Waste water engineering

Disposal of sewage treatment

🔸 Methods of disposing

👉 Dilution i.e. in water disposal

👉 Land disposal

♦️ Disposal by dilution

🔸 Disposing the waste water into high fresh water course the left overs in the waste water are removed by the water body on its own known as self purification capacity

🔸 Self purification of water bodies are due to

👉 Dilution & dispersion

👉 Sedimentation :- settleable solids will settle down into bed of the river.

👉 Sun light :- Algae plant by absorbing CO2 and releasing oxygen by a process as photo synthesis.

👉 Oxidation

👉 Reduction

🔸 Zones of pollution in river

👉 Zone I :-

~ Zone of degradation

~ DO levels reduce to 40% of original.

~ except fish, all organisms disappear.

~ Deoxygenation > Reoxygenation

👉 Zone II :-

~ Zone of active decomposition

~ DO level reduced to zero

~ heavy polluted zone

~ All aquatic organisms disappear (fish life will be absent).

👉 Zone III :-

~ Zone of recovery

~ DO level raised to 40% original

~ Fish appears in water.

~ Reoxygenation > Deoxygenation

👉 Zone IV :-

~ clear water zone

~ Reoxygenation only occur no Deoxygenation.

~ River is recoverd.

~ DO level rises to original

~ All aquatic organisms appears


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