Toxic Screening Models for Water Supply

Many water utilities in the United States depend upon surface water as their primary souce of drinking water. Toxic screening models can be used to provide a means for identifying and assessing the pollutants likely to be in water utility source water from point and nonpoint upstream dischargers. Two case studies are presented to evaluate this concept. One is based on the stretch of Ohio River between the Kanawha River and Cincinnati, Ohio and ranks the vulnerability of the utilities along this stream segment to organoleptic, toxic, and carcinogenic pollutants. The second case study uses the lower Mississippi to illustrate the use of flow routing models to predict the concentration of contaminants at downstream utilities, based on upstream industrial discharges. The important interaction between time of passage and disappearance coefficient of the pollutant is illustrated.