Freshwater aquaculture

Unit 6 - Sewage Fed Fish Culture

6.3. Use of raw sewage for fish culture
The raw sewage needs to be treated before using in fish ponds.
Mechanical, chemical and biological treatments are the three steps involved in treatment of raw sewage.

Mechanical Treatment
This step is required to remove suspended and floating solids from the raw sewage. The solids are removed first by using screens and then by skimming. Finally they are removed by sedimentation.

Chemical treatment
Chemical treatment of raw sewage involves steps such as coagulation/chemical precipitation, deodorization, disinfection and sterilization.

Biological treatment
Sewage is treated biologically by using natural bacterial activity for the oxidation of organic matter.

The treated sewage can than be used for fish culture after suitable dilution with freshwater.