In Situ Anaerobic Bioremediation of Petroleum Hydrocarbons in Groundwater of Typical Contaminated Site in Shanghai, China: A Pilot Study

摘要

In situ anaerobic treatment is an effective and sustainable method for petroleum hydrocarbon (PHC)-contaminated groundwater remediation. In this study, application of a formerly screened microbial agent with quinone-respiration ability for PHC removal in our previous study on an actual contaminated site has been investigated. The background characterization revealed that bioaugmentation should be applicable taking into consideration the contamination plume, N:P ratio, overall dissolved oxygen, toxic substances, and colony number. In single-well investigation, viable bacteria present in groundwater were not sharply decreased after injection and maintained around 80% on the 28th day. Removal rate of PHCs in groundwater in injection and monitoring wells on the 28th day was 96% and 52%, respectively, while it decreased to 36% with the distance from the injection well increasing to 2 m. In multiwell investigation, removal rate for PHCs (C 22) in injection wells was 95%, 89%, and 94%, respectively, after 63 days. Addition of nitrate nitrogen slightly improved the removal rate of PHCs, while presence of biological surfactants resulted in a quicker, greater, and more stable PHC removing process. A higher removal rate was found in monitoring wells on the downstream of the groundwater, with a maximum of about 76.5%. Degradation of PHCs in GW1-S3 (3 m from the injection well) reached 76.1%, which was much higher than that in single-well investigation, mainly due to the longer reaction time and groundwater flow. The remediation process in a stable period obeyed pseudo-first-order degradation kinetics. The results document the suitability of application of microbial agent to bioremediate PHC-contaminated sites.