Clarenville's Water Supply/Treatment

Clarenville Water Supply/Treatment/Distribution

Clean Water is something we easily take for granted, especially when the last thing we usually think about is turning on our tap. But a lot of work goes into ensuring that water flows and is clean and safe. That's where the Town's Public Works staff, who run our water treatment plant and make sure all the pipes flow as they should, come in!

The Clarenville Water Treatment Plant provides safe drinking water to approximately 7,000 residents by drawing water from the Shoal Harbour River and putting it through a multi-stage treatment process.

The plant can handle an average daily flow of 4,600 cubic meters but has a design capacity of 8,500 cubic meters per day. A network of surface water bodies feeds the Shoal Harbour River within a 114 square kilometre watershed, including the Shoal Harbour Pond and Andrews Pond. Andrews Pond has a control structure that can release water into the Shoal Harbour River during dry months to maintain adequate flow.

Stage 1: Raw Water Collection

Raw water is drawn from the SHR through an intake structure located on the river bottom. This structure is equipped with a traveling trash rack that removes large debris before the water is pumped to the Shoal Harbour River Water Treatment Plant.

• Low Lift Pump Station: The water flows to the LLPS, which contains three pumps. Typically, two pumps operate at a time, using variable frequency drives to adjust their speed and maintain a constant discharge pressure. The pumps then send the water to the water treatment plant.

Stage 2: Water Treatment

Once at the plant, the raw water undergoes a series of purification steps.

Coagulation and Flocculation

• Chemical Dosing: The water is first treated with aluminum sulfate (alum), a coagulant, and hydrated lime for pH adjustment. These chemicals are mixed into the water using a static inline mixer.

• Flocculation: The treated water is then split into two separate flocculation trains. Here, the water is gently mixed in a series of tanks. This process causes the coagulant to bind with suspended particles and impurities, forming larger, heavier clumps called "floc."

Sedimentation

• Clarifiers: The water flows into one of two clarifiers. These clarifiers use a series of inclined plates to enhance sedimentation. The dense floc settles to the bottom, separating from the cleaner water, which continues to the next stage.

Filtration

• Multimedia Filters: The water is then filtered through three rapid gravity multimedia filters. Each filter contains layers of anthracite, silica sand, and graded gravel. As water passes through, the layers trap any remaining fine particles, further improving clarity. The coarsest anthracite layer removes larger particles, followed by the finer sand layer, which captures smaller ones. The gravel supports the filter media and ensures even water flow.

• Backwashing: To keep the filters clean, they are backwashed every 24 hours. This process involves reversing the flow of water and air to dislodge the trapped particles, which are then flushed away.

Disinfection

• Chlorine Contact Tank: After filtration, the water enters a chlorine contact tank. Chlorine is injected to kill any remaining pathogens, a process known as disinfection. The tank is designed to provide sufficient residence time for the chlorine to be effective.

PH Adjustment

• Soda Ash: Soda ash is added to the finished water to raise its pH to between 6.5 and 8.5 before it enters the distribution system.

Stage 3: Distribution

The treated, disinfected water is stored in a clearwell before being pumped out into the distribution system.

• Network: The water is distributed to the Clarenville area through a network of water mains, including a booster station, a water storage tank on Bare Mountain Road, and several pressure-reducing chambers.

• Storage Tank: The storage tank has a capacity of 5,045 cubic meters. Hypochlorine is also manually added at this tank to maintain chlorine levels in the distribution system.

This comprehensive process ensures that the water delivered to residents is safe and meets all quality standards.