Finally, there are comminutors to shred floating material, and an open channel ultra sonic flow metering flume. Two sets of parallel tanks or trains. Each train consists of 6 sections in series. A mixture of primary effluent and return activated sludge flows first into 3 anaerobic selector zones that are mechanically mixed. The bugs convert dissolved and colloidal material into their body mass where it can be removed by settling in the next stage of the process.
Ammonia is oxidized to nitrate also during the aeration process.
The underflow from these tanks provides a source of material to re-seed the aeration stage. Clean water overflows the weirs of these tanks. We have 3 secondary tanks. Two 100' diameter tanks and one 142' diameter tank. Disinfection is by the addition of sodium hypochlorite solution.