Water Science and Technology Vol 33 No 6 pp 121–128 © IWA Publishing 1996
Aquatic toxicity emission from Tokyo: wastewater measured using marine luminescent bacterium, photobacterium phosphoreum
Mari Asami*, Noriyuki Suzuki** and Junko Nakanishi***
*Department of Water Supply Engineering, The Institute of Public Health, 4-6-1 Shirokanedai Minato-ku, Tokyo 108 Japan
**Society and Environmental Systems Core, Kanazawa Institute of Technology, 7-1 Ohgigaoka Nonoichi, Ishikawa 921 Japan
***Environmental Science Research Center, The University of Tokyo, 7-3-1 Hongo Bunkyo-ku, Tokyo 113 Japan
ABSTRACT
Aquatic toxicity of point-source discharges are examined with the MICROTOX system using luminescent bacteria, Photobacterium phosphoreum. Samples include treated wastewaters from industrial dischargers, municipal sewage treatment plants and community sewage treatment plants, all of which eventually flow into Tokyo Bay. Among 34 samples from industry, 11.7% exhibit high toxicity (EC50 =< 0.2), 17.6% exhibit low toxicity (0.2 < EC50 =< 1), and 70.7% were non- or only slightly toxic (1 < EC50). Aquatic toxicity of treated wastewater is mostly due to the chlorination process. Results suggest that 96% of the total toxicity load of all point-source discharges is caused by chlorination. The toxicity assessment with luminescent bacteria is shown to be effective and of practical use, since it facilitates the evaluation of the total toxicity which cannot be well embodied in the current regulation systems by specific indices.
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