DISINFECTIONDISINFECTION

CE326 PRINCIPLES OF ENVIRONMENTAL ENGINEERINGCE326 PRINCIPLES OF ENVIRONMENTAL ENGINEERINGIowa State UniversityIowa State University

Department of Civil, Construction, and Environmental Engineering Department of Civil, Construction, and Environmental Engineering Tim Ellis, Associate ProfessorTim Ellis, Associate Professor

March 22, 2010March 22, 2010

AnnouncementsAnnouncements

Wednesday lab in Town classroom Wednesday lab in Town classroom – Finish water treatment plant labFinish water treatment plant lab– Exam reviewExam review

22ndnd exam scheduled for this Friday, March exam scheduled for this Friday, March 2626thth

HISTORYHISTORY

J_____ S____ and the Broad Street pump in 1854J_____ S____ and the Broad Street pump in 1854 he was able to show that 59 of the 77 c________ he was able to show that 59 of the 77 c________

victims used the pump on Broad Streetvictims used the pump on Broad Street There was a w___________ in the vicinity where There was a w___________ in the vicinity where

cholera was endemic but nobody at this cholera was endemic but nobody at this workhouse got cholera. workhouse got cholera.

This particular workhouse had its own w___. This particular workhouse had its own w___. The cause of contamination turned out to be the The cause of contamination turned out to be the

d_____ of an infected person that was within three d_____ of an infected person that was within three feet of the well.feet of the well.

ohn nowholera

orkhouse

ell

rain

Broad Broad Street Street PumpPump

ChlorinationChlorination

Disinfection of water supplies by c____________ Disinfection of water supplies by c____________ began in Chicago and New Jersey in 1908, began in Chicago and New Jersey in 1908,

within 2 years chlorination of w_____ s________ within 2 years chlorination of w_____ s________ was practiced in N.Y., Montreal, Milwaukee, was practiced in N.Y., Montreal, Milwaukee, Cleveland, Nashville, Baltimore, and Cincinnati. Cleveland, Nashville, Baltimore, and Cincinnati.

By 1918, over 1000 c_____ treating more than __ By 1918, over 1000 c_____ treating more than __ bgd were chlorinating their water supplies.bgd were chlorinating their water supplies.

By 1923 the typhoid death rate had dropped more By 1923 the typhoid death rate had dropped more than 90%than 90%

By the beginning of WWII, typhoid, cholera, By the beginning of WWII, typhoid, cholera, dysentery were practically eliminated in U.S.dysentery were practically eliminated in U.S.

http://www.americanchemistry.com/100years/timeline.html

hlorination

ater upllies

ities 3

TheoryTheory Chick’s Law: Chick’s Law:

rate, k, is a function of c___________ and t______ (i.e., CT) and type of rate, k, is a function of c___________ and t______ (i.e., CT) and type of organismorganism

Typical disinfectants:Typical disinfectants:– Chlorine:Chlorine: ClCl22 + H + H22O → HOCl + ClO → HOCl + Cl--

– ChloraminesChloramines

NHNH33 + HOCl → NH + HOCl → NH22Cl + HCl + H2200

NHNH22Cl + HOCl → NHClCl + HOCl → NHCl22 + H + H2200

NHClNHCl22 + HOCl → NCl + HOCl → NCl33 + H + H2200

dN

dtkN

oncentration ime

monochloramine

dichloramine

trichloramine

Pellet dropper Tablet feeder

ChlorinatorsChlorinators

Gas – 2,000 pound

Courtesy Smith Group Consulting, LLC

ChlorinatorsChlorinators

+-battery

Electrolytic CellNaCl + H20 + 2e- NaOCl + H2

anode cathodeNa+ + e- Na 2Cl- Cl2 + 2e-

+-

Hand held chlorine producing unit (CPU)

If the products are mixed, the result is household bleach.2 NaOH(aq) + Cl2(g) = NaCl(aq) + NaOCl(aq) + H2O

Chlorine Contact TankChlorine Contact Tank

www.wsd.dst.il.us/tour/imgbig/contact_tk_1.jpg

OzonationOzonation

strong o______, but strong o______, but no residualno residual

no THM f_________ no THM f_________ but other (non-but other (non-chlorinated) DBPs chlorinated) DBPs possiblepossible

often used as a often used as a p__________ p__________ disinfectantdisinfectant

xidant

ormed

rimary

Chlorine DioxideChlorine Dioxide

strong oxidant, but not strong oxidant, but not a powerful as o_____a powerful as o_____

dose limited to 1.0 dose limited to 1.0 mg/L due to health mg/L due to health concerns of chlorite concerns of chlorite and c_______and c_______

residual is not long residual is not long l______l______

zone

hlorate

asting

Ultraviolet (UV) LightUltraviolet (UV) Light uses thin layer of water and uses thin layer of water and

mercury vapor arc l_____ mercury vapor arc l_____ emitting UV in the range of 0.2 emitting UV in the range of 0.2 to 0.29 micronto 0.29 micron

depth of light p_________ depth of light p_________ limited to 50 - 80 mmlimited to 50 - 80 mm

powerful, but no residualpowerful, but no residual

amp

enetration

ADSORPTIONADSORPTION takes advantage of physical/chemical bond of takes advantage of physical/chemical bond of

pollutant with adsorbent (typically g_______ pollutant with adsorbent (typically g_______ activated carbon or p_________ activated carbon)activated carbon or p_________ activated carbon)

one ounce of GAC has a surface area of ____ one ounce of GAC has a surface area of ____ acresacres

good process for removal of good process for removal of – THMsTHMs– DBPsDBPs– SOCsSOCs– VOCsVOCs

ranularowdered

5-10

ADSORPTIONADSORPTION PAC dose is typically _____ mg/L can be as PAC dose is typically _____ mg/L can be as

high as ___mg/Lhigh as ___mg/L GAC can be used instead of a_______ in GAC can be used instead of a_______ in

dual media filters, dual media filters, – called filter adsorbers called filter adsorbers – must replace GAC every ____ yearsmust replace GAC every ____ years

separate stage adsorption unit (contactor separate stage adsorption unit (contactor unit) unit) – GAC must be replaced or regenerated every __ GAC must be replaced or regenerated every __

to __ monthsto __ months

5-1050

nthracite

1-3

34

Particle Size vs. Treatment AlternativesParticle Size vs. Treatment Alternatives

Macromolecules Smaller ParticlesLarge

Suspended Particles

MF UF NF RO

Divalent salts

Monovalent salts

Water

Micro filtration (MF) - bacteria, algae, clay, large MW humic acids Ultra filtration (UF) - humic acids, viruses, proteinNanofiltration (NF) – viruses, divalent saltsReverse Osmosis (RO) – monovalent salts

Membrane TreatmentMembrane Treatment

Reverse OsmosisReverse Osmosis