1. Water Treatment CE 326 Principles of Environmental Engineering
Department of Civil, Construction and Environmental Engineering
Iowa State University
February 29, 2008
Tim Ellis, Ph.D., P.E.

2. 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

3. 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

4. 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