The State of Boston Harbor and Massachusetts Bay
MWRA Environmental Quality Department

Discharge Monitoring

There were marked improvements in effluent discharges after MWRA upgraded disinfection and primary treatment and then added secondary treatment. Secondary treatment increases the removal of solids and metals from sewage. Also, MWRA's Toxics Reduction and Control program increased enforcement of pretreatment of industrial wastewater, which significantly reduced the amounts of toxic metals and other pollutants being sent to the treatment plants.

 

The following graphs can be enlarged by clicking on them:

The proportion of wastewater receiving secondary increased after 1997, when secondary treatment began being phased in. (Enlarge Figure)
Solids in MWRA discharges have decreased since secondary sewage treatment began in 1997. (Enlarge Figure)
Effective industry source reduction programs have helped to bring down metals in MWRA discharges. (Enlarge Figure)