Impact of Soybean Waste and Pigeon Dropping in the Total Hydrocarbon Content of Crude-oil Polluted Soil

Abstract

The impact of soybean waste (SBW) and pigeon dropping (PD) in the bioremediation of crude oil polluted soil was investigated. Uncontaminated soil sample was collected from the Rivers State University Research FarmLand. Furthermore, soil sample was contaminated with 5% bonny-light crude oil. SBW and PD were used as the organic supplements. The experimental set-up consisted of 500g of contaminated soil supplemented with SBW and PD separately and in consortium with a control. Bacterial and fungal isolates were determined using standard microbiological methods while the physicochemical parameters were determined using the standard method. The total heterotrophic bacterial load of the soil ranged from 9.5×104 to 1.2×107 CFU/g. The hydrocarbon utilising bacterial load ranged from 7.1×104 to 2.5×105 CFU/g. Fungal load ranged from 7.5×103 to 1.4×105 SFU/g while the hydrocarbon utilising fungal load ranged from 1.3×104 to 5.6×104 SFU/g. Bacillus, Serratia, Pseudomonas and Mycobacterium sp were the hydrocarbon utilising bacteria while Mucor, Aspergillus, Penicillium sp and Saccharomyces sp represented the hydrocarbon utilising fungi. The physicochemical properties of the soil samples before bioremediation showed that the pH ranged from 6.14 to 7.75. The nitrate ranged from 0.813 to 1.216mg/kg; the phosphate ranged from 0.196 to 0.857mg/kg; the total organic carbon (TOC) ranged from 0.88 to 4.89mg/kg and the total hydrocarbon content (THC) ranged from 1419 to 5320mg/kg. The ranges of the physicochemical properties after bioremediation showed that the pH was 6.11 to 7.10, nitrate content 1.903 to 3.016mg/kg, phosphate 0.011 to 0.03 mg/kg, TOC 1.38 to 2.56mg/kg and THC 920 to 4631 mg/kg. The percentage reduction of the THC showed that the highest percentage reduction 52.26% was observed in the crude oil polluted soil amended with SBW followed by the crude oil polluted soil amended with the consortium (50.56%) and PD amended soil had 50.38%, respectively. The % reduction of THC of the unamended crude oil polluted soil was 12.95%). There was no significant difference (P>0.05) in the reduction of THC amongst the treatment. Thus, the use of soybean waste and pigeon droppings for bioremediation is recommended.