8. What is the key difference between primary and secondary sewage treatment?
The differences between the primary and secondary treatment of sewage are as follows:
|Primary sewage treatment||Secondary sewage treatment|
|Primary sewage treatment is a mechanical process that removes solid waste materials||Secondary sewage treatment is a biological process in which waste materials are enzymatically treated by bacteria and other microbes|
|It is a less expensive and simple process||It is an expensive and complicated process|