Restrictions on amounts of the pollutants discharged by industry into municipal sewage systems have existed in some localities for many years. The Milwaukee Metropolitan Sewerage District, for example, has regulated pH, oil and grease, and temperature levels in industrial wastewaters since the 1920s. Such regulations are the predecessors of modern pretreatment programs, which include national standards, and state and local programs to control industrial pollutants.

The federal government's role in pretreatment began with the passage of the Clean Water Act in 1972. The Act called for the EPA to develop national pretreatment standards to control industrial discharges into sewage systems. The standards are uniform national requirements, which restrict the level of certain pollutants in the wastewater from industries. The standards in effect today consist of two sets of rules: "categorical pretreatment standards" and "prohibited discharge standards."

Categorical pretreatment standards are organized by type of industry, and different requirements are mandated for each specific industry. For example, there is a categorical standard for the iron and steel industry which limits the concentrations of ammonia, cyanide, and other pollutants that may be present in the wastewater discharged into sewage systems by any firm in that industry.

Prohibited discharge standards prohibit any discharge to sewer systems of certain types of wastes from all sources. For example, the releases of any wastewaters with pH lower than 5.0 are forbidden, since such wastes may corrode the sewer system.

The overall framework for the National Pretreatment Program is contained in the General Pretreatment Regulations that EPA published in 1978 and modified in 1981. These regulations require all large POTWs - those designed to accommodate flows of more than 5 million gallons (19 million liters) per day - and smaller POTWs with significant industrial discharges, to establish local pretreatment programs. Approximately 1,500 POTWs are participating in the national Pretreatment Program by developing local programs.

The local programs may impose more stringent discharge requirements (i.e., local limits) to prevent disruption of the sewage treatment system, adverse environmental impacts, or disruption of biosolids use or disposal. Thus, the National Pretreatment Program consists of approximately 1,500 local programs designed to meet federal requirements and to accommodate unique local concerns. In Iowa the following cities have local pretreatment programs: Ames, Ankeny, Boone, Burlington, Cedar Falls, Cedar Rapids, Clinton, Council Bluffs, Davenport, Des Moines, Dubuque, Fort Dodge, Fort Madison, Iowa City, Keokuk, Marshalltown, Mason City, Muscatine, Ottumwa, Sioux City, Waterloo. Contact information for the local pretreatment coordinators can be found at the following link: Iowa Pretreatment Coordinators (*.pdf file).