Water Hygiene and Hygiene Water Hygiene and Hygiene of water-supply of of water-supply of inhabited places. inhabited places.

The lectureThe lecture

Author: Lototska O.V.Author: Lototska O.V.

Its main functions are that it:Its main functions are that it: Replaces loss of fluids from Replaces loss of fluids from

tissues.tissues. Maintains the fluidity of blood and Maintains the fluidity of blood and

lymph.lymph. Helps elimination of waste material Helps elimination of waste material

of the body.of the body. Acts as a vehicle for dissolved Acts as a vehicle for dissolved

food.food. Helps in the secretion of digestive Helps in the secretion of digestive

juices.juices. Regulates body temperature and Regulates body temperature and

acts as a distributor of body heat.acts as a distributor of body heat.

Water constitutes nearly two-thirds of the total weight Water constitutes nearly two-thirds of the total weight of the body, 79 % of blood, 80 % of brain and muscles of the body, 79 % of blood, 80 % of brain and muscles and 10 % even of bonesand 10 % even of bones

WatersWaters,, used for drink and everyday needs, used for drink and everyday needs, must correspond to the demands: must correspond to the demands:

good organoleptic properties: refreshing temperature, transparence, colorless, no smell and no taste . harmlessness of its chemical composition the absence of pathogenic microorganismssafety in the radiological attitude

The population should be provided not only The population should be provided not only with enough of water, but also with with enough of water, but also with qualitative water. Water should not cause qualitative water. Water should not cause any pathological change in the organism, any pathological change in the organism, should not cause of spread of infectious should not cause of spread of infectious diseases, and also not to cause unpleasant diseases, and also not to cause unpleasant sensations.sensations.

The pollution of water sources represents the The pollution of water sources represents the important ecological problem. Depending on important ecological problem. Depending on type of pollution there are: type of pollution there are:

chemical, chemical, physical (radioactive substances, hot water), physical (radioactive substances, hot water), bacterial, virus and biological. bacterial, virus and biological. Industrial wastewater is characterized by Industrial wastewater is characterized by

considerable quantity of components.considerable quantity of components.

Major categories of water pollutantMajor categories of water pollutant 1. Infections agents - Bacteria, viruses 2. Organic chemical - Pesticides, plastics,

detergents, oil, and gasoline 3. Inorganic chemicals - Acids, caustics, salts,

metals 4. Radioactive materials - Uranium, thorium,

cesium, iodine, radon

Sources of waterSources of water

Impure water may be purified by either of the following methods:

A. NaturalA. Natural (a) Pounding or Storage.(a) Pounding or Storage. (b) Oxidation and Settlement.(b) Oxidation and Settlement.

B. ArtificialB. Artificial I. PhysicalI. Physical Distillation.Distillation. Boiling.Boiling.II. ChemicalII. Chemical Precipitation.Precipitation. Disinfection or Sterilization.Disinfection or Sterilization.III. FiltrationIII. Filtration "Biological" or "Slow Sand" Filtration."Biological" or "Slow Sand" Filtration. "Rapid Sand" or "Mechanical" Filtration."Rapid Sand" or "Mechanical" Filtration. Domestic Filtration.Domestic Filtration.

PURIFICATION OF WATERPURIFICATION OF WATERPurification of water is of great Purification of water is of great

importance in community medicine. It importance in community medicine. It may be considered under two headings.may be considered under two headings.

Purification of water on large scalePurification of water on large scale Purification of water on small scalePurification of water on small scale

Three main steps in purification Three main steps in purification of water on large scale:of water on large scale:

Storage, Filtration, ChlorinationStorage, Filtration, Chlorination

1. Storage:1. Storage:Water is drawn out from source and Water is drawn out from source and

impounded in natural or artificial reservoirs. impounded in natural or artificial reservoirs. Storage provides a reserve of water from which Storage provides a reserve of water from which further pollution is excluded.further pollution is excluded.

AdvantagesAdvantages Physical Physical — About 90% of suspended impurities — About 90% of suspended impurities

settle down in 24 hours by gravity.settle down in 24 hours by gravity. Chemical Chemical — The aerobic bacteria oxidize the — The aerobic bacteria oxidize the

organic matter present in water with the aid of organic matter present in water with the aid of dissolved oxygen. As a result the content of free dissolved oxygen. As a result the content of free ammonia is reduced and a rise in nitrates occur.ammonia is reduced and a rise in nitrates occur.

Biological Biological — 90 % of total bacterial count drops in — 90 % of total bacterial count drops in first 5 - 7 days.first 5 - 7 days.

A complete system of water supply

Coagulation:  Alum and other chemicals are added to water to form tiny sticky particles called "floc" which attract the dirt particles.

How is water treated?

Sedimentation:  The heavy particles (floc) settle to the bottom

and clear water moves to filtration.

 

Filtration:  The water passes through filters that help to remove smaller particles.

      Disinfection:  A small amount of chlorine is added to kill any bacteria or microorganisms that may be in the water.

Storage:  Water is placed in a closed tank or reservoir where it flows through pipes to homes and businesses in the community.  

2. Filtration2. FiltrationFiltration is important because 98 – Filtration is important because 98 –

99 % of bacteria are removed by filtration, 99 % of bacteria are removed by filtration, a part from other impurities. Two types of a part from other impurities. Two types of filters are in use, they are:filters are in use, they are:

a.a. Slow sand filters (biological Slow sand filters (biological filters)filters)

b.b. Rapid sand filters (Mechanical Rapid sand filters (Mechanical filters)filters)

Slow sand filterSlow sand filter

Supernatant (raw) water:

Sand bed

Vital Layer

Under - drainage system

Filter control valves:Filter control valves:

The filter is equipped with certain valves and devices The filter is equipped with certain valves and devices which are incorporated in the outlet pipe system which are incorporated in the outlet pipe system maintaining a steady rate of filtration.maintaining a steady rate of filtration.

When the vital layer becomes dense and resistance to When the vital layer becomes dense and resistance to the passage of water is increased the supernatant water is the passage of water is increased the supernatant water is drained off Sand bed is cleaned by scrapping of the top drained off Sand bed is cleaned by scrapping of the top portion of the sand layer to a depth of 1 - 2 cms. Scrapping is portion of the sand layer to a depth of 1 - 2 cms. Scrapping is done 20 - 30 times. done 20 - 30 times.

The process is known as The process is known as Filter CleaningFilter Cleaning..

b. Rapid Sand Filterb. Rapid Sand FilterRapid sand filters are of two types, Rapid sand filters are of two types,

the gravity type and the pressure type. the gravity type and the pressure type. Both the types are in use. The following Both the types are in use. The following steps are involved in the purification of steps are involved in the purification of water by rapid sand filters.water by rapid sand filters.

i. Coagulation:i. Coagulation:

ii. Rapid mixing:ii. Rapid mixing:

iii. Flocculation:iii. Flocculation:

iv. Sedimentation:iv. Sedimentation:

v. Filtration:v. Filtration:

Filter Beds:Filter Beds:

Back - Washing:Back - Washing:Rapid sand filters need frequent washing daily or Rapid sand filters need frequent washing daily or

weekly. Washing is accomplished by reversing the flow of weekly. Washing is accomplished by reversing the flow of water through the sand bed, which is called "back-washing". water through the sand bed, which is called "back-washing". Back - washing dislodges the impurities and cleans up the Back - washing dislodges the impurities and cleans up the sand bed.sand bed.

Comparison of Rapid & Slow Sand Filters.

Slow Sand Filter Rapid Sand Filter

Space Occupies large space Occupies very little area

Rate of filtration 0.1 -0.4m3/m2/h 5- 15m3/m2/h

Effective size of sand 0.15-0.35 mm 0.6 - 2.0 mm

Preliminary treatment

Plain sedimentation Chemical coagulation

Washing By Scraping the sand bed

By back-washing

Operations Less skilled Highly skilled

Removal of turbidity Good Good

Removal of colour fair Good

Removal of bacteria 99.9-99.99 per cent 98 - 99 per cent

Advantages of Slow Sand Filter

Advantages of Rapid Sand filter

1. Simple to construct and operate

1. It deals with raw water directly. No. preliminary storage is needed

2. Cost of construction is cheaper

2. Occupies less space.

3. Physical, Biological and Chemical quality ' of filtered water is very high

3. Filtration rate is high.

4. Washing of filter is easy

5. More flexibility in operation.

CHLORINATIONCHLORINATIONChlorination is the process in which chlorine is Chlorination is the process in which chlorine is

added to water for purification. Chlorination-is more added to water for purification. Chlorination-is more effective when pH of water is around 7.effective when pH of water is around 7.

Effects of Chlorine:Effects of Chlorine:

a.a. Chlorine kills pathogenic bacteria, it has no effect on Chlorine kills pathogenic bacteria, it has no effect on spores and certain viruses.spores and certain viruses.

b.b. It has germicidal effects.It has germicidal effects.

c.c. It oxidizes iron, manganese and Hydrogen sulphide It oxidizes iron, manganese and Hydrogen sulphide

d.d. If destroys some taste and odour producing If destroys some taste and odour producing constituents.constituents.

e. e. It controls algae and slim organismsIt controls algae and slim organisms

f.f. It aids coagulation It aids coagulation

Action of ChlorineAction of Chlorine

When Chlorine is added to water, there is When Chlorine is added to water, there is formation of hypochlorous and hydrochloric formation of hypochlorous and hydrochloric acid. The hydrochloric acid is neutralised by acid. The hydrochloric acid is neutralised by alkalinity of the water. The hypochlorous acid alkalinity of the water. The hypochlorous acid ionizes to form hydrogen ions and hypochlorite ionizes to form hydrogen ions and hypochlorite ions as follows.ions as follows.

HH22O + CIO + CI22 ► HCI--+HOCI► HCI--+HOCIHOCI HOCI ► H++OCI“► H++OCI“

The disinfecting action of-chlorine is mainly due The disinfecting action of-chlorine is mainly due to hypochlorous acid and to a small extent due to hypochlorous acid and to a small extent due to hypochloriteon.to hypochloriteon.

Principles of Chlorination

a. First, water should be clear and free First, water should be clear and free from turbidity.from turbidity.b.b. Chlorine demand of water should be Chlorine demand of water should be estimated.estimated.c.c. At least one hour is essential as a At least one hour is essential as a contact period of free residual chlorine for contact period of free residual chlorine for killing bacterial and viruses.killing bacterial and viruses.d.d. Minimum recommended concentration Minimum recommended concentration of free chlorine is 0.5 mg/L for one hour.of free chlorine is 0.5 mg/L for one hour.e.e. The sum of the chlorine demand of the The sum of the chlorine demand of the specific water plus the free residual chlorine specific water plus the free residual chlorine of 0.5 mg/l constitutes the correct dose of of 0.5 mg/l constitutes the correct dose of chlorine to be applied.chlorine to be applied.

Methods of ChlorinationMethods of Chlorination

a.a. By means of chlorine gasBy means of chlorine gasIt is of first choice because it is cheap, quick It is of first choice because it is cheap, quick in action, efficient and easy to apply. in action, efficient and easy to apply. Chlorinating equipment is required to apply Chlorinating equipment is required to apply chlorine gas to water as chlorine gas is irritant chlorine gas to water as chlorine gas is irritant to eyes.to eyes.

b.b. By means of Chloramine:By means of Chloramine:Chloramines are loose compounds of chlorine Chloramines are loose compounds of chlorine and ammonia. They have slower action than and ammonia. They have slower action than chlorine. They give more persistent type of chlorine. They give more persistent type of residual chlorine. They have a less tendency residual chlorine. They have a less tendency to produce chlorinous taste.to produce chlorinous taste.

Chlorine Demand It is the difference between the amount of chlorine added to the water and the amount of residual chlorine remaining at the end of a specific period of contact (1 hour) at a given temperature and pH of water.

Residual Chlorine: Amount of untreated chlorine, remaining in the water after some time as an effective disinfecting agent i.e. 0.3 – 0.5 mg/liter Break point chlorination:The point at which the chlorine demand of water is met and if further chlorine is added free chlorine begin to appear in water Super Chlorination:It is addition of large doses of chlorine to the water and removal of excess of chlorine after disinfection.

Agents alternative to ChlorinationAgents alternative to Chlorination a.a. OzonationOzonation b.b. U.V. radiationU.V. radiation

The ozonization of waterThe ozonization of water   Ozone has been used in water treatment since 1903. It Ozone has been used in water treatment since 1903. It

is more effective against bacteria and viruses than chlorine and adds is more effective against bacteria and viruses than chlorine and adds no chemicals to the water. Ozone cannot be stored and requires an on-no chemicals to the water. Ozone cannot be stored and requires an on-site ozone generator. In general, ozonation equipment and operating site ozone generator. In general, ozonation equipment and operating costs are higher than other treatment procedures.costs are higher than other treatment procedures.

Ozone Ozone contains three oxygen atomscontains three oxygen atoms. It is destroyed in water, . It is destroyed in water, forming atomic oxygen: O3 → O2 → O. ozonization is one of the best forming atomic oxygen: O3 → O2 → O. ozonization is one of the best methods of disinfection: water is well disinfected, organic admixtures methods of disinfection: water is well disinfected, organic admixtures become destroyed, organoleptic features are improved. Water become destroyed, organoleptic features are improved. Water becomes blue and it is equated with spring water.becomes blue and it is equated with spring water.

Ozone dose is 0,5 - 6 mg/l. Sometimes, higher doses are Ozone dose is 0,5 - 6 mg/l. Sometimes, higher doses are necessary for the lighting of water and improving other organoleptic necessary for the lighting of water and improving other organoleptic features. The time of disinfection is 3-5 min. The remaining ozone features. The time of disinfection is 3-5 min. The remaining ozone should make up 0,1 – 0,3 mg/l. The concentration of the remaining should make up 0,1 – 0,3 mg/l. The concentration of the remaining ozone 0.4 mg/l provides the reliable inactivation of 99 % viruses for 5 ozone 0.4 mg/l provides the reliable inactivation of 99 % viruses for 5 min.min.

Asaka Water Purification Plant

                                                                    

 Advanced Water Purification System

                                                                      

Ultraviolet LightUltraviolet Light                 Ultraviolet irradiation will kill bacteria by creating Ultraviolet irradiation will kill bacteria by creating photochemical changes in its DNA. No chemicals are photochemical changes in its DNA. No chemicals are added to the water by this process. Most ultraviolet water added to the water by this process. Most ultraviolet water treatment units consist of one or more ultraviolet lamps treatment units consist of one or more ultraviolet lamps usually enclosed in a quartz sleeve, around which the usually enclosed in a quartz sleeve, around which the water flows. The UV lamps are similar to fluorescent water flows. The UV lamps are similar to fluorescent lamps and the quartz sleeve surrounding each lamp lamps and the quartz sleeve surrounding each lamp protects the lamp from the cooling action of water. The protects the lamp from the cooling action of water. The killing effect of the lamp is reduced when the lamp killing effect of the lamp is reduced when the lamp temperature is lowered. Ground water is usually a temperature is lowered. Ground water is usually a constant temperature year round and so it is possible to constant temperature year round and so it is possible to set a flow rate that will not lead to excess cooling. set a flow rate that will not lead to excess cooling.                 The effectiveness of UV irradiation depends on the The effectiveness of UV irradiation depends on the intensity of the light, depth of exposure and contact time. intensity of the light, depth of exposure and contact time. Water passes in a relatively thin layer around the lamp; Water passes in a relatively thin layer around the lamp; therefore, water flow must be regulated to ensure that all therefore, water flow must be regulated to ensure that all organisms receive adequate exposure. If the water is at organisms receive adequate exposure. If the water is at all turbid, or if it contains traces of iron, the effectiveness all turbid, or if it contains traces of iron, the effectiveness of UV is greatly reduced. In such cases, the water needs of UV is greatly reduced. In such cases, the water needs to be filtered before it reaches the UV system. to be filtered before it reaches the UV system.        

The maximal bactericidal effect is achieved by The maximal bactericidal effect is achieved by the waves 250-260 nm, which pass even through the the waves 250-260 nm, which pass even through the 25 cm layer of transparent and decolorized water.25 cm layer of transparent and decolorized water.

The disinfection proceeds very quickly: The disinfection proceeds very quickly: vegetative forms of microorganisms die in 1-2 min. vegetative forms of microorganisms die in 1-2 min. The turbidity, colour and iron salts decelerate the The turbidity, colour and iron salts decelerate the disinfection, decreasing the transparence of water. disinfection, decreasing the transparence of water. Consequently, it is necessary to light and decolorize Consequently, it is necessary to light and decolorize water beforewater before the disinfection.the disinfection.

There are some advantages of UV-There are some advantages of UV-irradiation over the chlorination:irradiation over the chlorination:

bactericidal rays don't denaturate the water and bactericidal rays don't denaturate the water and don't change its organoleptic features, don't change its organoleptic features,

they have wider biological action.they have wider biological action. Their bactericidal action is spread over the spores, Their bactericidal action is spread over the spores,

viruses and worm eggs, resistant to chlorine. viruses and worm eggs, resistant to chlorine.

Many investigators consider this method the Many investigators consider this method the best for the disinfection.best for the disinfection.

RIFICATION OF WATER ON SMALL SCALERIFICATION OF WATER ON SMALL SCALE•House hold purification of waterHouse hold purification of water•Disinfection of wellsDisinfection of wells

• HOUSE HOLD PURIFICATIONHOUSE HOLD PURIFICATIONa.a. By Boiling:By Boiling:Water should be boiled for 5 -10 minutes.Water should be boiled for 5 -10 minutes.It kills all bacteria, spores, cysts & ova.It kills all bacteria, spores, cysts & ova.It removes temporary hardnessIt removes temporary hardnessTaste is altered but is harmlessTaste is altered but is harmless

b.b. Chemical disinfectionChemical disinfectioni) Bleaching Powder (CaOCIi) Bleaching Powder (CaOCI22))Bleaching powder is a white amorphous powder.Bleaching powder is a white amorphous powder.Produced by action of chlorine on slaked lime.Produced by action of chlorine on slaked lime.When freshly made contains 33 % of available chlorine.When freshly made contains 33 % of available chlorine.It must be stored at dark, cool, dry place in a closed It must be stored at dark, cool, dry place in a closed container that is resistant to corrosion.container that is resistant to corrosion.In practise one cup (250 g) of laundry bleach is mixed In practise one cup (250 g) of laundry bleach is mixed with three cups (750 ml) of water to make a litre. Three with three cups (750 ml) of water to make a litre. Three drops of this solution are added to 1 litre water for drops of this solution are added to 1 litre water for disinfection. Contact period is 30 minutes to 60 minutes. disinfection. Contact period is 30 minutes to 60 minutes.

ii.) Chlorine SolutionChlorine solution may be prepared from bleaching powder.* If 4 kg of bleaching powder with 25 % available chlorine is mixed with 20 litres of water, it will give a 5% solution of chlorine.* This solution should be kept in dark, cool and dry place in closed container

v. Potassium Permanganate.It is a powerful oxidizing agent but not recommended as it alters colours, smell and taste of water.

iii. Chlorine tabletsAvailable under different trade name e.g. HalazoneOne tablet of 0.5 g is sufficient to disinfect 20 litres of water. Used in camps and during travel.

iv. Iodine:Two drops of 2 % ethanol solution of iodine is used. A contact period of 20 - 30 minute is sufficient for 1 litre water.

DUAL CHLORINE TABLET CHAMBER UNIT — CAN HOLD UP TO 50 TABLETS

The new filtration system uses centrifugal force to spin the untreated water above the filter media (sand). This helps remove suspended solids that accumulate on the inside walls of the tank

C. By Filtration Water can be filtered and is purified. Different filters are.

DISINFECTION OF DISINFECTION OF WELLWELL

Wells are main source Wells are main source of water in rural area. of water in rural area. The most effective The most effective and cheapest method and cheapest method of disinfecting wells of disinfecting wells is by bleaching is by bleaching powder. Disinfection powder. Disinfection of well is required in of well is required in normal days and normal days and during epidemics.during epidemics.

Steps:Steps:

1.1. Find volume of water in well.Find volume of water in well.Measure depth of water column — (h) Measure depth of water column — (h) metresmetresMeasure the diameter of well— (d) Measure the diameter of well— (d) metresmetresSubstitute (h) & (d) in:Substitute (h) & (d) in:

Volume (litres) = Volume (litres) = π x dπ x d22 x h x 1000 x h x 1000 π = 3.14 π = 3.14 44

One cubic metre - 1,000 litres of waterOne cubic metre - 1,000 litres of water

2.2. Find amount of bleaching Find amount of bleaching powder requiredpowder required

Measures by Horrock's apparatus.Measures by Horrock's apparatus.Roughly 2.5 gm of good quality Roughly 2.5 gm of good quality

bleaching powder would be required bleaching powder would be required to disinfect 1,000 litres of water.to disinfect 1,000 litres of water.

3. Dissolve bleaching powder in water3. Dissolve bleaching powder in waterThe calculated amount of bleaching powder is placed in a The calculated amount of bleaching powder is placed in a

bucket (not more than 100 g in one bucket) and made into a thin bucket (not more than 100 g in one bucket) and made into a thin paste. More water added till bucket is 3/4 full. The contents are paste. More water added till bucket is 3/4 full. The contents are stirred and allowed to stand for 5 - 10 minutes. When lime settles stirred and allowed to stand for 5 - 10 minutes. When lime settles down, the supernatant solution which is chlorine solution is down, the supernatant solution which is chlorine solution is transferred to another bucket.transferred to another bucket.

4. Delivery of Chlorine solution into the well.4. Delivery of Chlorine solution into the well.The bucket containing the supernatant chlorine solution is The bucket containing the supernatant chlorine solution is

lowered some distance below surface water. The well water is lowered some distance below surface water. The well water is agitated by moving the bucket violently both vertically and agitated by moving the bucket violently both vertically and laterally. Note: The precipitate or lime is never entered in well laterally. Note: The precipitate or lime is never entered in well because it increases the hardness of water.because it increases the hardness of water.

5. Contact period -5. Contact period - 1 hour contact period is required. 1 hour contact period is required.6. Ortho-Tolidine test:6. Ortho-Tolidine test: It is done to list for residual chlorine at the It is done to list for residual chlorine at the

end of one hour. If "free" residual chlorine level is less than 0.5 end of one hour. If "free" residual chlorine level is less than 0.5 mg/ litre, then procedure should be repeated, before water is mg/ litre, then procedure should be repeated, before water is drawn.drawn.

EXPRESS METHODS OF WATER QUALITY IMPROVINGEXPRESS METHODS OF WATER QUALITY IMPROVING Deodorization Deodorization - - elimination of smack and odour of water by elimination of smack and odour of water by

aeration, usage of oxidants (ozonization, dioxide of chlorine, large aeration, usage of oxidants (ozonization, dioxide of chlorine, large doses of chlorine, potassium permanganate), filtrating through a doses of chlorine, potassium permanganate), filtrating through a layer of absorbent coal, by introduction in water to sedimentation layer of absorbent coal, by introduction in water to sedimentation of absorbent coal.of absorbent coal.

Deironation Deironation is carried out by spraying water with the purpose of is carried out by spraying water with the purpose of aeration in graduation towers. Thus, bivalent iron is oxydated in aeration in graduation towers. Thus, bivalent iron is oxydated in ferric hydroxide, which sediments in settling tank, or delays on ferric hydroxide, which sediments in settling tank, or delays on the filter. the filter.

Softening.Softening. By an aged method of water softening is soda By an aged method of water softening is soda calcareous, at which calcium and magnesium settle in a settling calcareous, at which calcium and magnesium settle in a settling tank as unsolvable salts. Today is used filtrating water through tank as unsolvable salts. Today is used filtrating water through filters, which are completed by ion exchangers. Ion exchangers filters, which are completed by ion exchangers. Ion exchangers are firm, unsolvable, acinose stuffs, which have property to are firm, unsolvable, acinose stuffs, which have property to exchange their ions on ions of salts, which are solved in water.exchange their ions on ions of salts, which are solved in water.

Removal of hardnessRemoval of hardnessI.Temporary HardnessI.Temporary Hardness

a.a. BoilingBoilingb.b. Addition of limeAddition of limec.c. Addition of sodium carbonateAddition of sodium carbonated. Permutit processd. Permutit process

II. Permanent HardnessII. Permanent Hardnessa.a. Addition of sodium carbonateAddition of sodium carbonateb.b. Permutit process/ Base exchange process.Permutit process/ Base exchange process.

Boiling:Boiling:It removes temporary hardness by expelling It removes temporary hardness by expelling

carbon dioxide and precipitating the insoluble calcium carbon dioxide and precipitating the insoluble calcium carbonate. carbonate. Ca (HCO3)Ca (HCO3)22→ CaCO→ CaCO33 + CO + CO22 + H + H22OO

Addition of Lime:Addition of Lime:It removes temporary hardness. Lime absorbs It removes temporary hardness. Lime absorbs

carbondioxide and precipitates the insoluble calcium carbondioxide and precipitates the insoluble calcium carbonate.carbonate.Ca (OH)Ca (OH)22 + Ca (HCO + Ca (HCO33))22 →2 CaCO →2 CaCO33 + 2H + 2H22OO

Household water softeners typically use a different process, known as ion exchange.

Ion-exchange devices consist of a bed of plastic (polymer) beads covalently bound to anion groups, such as -COO-. The negative charge of these anions is balanced by Na+ cations attached to them. When water containing Ca2+ and Mg2+ is passed through the ion exchanger, the Ca2+ and Mg2+ ions are more attracted to the anion groups than the Na+ ions. Hence, they replace the Na+ ions on the beads, and so the Na+ ions (which do not form scale) go into the water in their

place.

Addition of Sodium Carbonate,Addition of Sodium Carbonate,It removes both temporary and permanent hardness.It removes both temporary and permanent hardness.

Na2CO3 + Ca (HCO3)2Na2CO3 + Ca (HCO3)2 → 2NaHCO3 + CaCOs→ 2NaHCO3 + CaCOsNa2CO3 + CaSO4 →Na2CO3 + CaSO4 → Na2SO4 + CaCO3Na2SO4 + CaCO3

Base Exchange MethodBase Exchange MethodIn this method sodium permutit is used, which is In this method sodium permutit is used, which is

a combination complex of Na, Al and Si (Naa combination complex of Na, Al and Si (Na22 Al Al22 SiSi22OHOH22O)O)Sodium permutit has property of exchanging the Sodium permutit has property of exchanging the sodium cation for Ca++ and Mg++ ions in water.sodium cation for Ca++ and Mg++ ions in water.NaNa22 Al Si Al Si22O + HO + H22O = Mg++/Ca++O = Mg++/Ca++

When hard water passed, sodium permutit When hard water passed, sodium permutit exchanges Mg/ Ca and is converted into calcium and exchanges Mg/ Ca and is converted into calcium and magnesium permutit.magnesium permutit.

With time permutit loses effectiveness, it is With time permutit loses effectiveness, it is regenerated by adding conc. sol of NaCI.regenerated by adding conc. sol of NaCI.* * By this process hardness of water is removed to By this process hardness of water is removed to zero. As zero hardness is corrosive, therefore a part of zero. As zero hardness is corrosive, therefore a part of raw water is mixed with softened water.raw water is mixed with softened water.

Desalting Desalting - - the sequential filtrating of water through the sequential filtrating of water through kationite, and then through anion exchanger permits to kationite, and then through anion exchanger permits to liberate it from solvable salts and consequently use with the liberate it from solvable salts and consequently use with the purpose of desalting. For desalting water on water pipes, sea purpose of desalting. For desalting water on water pipes, sea courts thermal method is used which bases on evaporation of courts thermal method is used which bases on evaporation of water with the following condensation of steams. Also is used water with the following condensation of steams. Also is used electro dialysis with usage of selective diaphragms, freezing electro dialysis with usage of selective diaphragms, freezing and other methods.and other methods.DecontaminationDecontamination - - at coagulation, settling and filtrating of at coagulation, settling and filtrating of water on waterpipes contents of radioactive substances in it is water on waterpipes contents of radioactive substances in it is reduced only on 70-80%. For more penetrating reduced only on 70-80%. For more penetrating decontamination water is filtrated through ionic exchanger of decontamination water is filtrated through ionic exchanger of resin.resin.Fluoridation of waterFluoridation of water - - synthetic adding of fluorine bonds synthetic adding of fluorine bonds with the purpose of decrease of its rate by caries of teeth.with the purpose of decrease of its rate by caries of teeth.

About 97 percent of the water on earth is in the salty oceans. People have found many ways to desalinate, the process for removing salt from seawater and brackish water. The desalination processes used most commonly today are distillation, reverse osmosis, and electrodialysis. These processes produce fresh water from salt water.

                 

This is a water purification plant.

Distillation is the oldest method of turning salt water into fresh water. Seawater can be distilled by simply boiling it in a teapot, and piping the steam into a cool bottle. The salt water turns to vapour under the sun's heat. The vapour rises until it hits the underside of the dome or glass, where it condenses.                  

Most modern distillation plants use a process Most modern distillation plants use a process called multistage flash called multistage flash distillation.distillation. This is a This is a type of the age-old method of type of the age-old method of boiling and boiling and condensationcondensation. In flash distillation, preheated . In flash distillation, preheated seawater flows into a large chamber in which seawater flows into a large chamber in which the pressure is low. The low pressure causes the pressure is low. The low pressure causes some of the water to instantly turn into steam some of the water to instantly turn into steam The steam is condensed into salt-free water. The steam is condensed into salt-free water. The seawater passes through several The seawater passes through several distillation chambers. Each of the chambers has distillation chambers. Each of the chambers has a lower pressure than the previous chamber. a lower pressure than the previous chamber. Often, the final water is so pure that it is Often, the final water is so pure that it is tasteless, and some salt must be tossed back in tasteless, and some salt must be tossed back in to give it flavour to give it flavour

Reverse osmosisReverse osmosis is a widely used method for is a widely used method for desalting seawater and brackish water. In normal desalting seawater and brackish water. In normal osmosis, a less concentrated liquid flows through a osmosis, a less concentrated liquid flows through a membrane into a more concentrated liquid. Thus, if salt membrane into a more concentrated liquid. Thus, if salt water and fresh water are separated in a chamber by a water and fresh water are separated in a chamber by a special semi-permeable membrane, the fresh water will special semi-permeable membrane, the fresh water will flow through the membrane into the salt water. flow through the membrane into the salt water.

ElectrodialysisElectrodialysis is used chiefly to desalt brackish is used chiefly to desalt brackish ground water and water from estuaries, or river mouths. ground water and water from estuaries, or river mouths. Electrodialysis is based on the fact that when salt is Electrodialysis is based on the fact that when salt is dissolved in water, it breaks up into ions, or electrically dissolved in water, it breaks up into ions, or electrically charged particles, of sodium and chloride. Sodium ions charged particles, of sodium and chloride. Sodium ions carry a positive charge, and chloride ions carry a carry a positive charge, and chloride ions carry a negative chargenegative charge..

Other desalting processes are also being studied. Other desalting processes are also being studied. During the 1970's, several plants experimented with During the 1970's, several plants experimented with freezing freezing as a method of desalination. When seawater as a method of desalination. When seawater freezes, the ice crystals produced are pure water in solid freezes, the ice crystals produced are pure water in solid form. The salt is separated and trapped between the ice form. The salt is separated and trapped between the ice crystals.crystals.

EXAMINATION OF WATEREXAMINATION OF WATERBefore water from any source is Before water from any source is

declared fit for human declared fit for human consumption, it is essential to consumption, it is essential to carry out the following carry out the following examination.examination.

For hygienic purposes the For hygienic purposes the examination of water is generally examination of water is generally done under the following heads:done under the following heads:

1.1. Physical Examination.Physical Examination.

2.2. Chemical Examination.Chemical Examination.

3.3. Microscopical Examination.Microscopical Examination.

4.4. Bacteriological Examination.Bacteriological Examination.

1. Physical qualities1. Physical qualitiesa.a. TuribidityTuribidityb.b. ColourColour c.c. OdourOdourd.d. TasteTaste

2. Chemical qualities:2. Chemical qualities: Analysis is made to determine :Analysis is made to determine :

• The amount of organic salts which determine the The amount of organic salts which determine the hardness of water and type of hardness.hardness of water and type of hardness.

• The nature and amount of organic pollution.The nature and amount of organic pollution.• The percentage and amount of poisonous metals.The percentage and amount of poisonous metals.• The chemist determines the reaction (by means of The chemist determines the reaction (by means of

a litmus paper or phenolphthalein), a litmus paper or phenolphthalein), • the type and degree of hardness, the type and degree of hardness, • the presence of chlorides, nitrites, nitrates, the presence of chlorides, nitrites, nitrates,

ammonia (free and albuminoid) and metals such as ammonia (free and albuminoid) and metals such as lead, copper, iron, calcium etc., before giving his lead, copper, iron, calcium etc., before giving his final opinion.final opinion.

3.3. Bacteriological IndicatorsBacteriological Indicators: :

The main object of bacteriological examination The main object of bacteriological examination of water is to find out whether excretal pollution is of water is to find out whether excretal pollution is present or not. The sewage bacteria can be divided into present or not. The sewage bacteria can be divided into three groups:three groups:

1.1. - E.coli and coliform group- E.coli and coliform group

2.2. - Fecal streptococci- Fecal streptococci

3.3. - Clostridium perfringens.- Clostridium perfringens.

4.4. Radiological StandardsRadiological Standards

Gross alpha activity 3 pico curie/L Gross alpha activity 3 pico curie/L

Gross beta activity 30 pico curie/LGross beta activity 30 pico curie/L

Sampling of waterSampling of water

For physical and For physical and chemical examination, about chemical examination, about 2 liters water is essential. It 2 liters water is essential. It must be collected in a clean must be collected in a clean glass stoppered bottle made glass stoppered bottle made of neutral glass. of neutral glass.

Before collecting the sample rinse the bottle well Before collecting the sample rinse the bottle well three times with the water filling it each time, about three times with the water filling it each time, about 1/3 full. For bacteriological examination about 300 ml 1/3 full. For bacteriological examination about 300 ml water is required. It must be collected in clean water is required. It must be collected in clean sterilized bottle made of neutral glass, provided with a sterilized bottle made of neutral glass, provided with a ground glass stopper having an overlapping rim. If the ground glass stopper having an overlapping rim. If the water to be sampled contains or is likely to contain water to be sampled contains or is likely to contain chlorine, a small quantity of sodium thiosulphate is chlorine, a small quantity of sodium thiosulphate is added to bottle before sterilization.added to bottle before sterilization.

Sampling from TapSampling from TapIf sample is If sample is

taken from a tap in taken from a tap in regular use, the tap regular use, the tap should be opened should be opened fully and the water fully and the water run to waste at run to waste at least for 2 minutes least for 2 minutes in order to flush the in order to flush the stagnant water in stagnant water in nozzle and pipe. If nozzle and pipe. If sample is taken sample is taken from tap not in from tap not in regular use, the tap regular use, the tap should be sterilized should be sterilized by heating it till it by heating it till it is red hot. Then is red hot. Then allow water to run allow water to run to waste for one to waste for one minute and then minute and then collect sample.collect sample.

Sampling from a well:Sampling from a well:Tie a sample bottle with a Tie a sample bottle with a

rope. Use a stone or piece of rope. Use a stone or piece of metal weighing about 500 gm as metal weighing about 500 gm as "the weight and attach the tube "the weight and attach the tube bottle just above it. After bottle just above it. After removing the cap aseptically, removing the cap aseptically, lower the bottle into the well into lower the bottle into the well into the well to a depth of 1m. When the well to a depth of 1m. When no more air bubbles rise to the no more air bubbles rise to the surface, raise the bottle out of surface, raise the bottle out of the well and carefully replace the the well and carefully replace the cap.cap.

C.C. Sampling from stream.Sampling from stream.Water is taken from middle of a stream, with the Water is taken from middle of a stream, with the

mouth of the bottle facing upstream, lower the bottle into mouth of the bottle facing upstream, lower the bottle into the stream and allow filling. Tilt bottle upwards to fill the stream and allow filling. Tilt bottle upwards to fill completely. The cap is carefully screwed back, taking care completely. The cap is carefully screwed back, taking care not to touch the screw thread at the top of the bottle.not to touch the screw thread at the top of the bottle.

After taking sample following information must be After taking sample following information must be given with bottle.given with bottle.

a.a. Source of water supplySource of water supplyb.b. Date, place and time of samplingDate, place and time of samplingc.c. Geological formation of soil, if available.Geological formation of soil, if available.d.d. In case of well, its depth, diameter and how it is used.In case of well, its depth, diameter and how it is used.e.e. Recent rainfall if there.Recent rainfall if there.f.f. Any suspected source of pollution in vicinityAny suspected source of pollution in vicinityg.g. Whether any method of purification is used.Whether any method of purification is used.

Sampling from stream.Water is taken from middle of a stream,

with the mouth of the bottle facing upstream, lower the bottle into the stream and allow filling. Tilt bottle upwards to fill completely. The cap is carefully screwed back, taking care not to touch the screw thread at the top of the bottle.

After taking sample following information must be given with bottle.

a. Source of water supplyb. Date, place and time of samplingc. Geological formation of soil, if available.d. In case of well, its depth, diameter and how it is used.e. Recent rainfall if there.f. Any suspected source of pollution in vicinityg. Whether any method of purification is used.

The principle of chlorination is based on the treatment by chlorineThe principle of chlorination is based on the treatment by chlorine or the or the

chemical compounds, containing active chlorine and able to oxidize and provoke chemical compounds, containing active chlorine and able to oxidize and provoke bactericidal action. Chlorine is subjected to hydrolysis in water: bactericidal action. Chlorine is subjected to hydrolysis in water:

ClCl22+HOH → HOCl+HCl, +HOH → HOCl+HCl,

so hydrochloric and chloricious acids are formed. Chloricious acid takes the central so hydrochloric and chloricious acids are formed. Chloricious acid takes the central

place in the mechanisms of bactericidal action. It was thought earlier that the latter was place in the mechanisms of bactericidal action. It was thought earlier that the latter was destroyed in water and discharged out atomic oxygen destroyed in water and discharged out atomic oxygen

(HOCl → HCl+O·), which was the main bactericidal agent. Now, such explaination is (HOCl → HCl+O·), which was the main bactericidal agent. Now, such explaination is considered insufficient. Chlorine in the structure of chloricious acid and hypochlorite-considered insufficient. Chlorine in the structure of chloricious acid and hypochlorite-ion (HOCl→H +OCl ) free active chlorine, which determines bactericidal action in ion (HOCl→H +OCl ) free active chlorine, which determines bactericidal action in water. Not large molecules and electric neutrality let chloricious acid penetrate quickly water. Not large molecules and electric neutrality let chloricious acid penetrate quickly through the bacterial membrane and influence upon the cellular enzymes, important for through the bacterial membrane and influence upon the cellular enzymes, important for the metabolism and reproduction. It is assumed, that it reacts with SH-groups of the metabolism and reproduction. It is assumed, that it reacts with SH-groups of enzymes, which become oxidized.enzymes, which become oxidized.

The reliable bactericidal effect of chlorine is achieved, if aboutThe reliable bactericidal effect of chlorine is achieved, if about

0,3 – 0,5 mg/l of free chlorine0,3 – 0,5 mg/l of free chlorine or 0,8 – 1,2 mg/l of connected or 0,8 – 1,2 mg/l of connected chlorine are left in water after 30 - 60 min. of exposure.chlorine are left in water after 30 - 60 min. of exposure.

The chlorination by the post-break doses.The chlorination by the post-break doses. By the results of some investigations the water can be By the results of some investigations the water can be

disinfected by 2 doses of chlorine: 1mg/l (before-break dose) and disinfected by 2 doses of chlorine: 1mg/l (before-break dose) and 5,2 mg/l (post-break doses), as the concentration of the rest 5,2 mg/l (post-break doses), as the concentration of the rest chlorine makes 0,5 mg/l in both cases.chlorine makes 0,5 mg/l in both cases.

However, by before-break dose the remaining chlorine is However, by before-break dose the remaining chlorine is determined as chloramin, and by post-break doses - as free determined as chloramin, and by post-break doses - as free chlorine. The bactericidal action of such method is very effective. chlorine. The bactericidal action of such method is very effective. At the same time we improve water organoleptic features at the At the same time we improve water organoleptic features at the expense of oxidation of organic substances with the bad smell. It is expense of oxidation of organic substances with the bad smell. It is necessary to use this method in hot countries widely.necessary to use this method in hot countries widely.

Double chlorination.Double chlorination. In many river water-pipes chlorine is given before the In many river water-pipes chlorine is given before the

settling and than after the filtration as usual. The introduction of settling and than after the filtration as usual. The introduction of chlorine before the settling improves the coagulation and chlorine before the settling improves the coagulation and decolourization of water, inhibits the development of decolourization of water, inhibits the development of microorganisms in the settling tanks, increases the reliability of microorganisms in the settling tanks, increases the reliability of disinfection. However, the possibility of chlororganic compounds disinfection. However, the possibility of chlororganic compounds formation increases too.formation increases too.

The chlorination with the preammonization The chlorination with the preammonization (chlorammination).(chlorammination).

First, they introduce ammoniac solution and than, in 0.5-1 min, First, they introduce ammoniac solution and than, in 0.5-1 min, chlorine to the water. As a result chloramines are formed in water: chlorine to the water. As a result chloramines are formed in water: NHNH22Cl - monochloramin and NHClCl - monochloramin and NHCl22 - dichloramin. The last one has the - dichloramin. The last one has the most expressed bactericidal action. The effectiveness of such method most expressed bactericidal action. The effectiveness of such method depends on the ratio NH3:Cl. That's why they use the doses of reagents depends on the ratio NH3:Cl. That's why they use the doses of reagents in the following ratios: 1:3, 1:4, 1:6, 1:8. The ratio should be chosen for in the following ratios: 1:3, 1:4, 1:6, 1:8. The ratio should be chosen for certain reservoirs individually.certain reservoirs individually.

This method prevents bad smells, which can appear by the This method prevents bad smells, which can appear by the chlorination of water, containing phenol and the matters from its group chlorination of water, containing phenol and the matters from its group (as chlorphenols are formed). Chlorphenols impart medicinal smell and (as chlorphenols are formed). Chlorphenols impart medicinal smell and smack to the water even in the small quantities.smack to the water even in the small quantities.

The speed of disinfection by this method is lower than that by The speed of disinfection by this method is lower than that by chlorine. The exposure time should be not less than 2 hours.chlorine. The exposure time should be not less than 2 hours.

If the water of reservoirs contains ammonium salts, chloramines If the water of reservoirs contains ammonium salts, chloramines are also formed. This fact decelerates disinfection. So, it is necessary to are also formed. This fact decelerates disinfection. So, it is necessary to define free and connected chlorine separately to determine the define free and connected chlorine separately to determine the reliability of disinfection. Obviously, the presence of only free chlorine is reliability of disinfection. Obviously, the presence of only free chlorine is evidence of reliable disinfection.evidence of reliable disinfection.

Overchlorination (superchlorination) By this method large doses of chlorine are used in to the water,

for example 10-20 mg/l and more. As a result the reliable bactericidal effect is achieved even after the exposure for 15 min. By the 30-60 min. of exposure even the turbid waters are disinfected reliably. Such agents, stable for the chlorine, as Berket's rikketsia, amoebic cysts, Koch’s bacillus, viruses become dead. But even such doses of chlorine cannont destroy spores of anthrax and helminthes eggs. A lot of residual chlorine remains after the overchlorination. Water is dechlorinated by the filtration through the layers of activated coal or by the addition of sodium hyposulphite (Na2S2O3*5H2O) in the concentration of 3.5 mg per 1 mg of chlorine.

advantages we don't need to determination chlorine's need of water, calculate the dose of chloric lime, time of water's disinfection is decreasing to 15-20 min in

summer and to 30-60 min in winter. disinfection of turbid water is very well too; during this, unpleasant smell and smack are eliminated better.

Thank your!Thank your!