ABSTRACT
In earlier times, water was regarded as polluted when it was found to be unfit to drink. An ecologically healthy aquatic system is self-cleaning. Through photosynthesis, large plants rooted to the bottom, and floating microscopic plants like algae and other phytoplankton, produce oxygen and provide food for consumers. The balance of such an aquatic ecosystem can be profoundly affected by a countless number of pollutants that may be added to it. The enormous number of waste contaminants that a modern industrial society produces defies cataloging. However, it is possible to categorize them into just a few classes which include: oxygen-utilizing wastes, synthetic organic compounds, plant nutrients, inorganic chemicals and minerals, pathogenic bacteria, sediments, radioactive materials, and heat. Because of the vast number of possible water contaminants, water pollution criteria, that is, the parameters used to generally characterize degrees of pollution, as well as discharges to waterways, are frequently nonspecific.
