Abstract

Palm oil mill effluent (POME) is characterised by high colour, COD and solids. Extraction and drying of the suspended solids for reuse as solid fuel shows great promise. However, the clarified wastewater may require further treatment to meet discharge limits. This study was aimed at evaluating the efficiency and kinetics of COD and colour removal from clarified POME using palm kernel shell (PKS) granular filter media and a sand filter as reference. The wastewater was collected from a small-scale palm oil processing mill in the Abura Aseibu Kwamankese District of Ghana and clarified using a solid-liquid separation system. The filter media of particle size 1.18mm was packed into acrylic cylinders (6cm dia.) to a height of 35.4 cm. The characteristics of influent wastewater and filter media were determined prior to the experiment following standard methods. Each filter was run as a batch system under anaerobic conditions by maintaining a minimum supernatant height of 10cm. Effluents were drawn from the bottom of each filter after 0, 24, 48, 72, 96, and 120 h for analysis using standard analytical methods. The removal efficiencies for the PKS and sand filters were, respectively, 77% and 79% for COD and 69% and 62% for colour. The COD removal was consistent with first-order kinetics for both PKS and sand filters. However, colour removal in PKS and sand filters followed second- and zero-order kinetics respectively. The correlation coefficients of the selected kinetic models show a strong correlation between the experimental and predicted results. Further research is required to establish the retention time required to bring the pollutant levels below the allowable limits for discharge into the environment.