purificationofwater-140607060543-phpapp02

7/23/2019 purificationofwater-140607060543-phpapp02

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CHEMISTERY PROJECT TERM I

BY A. HRUSHYANG

CLASS XI


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DEFINATION

Water purifcation isthe process oremoving undesirablechemicals, biologicalcontaminants,

suspended solids andgases romcontaminated waterto make it ft ordrinking.


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Need for WaterPr!"#at!o$ Although reasonably pure, it is

always variable due toseasonal variations, regionalvariation in water quality.

For removing impurities andcontrol microbes to avoidcontamination.

The treatment o water maorlydepends on water!s chemistryand contaminants, in"uencedby, e.g. rainall, erosion,pollution, etc.

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Pro#e%% ofPr!"#at!o$ ofWater

The process o

purifcation o thewater maorlyinvolves ourmethods i.e. 34

*edimentation tank /oading tank

Filtration tank

'hlorination tank


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Sed!&e$tat!o$Ta$'

Water entering into thesedimentation tankscontains suspendedparticles 5sediments6.These sediments settleto the bottom o the

tanks orms sludge whichis then driven to theoutlet using scrappers sothat the water is reerom suspended materiallike rocks, soil, etc.


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Load!$( Ta$'The addition o inorganic coagulantssuch as aluminium sulphate 5or alum6or iron 5###6 salts such as iron5###6chloride cause several simultaneouschemical and physical interactions onand among the particles. Within

seconds, negative charges on theparticles are neutrali8ed by inorganiccoagulants. Also within seconds, metalhydro9ide precipitates o thealuminium and iron 5###6 ions begin toorm. These precipitates combine intolarger particles under naturalprocesses such as 2rownian

motion and through induced mi9ingwhich is sometimes reerred toas "occulation. The term most otenused or the amorphous metalhydro9ides is :"oc.; /arge,amorphous aluminium and iron 5###6hydro9ides adsorb and enmeshparticles in suspension and acilitate

the removal o particles bysubse uent rocesses


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F!)trat!o$ Ta$'

#nthis tank the water movesvertically through sand whichoten has a layer o activatedcarbon or anthracite coal abovethe sand. The top layerremoves organic compounds,which contribute to taste andodour. The space between sandparticles is larger than the

smallest suspended particles,so simple fltration is notenough. -ost particles passthrough surace layers but aretrapped in pore spaces oradhere to sand particles.


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C*)or!$at!o$ Ta$'The most common disinectionmethod involves 'hlorination.

'hlorine is a strong o9idant thatrapidly kills many harmul micro4organisms. 2ecause chlorine is ato9ic gas, there is a danger o arelease associated with its use.This problem is avoided by theuse o sodium hypochlorite,which is a relatively ine9pensive

solution that releases reechlorine when dissolved in water.'hlorine solutions can begenerated on site byelectroly8ing common saltsolutions. Ater water passingrom this 'hlorination tank thewater is supplied to our houses.


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IF Water !% $ot Pr!"ed

Water is another ertile source o disease,many organic and inorganic impurities makingtheir way into it. #t is to the ormer that itsunhealthul is generally due. )early all waterrom the earth contains some mineralingredients, ew o which are harmul, some owhich are healthul. The waters o manymineral springs serve as remedies or seriousdisorders o the system. The chie source owater pollution lies in organic impurities,which are carried through the soil romcesspools, manure heaps, and similar sourcesinto wells, or are emptied by sewers into therivers rom which many cities now derive theirdrinking water. The lack o su=cient watermay also be a cause o disease. The personand clothes are not properly washed, housesand streets are dirty, and the sewers becomeclogged with flth. As a result there is ageneral lower state o health o thecommunity, and typhoid ever and diarrhoeamay be prevalent.


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D!%ea%e% #a%ed +, I&-reater

'1(/&A

'holera, whose germs are now thought to beconveyed only by water. The great epidemicat 1amburg in >?@, was traced to sewagewater rom cholera patients getting into the

river lbe, which supplies the city withwater. This requently, perhaps almostwholly, comes rom a like distribution o thebacterial germs o the disease by water.Typhoid ever has been traced to this causein numerous instances. This was the case at(ver +arwin in >?BC, when a draincontaining the e9creta o a typhoid patientwas blocked, and its contents got in themain pipe o the water supply. As a result,

out o a population o,DDD there were,DE cases o typhoid ever and >DC deaths.#n 2angor, in >??, there occurred anepidemic o typhoid ever, aD,DDD, owhom C died. This was ound to be causedby the e9creta o a single typhoid patientgetting into a small stream which dischargedinto the river supplying the town with water.


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D!-*t*er!a+iphtheria is probably conveyedand caused by impure water,but this is not yet absolutelyproved. +ysentery is well known

in tropical countries to becaused by impure water, as wasproved by an outbreak at 'ape'oast 'astle, where it wascaused by the passage osewage into one o the drinkingtanks. +iarrhoea has beencaused in epidemic orm by

impure water, as was shown inthe old *alord ail, where theuntrapped over"ow pipe rom acistern o drinking watercommunicated with a sewer,and the water had thusabsorbed sewer gas, andprobably germs.

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