This general information pamphlet is concerned with the types of wastewater treatment systems, the need for further treatment, and advanced methods of treating waste. Current methods are described, illustrated and evaluated. Pollution problems from oxygen-demanding wastes, disease-causing agents, plant nutrients, synthetic chemicals, inorganic chemicals, sediments, radioactivity and heat are discussed. Throughout, problems of water pollution control and waste disposal are presented to illustrate the need for planning, financing and building treatment facilities to meet water quality standards. A glossary of common sewage treatment terms is included. (CS)