By MEL ROTHENBURGER
Director, Electoral Area P, TNRD
The Thompson-Nicola Regional District shouldn’t rely on just one method for getting rid of sewage sludge, experts told a workshop attended by about 60 people on Friday (July 20, 2018).
The residual material left after sewage treatment is also known as biosolids, and it’s become increasingly controversial in recent years due to concerns about toxic contaminants and odour.
“When you’re doing your planning you need a basket of options,” Rob Simm, an engineer with Stantec, told the day-long workshop that included members of the public as well as elected officials.
He said changes in science, land availability and the market make it essential to “not put all your eggs in one basket.”
The workshop was organized as the TNRD and its member municipalities struggle with the issue of a long-term plan for alternatives to disposing of biosolids on land.
Land application, especially on agricultural land, is the most common use for biosolids. When pressed for an opinion on which disposal method carries the least risk to public health, Dr. Lalith Liyange, another Stantec engineer, said thermal technologies such as gasification are the most effective at killing pathogens.
But both he and Simm cautioned that it’s also more expensive than land application, and that each technology must be considered in the context of such things as transportation costs and which materials are mixed with the biosolids.
When he said the risks from land application appear minimal based on available knowledge, Kamloops director Denis Walsh commented, “You’re saying they’re minimal but you don’t know what they are.”
They said land application provides an opportunity to take advantage of the economic value of biosolids for such things as soil enhancement and land reclamation.
Sim and Liyange explained the various types of biosolids treatment such as aerobic, liquifaction and incineration.
The more processing that’s done the more options there are for what to do with the resulting biosolids, they said. However, the more water that’s removed from the sludge, the more energy is needed.
Various technologies are in a range of development from very early stages to well-tested.
Laurie Ford, an engineer with the Metro Vancouver Regional District, said her district is looking at various technologies to create dry biosolids. Considerations include cost, greenhouse gas emissions and volatility.
“We haven’t found that silver bullet yet,” she said.
The TNRD will follow up on the workshop with further discussion at a later meeting.