Performance-based characterization of a contact stabilization process for slaughterhouse wastewater

This paper evaluates the effluent treatment plant of a slaughterhouse in Hawalli City, Kuwait processing 1100 heads of livestock a day. Results indicated that the proposed process effectively reduces pollution potential of slaughterhouse wastewater. Influent Chemical Oxygen Demand (COD) ranged from 3335 to 7580 mg L-1, of which approximately 30% were in the form of suspended solids (SS). Removal efficiency was 77% for soluble COD and 82% for insoluble COD, at a volumetric load of 1.8 kg COD m(-3) d(-1). Values obtained for the biokinetic coefficients, floc uptake (FU), substrate removal efficiency (SRE), specific reaction rate (R-R), maximum reaction rate (R) and Yield (Y) of the contact tank were higher than the range of values reported for other continuously fed activated sludge systems. In contrast to the contact tank, the aeration basin biokinetic coefficients were within the range of values reported. Contact process testing demonstrated that controlling solid recirculation to maintain a contact loading of about 120-150 mg COD g(-1) VSS in the contact tank generally resulted in high SRE, R-R, R-m and also in good settleability as indicated by SVIs being consistently below 150 mL g(-1). In the other hand, higher contact loadings of more than 150 mg COD g(-1) VSS, resulted in a significant deterioration in SRE, R-R, R-m. and SVIs.