Pre-fermentation of a low-strength meat-processing wastewater in an upflow sludge blanket reactor

Pre-fermentation of low-strength wastewater from a meat processing facility (at 20 degrees C) was studied. A laboratory-scale upflow sludge blanket (USB) reactor was used for the experiments; 10 different operating conditions were tested with regard to the hydraulic residence time (HRT). At HRTs from 0.4 to 2.4 hours, the USB reactor produced effluent with acetate chemical oxygen demand from 82 to 100 mg/L. At HRTs shorter than 0.4 hours and upflow velocities greater than 0.5 m/h, biomass washout was observed. At HRTs longer than 2.4 hours, acetate concentration in the effluent and acetate production efficiency decreased. The transformation of organic nitrogen to ammonia-nitrogen occurred simultaneously with acetate production. Minimal accumulation of biomass in the USB reactor was observed. Pre-fermentation of the low-strength industrial wastewater in the USB reactor could be beneficial for biological nitrogen removal. The produced acetate is directly available for denitrification and the transformed ammonia-nitrogen is directly available for nitrification in the subsequent wastewater treatment steps.