Where does the poop go when you flush?
Most people don’t consider the winding journey wastewater takes, flowing through underground pipes in the Lower Mainland until it reaches one of Metro Vancouver’s five wastewater treatment centres. Few people think about how it sits, separating into liquids and solids before being purified by micro-organisms.
In early December, Delta council thought about Metro Vancouver’s sewage system. They were concerned about the 200 per cent development cost charge increase Metro Vancouver wants to impose. The Annacis Island treatment centre is undergoing its fourth expansion, bringing its capacity from one million people (and 175 billion litres of sewage a year) to 1.5 million people.
While Delta council and staff focused on the nickels and dimes of wastewater treatment, researchers were thinking about something else: the subtle intricacies that make treatment centres a unique blend of man-made and natural processes.
“I like to look at wastewater treatment as, it’s not necessarily the treatment of it, but it’s the recovery of resources,” Rick Gallilee, director of management systems and utility services with liquid waste services at Metro Vancouver, said.
In large treatment centres like the one at Annacis, those resources are recovered through two different kinds of purification: primary treatment, which uses basic physics to separate solids and liquids, and secondary treatment, which uses biology.
Secondary treatment features “bugs,” a colloquial term for the micro-organisms that consume the unwanted solid materials.
While some of the bugs help purify water, others use a process called anaerobic digestion (meaning the bugs are only happy without oxygen) to turn the unwanted solid material into biogas. It’s those biogas-producing bugs that Paul Kadota, program manager of utility research and innovation with liquid waste services, is turning his eye towards.
In the anaerobic digester, the bugs mix with solid material and produce a combination of carbon dioxide and methane. The gas, which is about 65 per cent methane and 35 per cent carbon dioxide, is used to generate power and heat at Annacis Island.
Using that gas in its raw form requires special equipment, but it’s also possible to separate the two types of gas and sell the methane to FortisBC — Metro Vancouver doesn’t yet, but is building equipment at its Lulu Island treatment plant in Richmond that will be able to do just that.
Getting a 65 per cent return on gas produced by bugs isn’t a bad deal, but Kadota believes it can be even better. He noticed a lab with the U.S. Department of Energy had succeeded in increases the methane content of their biogas from 60 per cent to 90 per cent.
“That’s really important when you’re trying to maximize the energy recovery from an ultimately infinitely renewable resource,” he said.
“As long as you have people, you’re going to have this biomass available to you. Why not make the best use of it?”
But maximizing the energy isn’t as simple as adding more bugs — Kadota needed to find out what kind of bugs produced the methane, and how they could become happier.
What he found was that gas producing organisms are actually from two distinct parts of the tree of life. Most of them — around 99 per cent — are bacteria, which are single-celled creatures with a nucleus that holds their DNA. But around one per cent are actually archaea, a type of single-celled organism that is distinct from bacteria because it doesn’t have a nucleus.
Those archaea are responsible for producing all the methane in the biogas.
“They’re actually going quite a bit of work when you think about one per cent of a total population,” Kadota said.
Now that Kadota knows what kind of bugs make the methane, he needs to figure out how to make them happy. He’s been developing incubators to help grow the archaea population, and will be testing them out with the help of UBC Okanagan researchers.
But it’s still early days. Funding for Kadota’s research was only granted in 2017, and he expects the project to go on for three or four years.
“Ultimately we have internal goals of producing future facilities that are greenhouse gas neutral, or energy neutral, and trying to do our part as far as greenhouse gas emissions into the environment,” he said.
“Advancements on technologies such as this, we’re hoping, can help pave the way to getting there.”