Beneath the streets of every city and most smaller communities, a system of sewers and pumps conveys wastewater away from homes, factories, offices, and stores. This disposed water, which may contain a variety of domestic, commercial, and industrial wastes, flows through the sewers to a wastewater treatment plant. There, pollutants are removed and the cleansed water is discharged into an adjacent water body, such as a river or stream, or in a few cases a wetland area. The residues of the treatment process (once called sludges, but now known as biosolids) are either used productively as a soil conditioner or disposed of as a solid waste.

Industrial plants are only one of the many sources of wastewater discharged into municipal sanitary sewers. But the wastewater discharged by industry often contains toxics or otherwise harmful substances not common to other sources. These wastes can pose serious hazards. Because municipal sewage collection and treatment systems have not been designed to treat them, industrial wastes can damage the sewers and interfere with the operation of treatment plants, can pass through the systems untreated, resulting in contamination of nearby water bodies, and can increase the cost and environmental risks of biosolids treatment and disposal.

The undesirable effects resulting from the discharge of industrial wastewater into municipal sewers can be prevented. Industrial plants, using proven pollution control technologies, can remove significant amounts of pollutants from their wastewaters before discharging them into the municipal sewage treatment system. This practice is known as "pretreatment."

Please refer to the following links for more information:

• The Need for Pretreatment
• Overview of the National Pretreatment Program and National Standards
• Local Pretreatment Programs
  • About Building Blocks
  • About Effluent Limits
  • About Implementation Activities
  • About Information Handling and Public Access