Where is all of the wastewater generated?

from the use of water in homes, businesses, and factories, as well as in kitchens and bathrooms. Over 2 million people in 43 communities, or nearly half the state's population, send their wastewater to the MWRA's treatment facilities in Boston Harbor. Additionally, wastewater is generated by over 5,500 businesses and industries. Additionally, rainy-weather street runoff and below-ground cracks and faulty connections that allow groundwater to enter the system account for nearly half of the total flow in MWRA sewers.

How is wastewater delivered to treatment plants?

There are three distinct sets of pipes through which sewage flows. Water that is used in a home or business is flushed through the pipes of the building until it reaches the local sewers, which are owned and run by the city and town sewer departments. The wastewater is transported into 227 miles of MWRA interceptor sewers by these 5,100 miles of local sewers. The wastewater from the region is transported to two MWRA treatment plants via interceptor sewers with diameters ranging from 8 inches to 11 feet. Even though the majority of wastewater moves by gravity, some low-lying areas need to be pumped.

WHAT WORKS IN SEWAGE TREATMENT?

At the Deer Island Treatment Plant, MWRA treats its wastewater flows as a preliminary primary and secondary treatment. In July 1997, the first phase of secondary treatment began. The treatment involves the following steps:

Collection and Pumping The sewage from the communities is piped to several headworks, where it is filtered out of bricks, logs, and other large objects. The sewage is pumped to Deer Island through deep rock tunnels beneath the harbor.

Preliminary Treatment A grit chamber is a tank in which mud and sand settle. After that, this material, which is called grit and screenings, is taken to a landfill for safe disposal away from the environment.

Primary Treatment The sewage then flows to primary settling tanks, where sludge and water make up up to 60% of the solids in the waste stream. Very few toxic chemicals are removed by this primary treatment.

Secondary Treatment Oxygen is added to the wastewater at the secondary treatment plant to speed up the growth of microorganisms. After that, the waste is consumed by these microbes, which then settle to the bottom of the secondary settling tanks. After auxiliary treatment, 80-90% of human waste and different solids have been taken out. This method also removes a significant amount of toxic chemicals.

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