GROWTH AND REMEDIATION PERFORMANCE OF ELEUSINE INDICA OBTAINED FROM OIL-POLLUTED SOILS IN BENIN METROPOLIS AFTER EXPOSURE TO GREY WATER

ABSTRACT

As a step towards the successful reduction of environmental degradation in Benin City, this study was conducted to evaluate the growth and remediation performance Eleusine indica obtained from oil-polluted soils in Benin metropolis after exposure to grey water. The polluted soil used in this study was pooled from four different locations in the Benin City metropolis,including soils from generator plant, within auto – mechanic workshop,auto spare parts stores, and soils around bakery. The categories of soils were obtained in 4 local Government Areas respectively.They are Egor, Ikpoba, Oredo and Ovia Local Government Areas. To determine its remediation performance, the test plant, E. indica, was grown in soil polluted with oil. Polluted soil was also wetted with grey water daily, twice weekly, weekly, twice monthly and monthly. Control experiment was wetted with tap water. Heavy metal and total hydrocarbon content of polluted soil was analysed before and after E. indica, was sown on it. Results obtained showed that Eleusine indica was able to grow on the polluted soil. However, the presence of grey water improved the growth of the plant in the polluted soil. E. indica watered twice weekly showed the best morphological growth. The removal of heavy metals and total hydrocarbon content by E. indica was also improved by the application of grey water, with plants watered weekly and twice weekly and twice monthly recording the highest percentage of removal of heavy metals and total hydrocarbons. The most remediated heavy metal by the test plant was chromium, which recorded up to 99.99% removal. This was followed by manganese and cadmium which had 96.77 and 89.13% respectively. Hydrocarbon reduction efficiency by grey water intervention was 81.19%These results suggest that Eleusine indica will be useful in the bioremediation of polluted soils in the Benin City metropolis and Nigeria at large. The study also validated the use of grey water for improving the remediation performance of the test plant.