EFFECTS OF PARTICLE SIZE DISTRIBUTION ON BIOREMEDIATION OF CRUDE OIL POLLUTED SANDY SOILS

Abstract

Bioremediation has been proven to be the most effective method of cleaning up oil contaminated soils through the application of nutrients and microorganism. Hence, this research presents the effects of particle size distribution on bioremediation of crude oil polluted sandy soils. Six different soil samples were sieved using the B.S sieve sizes. The sieve sizes were classified into X and Y such that X is fine to coarse sand while Y is very fine to coarse sand according to U.S Bureau and Public Roads Administration (PRA) soil classification system. The soil samples were polluted with escravous sweet crude oil at a uniform rate concentration of 4% under aerobic condition. Treatment commenced after four days using nutrients (N.P.K 15:15:15 fertilizer and cow dung) and microorganism (Pseudomonas). Soil samples were examined for physiochemical and microbial characteristics for a period of 42days. The parameters examined were: moisture content, particle size distribution, total hydrocarbon content, soil pH, available nitrogen, available phosphorus, total heterotrophic bacteria and fungi count. The analysis of the soil characteristics throughout the remediation period showed that total heterotrophic bacteria and fungi counts increased in all the soil samples. THBC was highest in sample G for both fine to coarse sand(X) and very fine to coarse sand (Y) with values of 250cfu x10⁵/g and 298cfu x10⁵/g at least values of coefficient of uniformity(cu) respectively. There was a decrease in nitrogen, phosphorus, organic carbon content, moisture content, pH and total hydrocarbon content.  The result of the study revealed that, the rate of hydrocarbon loss was higher in samples with less coefficient of uniformity values compared to samples of higher coefficient of uniformity (Cu) values, an indication that particle size distribution parameters could be one of the factors affecting bioremediation.The correlation coefficient(r) of Total hydrocarbon content versus Ccoefficient of uniformity for fine to coarse sand(X) is 0.867 while for very fine to coarse sand is 0.923.