1. Jackson, M. L. (1958) Soil Chemical Analysis, Prentice-Hall Inc., Englewood Cliffs, NJ, pp 331?335.
2. Kao, J. F., Hsieh, L. P., Cheng, S. S., and Huang, C. P., (1982) ?Effect of EDTA on cadmium in activated sludge system?, J. Wat. Poll. Cont. Fed. 54, 1118?1126.
3. Kobayashi, J., Morii, F., Muramoto, S., and Nakajima, S. (1970) ?Inorganic matters in feces and urine?, J. Water Waste 12, 635?642 (in Japanese).
4. Laxen, D. P. H. and Harrison, R. M. (1981) ?The physicochemical speciation of Cd, Pb, Cu, Fe, and Mn in the final effluent of a sewage treatment works and its impact on speciation in the receiving river?, Water Research 15, 1053?1056.
5. Ministry of Public Health and Welfare and Water Work Association of Japan (1971) 'Statistics of Water Works No. 48 (in Japanese).