Water engineering basics

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Answered Same Day Dec 26, 2021

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Robert answered on Dec 26 2021

113 Votes

a) Question:
Identify and concisely describe the main and auxiliary unit operations that are normally
used in potable water treatment. For each process clearly indicate the principle
mechanisms of impurity removal/attenuation in terms of physical, chemical or biological
action.
Water treatment is a combination of physical, chemical and biological processes. The
methods of treatment in which the application of physical forces predominates are
known as unit operations while the methods of treatment in which chemical or biological
activities are involved are known as unit processes. There are three types of unit
operations and prcesses; 1. Physical unit operations, 2. Chemical unit processes. 3.
Biological Unit processes.
In Water or wastewater treatment, unit operations are those procedures in which
changes produced are physical, chemical or biological.
Physical Unit Operations:
i) Screening
ii) Comminution
iii) Flow equalization
iv) Mixing
v) Flocculation
vi) Sedimentation
vii) Floatation
viii) Elutration
ix) Vacuum filtration
x) Micro screening
x) Air drying
Chemical unit process:
i) Chemical precipitation
ii) Gas transfer
iii) Adsorption
iv) Disinfection
v)Dechlorination
vi) Combustion
vii) Ion exchange and
viii) Electrodialysis
Biological Unit processes:
a) Aerobic Processes:
i) Activated Sludge process
ii) Trickling filters
iii) Aerobicc stabilization ponds
iv) Aerated lagoons
) Anaerobic process:
i) Anaerobic sludge digestion
ii) Anaerobic contact processes
iii) Anaerobic filters
iv) Anaerobic lagoons or ponds
c) Aerobic-anerobic process
Normally for potable water treatment (water coming from river)through following unit
operations are involved.
I) Screening
II) Coagulation preferencly aided by Alum polymers( Auxiliary unit)
III) Floculation ( Auxiliary unit)
IV) Sedimentation
V) Filtration
VI) Disinfection aided by chlorine
VII) Storage (Auxiliary Unit)
VIII) Distribution (Auxiliary Unit)
Screening: Surface straining is the principle mechanism for removal of course/settleable
solid
Coagulation: The process of adding coagulant is called coagulation. In coagulation we
added a chemical such as alum which produces...

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