The lagoon received about 114 m3/d of domestic wastewater. Typical effluent ammonia-N concentrations prior to installation of the FRBC were about 20 mg/L. With the FRBC operating in the third (polishing) cell of the lagoon system, typical effluent ammonia-N concentrations were less than 2 mg/L at temperatures above 10 °C. As long as wastewater temperatures were 10°C or higher, 90+% ammonia-N removal was achieved. The maximum nitrification rate was 2.47 g/m2/d at an average temperature of 11°C. The FRBC also increased effluent dissolved oxygen (DO) levels by 20%.
Achieving nitrification in sewage lagoons with an innovative floating RBC
The research involved the newly developed floating rotating biological contactor (FRBC), a unique unit consisting of a rotating cage filled with hollow, spherical packing of injection molded plastic. The cage rotates to provide biomass a chance to contact both substrate and air. A partially mixed three-cell aerated lagoon was selected for the study.