water treatment i

8/9/2019 Water Treatment I

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II. Water Treatment

II. Water Treatment

A. Treatment of wastewater andA. Treatment of wastewater and

B. Treatment of drinking waterB. Treatment of drinking water


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Objectives - students shouldObjectives - students should

!ist and describe treatment methods for!ist and describe treatment methods for

wastewater.wastewater.

!ist and describe treatment methods for!ist and describe treatment methods for

drinking water.drinking water.

"om#are and contrast treatment methods"om#are and contrast treatment methods

and goals of wastewater and drinkingand goals of wastewater and drinking

water.water.


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$ustification for wastewater$ustification for wastewater

treatmenttreatment %ollution from sewage is a #rimar&%ollution from sewage is a #rimar&

environmental health ha'ardenvironmental health ha'ard

(wastewater effluent).(wastewater effluent).

The #ur#ose of munici#al wastewaterThe #ur#ose of munici#al wastewater

treatment is to limit #ollution of thetreatment is to limit #ollution of the

receiving watercourse.receiving watercourse.

The receiving watercourse ma& also be aThe receiving watercourse ma& also be a

source of drinking water.source of drinking water.


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*oals of wastewater treatment*oals of wastewater treatment

+eduction of+eduction of organic loadorganic loadof theof the

wastewater effluent to limitwastewater effluent to limiteutro#hication (BO, "O, limits)eutro#hication (BO, "O, limits)

+eduction of+eduction of microbiologicalmicrobiological

contaminationcontaminationthat ma& transmitthat ma& transmitinfectious disease.infectious disease.


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unici#al wastewater treatmentunici#al wastewater treatment

facilit& and regulationsfacilit& and regulations unici#al wastewater treatment facilities orunici#al wastewater treatment facilities or

/%ublicl& Owned Treatment Works0 (%OTWs) or/%ublicl& Owned Treatment Works0 (%OTWs) or

/Water +eclamation ,istricts0 are designed to/Water +eclamation ,istricts0 are designed toreduce environmental health risks of untreatedreduce environmental health risks of untreated

wastewater.wastewater.

!evels of treatment re1uired are based on 2%,34!evels of treatment re1uired are based on 2%,34

regulations.regulations.


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Wastewater Treatment SchemeWastewater Treatment Scheme

Preliminary Secondary

WW

influent

WW effluent

sludge

Primary Tertiary

Disinfectant

Sludge Treatmentand Disposal


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Wastewater treatmentWastewater treatment

#rocesses#rocesses %reliminar&%reliminar&treatment is a #h&sicaltreatment is a #h&sical

#rocess that removes large contaminants.#rocess that removes large contaminants.

%rimar&%rimar&treatment involves #h&sicaltreatment involves #h&sical

sedimentation of #articulates.sedimentation of #articulates.

4econdar&4econdar&treatment involves #h&sical andtreatment involves #h&sical and

biological treatment to reduce organicbiological treatment to reduce organic

load of wastewater.load of wastewater.

Tertiar&Tertiar&or advanced treatments.or advanced treatments.


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2itrification-denitrification #rocess to2itrification-denitrification #rocess to

remove 2 and %remove 2 and %

5iltration5iltration

"arbon Adsor#tion"arbon Adsor#tion

"onstructed (an-made6 Wetland"onstructed (an-made6 Wetland

Tertiar& or Advanced TreatmentTertiar& or Advanced Treatment


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ore than 789 of all households in the :.4. areore than 789 of all households in the :.4. are

served b& on-site treatment s&stems.served b& on-site treatment s&stems.

About ; billion gallons of wastewater isAbout ; billion gallons of wastewater isdischarged each da& to on-site wastewaterdischarged each da& to on-site wastewater

treatment s&stems.treatment s&stems.

%otential disease transmission risks through%otential disease transmission risks through

wastewater should be limited.wastewater should be limited.

On-site wastewater treatment

n-site wastewater treatment


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4e#tic s&stems4e#tic s&stems ticall& consist ofticall& consist of

A se#tic tankA se#tic tank(concrete with inlet and outlet(concrete with inlet and outlet

baffles and removable to# for cleaning) whichbaffles and removable to# for cleaning) whichcollects and holds wastecollects and holds waste

A drain fieldA drain fieldorortile fieldtile field (#lastic or tile #i#e(#lastic or tile #i#e

with outlets) which allows wastewater effluentwith outlets) which allows wastewater effluent

to infiltrate slowl& into soils.to infiltrate slowl& into soils.

%lumbing connections%lumbing connections..

Tical se#tic s&stem designTical se#tic s&stem design


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%eriodic summer&%eriodic summer&

Treatment of wastewater is necessar& to #rotectTreatment of wastewater is necessar& to #rotect

the environment and #reserve the 1ualit& of waterthe environment and #reserve the 1ualit& of water

for drinking.for drinking.

Treatment of munici#al wastewater ticall&Treatment of munici#al wastewater ticall&

includes #reliminar& #rimar& treatmentincludes #reliminar& #rimar& treatment

secondar& treatment and tertiar& treatment.secondar& treatment and tertiar& treatment. On-site wastewater treatment is facilitated b&On-site wastewater treatment is facilitated b&

se#tic tank s&stems.se#tic tank s&stems.


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B. ,rinking water treatmentB. ,rinking water treatment

"larification"larification- #rimaril& a- #rimaril& a #h&sical#h&sical

#rocess but ma& be aided b& addition of#rocess but ma& be aided b& addition ofchemicals.chemicals.

5iltration5iltration- also #rimaril&- also #rimaril& #h&sical#h&sical but but

chemicals ma& aid the #rocess.chemicals ma& aid the #rocess.

,isinfection,isinfection- ticall& a- ticall& a chemicalchemical#rocess#rocess

that reduces #athogenic microorganisms.that reduces #athogenic microorganisms.


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B


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B7. 5iltrationB7. 5iltration

4e#arate nonsettleable solids from water.4e#arate nonsettleable solids from water.

"ombined with coagulation=clarification"ombined with coagulation=clarification

filtration can remove >?9-@9 turbidit&filtration can remove >?9-@9 turbidit&

coliform bacteria @-@@.@89 and C@@9coliform bacteria @-@@.@89 and C@@9

*iardia.*iardia.


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+a#id filtration

a#id filtration - uses gravit& (faster flow).- uses gravit& (faster flow).

4low filtration

low filtration - uses gravit& Dslower flow6.- uses gravit& Dslower flow6.

%ressure sand filters

ressure sand filters -use water #ressure.-use water #ressure.

E,iatomaceous earth (,3) filtration

iatomaceous earth (,3) filtration

icrostraining

icrostraining - uses fine steel fabric- uses fine steel fabric

(sometimes used #rior to other filtrations).(sometimes used #rior to other filtrations).

Te of 5iltrationTe of 5iltration


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5ilter edia5ilter edia

5ilter media should be5ilter media should beE coarse enough to retain large 1uantities of floccoarse enough to retain large 1uantities of floc

E sufficientl& fine to #revent #assage of sus#ended solidssufficientl& fine to #revent #assage of sus#ended solidsE dee# enough to allow relative long filter runsdee# enough to allow relative long filter runs

*ranular-medium filters (+a#id 4and 5ilters6*ranular-medium filters (+a#id 4and 5ilters6E Anthracite on the ver& to# (least dense)Anthracite on the ver& to# (least dense)

E fine sand on to# of su##orting coarse sand(less dense)fine sand on to# of su##orting coarse sand(less dense)which la&s on to# ofwhich la&s on to# of

E gravel la&er (highest densit&).gravel la&er (highest densit&).


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"leaning (backwashing) filters"leaning (backwashing) filters

,etermination of how often to back-wash,etermination of how often to back-wash

can be made on the basis ofcan be made on the basis of

E Fead loss (#ressure loss)Fead loss (#ressure loss)

E !oss of water 1ualit& (e.g. increased turbidit&)!oss of water 1ualit& (e.g. increased turbidit&)

oror

E Time since last backwash.Time since last backwash.


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Backwashing #rocessBackwashing #rocess

Water flow is reversed through the filterWater flow is reversed through the filter

bed.bed.

E TheThe raterateof backwash is designed to #artiall&of backwash is designed to #artiall&

eG#and (fluidi'e) the filter bed.eG#and (fluidi'e) the filter bed.

E 4us#ended matter is removed b&4us#ended matter is removed b& shearshearforcesforces

as the water moves through the fluidi'ed bed.as the water moves through the fluidi'ed bed.E AdditionalAdditionalcleaning occurs when #articles ofcleaning occurs when #articles of

the bed abrade against each other.the bed abrade against each other.


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5low control through filters5low control through filters

"onstant-rate filtration"onstant-rate filtration

E 5low rate is controlled b& limiting the5low rate is controlled b& limiting the

discharge rate limiting the rate of inflow b& adischarge rate limiting the rate of inflow b& aweir orweir or

E b& #um#ing or use of influent flow-s#littingb& #um#ing or use of influent flow-s#litting

weir.weir. ,eclining-rate filtration,eclining-rate filtration

E +ate of flow declines as the rate of head loss+ate of flow declines as the rate of head loss

builds (influent- or effluent-controlled).builds (influent- or effluent-controlled).


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VII. Water TreatmentVII. Water Treatment

B;. ,isinfection of drinkingB;. ,isinfection of drinking

waterwater


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Objectives - students shouldObjectives - students should

,efine and give eGam#les of tes of,efine and give eGam#les of tes of

disinfection techni1ues for drinkingdisinfection techni1ues for drinking

water.water. ,istinguish between #h&sical and,istinguish between #h&sical and

chemical disinfection techni1ues.chemical disinfection techni1ues.

3valuate the safet& cost effectiveness3valuate the safet& cost effectivenessand #o#ularit& of various disinfectionand #o#ularit& of various disinfection

techni1ues.techni1ues.


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Tes of disinfectionTes of disinfection

%h&sical disinfection techni1ues include%h&sical disinfection techni1ues include

boiling and irradiation with ultravioletboiling and irradiation with ultraviolet

light.light.

"hemical disinfection techni1ues include"hemical disinfection techni1ues include

adding chlorine bromine iodine and o'oneadding chlorine bromine iodine and o'one

to water.to water.


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%h&sical disinfection (boiling)%h&sical disinfection (boiling)

Boiling kills vegetative bacterial cells butBoiling kills vegetative bacterial cells but

s#ores viruses and some #roto'oa ma&s#ores viruses and some #roto'oa ma&

survive long #eriods of boiling.survive long #eriods of boiling. Boiling ma& also volatili'e VO"Hs.Boiling ma& also volatili'e VO"Hs.

Boiling is an effective method for smallBoiling is an effective method for small

batches of water during water emergencies.batches of water during water emergencies.

Boiling is #rohibitivel&Boiling is #rohibitivel& eG#ensiveeG#ensivefor largefor large

1uantities of water.1uantities of water.


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%h&sical disinfection%h&sical disinfection

(:V radiation)(:V radiation)

:ltraviolet radiation is an effective and:ltraviolet radiation is an effective and

relativel& safe disinfection method but isrelativel& safe disinfection method but is

relativel& eG#ensive and not widel& used.relativel& eG#ensive and not widel& used. :V light disru#ts ,2A of microbial cells:V light disru#ts ,2A of microbial cells

#reventing re#roduction.#reventing re#roduction.

4#ecific wavelengths intensities distances4#ecific wavelengths intensities distancesflow rates and retention times are re1uired.flow rates and retention times are re1uired.


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"hemical disinfection"hemical disinfection

"hemicals added to water for disinfection"hemicals added to water for disinfection

include chlorine bromine and iodine.include chlorine bromine and iodine.

Bromine is not recommended for drinkingBromine is not recommended for drinkingwater disinfection but ma& be used forwater disinfection but ma& be used for

#ool water.#ool water.

Iodine is sometimes used for drinkingIodine is sometimes used for drinkingwater disinfection but causes a badwater disinfection but causes a bad

aftertaste.aftertaste.


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"hlorine disinfection"hlorine disinfection

"hlorination is a chea# effective relativel&"hlorination is a chea# effective relativel&

harmless (and therefore most #o#ular)harmless (and therefore most #o#ular)

disinfection method.disinfection method. "hlorine is added as a gas or hochlorite"hlorine is added as a gas or hochlorite

solution.solution.

Fochlorous acid and hochlorite ionsFochlorous acid and hochlorite ionsform in solution which are strong chemicalform in solution which are strong chemical

oGidants and kill microbes.oGidants and kill microbes.


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"hlorine disinfection (cont.)"hlorine disinfection (cont.)

"ombined chlorine is the #ro#ortion that"ombined chlorine is the #ro#ortion that

combines with organic matter.combines with organic matter. 5ree chlorine is the amount that5ree chlorine is the amount that remainsremains

to kill microbes in the distribution s&stemto kill microbes in the distribution s&stem

(.8 ##m


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,isinfection B&-%roducts (,B%s),isinfection B&-%roducts (,B%s)

"hlorine (or bromine or iodine) J /#recursors0"hlorine (or bromine or iodine) J /#recursors0

(organic com#ounds) K TF(Trihalomethanes)(organic com#ounds) K TF(Trihalomethanes)

E eg. "hloroform ("F"leg. "hloroform ("F"l;;) Bromoform ("FBr) Bromoform ("FBr;;) Iodoform) Iodoform("FI("FI;;) chlorobromoform ("FBr"l) chlorobromoform ("FBr"l77) Bromochloroform) Bromochloroform

("FBr("FBr77"l) Bromoidodform ("FBr"l) Bromoidodform ("FBr77I) etc.I) etc.

TFs are carcinogenicTFs are carcinogenic

"horoamine disinfection reduce TFs #roduction"horoamine disinfection reduce TFs #roduction

due to #referential reaction of chlorine withdue to #referential reaction of chlorine with

ammoniaammonia


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O'onationO'onation

O'one (OO'one (O;;) is an effective relativel&) is an effective relativel&

harmless disinfection method but isharmless disinfection method but is

eG#ensive (and therefore less #o#ular thaneG#ensive (and therefore less #o#ular thanchlorine).chlorine).

O'one is a strong oGidant that #roducesO'one is a strong oGidant that #roduces

h&droG&l free radicals that react withh&droG&l free radicals that react withorganic and inorganic molecules in waterorganic and inorganic molecules in water

to kill microbes.to kill microbes.


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4ummar&4ummar&

,isinfection is the destruction of,isinfection is the destruction of

microorganisms in drinking water to safemicroorganisms in drinking water to safe

levels.levels. ,isinfection techni1ues include #h&sical,isinfection techni1ues include #h&sical

(boiling ultraviolet light) and chemical(boiling ultraviolet light) and chemical

methods (chlorine bromine iodine andmethods (chlorine bromine iodine ando'one).o'one).

water treatment i

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