What do our sanitary and storm sewers do?
The main function of a sanitary sewer system is to protect water quality and public health. A series of underground pipes and manholes, pumping stations, and other appurtenances convey sewage from homes, businesses and industries to wastewater treatment plants where it is cleaned and returned to the environment.
The storm sewer system collects rain and melting snow, referred to as runoff. The water flows through pipes and manholes, ditches, swales, and other conveyance methods. Most stormwater is diverted directly to local streams and waterways without treatment.
What are some of the characteristics of these systems?
While most of the sanitary sewer system utilizes gravity to convey the wastewater, there are some cases where it is pumped from low points or low lying areas up to higher elevations where it can then utilize gravity again to convey flows to treatment plants. Manholes are positioned in the system to provide access to the buried pipelines for maintenance and repairs. Manholes are also used whenever there is a change in pipe sizes, change in the direction of the sewer line, or a large change in elevation.
In the storm sewer system, water or runoff is conveyed much the same way as in the sanitary system, but again typically no treatment is provided.
There is also a third type of sewer system called a combined sewer. In this system, one pipe carries both sanitary wastewater and storm runoff together. The City of Buffalo is served by a combined system that was built many years ago. None of the Erie County Sewer Districts are combined sewer systems.
For more information on conveyance and treatment systems, visit the Water Environment Federation’s “Go with the flow” website.