NPDES Pretreatment Program in Iowa

Industrial treatment facility.

Beneath the streets of every city, a system of sewers and pumps conveys wastewater away from homes and businesses. This wastewater can contain domestic, commercial, and industrial wastes. The sewer and pump systems that convey wastewater are known as municipal sanitary sewers, and wastewater flows through sewers to a wastewater treatment plant. There, pollutants are removed and the cleansed water is discharged into a nearby waterbody. The residues of the wastewater treatment process (once called sludges, now known as biosolids) are either used productively as a soil conditioner or disposed of as a solid waste.

Industrial facilities are one of the sources of wastewater discharged to municipal sanitary sewers. Industrial wastewater often contains toxic substances and it can pose serious hazards.

Because municipal sewage treatment systems are not designed to treat industrial wastes, these wastes can damage sewers and interfere with treatment plants. Industrial wastes can increase the costs and risks of biosolids treatment and disposal, and can pass through municipal systems untreated, resulting in contamination of waterbodies.

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

Overview of the Pretreatment Program

Modern pretreatment programs consist of two parts: national pretreatment standards and local pretreatment programs.

National pretreatment standards are uniform national requirements that restrict the level of pollutants in the wastewater from industries. These national standards consist of two sets of rules: "categorical pretreatment standards" and "prohibited discharge standards".

Categorical pretreatment standards: specific requirements for different industries, organized by type of industry. For example, the categorical standard for the iron and steel industry limits pollutants in wastewater discharged by any firm in that industry.

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

Local pretreatment programs are established by municipalities based on the National Pretreatment Program. The framework for the National Pretreatment Program is contained in EPA's General Pretreatment Regulations. These regulations require all large publicly owned treatment works or POTWs (design flows more than 5 MGD) and smaller POTWs with significant industrial discharges to establish local pretreatment programs. These local pretreatment 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 local pretreatment 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, and Waterloo. 

Local pretreatment coordinators contact information: Iowa Pretreatment Coordinators

The Need for Pretreatment

Local pretreatment programs are implemented by municipal authorities. These local programs are needed to eliminate potentially serious problems that can occur when industrial wastewater is discharged to municipal sewage systems.

Below is a list of potential problems that can arise from the disposal of industrial wastes.

  • Toxic industrial pollutants may pass through the treatment plant, polluting a receiving water body and threatening aquatic life and human health.
  • Industrial wastes may interfere with the operation of the treatment plant, rendering treatment of other wastes less effective.
  • Industrial wastes containing high levels of toxic metal or organic compounds can contaminate biosolids, making disposal options more expensive and limited.
  • Industrial wastewater can corrode the pipes and equipment in the collection system and at the treatment plant.
  • Highly volatile wastes can explode, causing considerable damage.
  • Some wastes may interact to produce toxic gases, which pose health hazards to workers in the sewers and the treatment plant.

For more information regarding the development a requirements of local pretreatment programs, see the Pretreatment Local Limits page.

For more information regarding treatment agreements between cities and industries, where a city has not established a local pretreatment program, see the Treatment Agreements page.

For questions regarding pretreatment, please contact Ben Hucka at 515/725-8406 or