Impact of Palm Kernel Oil Mill Effluent on the Soil's Physicochemical Characteristics and Growth of Tomato Plant

Effluent is wastewater flowing out of a sewer which constitutes environmental problems ranging from long-term ecological damage to increased water-borne diseases. In Nigeria, palm kernel oil is extracted from oil palm fruits in oil mills and the effluent is discharged without treatment to the soil in the vicinity of such mills. The effluent-receiving soil has been observed not to support the growth of vegetation. Hence in this work, the impact of palm kernel oil mill effluent on the soil physicochemical characteristics and growth of tomato plant was determined and compared with the effluent discharge limit established by the Federal Environmental Protection Agency. Samples of untreated and treated effluent, untreated and treated effluent-polluted soil and unpolluted soil were used for the study. The physicochemical analysis was carried out using standard physicochemical methods. The physicochemical values of the untreated effluent, except the pH, which was acidic, were higher than those of the treated effluent. Most of the physicochemical values of the untreated effluent-polluted soil were higher than those of the treated effluent-polluted soil and the unpolluted soil. The tomato plant grown in the unpolluted soil had better growth characteristics and yielded more fruits than those grown in the treated effluent-polluted soil. In addition, the tomato plant grown in the untreated effluent-polluted soil showed the lowest growth characteristics and yielded no fruits due to its elevated level of heavy metals and total petroleum hydrocarbons. The study showed that the untreated palm kernel oil mill effluent had a negative impact on the soil's physicochemical and growth characteristics of the tomato plant. Therefore, the effluent must be adequately treated to remove hazardous substances before its discharge into the terrestrial environment.