Sewage treatment, or domestic wastewater treatment, is the process of removing contaminants from wastewater and household sewage, both runoff (effluents) and domestic. It includes physical, chemical, and biological processes to remove physical, chemical, and biological contaminants. Its objective is to produce an environmentally-safe fluid waste stream (or treated effluent) and solid waste (or treated sludge) suitable for disposal or reuse (usually as farm fertilizer).
The objective of sewage treatment is to produce a disposable effluent without causing harm to the surrounding environment, and also prevent pollution.
Sewage is generated by residential, institutional, and commercial, and industrial establishments. It includes household waste liquid from toilets, baths, showers, kitchens, sinks, and so forth that is disposed of via sewers. In many areas, sewage also includes liquid waste from industry and commerce. The separation and draining of household waste into greywater and blackwater is becoming more common in the developed world, with greywater being permitted to be used for watering plants or recycled for flushing toilets.
Sewage may include stormwater runoff, Sewerage systems capable of handling stormwater are known as combined systems. Combined sewer systems are usually avoided now because precipitation causes widely varying flows reducing sewage treatment plant efficiency. Combined sewers require much larger and more expensive treatment facilities than sanitary sewers. Heavy storm runoff may overwhelm the sewage treatment system, causing a spill or overflow. Sanitary sewers are typically much smaller than combined sewers, and they are not designed to transport stormwater. Backups of raw sewage can occur if excessive Infiltration/Inflow is allowed into a sanitary sewer system.
Modern sewered developments tend to be provided with separate storm drain systems for rainwater. As rainfall travels over roofs and the ground, it may pick up various contaminants including soil particles and other sediment, heavy metals, organic compounds, animal waste, and oil and grease. Some jurisdictions require stormwater to receive some level of treatment before being discharged directly into waterways. Examples of treatment processes used for stormwater include retention basins, wetlands, buried vaults with various kinds of media filters, and vortex separators (to remove coarse solids).
The Fort Madison Pretreatment Program has been delegated primary responsibility for enforcing against discharges prohibited by 40 CFR 403.5 and applying and enforcing any national Pretreatment Standards established by the United States EPA in accordance with Section 307 (b) and (c) of the Clean Water Act (CWA, as amended by the Water Quality Act (WQA), of 1987.
The General Pretreatment Regulations set responsibilities for federal, state, local government, industry, and the public to achieve the National Pretreatment Program Objectives.
Publicly Owned Treatment Works, (POTW) collect wastewater from homes, commercial buildings, and industrial/commercial facilities and/or locations. This wastewater leaves these locations through a complex series of under-ground sewer lines called the sanitary wastewater collection system. The collection system transports wastewater to the POTW here called the Fort Madison Wastewater Treatment Facility, (FMWTF). Once the wastewater enters the FMWTF, it is directed through a series of treatment technologies effectively removing harmful organisms and other contaminants.
Generally, POTWs are designed to treat domestic sewage only. The FMWTF is no exception to this point. However, as with other cities, the FMWTF also receives wastewater from industrial and commercial sources, (non-domestic).
The General Pretreatment Standards and Regulations establish legal responsibilities of Federal, State, Local government, industry and the public to implement applicable Pretreatment Standards. The Pretreatment Standards protect the FMWTF from pollutants which may pass through or interfere with the FMWTF treatment processes or which may contaminate the beneficial use of the FMWTF sewage sludge, (i.e. Biosolids).
"Pretreatment" is also defined in the Title 40 Code of Federal Regulations (40 CFR) Subsection 403.
Objectives of Pretreatment Program
- Regulate the disposal of industrial wastewater into the sanitary wastewater collection system.
- Protect the physical structures and the safety of operation; maintenance personnel of the sanitary wastewater collection system and the FMWTF.
- Protect the health and safety of the public and the environment.
- Comply with Pretreatment Regulations as required under the Federal General Pretreatment Regulations and Categorical Standards