The Billerica Wastewater Treatment Facility treats the wastewater from all homes, businesses, and industries connected to the sewer system in Billerica. The facility is located in the north end of Billerica near the Concord River.  It is a Grade 7 plant with a capacity of 5.4 million gallons per day (MGD) and an average flow of 4.0 MGD. The plant operates 24-hours-a-day, every day of the year and currently serves 75% of the town's population.

Used water or wastewater travels from your home, business, or industry through a series of increasingly larger pipes. In many locations, pump stations are necessary to move the wastewater further down the pipe until it reaches the wastewater facility. Billerica has 27 pump stations located throughout the town.

Once the water arrives at the treatment facility, it moves by gravity through a series of processes that remove pollutants. First the wastewater runs through channels where large debris, sand, and grit are removed. After this, the wastewater moves through very large circular tanks to allow settling of solids. The wastewater then is aerated to encourage natural bacteria to use any dissolved pollutants as food and turn it into material that will settle out. The next series of tanks allows this settling to happen. The wastewater is then disinfected with sodium hypochlorite, a strong bleach solution, aerated, and discharged to the Concord River. The facilities discharge is tested daily and must meet pollutant limits set by the Massachusetts Department of Environmental Protection. Our facility has an excellent record of compliance with these limits.

Next, solids that have been removed from the waste stream are thickened further and more water is removed using a rotary press. The removed water is sent back to the head of the plant for treatment and the solids are brought to an incinerator for disposal.

In 2009, construction began on a new process that will remove phosphorus from the wastewater prior to discharge. Phosphorus is a nutrient that increases the growth of plants and algae in the river. As these plants and algae grow, they use up the oxygen in the river. This new process will reduce the amount of phosphorus discharged by the plant by converting it to a settleable compound, mixing it with a magnetic compound and removing it with a magnet.