Erie County
Water Authority
Providing Water You Can Trust

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ECWA Water Treatment Process

Raw Water is drawn from Lake Erie and the Niagara River at the Sturgeon Point and Van de Water Treatment Plants, respectively. By gravity, water flows through intake tunnels into a distribution chamber in each plant's raw water building. Vertical pumps draw the water through a series of traveling screens, which prevent large debris, such as fish and seaweed, from entering the system. It is then pumped to the main treatment plant to begin the treatment process.

The water flows through rapid mixers where polyaluminum chloride is added. The chemical reaction causes dirt, clay, and bacteria to form a product known as floc, which settles easily out of water. In flocculation basins, large paddles gently stir the water causing the floc to increase in size and density helping it to settle at the bottom of the basin.

Next the water flows to settling basins. The sludge at the bottom of the basin is removed by scrapers and sent to the waste water system.

The partially treated water flows to the filter beds. Chlorine is added to the water for disinfection. The water flows through layers of sand, gravel, and anthracite coal. The filters remove particles, such as viruses, cysts, bacteria and any remaining floc.

Filters are cleaned by backwashing, in which clean water removes the collected sludge from the top of the filter to settling clarifiers. When the backwash water settles, the clear water is recycled back into the water treatment process and the sludge is removed.

Before water enters the distribution system, more chlorine is added to prevent bacteria build up. Fluoride is also added to fight tooth decay. Caustic soda is added to neutralize the acidity and prevent the corrosion of pipes. Finally, high service pumps push the treated water from a clear well reservoir into the distribution system.

Water is sampled and tested throughout the treatment plant to make sure that treatment processes are working and that the water is safe before it leaves the plant. In North America, governments have set strict rules for safe drinking water. When water leaves a treatment plant, it is as clean or cleaner than required by those standards.

ECWA maintains a rigorous purification program that meets and/or exceeds the regulations set by the federal government's Safe Drinking Water Act and the New York State Department of Health.

Water quality is strictly monitored at the ECWA's laboratories to make sure the water is safe and clean to drink. Highly trained chemists test for bacteria, pH levels, turbidity, chlorine residual and other related analysis. The ECWA conducts more than 70,000 tests annually to make sure all federal and state drinking water regulations are met.

ECWA's testing laboratories can find a drop of contaminant in up to 10,000,000 gallons (one part per trillion).


Intake: Water is taken from a source such as a lake or river. Large items such as logs, fish and plants are screened out at the intake. Only then is the water drawn into the treatment plant. If the source is groundwater, the screening is, in fact, done by the soil as the water travels under the earth's surface. Sometimes very little treatment is required for groundwater.

Chemical Addition: Polyaluminum chloride, polymers, carbon and/ or chlorine are added to the water. These chemicals kill germs, improve taste and odor, and help settle solids remaining in the water.

Coagulation and Flocculation: The chemicals added to the water cling to particles already in the water, a process called coagulation. These particles subsequently stick together and form larger particles called floc, a process called flocculation.

Sedimentation: Water containing floc particles flows into a sedimentation basin, where floc settles to the bottom and is removed from the water.

Filtration: From the sedimentation basin, water flows through filters made of sand and gravel layers, which remove any remaining particles in the water.

Disinfection: A small amount of chlorine is added or other disinfecting chemicals may be added to kill any remaining germs and keep the water safe as it travels through the distribution system to the public. In some water systems, especially those with groundwater sources, chlorination is the only treatment provided.

Storage: Water is placed in a closed tank or reservoir called a clear well to allow time for the chlorine to mix throughout the water in order to disinfect it. The water then flows into the distribution system.

Learning Center Treatment Process Water Cycle
Story of Drinking Water Conservation and Storage Water Use