Which of the following statement is correct regarding activated sludge process?

I. The activated sludge process provides an method of treating either raw sewage or settled sewage

II. The sewage effluent from primary sedimentation tank is utilised in activated sludge process 

Explanation:

Activated Sludge Process: The activated sludge process is a biological wastewater treatment process that uses aeration and a biological floc composed of bacteria and protozoa. It is commonly used to treat sewage and industrial wastewater.

The characteristics of the activated sludge process include:

• Treating raw or settled sewage (I): The activated sludge process can be used to treat both raw sewage and settled sewage. However, it is more common to treat settled sewage (sewage that has undergone primary sedimentation) in the activated sludge process to reduce the load on the aeration system.
• Use of effluent from primary sedimentation tank (II): The effluent from the primary sedimentation tank, which is partially treated sewage, is typically used in the activated sludge process. This effluent is introduced into the aeration tank where it is mixed with the activated sludge and aerated to promote the growth of microorganisms that degrade organic matter.

Therefore, both statements I and II are correct.