Question

List the events that lead to biogas production from waste water whose BOD has been reduced significantly.

Answer 1

Once the biological oxygen demand (BOD) of waste water is significantly reduced, the effluent is passed into a settling tank for sedimentation. From the settling tank, the sedimented material, called activated sludge, is transferred into another large tank called anaerobic sludge digester. In the anaerobic sludge digester, anaerobic bacteria grow and digest the rest of the organic matter and the flocs present in the sludge to produce a mixture of gases such as methane, hydrogen sulphide and carbon dioxide. These gases are collectively known as biogas.