Aerobic Biodegradation of Petroleum Hydrocarbons in Laboratory Contaminated Groundwater

Two treatment options A and B were set up in quadruple using Erlenmeyer flasks containing spiked groundwater samples from a hand dug well to study the effects of nutrient amendment and natural attenuation on hydrocarbon removal under laboratory aerobic conditions. Treatment A received 0.5g of N.P.K (15:15:15) fertilizer as nutrient amendment while treatment B received no treatment in order to measure the rate of hydrocarbon removal by natural attenuation. The bioremediation process was monitored for 56 days by periodic (0, 14, 28, 42, 56) measurements of total hydrocarbon content, pH, nitrate, phosphate, sulphate and dissolved oxygen to establish their effects on hydrocarbon removal under laboratory conditions. Enumeration of total heterotrophic bacteria and total hydrocarbon utilizing bacteria was also periodically carried out. The total hydrocarbon content removal in nutrient amendment and natural attenuation at day 56 showed percentage removal of 89 and 74, respectively. Total heterotrophic and total hydrocarbon utilizing bacterial count increased progressively in all the treatment options. The nutrient amendment (treatment A) showed greater removal of the hydrocarbon pollutants. The physicochemical analyses at day 56 were within the World Health Organization standard for drinking water. Statistical analysis revealed that there was significant difference in the data obtained from treatment A and B for total hydrocarbon content, total heterotrophic bacteria, hydrocarbon utilizing bacteria, conductivity and nitrate at p<0.05. Bacterial strains isolated include Bacillus sp., Arthrobacter sp., Micrococcus sp., Pseudomonas sp., Alcaligenes sp. and Flavobacterium sp. Biodegradation of petroleum hydrocarbons in laboratory contaminated groundwater under nutrient amendment conditions was found to be higher than the untreated, unamended condition.