Start-up of a decentralized pilot plant for the anaerobic treatment of domestic wastewater

This paper is about the set-up and start-up of a decentralized anaerobic pilot plant for producing domestic service water from domestic wastewater. The plant consists of a two-stage anaerobic digestion process for degrading organic matter and a third-stage for ammonium removal using the Anammox process. Each reactor was started independently with synthetic wastewater of stage-specific composition. They were then fed incrementally with municipal wastewater (MWW). The average removal efficiency of the two-stage digestion process operated with 100% MWW was 62% with 24-hour retention time. The Anammox stage achieved a maximum ammonium removal efficiency of 95% with 100% MWW, if the NO₂-N to NH₄-N ratio was set at 1.14. The plant was operated for 200 days. The average removal efficiencies were 81% for COD and 96% for NH₄-N, with average treated effluent concentrations of 39 mg-COD/l and 1 mg-NH₄-N/l. Thus the self-defined service water limits of 75 mg-COD/l and 10 mg-NH₄-N/l were achieved easily.