Discuss the possible impact of sidestreams or recycle flows back to the activated sludge process.
Sidestreams or recycle flows usually come from solids handling treatment or dewatering processes, such as decanting digesters or sludge storage tanks. Sidestreams may be highin BOD, suspended solids, ammonia, phosphorus, and sulfides or very low in temperature.It is best to return sidestreams slowly and regularly so microorganisms adjust and acclimateto this loading. If permit limits phosphorus or ammonia, it is critical to know the loading fromsidestreams. Sidestreams can upset a treatment plant or result in a pass-through of pollutants to the effluent, resulting in permit violations. If permit limits phosphorus or ammonia, sometimes it is necessary to separately treat the sidestream.