Today there is a tremendous volume of waste material that is being deposited daily into the streams and rivers throughout the United States. The waste material is a by-product of an industrial and population expansion and is increasing in volume and complexity daily. These wastes cannot all be treated and transformed into inert, non-toxic compounds prior to being let into the streams. In the la.st decade the problem received considerable attention and state and federal water-pollution laws have been enacted. When a regulatory agency wishes. to restrict the quality of organic waste discharged into a body of water, it will need some criteria for judging the pollutants introduced into the stream. A sanitary engineer within the regulatory agency has several general methods at his disposal...