Application of a Toxicity Identification Evaluation for a Sample of Effluent Discharged from a Dyeing Factory in Hong Kong Y. K. Chan, 1 C. K. Wong, 1,2 D. P. H. Hsieh, 3 S. P. Ng, 1 T. K. Lau, 2 P. K. Wong 1,2 1 Environmental Science Program, The Chinese University of Hong Kong, Shalin, N.T., Hong Kong, SAR, China 2 Department of Biology, The Chinese University of Hong Kong, Shatin, N.I., Hong Kong, SAR, China. 3 Department of Biology, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong SAR, China Received 27 November 2002; revised 25 May 2003; accepted 2 July 2003 ABSTRACT: A first toxicity identification evaluation (TIE) was conducted in three phases using the Microtox  test to identify the major toxicant(s) in effluent discharged from a dyeing plant in Hong Kong. In Phase I toxicity characterization indicated that anions were likely to be the major toxicants for the entire effluent. In Phase II concentrations of sulfite and other anions in the original and the anion exchange resin-treated effluent samples were determined by ion chromatography. Anions, which were found in the effluent at comparatively high concentrations and were suspected of being responsible for the toxicity to luminescent bacteria, were selected for further study in Phase III. Investigation in Phase III using the spiking and mass balance approaches confirmed that the sulfite ion was the major toxicant in the effluent. © 2003 Wiley Periodicals, Inc. Environ Toxicol 18: 312–316, 2003. Keywords: toxicity identification evaluation; effluent; dyeing factory; Microtox text INTRODUCTION In Hong Kong water pollution is a problem receiving major attention from both the government and public sectors. Numerous studies have indicated that effluents from various industries are the main source of pollutants in coastal and inland waters. To improve water quality, stringent discharge standards have been implemented in various regions to minimize pollution problems caused by industrial effluent. Chemical-specific approaches for regulating effluent com- position cannot reveal the biological impact on the ecosys- tem of the receiving water bodies (U.S. EPA, 1991). A recently developed toxicity-based approach is widely ac- cepted for preparing criteria for effluent discharge in various regions (Coombe et al., 1999). The toxicity identification evaluation (TIE) method was developed by the U.S. Envi- ronmental Protection Agency (EPA) to identify key toxi- cants among thousands of potentially toxic compounds that can be detected by chemical analyses (U.S. EPA, 1991, 1993a, 1993b). The TIE approach has been applied exten- sively to identify major toxicity-causing compounds in ef- fluent or sludge of industrial wastewater, leachate, and Correspondence to: P. K. Wong; e-mail: pkwong@cuhk.edu.hk. Contract grant sponsor: Research Committee, The Chinese University of Hong Kong, Hong Kong SAR, China. Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/tox.10130 © 2003 Wiley Periodicals, Inc. 312