Simultaneous Clarification and Endogenous Post Denitrification by Up-flow Through a Layer of Floating Media

Low Total-Nitrogen (TN) requirements in wastewater treatment effluents, eventually require a post denitrification step. This is commonly done by addition of an external carbon source, which adds to the cost of wastewater treatment. Some work has been done in recent years on different methods for onsite production of suitable carbon source, by fermenting primary sludge or secondary sludge. In this work an attached growth pilot system, wherein plastic biomass carriers are aerobically mixed, was operated to treat municipal wastewater. The effluent, generally having less than 200 mg/l TSS, was directly passed through an un-aerated layer of similar media, in which most of the suspended solids were retained, and could be controllably discharged. Most probably due to endogenous decay below and within the layer of media, nitrate was removed to very low levels at retention times of about 3 hours. The main design and operation issue is sludge wasting, still being optimized.