Efficacy of Amendments in TPH Removal during Bioremediation of Agricultural Crude Oil-polluted Soil

Abstract

This study identified the efficacy of different amendments as biostimulants in bioremediation. This experiment was carried out for 4 weeks in the laboratory. One kilogram of pristine soil was spiked with one liter of crude oil in earthen pots, to each pot 10 grams of amendments were added and mixed thoroughly. The amendments used were poultry dropping (C-PD), cow dung (D-CD), N.P.K (E), and a control (A and B) setup undergoing natural attenuation. The microcosms’ initial physicochemical characteristics such as total organic nitrogen, pH, temperature, total organic carbon, total petroleum hydrocarbon (TPH), and polyaromatic hydrocarbon (PAH). The microbial enumeration was done for total heterotrophic bacteria (THB) and hydrocarbon utilizing bacteria (HUB). The molecular characterization of the pristine soil (A) and contaminated soil (B) was also done using the shotgun analysis. The THB of A and B was 1.3 x 107 and 2.1 x 102 while the HUB was 1.63 x 105 and 1.1 x 101on day 1 respectively. The THB of treatments during bioremediation at week 2 was 1.75 x 108, 1.89 x 108, 1.5 x 108 and 2.2 x 108 while at week 4, the THB was 1.90 x 108, 2.1 x 108, 2.20 x 108 and 2.25 x 108 while the HUB at week 2 was 1.20 x 105, 3.0 x 105, 2.5 x 105 and 1.98 x 105 while at week 4, the HUB was 2.0 x 106, 2.19 x 106, 2.46 x 106 and 2.1 x 106 for B, PD, CD ,and N.P.K respectively. The molecular characterization of A and B showed there was a higher microbial diversity in the contaminated soil than in the pristine soil. This study has shown that cow dung is more effective in the bioremediation of total petroleum hydrocarbon, and polyaromatic hydrocarbon in crude oil-contaminated soil.