as FTN (Flavor Threshold Number)
• Odour is expressed as TON (Threshold Odour Number)
• TN = Dilution ratio.
• Dilution Ratio= (A+B)/A                                                                                         
• A =Vol. of raw water sample
• B = Vol. of distilled water used for dilution.
• Permissible Limit: I to 3.
• The odour changes with tcmperature.
• it is tested normally at 20° C to 25° C.
• Odour is measured by an apparatus called osmoscope.

Osmoscope

The Osmoscope is graduated with Po values from 0 to 5.

Po value of O indicates ‘no perceptible odour’

Po value of 5 indicates ‘extremely strong odour’

Temperature: 100 C is desirable.

Specific conductivity: To know the dissolved salt content. Determined by Dionic water tester ,

Impurities in water:

Suspended impurities : They cause turbidity. The concentration of suspended impurities is measured by turbidity. eg : silt, clay, bacteria, fungi, algae.

Colloidal Impurities : These are finely divided dispersion of solid particles, not visible to the naked eye. These impurities if associated with organic matter having bacteria becomes the. chief source of epidemic.

Dissolved Impurities : h includes organic compounds. inorganic salts and gases. The following are various dissolved impurities and their effects.

1. Salts : CaCl2 , MgC1 , CO3 ,  HCO3, They cause hardness and alkalinity in water.
2. Metals : iron causes red colour, Manganese causes brown colour
3. Lead and arsenic cause poisoning
4. Gases : Oxygen causes corrosion of metals

• Chlorine and ammonia cause bad taste and odour
• CO2 and Hydrogen sulphide cause acidity in water.

CEMICAL CHARACTERISTICS 

Total solid , suspended solids and dissolved solid:

• Total solids can be found by evaporating a sample of water and weighing the dry residue left
• Suspended solids can be found by filtering water sample through Whatman filter paper No.44
• Permissible TDS limit: 500 to 1000 ppm

PH value of water: It indicates hydrogen ion concentration in water

• PH = log1o (l/H+),
• If pH >7 it is alkaline: If pH < 7 it is acidic
• Alkalinity is caused bicarbonates (HCO3) of Ca and Mg and carbonates (CO3), hydroxides (OH) of Ca. Mg, K. Na..
• Acidity is caused by Mineral Acids, Free CO2 Sulphates of Fe & Aluminum.

Alkalinity Effects : Incrustation and sediment deposit in pipelines and difficult in chlorination .

 Acidity Effects : Tuberculation & Corrosion of pipe lines.

• Permissible limit: 6.6 to 8.5
• PH is measured by Potentiometer and Colorimetric method.

Hardness:

A CHARACTERISTICS  which prevents formation of Lather or foam with soap.

Effects of Hardness : Scaling of boilers, greater: soap consumption, corrosion and incrustation of pipe lines, food becomes tasteless etc.,

Types of Hardness :

1. Carbonate hardness (CH) 
2.  Non Carbonate  hardness (NCH) .

Temporary or carbonate hardness : Caused by HCO3, and CO3 of Ca & Mg.

• Can be removed to some extent by simple boiling or removed fully by addition of lime.
• Permanent or non Carbonate hardness Caused by SO4, Cl, NO3 of Ca & Mg.
• Can be removed by water softening methods such as Lime soda process, Demilitarization process and Zeolite Process
• Permissible limits: For boiler feed waters < 75 ppm.
• For drinking purpose, between 75&115 ppm 
• If Hardness is <75 ppm is called ‘Soft’
• If Hardness is >200 ppm is called ‘Hard’
• Measurement: Measured in terms of ppm or mg/lit of CaCO3
•  Measured by EDTA test (Ethlyene Diamine Tetraacetic Test). In the titration process, Ericrome Black Tea is used to show the end of the titration .
• After determining amount of Ca & Mg ions presents in water, by nitration process with Versante solution, Hardness is estimated as followers

• 

Combining weight  or equivalent weight =Molecular weight/ Valence

• Hardness is also expressed in degree of hardness
• One British degree of hardness(Clark’s Scale) =14.25 ppm of CaCo3
• One French degree of hardness =10 ppm of CaCo3
• One American degree of hardness =17.15 ppm of CaCo3

Alkalinity in mg/l as CaCo3  =

Total Alkanity =HCo3 mg /L X (50/61) + Co3 mg/L X (50/30)

•  Chloride content: Present in the form sodium chloride imparts salty taste.
• Permissible limit :250 mg/l.Presence of the high quantity indicates pollution from sewage and other human & industrial waste.
• Nitrogen content Indicates presence  of   Organic matter and the extent to Which it has undergo decomposition.

 Different forms :

1. Free Ammonia 
2. Albuminoid Nitrogen  (organic nitrogen)
3. Nitrites             
4. Nitrates.

 Free  Ammonia indicates presence of under composed  organic  matter and it represents  first stage  decomposition

Permissible limit: less than 0.15 ppm

Albuninoid Nitrogen: Indicates decomposition of organic matter has started,limit shall not exceed 0.3 mg/lit

1. Nitrites: Indicates presence of partly decomposed organic matter.                                             Permissible limit : Nil
2. Nitrates:Indicates fully oxidized organic matter.                                                                               Permissible limit : <45 ppm

• Excess causes the disease called "Methemoglobenima " (Blue baby disease)
• Total Kjeldahl Nitrogen (TKN)=Free ammonia + organic nitrogen

Metal &Chemical Substance:

 Iron & Manganese: Permissible limit * Iron  <0.3 ppm, Mn <0.05 ppm.

• Excess Iron & Mn cause dis colouration of clothes washed in such water and incrustation of water mains due to deposits.

Copper : Permissible limit — 1 to 3 mg/l

• Affects human lungs and other respiratory organs

Sulphate: Permissible <250 mg /l

• Causes laxative effect en human body and diarrhea < 0.3 ppm.

 Fluoride:

• fluoride < 1 ppm, cause formation of fever cavities in the teeth.
• fluoride  > 1.5 ppm causes Flourosis (mottling and discolouration of teeth)and deformation of bones.
• Permissible limit: between 1 ppm and 1.5 ppm.

Dissolved  gases:

1. H2S                               
2. C02
3. Dissolved oxygen         
4. Nitrogen

• H2S gives bad taste and odour.
• CO2 indicates biological activity and causes corrosion in pipe lines.

Dissolved oxygen (D.O) : To know  the extent of pollution of water.

• Determined by Winkler's method
• Since D.O is consumed by unstable organic matter, D.O less than its saturated level indicates presence of organic matter, therefore pollution.
•  For fresh river water saturation D.O at 20°C = 9.2 mg/I.

Permissible Limit : For potable water should be bet 5 to 10 ppm.

Nitrogen gas: Indicates presence of Organic matter.

 Biochemical oxygen Demand (B. O.D)

Permissible Limits : B.O.D. of safe Water= Nil . 

 MICROSCOPIC CHARACTERISTIC

• To study about the presence of Bacteria,Virus, Algae. Protozoa.
• bacteria is single celled organisms

1 Bacteria (I to 4 microns in size) :

Classification

1. Non pathogenic bacteria: They are harmless; e.g Escherichia coliform or E-coil
2. Pathogenic bacteria: They are harmful & causes water borne disease.

• Detection of “E-Coil”Indicates the probable presence of 'pathogens’
• E — Coil bacteria is used as indicator organism

Classifaction based on shape:.

• Cocci — Sphere shaped bacteria
• Bacilli — Rod shaped bacteria
• Spirilla — twisted rod shaped bacteria

Classification based on living conditions;

1. Aerobic bacteria: It survives in the presence of Oxygen.

2. Anaerobic bacteria: It survives in the absence of Oxygen.

3. Facultative bacteria: Survives with or without Oxygen.

To detect and measure coliform bacteria, the following tests are available.

• 1 .Total count or agar plate count fest
• 2. E—coil test :
• 3. Membrane filter technique

Total count test : In this test bacteria are cultivated on specially prepared medium of agar for different dilutions of sample of water with distilled water. The diluted sample is placed in an incubator for specified time at specified temperature. The bacteria colonies so formed are counted and results are computed  per 100 ml

• For drinking water, the total count shall not be more than 1 per 100 ml

E — coil test : Divided into

1) Presumptive test

2) Confirmed lest

3) Completed test

In this test gas produce after incubation, it is reported as positive and further tests are to be followed to confirm E-coil. If no gas is produced it is presumed that there is no bacteria and the test is treated as negative

Membrane filter technique: Recent method. Sample is filtered through sterile membrane

with pore size 5 to 10 mu. The bacteria is retained on the membrane. The membrane is put in contact with suitable nutrient. [ M — Endo’s medium ] which inhibits growth of bacteria other than coil form group. Then 

placed in incubator at prescribed conditions and the visible colonies are counted with microscope.

MPN (Most Probable Number): It is the bacterial density which is most likely to be present in water. It is used to report the amount of bacteria present. 

• To determine MPN, confirmed or completed tests results are required.
• Permissible limits : - MPN should be Nil.

Micro Organic Plants: Thesc are tiny plants. eg: Algae, plankton etc 

• They cause bad taste & odour and interface with smooth working of filter.
• To control algae, copper sulphate chemical is mixed in water

 Protozoa: These are unicellular animals.

Water borne diseases: Diseases which spread primarily through contaminated, water and

important of these water borne diseases are:

Bacterial infections:

• Typhoid fever 
• Diarrhea
• Cholera 
• Bacillary dysentery

Viral infections:

• Infection Hepatitis 
• Poliomyelitis.
• Gastroenteritis

Protozoal infections:

• Amoebic dysentery.