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Allegheny County Sanitary Authority

Allegheny County Sanitary Authority, also known as ALCOSAN, is the regional wastewater treatment authority for Allegheny County, Pennsylvania. Established in 1946, ALCOSAN is responsible for treating wastewater from 83 municipalities in the county, including the city of Pittsburgh. The authority’s mission is to ensure clean water and a healthy environment for the region by treating wastewater to remove pollutants before it is discharged into the region’s rivers.

ALCOSAN operates one of the largest wastewater treatment facilities in the region, treating an average of 250 million gallons of wastewater per day. The Authority’s treatment process involves several steps to remove pollutants and contaminants from the wastewater before it is discharged back into the environment. These steps include screening, primary treatment, secondary treatment, and disinfection.

Screening is the first step in the treatment process, where large debris such as plastics, paper, and other solid materials are removed from the wastewater. This helps prevent damage to the treatment equipment and ensures that smaller particles can be effectively removed in the subsequent treatment steps.

After screening, the wastewater undergoes primary treatment, where suspended solids are settled out of the water using gravity. This process helps remove organic matter, fats, oils, and grease from the wastewater, which can cause odors and clog pipes if not properly treated. The primary treatment step also helps reduce the amount of pollutants that need to be removed in the later treatment steps.

Secondary treatment is the next step in the process, where microorganisms are used to break down organic matter in the wastewater. This biological treatment process helps remove nutrients such as nitrogen and phosphorus from the water, which can cause algae blooms and harm aquatic life if not properly treated. ALCOSAN uses a combination of activated sludge and trickling filter systems to effectively treat the wastewater and remove pollutants before it is discharged back into the environment.

Once the wastewater has been treated through the primary and secondary treatment steps, it undergoes disinfection to kill any remaining pathogens in the water. ALCOSAN uses chlorine to disinfect the wastewater before it is discharged into the region’s rivers, ensuring that the water is safe for humans and the environment.

In addition to treating wastewater, ALCOSAN is also committed to promoting environmental stewardship and education in the region. The authority offers educational programs for students and residents to learn about wastewater treatment, water conservation, and environmental protection. ALCOSAN also works with local partners to implement green infrastructure projects that help reduce stormwater runoff and improve water quality in the region.

Overall, ALCOSAN plays a vital role in protecting the region’s water resources and ensuring a healthy environment for residents and wildlife. The authority’s wastewater treatment facility and programs help prevent water pollution, promote sustainable water management practices, and support the region’s economic development. By working together with local communities and stakeholders, ALCOSAN is able to fulfill its mission of providing clean water and a healthy environment for the residents of Allegheny County.


1. ALCOSAN official website:
2. Allegheny County Sanitary Authority, “About Us” page:—in-the-community


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