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Boston Harbor and Massachusetts Bay

Massachusetts Water Resources Authority

Effluent Monitoring

MWRA monitors the effluent, or treated sewage, that is discharged from the Deer Island Treatment Plant (DITP) into Massachusetts Bay, to ensure that it meets the standards set out in the NPDES discharge permit.

Solids Reduced by Over 90% in Deer Island Treatment Plant Effluent

Solids discharges from MWRA's Deer Island Treatment Plant (DITP) have fallen and remained low since the beginning of the Boston Harbor Project. Discharges of sludge (sewage solids) to Boston Harbor ended in 1991. Improved, secondary treatment began at DITP in 1997, resulting in an 80% decrease in solids discharges by 2000.

Discharged Metals Remained Low in 2016

Metals attach to solids in wastewater, so discharged metals have reduced along with solids. In addition, MWRA increased its enforcement of industries that are required to pre-treat their wastewater, preventing metals and other pollutants from entering the sewage system.

More information on effluent monitoring is available in the annual Outfall Monitoring Overview.