Generation and characterisation of wastewater in the small-scale palm oil processing industry in Ghana: A step towards sustainable management solutions

The palm oil processing industry in Ghana is dominated by informal small-scale mills. However, the waste management of the informal mills have received little attention in research. The aim of this research was to determine the sources and quantity of water used, quantity and quality of wastewater produced to guide sustainable management of the wastewater. Twenty-five mills were selected for assessing the water sources and quantities, wastewater quantities and disposal practices. Wastewater samples were collected from four of the processing mills in both lean and peak production seasons for characterization. Empty palm fruit bunch fibre was used for solids-liquid separation of wastewater and the sludge was sun-dried for potential use as soil conditioner or solid fuel. The effluent from the solid-liquid separation was subjected to column filtration using palm kernel shell and charcoal as granular media. Boiling of fresh fruits, clarification of oil (optional), and cleaning of working tools were the unit processes which consumed fresh water and produced wastewater. Water consumption was influenced by the distance to the water source but not the price of water. For a litre of crude palm oil produced, 0.76-2.39 litres of water were consumed with a wastewater return factor of 68-82%. The mean concentrations of 6 out of the 7 parameters were over 2-orders of magnitude higher than the Ghana effluent discharge standards. The current practice of disposing raw wastewater into the natural environment could be negatively affecting the environment. The nutrients content and calorific value of the sun-dried wastewater sludge was high showing their potential as sustainable soil conditioner or solid fuel. The performance of charcoal and palm kernel shell filters were creditable compared to the sand. However, charcoal and palm kernel shells show limited potential for use as granular filter media for treating high strength palm oil mill wastewater.