Effluent from local palm oil mill refinery in Nigeria is excessively oily and potentially genotoxic

In spite of the fact that the informal, local mills in countries like Nigeria constitute a major portion of the palm oil refinery, adequate attention has not been paid to the quality of the palm oil mill effluent (POME) they generate. In this study, therefore, the physicochemical properties and genotoxic potential of POME generated by a local mill in Nigeria were investigated using the methods prescribed by the American Public Health Association and Allium cepa chromosomal assay, respectively. In addition to the presence of trace/toxic metals (Zn, Pb, Cd, Cr, Cu) and high biochemical oxygen demand, POME contained a very high oil and grease concentration of 10,500 mg L-1 as against the maximum limit of 25 mg L-1 prescribed in the Environmental Management Guideline for the Palm Oil Industry. Mitotic activities in A. cepa roots exposed to POME showed that the number of dividing cells and percentage mitotic index generally decreased with increasing POME concentrations. The major chromosomal aberrations induced by POME were sticky, C-mitosis, bridged anaphase, vagrant, and attached chromosomes. However, no chromosomal aberrations were observed in onion roots exposed to water (control). These results indicate that the local refinery from where the POME was obtained is inefficient at recovering oil from palm fibre. The effluent generated by the mill is also a potential pollutant capable of inducing genotoxic and other adverse effects. These results may be typical of many more local palm oil refineries who use mainly manual methods to extract oil from oil palm fruits.