Start-up and performance of a downflow fluidised bed reactor for biological treatment of yellow wastewater and nutrient recovery

The treatment of yellow water (human urine) in a downflow fluidised bed reactor (DFFBR) was investigated to evaluate biological ureolysis and nutrient recovery. The reactor was operated at 30 +/- 4 degrees C in batch mode, and hydraulic retention time=1 d. The average immobilised biomass (as volatile solids, IVS) in the reactor was 2.5 +/- 0.9 g L-support(-1), and specific ureolytic activity was 121 g(-1) Urea-N g(-1) IVS d(-1). The kinetic parameters were 0.152 mol L-1 (K-m) and 8 mol g(-1 )IVS d(-1) (V-max). The ureolysis efficiency was 93.4% and chemical oxygen demand removal efficiency was 31.2%, while total ammonium nitrogen (NH4+-N) production rate was 7 g L-1 d(-1) and phosphate removal reached 26%. Precipitates recovery during biological treatment was 1.72 +/- 0.8 g. These results suggest that the treatment of yellow water in a DFFBR is a viable option for partial recovery of N and P.