Q9. A Waste water treatment units is proposed to be designed forthe Wilayat of Sur. Population of Sur is 200,000 and an averagesewage generation is 210 liter per capita per day. Design anappropriate waste water treatment plant using the following givendata. If needed assume other necessary data.

Approach channel velocity = 42 m/min, d = 1.5 w Design threeaerated grit chamber Detention time in grit chamber = 3 min Depthof aerated grit chamber = 2.0 m Depth to width ratio in aeratedgrit chamber is 1:1.2 Total depth of primary clarifier = 3 m(Mechanical Sludge removal) Overflow rate = 20 m3/m2.d Detentiontime in the primary clarifier should be greater than 1.5 hoursSecondary clarifier with a depth of water equal to 0.5 times theLength (Mechanical Sludge removal) Detention time in secondaryclarifier = 2 hours

a. List and explain briefly the important parameters to be analyzedfor the waste water before and after treatment. (2)

b. Is waste water treatment is compulsory before disposing it tothe land? Justify. (2)

c. What is meant by sludge? Is sludge resource or waste? Explain.(2)

d. Why is the aeration tank followed by primary sedimentationprocess? (2)

e. Design (size of the unit) the following units of the treatmentprocess: Rectangular Bar screen channel, Rectangular Aerated Gritchamber, Six Circular Primary Clarifier, and Six Square SecondarySedimentation tank.