Water TreatmentWater Treatment

CE 326 Principles of Environmental EngineeringCE 326 Principles of Environmental EngineeringDepartment of Civil, Construction and Environmental EngineeringDepartment of Civil, Construction and Environmental Engineering

I St t U i itI St t U i itIowa State UniversityIowa State UniversityMarch 2, 2009March 2, 2009

Tim Ellis, Ph.D., P.E.Tim Ellis, Ph.D., P.E.

Announcements Announcements

• Water Chemistry II Problem Set due todayy

• Schedule change: Wednesday, March 4lab will be part 1 of the water treatment lab will be part 1 of the water treatment plant design

• The Water Treatment Plant Field Trip has • The Water Treatment Plant Field Trip has been moved to Wednesday, March 11

Water Treatment Water Treatment

• Groundwater– hardness (aesthetic consideration)( )– disinfection (required by SDWA)

• Surface Water• Surface Water– turbidity and color removal

filtration (required by SDWA)– filtration (required by SDWA)– disinfection (required by SDWA)

CE 326 Principles of Environmental Engineering, Copyright © 2008 Tim Ellis, Iowa State University

Coagulation = Charge reductionl l C f lFlocculation = Contact of particles

Charge Neutralization/ReversalCharge Neutralization/Reversal

Alkalinity in CoagulationAlkalinity in Coagulation

N d d t t li id f dNeeded to neutralize acid formed

Rapid MixRapid Mix

Rapid Mix Tank In line Blender Static MixerRapid Mix Tank In-line Blender Static Mixer

http://www.postmixing.com/mixing%20forum/Macro/Fluid%20Motion/process_intensifier/images/hga%20model.jpghttp://www.pumppackage.co.uk/images/KOFLO_Page%206/Kofloflowani.gif

Paddle Mixer Details

P ddl Mi i L ft Ch b Paddle Mixers in Left Chamber and Flocculators in Right Two Chambers

Mixing CalculationsMixing Calculations

• Find P for a rapid mix basin where Q=0.05 m3/s; detention time= 60 s, Q / ; ,T=20°C, G=700 s-1;= 1.002 x 10-3 Pa·s

Mixing CalculationsMixing Calculations

h ld d f• How many hp would you need for a flocculation basin to provide a G=100 s-1

l f f d flGt value of 100,000 for a 10 mgd flow (1 mgd = 0.0438 m3/s);

3 h= 0.89 x 10-3Pa·s; 1 hp = 745.7 Watts

Settling/SedimentationSettling/Sedimentation

Groundwater Treatment PlantTreatment of Groundwater for Hardness Removal

AerationHard WaterCa+2 + Mg+2

to remove CO

RapidMix

SlowMix Recarbonation

addCO2

d Hadd D. O.

Bore Hole

to remove CO2and H 2S Fe2+ → Fe3+ Sedimentation

weir overflow rate: 268-322 m3/m. dsurface overflow rate:

to decrease pH

add lime (for CH)and soda ash (for NCH)raise pH to 10 11 5 Well

surface overflow rate:57-70 m3/m2 . d105-130 m3/m2 . d for upflow solids contact

raise pH to 10 - 11.5 to precip. hardness

to distri-b

Filtration Clear-well

bution

add Cl2 , polyphosphateG values for Rapid Mix: 700-1000 s-1

In-Line blender: 3000-5000 s-1

l f l lE.S. = 0.35 - 0.55 mmU C = 1 3 1 7 and F-Gto values for Flocculation

Type G(s-1) GtoSoftening (10%) 130-200 200,000-250,000Softening (39%) 150-300 390,000-400,000

U.C. = 1.3 - 1.7depth = 0.3 - 0.75loading rate = 120 - 240 m3/m2d

CE 326 Principles of Environmental Engineering, Copyright © 2008 Tim Ellis, Iowa State University

Surface Water Treatment PlantSurface Water Treatment for Turbidity and Color Removal

SedimentationIntake and P St ti

Bacteria, Color,Turbidity

RapidMix

SlowMix

Sedimentationweir overflow rate: surface O. R.: 143-179 m3/m. d light floc 20 - 40 m3/m2 . d179-268 m3/m. d heavy floc

Pump Station

G: 700-1000 s-1

t 30 60flocculationbasin

sedimentationbasin

Streamalum or iron salts for coagulation

add Cl2 or O3 for taste and odor

t: 30-60s basin basin

to distri-

and odor

Filtration Clear-well

bution

add Cl2 , polyphosphate,

G values for Rapid Mix: 700-1000 s-1In-Line blender: 3000-5000 s-1Gto values for Flocculation E.S. = 0.35 - 0.55 mm

U C = 1 3 1 7 and F-

lime for pHType G(s-1) GtoLow turbidity 20-70 60,000-200,000High turbidity 30-80 36,000-96,000

U.C. = 1.3 - 1.7depth = 0.3 - 0.75loading rate = 120 - 240 m3/m2d

CE 326 Principles of Environmental Engineering, Copyright © 2008 Tim Ellis, Iowa State University