JOURNAL OF ENVIRONMENTAL SCIENCES AND HEALTH Part A—Toxic/Hazardous Substances & Environmental Engineering Vol. A39, No. 3, pp. 639–650, 2004 Characterization of Biofilms Occurred in Seepage Groundwater Contaminated with Petroleum Within an Urban Subway Tunnel Kyung-Suk Cho, 1 Ok Kyoung Choi, 1 Yang Hee Joo, 1 Kyung Mi Lee, 2 Tae Ho Lee, 2 and Hee Wook Ryu 3, * 1 Department of Environmental Science and Engineering, Ewha Womans University, Seodaemun-Gu, Seoul, Korea 2 Research Institute of Biological and Environmental Technology, Biosaint Co. Dongjak-Gu, Seoul, Korea 3 Department of Chemical and Enviromental Engineering, Soongsil University, Dongjak-Gu, Seoul, Korea ABSTRACT Biofilms occurring in seepage groundwater contaminated with petroleum in an urban subway drainage system were characterized. The development of biofilms was observed only in the sites where petroleum-contaminated groundwater had seeped or was seeping. Moreover, the conditions of the biofilms such as color and development extent were influenced by the amount of spilled petroleum: By increasing the amount of spilled petroleum, the amount of biofilms increased and its color whitened. It deteriorated and became dark-brown if the contaminated groundwater did not seep any more. These facts indicate that the biofilms can be used as a preliminary indicator to identify the locations of fuel contaminated sumps and seeps without a more detailed assessment such as instrumental analysis. The biofilms were capable of degrading petroleum at 15  C, which is *Correspondence: Hee Wook Ryu, Department of Chemical and Environmental Engineering, Soonsil University, 1-1 Sangdo-5 Dong, Dongjak-Gu, Seoul 156-743, Korea; E-mail: hwryu@ssu.ac.kr. 639 DOI: 10.1081/ESE-120027730 1093-4529 (Print); 1532-4117 (Online) Copyright & 2004 by Marcel Dekker, Inc. www.dekker.com