ABSTRACT
Worldwide, large quantities of municipal, industrial and agricultural wastewater are generated every year. Most of these wastewaters are treated to remove solids, pathogens and other contaminants, and the resulting relatively clean water is recycled into the environment. However, these treated wastewaters may still retain large concentrations of organic matter, nutrients such as nitrogen and phosphorus, as well as other contaminants. In many countries, municipal wastewater is discharged into receiving waters such as rivers, lakes and the sea (UNEP, 1993). Such discharges can result in depletion of dissolved oxygen and, ultimately, eutrophication.
