Biological Treatment

The effluent from the Primary settling tanks overflows towards the secondary treatment system which consists of two aeration tanks and four circular secondary settling tanks.

The biological treatment is provided in an activated sludge plant where nitrogen, organic matter and part of the phosphorus are removed using the Bio-Denitro process. This process involves two interconnected aeration tanks where nitrogen is removed biologically in two stages – Nitrification and Denitrification. In the aerobic (oxygen present) phase ammonia is converted to nitrate. In the anoxic (oxygen absent, but nitrates present) phase the nitrate is converted to nitrogen which is released to the atmosphere.