LAB SCALE STUDY OF HRT AND OLR OPTIMIZATION IN A UASB TREATING SLAUGHTERHOUSE WASTEWATER

Abstract

As the quality of most water sources and the environment continue to deteriorate, the public is increasingly concerned about the issues of sustainability. To combat this, strict policies and legislations are being placed to enable the treatment of wastewaters before discharging and possibly reusing it.  Animal slaughterhouses have proven to be important sources of wastewater with high levels of organics such as chemical oxygen demand (COD), biological oxygen demand (BOD), total suspended solids (TSS), volatile suspended solids (VSS), fats and proteins. Discharging wastewater without any form of treatment into receiving water bodies has shown to contaminant water sources and as well to be detrimental to aquatic animals. Anaerobic processes have been proposed as a good alternative for the treatment of wastewaters with high or medium organic loads. The production of biogas through anaerobic digestion offers substantial advantages over other biological methods of waste treatment. The aim of this study was to elucidate the effect of process operational parameters on the performance of an up-flow anaerobic sludge blanket reactor (UASB). The reactor was used for the treatment of a synthetic wastewater which was synthesised to emulate that obtainable from a slaughterhouse. Organic loading rate (OLR) was increased by varying the hydraulic retention times (HRT) from 8−16 hours. The temperature of the reactor was maintained at a constant 35 ̊C while the pH was varied from 6.5 to 7.5. The result of the work indicated an optimum OLR of 4.5−7.5 kgCOD.m-3.d-1 and an optimum COD of 75−86%. Similarly, a biogas yield of 2850 ml/day was found to be the highest at a HRT of 12 hours at the optimum OLR. At the highest OLR, flotation occurred and consequently the active biomass was washed out from the reactor. The results indicated that anaerobic treatment systems are applicable to the treatment of wastewaters with high levels of organics.