Kinetic Studies of Bioremediation of Hydrocarbon Contaminated Groundwater

摘要

Bioremediation experiments were conducted at ambient temperature of 28-32~(0)C and pH 5.6-8.9 to investigate the effectiveness of the process in the clean-up of groundwater contaminated by diesel. Polluted groundwater samples were simulated in the laboratory by contaminating 900ml of groundwater sample with 100ml of diesel to achieve 10% pollution in two different plastic microcosms. Two tests series were performed for a 1008-hour (42-day) residence time. In the first test, polluted groundwater sample was taken in a plastic microcosm without organic amendment (mixed-culture of pig, cow and poultry wastes). In the second test, organic amendment was added to the polluted groundwater sample in the second plastic microcosm and the bioremediation process in both cases allowed to proceed. Microbiological and TPH analyses were carried out weekly for six weeks on the second microcosm and at the sixth week for the first microcosm which acted as control. The indices of biodegradation monitored included total changes in: total heterotrophic bacteria (THB), total hydrocarbon utilizing bacteria (THUB), total fungal (TF) counts and changes in total petroleum hydrocarbon (TPH).The response of the indigenous microbes (heterotrophs, hydrocarbon utilizers and fungal) was positive in the second microcosm where biodegradation occurred as a result of the microbial activities. No appreciable biodegradation occurred in the control microcosm, except for about 3% loss of total petroleum hydrocarbon due to evaporation. 91.53% removal efficiency for total petroleum hydrocarbons was obtained in the first microcosm at the end of the sixth week. Bioremediation of groundwater polluted with diesel is a first order reaction with rate constant of 0.002hour-1 and half-life (t1/2) of 346.5 hours. The overall assessments of the quality of the contaminated water samples after remediation were close match to the unpolluted water sample with some selected physicochemical parameters (pH, DO, BOD5, and salinity as chloride) within the WHO standard for surface/underground water while COD was far above limits recommended by W.H.O.