Thursday, December 8, 2022
December 8, 2022

Ganges sewer upgrades shared

About a dozen people on Salt Spring can now say they’ve got the poop on Ganges poop.

They’re the ones who attended the Capital Regional District’s Ganges sewer plant open house on Thursday. The event was an opportunity for CRD staff to share details about the system’s recently completed $3.9-million upgrade and for people to ask questions about how the service operates.

Malcolm Cowley, manager of CRD engineering design services, led the proceedings, beginning with the innocuous-looking influent pump station, where all flushed waste arrives via the system’s sewer pipes about 25 feet below ground level.

“The pumps and the pipes and the valves were really old,” said Cowley. “They were all corroded and weren’t working very well anymore. It all needed to be replaced.”

Waste is then pumped into a tank for screening, with the solids put into a bin for hauling to either the Burgoyne Bay septic site for transfer to the Capital Regional District Hartland Road facility or direct hauling to Hartland.

Wastewater then goes into an “equalization tank,” which allows for variations in the flow of incoming waste. It can store extra water arising from rainy days and control the amount of water going into the treatment system.   

“From there it goes to a concrete tank divided into two,” explained Cowley. “The first half is what’s called the anoxic tank and then it goes to the aeration tank, and then the membranes that do all the biological treatment and filtering are located in another tank.”

And what comes out at the end of the process?

According to sewer plant lead Luke Sturdy, who at participants’ insistence brought out samples of pre- and post-treatment effluent at the open house, the final product is water with a fecal coliform count of two or three units per 100 millilitres of water, so virtually negligible. Swimming beaches are not closed to the public in B.C. unless the fecal coliform level exceeds 200 units.

Tom Toynbee was chair of the Ganges Sewer Local Services Commission when the membrane bioreactor (MBR) technology was chosen in 1996 to replace the rotary biological contactor system originally used at the plant when it opened in 1985.

“At that time [the MBR] was leading-edge technology,” Toynbee said. “It continues to be extraordinarily good compared to any others.”

“It is considered tertiary treatment,” Cowley confirmed. “It was kind of piloted here in Ganges,” he added. “It was a new technology back then and it has proven itself to be a very effective technology . . . [The effluent] has a negligible impact on the environment.”

Some people at the open house were surprised to learn that the outfall pipe extends 4.8 kilometres from the harbour into Swanson Channel. Cowley said the less effective original sewage treatment process would have determined the outfall length in the 1980s.

For more on this story, see the September 4, 2019 issue of the Gulf Islands Driftwood newspaper, or subscribe online.

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