Lawrence, MA Water Quality Report
Where Your Drinking Water Comes From
The City of Lawrence began supplying drinking water in 1874. In 2007, a new water treatment plant began providing treated water, replacing the City’s 70-year old plant. Water from the Merrimack River is treated at the plant through a process known as conventional treatment, described below. The treated water is then pumped to the distribution system or stored for later use.
During emergencies or periods of unusually high demand, Lawrence has the ability to buy water from surrounding communities through existing interconnections with Andover, Methuen, and North Andover. Water from these interconnections was not required in 2019. The sources of these interconnections are the Merrimack River and Haggets Pond in Andover, the Merrimack River in Methuen, and Lake Cochichewick in North Andover.
How We Treat Your Water
- Water from the Merrimack River is pumped to the water treatment plant.
- Raw water flows to the mixing tanks, where chemicals are added (coagulation) and where particles are clumped together (flocculation) to be settled or filtered.
- In the settling tank process, flocs sink to the bottom of a settling tank and clarified water flows out of the top of the tank. The settled floc is removed from the bottom of the tank for disposal. About 90% of the solids are removed here.
- About 10% of the solids do not settle in the settling tank and are removed by filters made of granular activated carbon.
- Water flows through an Ultraviolet (UV) reactor to disinfect any pathogens (such as viruses and bacteria) that may have passed through the filtration process.
- Water enters the clearwell, where a form of chlorine residual is added to further disinfect any pathogens (such as viruses and bacteria) that passed through the filtration and UV process. A tank is needed to provide sufficient time for the disinfection process to occur.