Until the early 1970s, in the United States, wastewater treatment mostly consisted primarily of the removal of suspended and floating material, treatment of biodegradable organics, and elimination of pathogenic organisms by disinfection. Standards were not uniformly applied throughout the country. In the early 1970s until about 1980, aesthetic and environmental concerns were considered. Treatment was at a higher level and nutrients, such as nitrogen and phosphorus, were removed in many localities. Since 1980, focus on health concerns related to toxics has driven the development of new treatment technology. Water-quality standards were established by states and the federal government and had to be met as treatment objectives. Not just direct human health but aquatic-life parameters were considered in developing the standards.
