1. Water Treatment CE 326 Principles of Environmental Engineering
Department of Civil, Construction and Environmental Engineering
Iowa State University
March 2, 2009
Tim Ellis, Ph.D., P.E.

2. Announcements Water Chemistry II Problem Set due today
Schedule change: Wednesday, March 4 lab will be part 1 of the water treatment plant design
The Water Treatment Plant Field Trip has been moved to Wednesday, March 11

3. Water Treatment Groundwater Surface Water
hardness (aesthetic consideration)
disinfection (required by SDWA)
Surface Water
turbidity and color removal
filtration (required by SDWA)
CE 326 Principles of Environmental Engineering, Copyright © 2008 Tim Ellis, Iowa State University

4. Coagulation = Charge reduction Flocculation = Contact of particles

5. Charge Neutralization/Reversal

6. Alkalinity in Coagulation Needed to neutralize acid formed

7. Rapid Mix Rapid Mix Tank In-line Blender Static Mixer

8. Paddle Mixer Details

9. Paddle Mixers in Left Chamber and Flocculators in Right Two Chambers

10. Mixing Calculations
Find P for a rapid mix basin where Q=0.05 m3/s; detention time= 60 s, T=20°C, G=700 s-1;= x 10-3 Pa∙s

11. Mixing Calculations
How many hp would you need for a flocculation basin to provide a G=100 s-1 Gt value of 100,000 for a 10 mgd flow (1 mgd = m3/s); = 0.89 x 10-3Pa∙s; 1 hp = Watts

13. Settling/Sedimentation

16. Groundwater Treatment Plant Treatment of Groundwater for Hardness Removal
Rapid
Mix
Slow
Mix
Recarbonation
Aeration
Hard Water
Ca+2 + Mg+2
add
CO2
to decrease pH
add D. O.
to remove CO2
and H 2S
Fe2+ → Fe3+
Sedimentation
weir overflow rate:
m3/m. d
surface overflow rate:
57-70 m3/m2 . d
m3/m2 . d for upflow solids contact
add lime (for CH)
and soda ash (for NCH)
raise pH to
to precip. hardness
Bore Hole
Well
to distri-
bution
Clear-
well
Filtration
G values for Rapid Mix: s-1
In-Line blender: s-1
Gto values for Flocculation
Type G(s-1) Gto
Softening (10%) , ,000
Softening (39%) , ,000
E.S. = mm
U.C. =
depth =
loading rate = m3/m2d
add Cl2 , polyphosphate
and F-
CE 326 Principles of Environmental Engineering, Copyright © 2008 Tim Ellis, Iowa State University

17. Surface Water Treatment Plant Surface Water Treatment for Turbidity and Color Removal
Intake and
Pump Station
Sedimentation
weir overflow rate: surface O. R.: m3/m. d light floc m3/m2 . d
m3/m. d heavy floc
Rapid
Mix
Slow
Mix
Bacteria, Color,
Turbidity G:
s-1
t: 30-60s
flocculation
basin
sedimentation
basin
alum or
iron salts for coagulation
add Cl2 or
O3 for taste
and odor
Stream
to distri-
bution
Clear-
well
Filtration
G values for Rapid Mix: s-1
In-Line blender: s-1
Gto values for Flocculation
Type G(s-1) Gto
Low turbidity , ,000
High turbidity ,000-96,000
E.S. = mm
U.C. =
depth =
loading rate = m3/m2d
add Cl2 , polyphosphate,
and F-
lime for pH
CE 326 Principles of Environmental Engineering, Copyright © 2008 Tim Ellis, Iowa State University