Panoramic View of the plant
The Wastewater Division has responsibility for the operation and maintenance of the wastewater collection system, 21 pump stations, and the Wastewater Treatment Plant.

Wastewater Collection System

Wastewater from homes, commercial establishments, and industries flow to the public wastewater collection system. The collection system is a series of pipes that carry wastewater to the plant. In some locations, pump stations must pump the wastewater up the pipe to a location where it can then flow by gravity. The Town of Billerica has over 200 miles of sewer collection system.


Primary Treatment

Once the wastewater reaches the plant, solid material is allowed to settle out in large tanks. This is known as primary treatment. The water flows to the next series of tanks while the solids are pumped to solids holding tanks.


In the next series of tanks, bacteria is used to convert dissolved biological material to carbon dioxide, water, and more settle-able material. Air is added to these tanks for the bacteria while the dissolved material in the wastewater is food for the bacteria. The water continues on to another set of tanks while the solids are pumped to the holding tanks.

CoMag Effluence

Removing Ammonia & Phosphorus

Chemicals are used to remove ammonia and phosphorus to protect the quality of the water in the Concord River. Ammonia and phosphorus are nutrients which allow algae to grow in the river using up the oxygen that fish need to survive.

The solids removed from the wastewater are dewatered and transported from the site by a contractor, for disposal.

Additional Information

The Billerica Wastewater Plant has the capacity to treat 5.4 million gallons of wastewater a day. About 85% of Billerica's residents are connected to the sewer collection system.