Evaluation of the Microbial Population of Soil around Oilfield Wastewater Pond

The microbial quality of soil around the oilfield wastewater discharge pond was investigated to determine the microbial dynamics in the soil. Soil samples were randomly collected at four different parts around the pond and 80 meters away from the pond (control) at a depth of 0-15cm with a clean auger into sterile polythene bags from Ogbogu flow Station. The total heterotrophic bacteria, total heterotrophic fungi, hydrocarbon utilizing bacteria, and fungi were determined using standard microbiological methods. The bacterial isolates were identified using standard biochemical tests while fungal isolates were identified based on appearance on plates and microscopy. The mean counts for the total heterotrophic bacteria, fungi, hydrocarbon utilizing bacteria and fungi in the rainy season for the soil within the pond was 2.10×107, 4.63×104, 1.38×104, and 2.93×104 CFU/g, respectively. The mean counts for the total heterotrophic bacteria, fungi, hydrocarbon utilizing bacteria and fungi in the dry season for the soil within the pond was 5.72×106, 1.87×104, 2.80×103, and 1.37×103 CFU/g, respectively. The mean counts for the total heterotrophic bacteria, fungi, hydrocarbon utilizing bacteria and fungi in the rainy season for soil 80 m away from the pond was 2.50×107, 1.07×105, 2.4×103, and 1.9×103 CFU/g, respectively. The mean counts for the total heterotrophic bacteria, fungi, hydrocarbon utilizing bacteria and fungi in the dry season for soil 80 m away from the pond was 6.17×106, 2.0×104, 1.83×103, and 1.23×103 CFU/g, respectively. Statistical analysis showed a significant difference (P≤0.05) in the total heterotrophic bacterial count from the pond and that of soil around 80 m away from the pond. The heterotrophic counts during the dry season were significantly lower (P≤0.05) from that of the rainy season in all the samples analyzed. There was a significant difference (P≤0.05) between the fungi count of soil 80 m away in the dry season from that of soil around the pond. There was no significant difference (P≥0.05) in the total fungal counts recorded for the dry and rainy season in the various samples except that of the soil 80 m away. Hydrocarbon utilizing fungi was higher in the soil around the pond and was significantly different (P≤0.05) from that of soil 80 m away from the pond during the dry season. Bacillus spp., Aeromonas spp., Micrococcus spp., Staphylococcus spp., Chryseomonas spp., Proteus spp., Pseudomonas spp., Klebsiella spp., Actinomyces spp., Enterobacter spp., Rhodococcus spp., and E. coli were identified from the soil. While Bacillus spp, Micrococcus spp, Staphylococcus spp, Proteus spp, and Pseudomonas spp were the hydrocarbon utilizing bacteria. Eight fungal genera isolated from the samples include Aspergillus fumigatus, Aspergillus niger, Aspergillus flavus, Saccharomyces cerevisiae, Geotricum, Trichoderma, Fusarium, and Penicillium spp. Hydrocarbon utilizing fungi isolated includes Aspergillus niger, Aspergillus flavus, Fusarium spp., Penicillium spp., and Saccharomyces cerevisiae. This investigation revealed high microbial population in the soil 80m away from the pond than those within the soil around the wastewater pond. The microbial population was affected by the season with the rainy season having a higher microbial population than the dry season.