Bioremediation of soil contaminated with crude oil using fresh and decomposed animal manure

Abstract

Vast majority of rural dwellers stands to bear the brunt of oil spillage and soil pollution, hence the need to develop remediation options using materials that are cheap and readily available. A laboratory incubation study was conducted to evaluate the bioremediation potentials of different types of animal manure on soil contaminated with crude oil (Forcados). Treatments consisting of 20 t ha^-1 each of poultry dropping (PD), swine manure(SM) and beef cattle manure (BCM) both in fresh (f) and partially decomposed (p) forms were applied to soils contaminated with (5 % w/w) the crude oil. Their effects were evaluated on total hydrocarbon content (THC), microbial respiration (MR) based on amount of CO₂ evolved and pH in situ during a period of 8 weeks of remediation. There was an improvement in the degree of remediation offered by the various bio-stimulants over time. At 4 weeks after amendment (WAA) the level of degradation of THC was in the order: BCMf> control > SMf = PDf > PDp > SMp>BCMp with 17.2, 16.4, 9.6, 9.6, 9.2 and 5.6>4 % of THC degraded respectively. At 8 WAA, % degradation was in the order: BCMf >PDp = PDf >SMf > SMp > BCMp > control with 66, 65.2, 65.2, 64.4, 63.6,62.8 and 61.6 % degradation, respectively. Control was the least while BCMf was the most efficient. Microbial respiration consistently reduced with time in un-remediated soils but BCMf enhanced it over time. This further validates BCMf to be the most efficient in terms of soil remediation. It is, therefore, concluded that fresh beef cattle manure applied at 20 t ha^-1 could be very efficient in remediating crude oil polluted soil.

Key words: Total hydrocarbon content, microbial respiration, remediation, biostimulant.