Slaughterhouse effluent treatment by thermophilic aerobic process

Abstract

A pig slaughterhouse effluent was submitted to laboratory runs in order to assess the potentiality of the thermophilic aerobic process for the treatment of meat processing industry's effluents. A mixed aerobic bacterial culture was successfully maintained at 52 and 58°C in a semi-continuously fed bioreactor, without recycling the cells. Operation was conducted at 6, 12, 18, 24 and 30 h of solids retention time. Over 93% of the CODs (Chemical Oxygen Demand) were removed during the treatment at 52°C for all the retention times investigated, as compared to 86% of removal at 58°C, with an exception for the case of 6 h retention time. Reduction of phosphorus in the form of orthophosphate ranged between 72–90% with the best efficiency noted at 52°C and 6 h retention time. Extremely high specific utilization rates ( q m) were observed and revealed that the process is about 10 times faster than the mesophilic process for slaughterhouse effluent treatment. Biokinetics parameters μ m (maximal specific growth rate) and k d (endogenous respiration coefficient) were evaluated by fitting to appropriate mathematical models. They were found superior to those reported in the literature for mesophilic process, with the exception of the Y (actual yield) coefficient which is of the same magnitude. High k d values had a marked effect on the apparent yield of sludges which showed low values as compared to those found in mesophilic systems.