Evaluation of Organic Nutrient Supplements and Bioaugmenting Microorganisms on Crude Oil Polluted Soils
Authors: Ogbonna David N. , Ekweozor I. K. E. , Nrior Renner R. , Ezinwo Festus E. 
Published: December 2019

Aim: The aim of the study was to evaluate the impact of organic nutrient supplements and bioaugmenting microorganisms on crude oil polluted soils.

Place and Duration of Study: Faculty of Agriculture Demonstration Farm, Rivers State University, Port Harcourt Nigeria.

Methodology: Baseline study of a deliberately polluted agricultural soil was investigated for its microbiota from which selected fungal and bacterial isolates were obtained. Microbial analyses of goat manure, fish wastes and crude oil polluted soil were investigated. Using the Randomized Complete Block Design (RCBD) the land was partitioned into nine (9) blocks of 100 cm x 50 cm x 20 cm (Length x Breath x Height) giving 100,000 cm3 each. Two of these plots were designated as pristine (Unpolluted soil) and crude oil polluted soil without nutrient organics and bioaugmenting microbes to serve as controls respectively. Each of the experimental plots, except the control, was contaminated with 1,700 g of crude oil giving initial Total Petroleum Hydrocarbon (TPH) value of 9.296.825 mg/kg. The plots were left for 21 days to ensure even distribution and soil-oil bonding. All plots except Control 1 (plot 1) were separately and deliberately contaminated with 1,700 g of crude oil given Total Petroleum Hydrocarbon (TPH) value of 9.296.825 mg/kg. Sampling was done at seven day interval (Day 1, 7, 14, 21, 28, 35, 42, 49, 56).  Parameters monitored were Nitrate, Sulphate, Phosphate, Total Organic Carbon (TOC) and Total Petroleum Hydrocarbon (TPH), were monitored throughout the experimental period. Microbial analyses such as Total Heterotrophic Bacteria (THB), Total Heterotrophic Fungi (THF), Hydrocarbon Utilizing Bacteria (HUB) and Hydrocarbon Utilizing Fungi (HUF). Percentage (%) Bioremediation was estimated from percentage (%) reduction of Total Petroleum Hydrocarbon (TPH) from day 1 to day 56 in relation to control plots.

Results: Two fungal; Aspergillus niger (Asp), Mucor racemosus (Muc); and two bacterial species – Bacillus armyloliqquefaciens strain FJAT-45825 (Bac) and Pseudomonas aeruginosa strain CL 9 (Pse) isolated from a baseline study showed biodegradability potentials. The physicochemical characteristics of organic nutrient supplement - goat manure (GM) and fish wastes (FW) employed in the study showed that it contained valuable sources of organic nutrients which enhanced the bioremediation process of the Crude oil polluted soil (PS). Mean counts of Hydrocarbon Utilizing Bacteria (HUB) and Hydrocarbon Utilizing Fungi {HUF} (Log10 CFU/g) respectively were: Control 2 which is crude oil Polluted soil (PS) (5.52±0.47, 4.92±0.29); PS+GM (5.832±0.68, 5.33±0.54); PS+FW (5.76±0.40, 5.10±0.40); PS+GM+FW (5.706±0.61, 5.17±0.27); PS+Asp+Muc (5.722±0.48, 5.08±0.49); PS+Bac+Pse (5.34±0.69, 5.01±0.52}; PS+Asp+Muc+Bac+Pse (5.652±0.48, 5.10±0.52}; PS+Asp+Muc+Bac+Pse+GM+FW (5.212±0.40, 4.76±0.53}. Evaluation of Bioremediation revealed the actual amount of crude oil (hydrocarbon) reduction and its percentage value from the initial contamination value of 9296.83 mg/kg during the period of 56days as PS+Asp+Muc+Bac+ Pse+GF+FW (9152.315 mg/kg; 98.45%) > PS+Bac+Pse+GF+FW (8032.825 mg/kg; 86.40%) > PS+GF+FW (6867.825mg/kg; 73.87%) > PS+Asp+Muc+GF+FW (6599.825 mg/kg; 70.99%) > PS+Bac+Pse (6587.825mg/kg; 70.86%) > PS+FW (6441.825 mg/kg; 69.29%) > PS+GM (5909.825 mg/kg; 63.57%) > PS+Asp+Muc+Bac+Pse (5081.825 mg/kg; 54.66%) > CTRL 2 (Polluted soil without amendment) (3604.825 mg/kg; 38.78%).

Conclusion: Results obtained from this study has shown that goat manure and fish wastes due to their high moisture and nutrient content properties makes them appropriate agents for enhanced bioremediation. It further revealed that a combination of biostimulating and bioaugmentating agents creates more favorable conditions for biological activity to thrive and has shown to be effective, economical, eco-friendly and sustainable in remediating organic pollutants from polluted soils.