Abstract:

This study analysed the physico-chemical properties of palm oil mill effluent (POME) before and after biogas extraction using the anaerobic digestion method. Two locally manufactured anaerobic bio-digesters were used for the digestion of the POME, one for the control and the other for the catalysed sample. The samples were digested for a total of 110 days. Samples for laboratory analysis were collected on the 60th day of the experiment (referred to as mid digestion) and the last day of the experiment (referred to as end of digestion). Standard routine laboratory techniques were used to analyse the samples. The results revealed that fresh POME is acidic (with a pH of 4.43) whereas anaerobic digestion gradually leads to a drop in its acidity (from an average of 4.43 to 4.83 in the control and also 4.43 to 5.50 in the catalysed setup) translating to a drop in acidity in both setups. The organic carbon content of the samples was high (27.37% to 30.89%). Likewise, the nitrogen content of the samples also increased (0.73% to 1.38%). The carbon to nitrogen (C/N) ratio of POME dropped from 37.5 to 22.38 at the end of the digestion process. Dissolved oxygen (DO) showed a remarkable increase while biological oxygen demand (BOD) and chemical oxygen demand (COD) decreased in the both experimental setups. Also, Magnesium, electric conductivity, total dissolved solids and nitrate increased while the chloride, Sodium and Potassium contents decreased in both the control and catalysed experimental setups. Findings revealed that the anaerobic digestion of POME leads to a drop in acidity, COD and BOD, it therefore does not only serve as a resource from which valuable biogas can be obtained but could also serve as value added means of POME treatment with an added advantage of the digestate being quality compost that can be used as biofertilizer. It is also recommended that the microbial aspect be studied in a similar study.