There’s a new hope that a practical solution can be found to the problem of the odour coming from the City of Revelstoke’s sewage treatment plant in Southside.
New testing has determined that the vast majority of the summertime smell is emanating from the headworks building, not the sewage treatment lagoons.
The brick headworks building looks like a big four-car garage and is located right next to the city’s two sewage lagoons. Sewer pipes from across the city lead to the building, where the sewage undergoes initial screening and treatment upon discharge, before flowing into the lagoon. In addition to liquid sewage, the pipe also discharges a considerable amount of smelly gas, including hydrogen sulphide gas, the main culprit behind the summer smell issues in Southside.
City of Revelstoke Director of Engineering & Development Mike Thomas said testing conducted in mid-August found that hydrogen sulphide gas concentrations coming from the building’s exhaust fan are “a thousand of times higher” than from concentrations at the edges of the two side-by-side sewage lagoons. Testing showed 2.7 parts per million at the headworks building fan, and only 0.004 parts per million at the perimeter of the lagoon.
Both of these numbers seem small, but the human olfactory system is finely tuned to detect hydrogen sulphide; the rotten egg smell can be easily picked up at levels below one part per million.
Thomas said the smell around the building is strong, whereas at the far edge of the lagoon, “you can smell it but it’s not a really strong smell. That’s why I’ve got a real concern about that building.”
The new testing points to a whole different set of possible solutions. In the past, city officials indicated the lagoons were the source of the smell problem, saying seasonal weather affected the lagoons’ biology, creating smells during the summer. The solution was thought to be prohibitively expensive, and could be the source of political inertia on the Southside smell issue; a new, mechanical lagoon costs tens of millions of dollars.
Options for treating a problem emanating from the sewers themselves may be far less expensive, and therefore more doable.
Thomas is proposing bringing in a sewage expert to study the problem and potential solutions.
So, what’s causing the sewers to belch out gas, and why is it worse in the summer?
Oil and grease in the system is one potential culprit. Fresh in news consumers’ minds is the giant, 15-tonne, bus-sized ‘fatberg’ defeated by heroic sewer workers in the London, U.K., borough of Kingston upon Thames this summer. In fact, fatty buildup is a known major cause of sewer stench and gas. Thomas said upping inspections of restaurant fat traps is an option, as is possible public education campaigns about proper disposal of oils and fats.
What else could be a cause? Added RV tank dumping at the free city sani-dump may or may not have an effect, Thomas said. Discovering the factors leading to the smell can help isolate more effective treatment options.
“Understanding where it’s coming from is part of the path to a solution. If you can mitigate that earlier on in the sewer system, potentially you’re not treating all of the sewer for the smell,” Thomas said.
At this point, Thomas said he’s can’t pinpoint a cause. “There’s not one piece of the puzzle that’s sticking out at the moment,” he said. “It could just be a combination of all of the pieces we’ve talked about.”
There are many engineering solutions to the issue. A quick Internet search turns up all kinds of systems created by engineering companies. Some are expensive, others less so.
“I’d be thrilled if we could find a solution that was very low-impact, environmentally friendly, easy to maintain and a cost-effective solution,” Thomas said.
In another development, an operating problem was discovered at the lagoons, and has now been rectified. Thomas said a piece of equipment that measured dissolved oxygen levels in the lagoons was located in the wrong place. As a result, the detector was indicating dissolved oxygen levels were too low, causing the system that circulates air to bubble up through the lagoon to be ‘always on.’ The oxygen in the bubbles helps drive the biological process that breaks down the sewage.
As a metaphor, picture a swimming pool with an attached hot tub, but the installer accidentally put the hot tub thermometer in the swimming pool. The automatic heating system works overtime, and never shuts off because the thermometer is telling it to keep going.
Thomas said there was a concern the mechanical system operating the oxygen pumps could have overheated. The effect on smell is unknown.
For Southside residents, the stifling summertime smell is enough to create demands for a solution. But is it just a smell issue? Are there health concerns?
The answer is yes, but the relative danger is harder to determine. Hydrogen sulphide gas can be almost instantly fatal in high concentrations – doses many, many, many times higher than those coming from the sewer. Oil and gas industry workers are required to take sour gas (hydrogen sulphide) training as a prerequisite for most work sites.
Many scientific studies have shown many adverse health effects associated with lower dosages of hydrogen sulphide, but the relative danger at much lower doses, like the concentrations around the Southside sewage treatment plant, is harder to determine. Both Health Canada and the U.S. Environmental Protection Agency maintain webpages (Health Canada hydrogen sulphide page, U.S. EPA hydrogen sulphide page) that summarize the scientific literature on the health effects of hydrogen sulphide.
The Health Canada website notes the lack of long-term epidemiological studies on the effects of chronic low-level exposure like someone living near a sewage treatment plant would experience. Some medical experts argue that the presence of a smell alone is enough to create health issues.
What is clear is that once ingested through the lungs, hydrogen sulphide is metabolized, meaning it enters your bloodstream and is broken down in your liver and kidneys.
Thomas was scheduled to give an oral report to Revelstoke City Council at their Aug. 27 regular meeting.
Southside resident Beckie Campbell expressed mixed optimism about the finding that the bulk of the smelly gas is coming from the headworks building.
“I’m obviously relived that they’re finally finding something,” Campbell said. “Maybe next summer it will be more bearable.”
She questioned why it took city officials 15 years to discover the source of the issue.
Campbell said she hoped city council would follow up with community members once the options became available. “People don’t go to council meetings.”
The working mother said that like most Revelstokians, she’s at work at 3 p.m. on Tuesdays and can’t attend the Revelstoke City Council meeting where Thomas is presenting on the results of his explorations. She’d like to see some kind of report available to residents.
She was hopeful a solution could be put into place by next summer. “I don’t know why it’s taken so long,” she said.
