What Scarborough Sanitary
District Does

How Does Wastewater Treatment Work?

Using a state-of-the-art wastewater treatment facility, the Scarborough Sanitary District has the capacity to purify an astounding 2.5 million gallons of raw sewage every single day. Our secret weapon? A remarkable process known as "activated sludge." In this innovative method, we deploy armies of microorganisms that work tirelessly to cleanse and rejuvenate the wastewater. These tiny heroes effectively remove waste products from the discharge stream, ensuring that every drop of water leaving our facility is clean, safe, and ready to be returned to the environment.

Map of the Scarborough Sanitary District steps


The wastewater treatment process begins with influent; the raw wastewater that flows into our treatment plant via a complex network of sewer mains.


Next, we screen out larger debris like roots, rags, and cans to ensure only manageable materials continue in the process.

Grit Removal

Grit removal is an essential step that filters out sand and gravel, further refining the wastewater for subsequent stages of treatment.


Primary Treatment

During primary treatment, we use sedimentation and flotation techniques to remove settleable and floatable materials. This helps to clear the way for further treatment.



In large aeration tanks, the wastewater is exposed to aerobic bacteria. These bacteria work diligently to break down the waste, while the resulting sludge is separated for dewatering.

Secondary Clarification system at Scarborough Sanitary District

Secondary Clarification

After Aeration, the secondary clarification process allows the bacteria used during aeration to be collected and returned to aeration. Clarified wastewater flows from this process to disinfection prior to final disposal.


Disinfection & Testing

Before the treated wastewater can be released, it undergoes a thorough disinfection and rigorous testing process to ensure it meets all safety standards.

Scarborough Sanitary District to the ocean


Finally, the once raw wastewater is now fully treated, and ready for safe release back into the ocean.

Sludge treatment at Scarborough Sanitary District

Sludge Treatment

Settle Sludge is pumped to a holding tanks prior to the sludge dewatering process.

Sludge Dewatering

Sludge Dewatering

Sludge is dewatered using chemicals and filtration. Solids concentration of the sludge is increase to greater than 25%. The excess liquid is recycled back to the aeration process for further treatment. Dewatered sludge is discharge into trailers and hold off site for disposal.

GIS map of Scarborough, Maine with Sewer Utilities layover.


To get more information about the exact location and to help with planning your permits, please visit the Scarborough GIS map, click on layers, then turn on the Sewer Utilities to view them on the map.

Click here to view the Scarborough GIS mapping platform.