Overview
The City of Bellingham’s Water Treatment Plant, constructed in 1968 and upgraded in 2018, can process up to 24 million gallons of water daily. These days, the plant uses modern treatment technology, including computer controls and specialized water quality testing instruments. It utilizes a process known as in-line, or contact filtration. In this process, staff add a special chemical that causes unwanted particles to clump together, allowing them to be removed during filtration. This method works especially well with the high-quality water available in Bellingham.
Lake Whatcom
Lake Whatcom is the primary source of drinking water for Bellingham and its surrounding areas. Additional water comes from the Middle Fork of the Nooksack River, fed by the Deming Glacier on Mount Baker. From the lake, water flows by gravity through an underwater pipe towards the Water Treatment Plant. It first enters the gatehouse, where it moves from the pipe into a tunnel that leads to the screenhouse in Whatcom Falls Park.
Screenhouse
In the screenhouse, large debris is removed by a screen. In the past, water leaving the screenhouse flowed directly into distribution lines and out to homes. Today, the water continues through a pipe to the City’s Water Treatment Plant near Whatcom Falls Park. There, it enters the pretreatment system known as Dissolved Air Flotation (DAF).
Pretreatment System
In the Dissolved Air Flotation (DAF) system, staff add aluminum sulfate (alum) to the water. This chemical causes small particles and algae to clump together. Operators then release tiny bubbles of air that lift the clumps to the surface. At the surface, we skim off the clumps and send them to the Wastewater Treatment Plant. After DAF, we add a small amount of chlorine. This step supports the filtration process and helps prevent algae from growing in pipes that carry unfiltered water.
Filtration
After Dissolved Air Flotation (DAF), the water flows into a flume where staff add a polymer. This material helps clump even smaller particles such as dirt, algae, and sediment. The water then moves into one of six filter-lined chambers filled with layers of anthracite coal and silica sand. As the water passes through these layers, the remaining particles are trapped. We then collect the clean, filtered water at the bottom through an underdrain system.
Sanitation
After filtration, the water flows from the underdrain system into a one‑million‑gallon reservoir beneath the plant called the clearwell. Here, staff add chlorine to ensure proper levels before the water enters the Contact Time (CT) Reservoir. This 16‑million‑gallon reservoir holds the water long enough for the chlorine to blend thoroughly. As the water leaves the CT reservoir, staff add a final dose of chlorine to maintain safe levels. At this stage, they also add sodium carbonate (soda ash) to raise the pH. This step protects the City’s 410 miles of water mains and customers’ plumbing from corrosion.
Water Quality Testing
Staff test water quality throughout the day at multiple points in the Water Treatment Plant using online monitors, ensuring safety 24 hours a day. The City also operates a state‑certified laboratory at the plant. Additionally, staff conduct daily monitoring throughout the distribution system. We test all treated water to ensure it meets the requirements of the Safe Drinking Water Act and the Washington State Department of Health. We analyze results regularly for more than 160 different constituents.
After leaving the Water Treatment Plant, staff collect samples each month from more than 90 designated stations across the City’s water distribution system. These stations, located in different neighborhoods, help verify the safety of treated drinking water and track its quality as it moves through the system.
For more information about treated water quality and monitoring programs, visit Water Treatment Steps or contact the Technical Supervisor at the Operations Division of the Public Works Department.
Public Education
Over the last several years, the City of Bellingham has developed and implemented an extensive and highly successful public education program focusing on the City’s water supply. The program serves schools, civic groups, drinking water customers, watershed residents and other community interests, with the goal of increasing public awareness of water resources, water quality, and water conservation issues.
