Treatment of Slaughterhouse Wastewater Using Fluidized Bed Biofilm Reactors

Abstract

The oxygenic fluidized bed biofilm reactor(FBBR) was evaluated in a laboratory investigation for treatment of pig slaughtering wastewater (slaughterhouse wastewater). Because the slaughterhouse wastewater contains a high concentration of grease, chemical coagulation/flocculation was adopted as the pretreatment step prior to FBBR treatment. The performance of the FBBR was evaluated at BOD loadings of between 8.5 to 98.5 kg/m3-day, hydraulic retention times of between 8.8 to 30.8 minutes, recirculation ratios of between 1 to 6, and feed BOD concentrations of between 305 to 602 mg/L. Under these operating conditions, removal efficiencies of BOD, grease, and NH3-N were in the range of 71 to 94%, 29 to 84%, and 20 to 73%, respectively. Both BOD and grease of the slaughterhouse wastewater used could be lowered to 40 and 10 mg/L, respectively, at a BOD loading of 20 kg/m3-day in order to meet effluent requirements to be enforced in Taiwan in 1990. Because the maximum amount of oxygen that could be dissolved in the oxygenation device used in this investigation was 40 mg/L, the FBBR would become anaerobic when the BOD loading applied exceeded 50 kg/m3-day. Relatively constant biomass holdups (10,000 mg TVS/L) could be maintained in FBBRs over the BOD loadings applied via the practice of regular biofilm separation and biomass wasting. The combined chemical coagulation/flocculation-FBBR process provides a feasible and cost-effective alternative for treatment of slaughterhouse wastewater.