Primary sewage treatment
Secondary sewage treatment
1.
It is a physical method of treatment
It is a biological method of treatment
2.
It involves in removal of large particles and floating materials such as leaves, papers, rags, solids such as sand, grit and oily substances
It involves the removal of fine suspended and dissolved organic matter.
3.
It makes the used of sedimentation and filtration process
It makes the use of aerobic or anaerobic biological units
4.
It is relatively simple and less time consuming process
It is relatively complex and takes a long time for its completion
