The Beijing Wastewater Canal is a main one for discharge of wastewa-ter from Beijing city. It receives a great deal of domestic sewage and industrial Wastewater from urban districts.To monitor the toxic stress of the Wastewater and the effectiveness of self-purification at various sections of the water body,the artificial substrate, polyurethane foam unit (PFU) method developed by Cairns(1969)was taken for colonizing microbial community in August, 1984. Examination of the PFU samples revealed a total of 60 ...