1. Overview of Water Treatment
Physical, chemical, and biological processes are used for treating water.
Unit operation: physical treatment.
Unit process: chemical or biological treatment.
A series of unit operations and unit processes are selected by the process engineer based on influent characteristics to achieve the desired effluent quality.

2. Water Treatment Problem
A water treatment plant is to be designed to treat
water with the following characteristics:
High turbidity
High bacteriological concentrations
No carbon dioxide
Medium color
Low hardness
What is the source of the water?
Prepare schematic of treatment train.

3. Items to Consider Source: River– variable flow and quality
High turbidity: removed by sedimentation and filtration; suggest presedimentation.
High bacteriological concentrations: removed by disinfection; some microbes removed by coagulation, flocculation and settling; suggest predisinfection.
Carbon dioxide: aerate or add lime if present.
Medium color: ozonation and chlorination will reduce,
may be necessary to use activated carbon
Low hardness : would soften if moderately hard.

4. Screening: unit operation, removes large debris and tree limbs.
Disinfectant
Screens
Flow Meter
Low Lift Pumps
Plain
Sedimentation
Screening: unit operation, removes large
debris and tree limbs.
Low Lift Pumps: unit operation, provides
energy to lift water up to the treatment plant
Flow Meter: unit operation, measures flow.
Pre-disinfection: unit process, disinfectant added to lower bacterial and pathogen levels.
Plain sedimentation: unit operation, removes
suspended solids lowering turbidity.

5. Mixing: unit operation, dispersion of coagulant.
Sedimentation
Disinfectant
Focculation
Mixing: unit operation, dispersion of coagulant.
Flocculation: unit process, destabilization of
colloidal particles and promotion of floc growth.
Sedimentation: unit operation, removal of suspended solids, lowers turbidity.
Disinfection: unit process, addition of disinfectant to kill pathogens.

6. Filtration
Clear Well
Disinfectant
High Service Pumps To
Distribution
System
Filtration: unit operation, removes remaining turbidity and microbial cysts.
Disinfection: unit process, disinfectant added to ensure pathogens are destroyed. Clear well provides necessary contact time with disinfectant.
High Service Pumps: unit operation, energy provided to pump water throughout distribution system.

7. Water Treatment Problem
A water treatment plant is to be designed to treat
water with the following characteristics:
Low turbidity
Low bacteriological concentrations
Moderate carbon dioxide
Low color
High hardness
What is the source of the water?
Prepare schematic of treatment train.

8. Items to Consider
Source: Well– relatively constant flow and high quality.
Low turbidity: removed by coagulation, flocculation, sedimentation and filtration; may need to add turbidity in the form of clay to provide nuclei
for coagulation.
Low bacteriological concentrations: removed by disinfection; some microbes removed by coagulation, flocculation and settling; lime-soda ash
treatment followed by sedimentation and filtration should remove microbes .
Carbon dioxide: aerate or add lime if present.
Low color: ozonation and chlorination will reduce.
High hardness : soften if moderately hard using lime-soda ash; alternative
treatment would be to used membranes rather than conventional treatment.

9. Wells: unit operation, source of groundwater.
Low Lift Pumps
Aeration
Trasy
Disinfectant
Wells
Flow Meter
Wells: unit operation, source of groundwater.
Low Lift Pumps: unit operation, provides
energy to lift water up to the treatment plant
Flow Meter: unit operation, measures flow.
Pre-disinfection: unit process, disinfectant added to
reduce pathogen levels and oxidize H2S, Fe & Mg.
Tray Aeration: unit operation, removes
CO2, H2S, and other gases.

10. Flocculation: unit process, destabilization of
Lime & Soda
Mixing
Sedimentation
Disinfectant
Focculation
Mixing: unit operation, dispersion of lime & soda-ash for hardness removal.
Flocculation: unit process, destabilization of
colloidal particles and promotion of floc growth.
Sedimentation: unit operation, removal of suspended solids, lowers turbidity.
Disinfection: unit process, addition of disinfectant to kill pathogens.

11. Filtration
Clear Well
Disinfectant
High Service Pumps To
Distribution
System
Filtration: unit operation, removes remaining turbidity and microbial cysts.
Disinfection: unit process, disinfectant added to ensure pathogens are destroyed. Clear well provides necessary contact time with disinfectant.
High Service Pumps: unit operation, energy provided to pump water throughout distribution system.