Environmental engineering. Theory questions a- What is the main objective of the

Question

Environmental engineering. Theory questions

a- What is the main objective of the primary and secondary wastewater treatment.

b- Name two types of material for geomembrane liners

c- What is the difference between municipal and hazardous waste landfill liners?

d- List four recyclable components of MSW e- Name two sludge dewatering technologies

f- What type of sedimentation occurs in primary clarifies and in gravity thickeners?

g- Name two types media used in trickling filters?

h- Name two types each for suspended growth and attached growth secondary treatment

i- What are the two key factors for successful secondary wastewater treatment?

j- Name two compostable solid waste water components

Explanation / Answer

Prob.(a)

Primary treatment mainly uses the sedimentation to remove the suspended waste particles and thus reduce the BOD of the waste water by 20 to 30%. This process takes place after filtering out the large debris or particles. Wastewater is passed through several sedimentation tanks and filters. The suspended solids are removed by up to 60%.

Secondary treatment takes place after the primary treatment has been done. The primarily treated sludge is treated with the methods of oxidation to reduce the BOD by 85%. All the suspended solids are removed. The biological oxidation used in secondary treatment is able to remove the organic matter desolved in the water. Secondary treatment can be done with these three methods:

Biofiltration: Sand Filters, trickling filters and contact filters are used to remove the sediments. Trickling filters are most efficient.

Aeration: In this process micro-organisms are fed into the sludge which helps in removing the organic matter. This is a long but effective process.

Oxidation Ponds: Natural water bodies such as lagoons are used for storing the waster water for a definite period, and thus the impurities are removed naturally by natural oxidation.

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