Chlorination ppt.pdf chlorine function in disinfection

Chlorination

1. Chlorination
WAT-E2120 Physical and Chemical Treatment of Water and Waste
Pirjo Rantanen Lic. Tech.
Aalto University

2. Pre-readingassignment
•AWWA Staff, 2006. WaterChlorination/ChloraminationPracticesand
Principles. AWWA ManualSeriesM20. American WaterWorks Assoc.
2
nd
ed. eBookISBN 9781613000267
•Pages19-29

3. Contents
•Mechanismsof chlorination
•Disinfectionkinetics
•Chemistryof chlorine
www.livescience.com

4. Usesof chlorination
•Disinfectionof drinkingwaterat treatmentplants(primary
disinfection)
•Secondarydisinfectionin distributionnetworks
•Treatedwastewaterchlorination
•Shockchlorinationof contaminated:
•Distributionnetworks
•Storage tanks
•Private wells...
•Swimmingpools
•Domesticcleaning
www.livescience.com

5. Chlorinationchemicals
•Chlorinegas
•Chlorinedioxide
•Hypochlorites
•Sodium hypochlorite (NaOCl)
•Calciumhypochlorite (Ca(OCl)
2
•Chloramine
•Hypochlorite + ammonium = NH
2Cl (monochloramine)

6. Chlorinereactionsin water
Chlorinegashydrolyzationreactionresultsas hypochlorousacid:
Hypochlorousaciddissociatesto hypochlorite ionaccordingto pH:
Bothhypochlorousacidand hypochlorite areregardedas freechlorine, thoughhypochlorousacidis moreeffective
disinfectant. In fact, it is themosteffectivechlorineform.
pKa= 7,6, 20 ° C
MeansthatbelowthispH hypochlorousacidis thepredominantform.

7. pH and hypochlorate /hypochloricacidratio
Calculatedsimilarlyas theexamplewith
NH
3/NH
4
+on thesecondlecture
Chlorinationis mosteffectivein pH 5.5-
7.5

8. Hypochloritechlorinationpractices
•Liquid solution
•Typicalconcentration10 or15% as Cl
2
•Storage timein a cooledtankshouldnot
exceed3-5 months
•Typicalfeed0.5 –1.0 g/m
3
•Addeddoseof solution0.5 –1 l/100 m
3
•If needed, thesolutionis dilutedfor
dosing
•Chemicaltanksneedsafetybasins

9. Hypochlorite
solutiondecay
Hypochlorite solutiondecayreactions
Decayis modeledwithsecondorderkinetics
•Half-life of hypochlorite solutionin storagedependson
temperature
•Hasto betakeninto accountin designingstoragetanks
and dosing.

10. Chlorinecontactchambers
•It’simportantthetthewholevolumeof waterin contactedwiththedisinfectant
•Pipeloopcontactor
•Plug flowreactor
Colorado.gov
Colorado.gov

11. Baffledcontactchambers
Properlyplacedbafflesin thechloriencontactchamberspreventshortcircuitsand deadspaces
Bafflesarewallswithopenings
Poorbaffling Averagebaffling Goodbaffling

12. CFD modelingof
baffledbasins
Modelingof flowconditions, contacttime
profilesand concentrationprofilesof
disinfectant, disinfectionby-products, and
survivingpathogensin differenttypesof
baffledcontactchambers
https://
www.researchgate.net/publication/262386893

13. Controlling
chlorine
feed

14. Disinfection
mechanisms
•Disruptingcellpermeabilityleadto cell
death
•Leakageof proteins, RNA, DNA
•Decreasein potassiumuptakeand in protein
and DNA synthesis
•Damageto nucleicacidsand enzymes
•Repression of genetranscription
•E.g. in staphylococcusaureushypochlorous
acidrepressedgenescontrollingcellwall
synthesis, proteinsynthesis, membrane
transport and primarymetabolism
•Othermechanisms

15. Biofilmgrowthwithchlorineand without
•A biofilm protects the bacteria against
chlorine.
•Notice the extra-cellular polymeric
substance (EPS) in pictures c and d.
Apparently bacteria have grown more
EPS with chlorine.
© 2013 Nature Education Reproduced from Wang
et al.2012 with permission from Elsevier.
No chlorine, 37 d No chlorine, 70 d
Withchlorine, 37 d Withchlorine, 70 d
Scanning electron microscopy (SEM) micrographs of the biofilm formed on cast iron coupons

16. Bacteriacanstayviableafterchlorination
•Effectsof chlorinedisinfectionon theviabilityof drinking
watermultispeciesbiofilmsand theirabilityto recoverafter
treatment
•Theepifluorescencephotomicrographsshow thebiofilms
(a) beforetreatmentwith10 mg l
−1
sodium hypochlorite; (b)
immediatelyafterand (c) 24 h later
•Magnification, ×400; bar= 50 μm
•Viablecellsaregreenand non-viablecellsarered
•Thedrinkingwaterbiofilmwascomposedof A.
calcoaceticus, B. cepacia, Methylobacteriumspp., M.
mucogenicum, S. capsulataand Staphylococcusspp.
a
b
c

17. Logremoval
99 % removal
in filtration
90 %
Inactivationin
chlorination
•Log-reductionscanbesummed
withsequencingprocessunits
•Example:
•2-log removalof pathogensin
filtrationAND
•1-log inactivationof pathogensin
chlorination
•Resultsas 3-log totalreduction
(99.9 %)Roughly: ”Numberof
ninesin thereduction
percentage”

18. Ct
•Ct= chlorineconcentrationas mg/l multiplied byinactivationtimeas
minutes
•2-log removalefficiency
•Sometimesexpressedwithoutunits(=> extracarefulnessneeded!)
•ThehigherCtthemoreresistantmicro-organism
•Resistanceto disinfectionincreasesin thefollowingorder:
•Non-sporeformingbacteria< entericviruses< spore-formingbacteria< protozoan
cysts
•E.g. in pH 6 withhypochlorousacid:
•E. coli, Ct= 0.04
•Poliovirus type1, Ct= 1.05
•Giardia lambliacysts, Ct= 80

19. Ct,
cont’d
•Ctvaluesof selected
pathogens
•E.g. C. Parvumrequireshigh
chlorineconcentrations
and/orlong HRT

20. Effectivenessof differentchlorineproducts
•Hypochlorousacidis the
mosteffective
•Chlorinedioxideis next
effective
•Afterthatcomes
hypochlorite ion
•Noticethedifferenceof
hypochlorousacidand
hypochlorite ion. Theyare
presentin thesamesolution
dependingon pH
•Monochloramine is the
weakestdisinfectantof all
theshown(leastreactive)

21. Chlorinedioxide
•Becomingmorepopularbecause
•ClO
2produceslessTHMsand HAAsthanfreechlorine
•Doesnotreactwithammoniato formchloramines
•ClO
2mustbegeneratedat thesite:
•ClO
2is effectiveagainstbacterialand viralpathogensand protozoan
parasites

22. Chloraminechlorination
Chloramineformationreactionswithammoniaand
hypochlorite:
•Monochloramine is thedesiredproduct
•Usedespeciallyfor secondarydisinfectionin
distributionnetworks
•Lessreactivethanchlorine=> disinfectionfor
longerHRTsin thenetwork
•Cl
2:NH
4
+-N massratio(maximum) 4.5 -5 to reducethe
amountof freeammonia
•Monochloramine formationdependson pH
•OptimumpH is 8.3
•WithpH below7.5 and Cl
2:NH
4
+-N massratioabove5
•Dichloramineand trichloramineformation
increases
•Bothhavestrongchlorinoustaste
NH
2Cl
NCl
3
NHCl
2

23. Breakpointchlorination
•If watercontainsammonia, it has to beremoved
beforechlorination(otherwiseit’schloramination)
•In breakpointchlorinationchlorineis addedto
removefirstammonia
•Thebreakpointoccursat moleratioCl
2:NH
3= 1.5
•Abovethemoleratioammonium is oxidizedinto
nitrogengasornitrateionand freechlorine
concentrationincreasesInfobox

24. Modelingbacteriainactivation:
Chick’slaw(1908)
HarrietteChick
6.1.1875 –9.7.1977
WellcomeImages •Firstorderkineticsof themicro-organismconcentration
•Temperaturedependenceof reactionratecoefficient(k) is
calculatedwithArrheniusequation(2
nd
lecture)
•Chlorinecontactchambervolumeis calculatedsimilarlyas
dimensioninga reactor(2
nd
lecture)
•Rateequation
•Requiredremoval
•Reactortype
=> Hydraulicretentiontime

25. Modelingbacteriainactivation:
Chick-Watson’slaw
Watson’slaw(1908)
(Incl. disinfectantconcentration)
Chick-Watson model(Haas& Karra, 1984)
(bothdisinfectantand pathogenconcentrations)
Integratedform:

26. Modelingbacteriainactivation:
Exampleof Rennecker-Mariñaskinetics
C t log(N/N
0
)
mg/l min data
0,96 0 -0,21
0,96 15,5-0,25
0,96 30,8-0,38
0,96 46,1-0,55
0,96 61,2-1,04
0,96 76,2-1,66
0,96 91,1-2,03
0,48 0 -0,17
0,48 32 -0,12
0,48 61,6-0,31
0,48 92 -0,6
0,48 122 -1,08
0,48 152 -1,68
4,64 0 -0,15
4,64 2,1 0,02
4,64 4,2-0,11
4,64 6,2-0,19
4,64 8,2-0,29
4,64 10 -0,56
4,64 12 -0,79
4,64 13,9-1,19
4,64 15,8-1,47
Task:ApplytheRennecker-Mariñasmodelevaluatetheinactivationof C.
parvumbychlorinedioxide. AssumethatN
0wasunderestimated(ln(N/N
0)=
log(S
0) < 0). UseExcel spreadsheetand Solverfunctionto determinethemodel
parameters.Rennecker-Mariñasmodel:
N = Concentration of microbes at time t
N
0= Concentration of microbes at time 0
b = Lag coefficient (mg*min/l)
Λ
CW= Chick-Watson coefficient of specific lethality (l/mg*min)
C = Disinfectantconcentration(mg/l)
t= Time (min)
R-M modelis usedwhenthereis lag in theeffectof thedisinfectantto the
specificorganism. Withoutlag R-M modelreducesto Chick-Watson model.
Data:

27. Solution
C t Ct log(N/N
0
)log(N/N
0
)(Data-Model)^2(Data-avg(Data))^2
mg/l min mg*min/ldata Model
0,96 0 0 -0,21-0,19 0,00 0,21
0,96 15,514,88-0,25-0,19 0,00 0,18
0,96 30,829,568-0,38-0,19 0,04 0,09
0,96 46,144,256-0,55-0,52 0,00 0,02
0,96 61,258,752-1,04-1,04 0,00 0,13
0,96 76,273,152-1,66-1,56 0,01 0,97
0,96 91,187,456-2,03-2,07 0,00 1,84
0,48 0 0 -0,17-0,19 0,00 0,25
0,48 3215,36-0,12-0,19 0,00 0,31
Excel table
avg(Data) -0,67
sum(Data-model)^2 0,184
sum(Data-avg(Data))^2 7,70
b 35
Λ
CW
0,036
log(S
0
) -0,19
Λ
CW
(basee) 0,083
r
2
0,98
... 22 rowsof data ...
Themodelfunction: =IF(Ct>b;
log(S
0);log(S
0)+Λ
CW*(b-Ct))
The sum of squares of errors is
minimized with Solver
Thesearechangedin Solver
Constraintin Solver: log(S
0)< 0

28. Data and modeledvalues
-2,5
-2
-1,5
-1
-0,5
0
0,5
0 20 40 60 80 100
log(S) =ln(N/N
0
)
Ct (mg*min/l)
data
model
ln(N/N
0
)= -0,19WhenCt<35
-0,083*(Ct-35) whenCt>=35
Note: Exercise

29. Disinfectionby-products
•Formedin chlorinationwithorganiccompounds
•Trihalomethanes(THMs)
•Carcinogenicin animaltests
•Possiblereproductiveand developmentaltoxicityin animaltests
•Haloaceticacids(HAAs)
•Carcinogenicin animaltests
•Neurotoxinin higherdosesin animaltests

30. DBPs, cont’d
DBPsformedwithchlorine
DBPsformedwithchlorinedioxide
DBPsformedwithchloramine
More DBPsformedwithchlorine

31. Approachesfor reducingand controllingDBPs
in drinkingwater
•Removalof DBP precursors(NOM, extra-cellularproducts of micro-organims)
beforedisinfection
•Removalmethods: enhancedcoagulation, granularactivatedcarbon(GAC), membrane
filtration
•SomeDBPscanberemovedwithbiodegradationin GAC orsandfilters
•Preozonationreducesformationof THMs, HAAsand totalorganichalogens(TOX)
•If THMsareformed, theycanberemovedwithpost-aerationafterdrinkingwater
treatment.
•Using alternativedisinfectants: E.g. ChloramineusereducesTHMs.
•Riskfor otherDBPs

32. Chlorineresidualmodeling
•Thiswastopiccoveredin thecourseWAT-E2110 -Design and
Management of Water and Wastewater Networks
•If you did not go to that course, the slides are included as material on
the current course

33. Shockchlorination
•Shockchlorinationis neededin contaminationcases
•Pathogenscanbeprotectedbybiofilms
•Highchlorineconcentrationsand long HRT
•Example:
•10 mg/l Cl
2
•180-240 min
•=> InactivatedYersiniapseudotuberculosisfrombiofilm( Räsänen et al. 2013)
•Flushingaftershcokchlorinationto getridof thechlorineand
possibleDBPs

34. Mostrecenttopicsin chlorinationresearch
1.DBPs
2.Chlorine-resistantpathogens

35. Digestiontask
•Recognizethedisinfectionunitsof Vanhakaupunki WTP
•Whyarethetreatmentunitsin thisorder?
•How is the formationof DBPstakeninto account?
•Whyis coagulation-flocculationin thebeginningof theprocesstrain?
•Whyis chlorineaddedafterGAC filtration?
•Whyis chloramineusedfor secondarydisinfection?
•Whyis thepH of distributedwaterratherhigh(8.6)?
Digest withyourfavouritemethod(discussion, self-talking, walking,
drinkingcoffeeetc.)

36. Literature
•Availableat EbookCentral:
•AWWA Staff, 2006. WaterChlorination/ ChloraminationPracticesand Principles.
AWWA ManualSeriesM20. American Water Works Assoc. 2
nd
ed. eBookISBN
9781613000267
•LeChevallier, MW, Au, KK, 2004. Watertreatmentand pathogencontrol. WHO, IWA
Publishing. 116 p. ISBN 92 4 1562255 2
•Bitton, G, 2014. Microbiologyof DrinkingWaterProductionand Distribution. Wiley.
316 p. eBook ISBN 9781118744017 (Chapter3, Chlorination, p. 65)
•Others:
•Shockchlorinationof privatewells
http://www.water-research.net/index.php/shock-
well-disinfection
•Inactivationof bacteriaat epa.gov:
https://www.epa.gov/sites/production/files/documents/giardiaandvirusCTcalculatio
n.pdf