Sunday, June 16, 2024
June 16, 2024

LCC aims to shrink septage, sludge trucking costs

Salt Spring’s Local Community Commission (LCC) is digging into one of its perhaps less-glamorous delegated services — but some innovative ideas may save ratepayers millions of dollars in coming years. 

Troy Vassos, senior environmental engineer from consulting firm Integrated Sustainability, presented the LCC his team’s analysis of waste treatment options at the Capital Regional District’s (CRD) Burgoyne Bay facility on Salt Spring Island — acknowledging the reality that human waste is rarely a topic delved into eagerly. 

“It’s not everybody’s favourite subject, I’m sure,” chuckled Vassos, who explained for the uninitiated that the material in question — the accumulation of solids from Salt Spring’s septic tanks, as well as biosolid “sludge” from the island’s two wastewater treatment facilities, at Ganges and on Maliview — is collected, alongside water treatment sludge and that gathered from restaurant grease traps, at a facility at Burgoyne Bay, where it all waits to be eventually transferred by truck and ferry to Vancouver Island. 

Commissioning the report was one of the last actions taken by the now-dissolved Salt Spring Island Liquid Waste Disposal Local Services Commission, whose responsibilities now lie with the LCC. Commissioners anticipated a “technical demo” report on the order of 10-12 pages, but were delighted Vassos brought a more fulsome examination to their meeting on Tuesday, Aug. 22. 

“I think it’s about 50 or 60 pages,” said Vassos. “So you got a lot more than you originally hoped for. But we felt it was necessary to enable you to make these decisions.” 

Vassos has more than a passing familiarity with Salt Spring, and particularly with the Ganges wastewater treatment plant; he was the engineer responsible for upgrading equipment there when the ultra-filtration membranes had failed and needed replacement. Projects like this, he said, need to be thought about with 20-year horizons, and designed for the future; otherwise, he said, “you’re constantly paying for infrastructure.” 

The report explained the current operating budget for the handling, transportation and disposal of Salt Spring’s septage and sludge was $817,000 for the year. If the island’s population grows at the same rate it has over the last two decades — and the volume of material goes up accordingly — Vassos’ team predicted the average cost would top $1 million per year quickly, reaching nearly $1.4 million in 2043. That represented a total of $22 million in operations cost over two decades, “plus inflation,” said Vassos. 

“But two things septage and biosolid sludge have in common is that they’re mostly water — about 98.5 per cent,” said Vassos. “So what we’re disposing on Vancouver Island is mostly water.” 

To save trucking costs, the consultants looked for ways to thicken — or “dewater” — the material, and then deal with the liquids and solids created separately — possibly even avoiding off-island transportation.  

For the liquid, one idea was to dispose of it in the already-oversized Ganges treatment plant; but while Vassos said it could “easily” handle the additional liquid load, the cost of trucking the liquid from Burgoyne was far higher than treating it and dispersing it into the ground at the Burgoyne site — even after factoring in the capital expenditure of building that septic-field-like system.   

“The option we’re suggesting would be the most environmentally sensitive, to treat it biologically — using in this case a recirculating filter-type treatment process. Very limited operations cost, it basically operates on its own quite nicely for six to eight months before it needs someone to take a look at it, and we disperse the treated liquid into the ground.” 

Several options for solids had to be discarded, but as much for regulatory reasons as costs. Composting on-site, for example, requires adding wood chips and sawdust, increasing the volume of solids to deal with. Moreover, the CRD currently prohibits use of that sort of compost — and on-site dehydration, similarly, produces a soil nutrient product subject to a provincial prohibition. 

The best value, according to the analysis, could be to “thermally degrade” the biosolids into biochar — killing off all the proteins associated with viruses, parasites and bacteria with heat. 

“Because you change the chemical and physical nature of it, it wouldn’t classify as a biosolid,” said Vassos, who posited it might therefore not fall under current CRD prohibitions for use. “You’ve got an inert carbon, phosphorus and nitrogen material that can be used for agricultural applications — or we could transport it to Hartland [landfill] at much less cost, because we’re not transporting all of that liquid with it.” 

The recommended approach — separating most liquids from solids with a press, treating the liquid with a recirculating biofilter process and dispersing it into the ground, then burning the solids with a pyrolysis system — “A bit like running a barbecue,” quipped Vassos — appealed to commissioners partly for the potential for generating biochar for soil, and partly for cost savings. The 20-year aggregate operational cost would run about $2.6 million, compared to $22 million currently projected with the status quo, according to Vassos. 

“It’s the most logical, sustainable approach,” said Vassos. “The disposed-of water becomes part of the groundwater, returning to the environment. And with the pyrolysis, you’re recovering nutrients that were waste products.” 

“I know all biochar is not the same,” said commissioner Gayle Baker. “Are you comfortable that the biochar would be heavy-metal free and appropriate for soil use?” 

“Biochar will reflect the habits of the homeowners in Ganges and the surrounding area of Salt Spring,” said Vassos. “If people discharge paints, heavy metals, waste batteries and so forth into their septic tanks, that is going to be reflected in the quality of the biosolids being produced.” 

Typical domestic wastewater is fairly innocuous, Vassos said — unless you’ve got industry nearby.  

“Metro Vancouver you’ll find a higher concentration of metals in the biosolids than you will in Victoria,” said Vassos. “And of course you’ll have a higher level in Victoria, with its minor industries, than you would on Salt Spring.” 

The LCC moved to accept the recommendation and asked staff to prepare a strategy that includes verifying biochar’s status under the CRD’s biosolids restrictions. 

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