The wild world of wastewater

Few of us think about what happens down the drain. But there’s a surprising amount of innovation going on — including new ways to clean wastewater and novel methods to generate power from it.

Canadians flush the toilet. A lot. The average Toronto household uses 630 litres of water a day, about a third of which goes down the drain. And while wastewater treatment usually only makes headlines when it goes wrong — like in January, when Hamilton discovered it had been leaking sewage into Lake Ontario for 26 years — there’s a lot burbling beneath the surface of this vast industry.

Scientists are coming up with more efficient ways to treat wastewater that cut electricity use and reduce the amount of pollution seeping into waterways. Sewage is even being seen as a source of energy.

“That’s the holy grail,” says Patrick Kiely, founder of Sentry, a company that creates biosensors to help wastewater treatment facilities reduce their power consumption. To Kiely, this waste is “gold” because of the untapped potential it holds for uses like renewable power.

Here are four things you need to know about the world of wastewater.

Wastewater treatment facilities are eye-wateringly expensive

First, the dirty truth we don’t like to think about: 80 percent of the world’s wastewater is discharged into waterways untreated. Even in an advanced country like Canada there is enormous variability in how we deal with our waste. While nationally, only 3 percent of wastewater goes untreated according to Statistics Canada, in Nova Scotia it’s 25 percent and in Newfoundland and Labrador it’s 38 percent.

The reason for this is that centralized treatment systems are expensive to build and maintain. Just look to Vancouver, where reports have emerged that the new facility under construction on its North Shore may cost five times more than its initial $700-million budget. Upgrading another facility in the city could take $10 billion. Toronto is currently facing a $3-billion price tag on upgrades to its century-old sewer system to separate sewage from stormwater and reduce the need to discharge untreated wastewater into Lake Ontario after heavy rains. But coastal towns often still rely on the dilution power of the sea to take care of their human waste. Halifax only built its first treatment plant in 2008 — previously it discharged sewage directly into its harbour. And while engineers and researchers can be involved in monitoring everything from ocean currents to impacts on wildlife, these situations are far from ideal. “We can do better here,” says Kiely.

Sewage digesters are power hungry

There’s a hidden cost to using the bathroom that few people know about: Wastewater treatment can account for more than 20 percent of a municipality’s energy usage. Why so much? It has to do with the oxygen required by the microbes that break down the waste. Many treatment plants bubble air into these digester tanks at rates needed to meet peak demand. But researchers have found that wastewater treatment plants have low-volume and high-volume periods that are reflective of human behaviour — “We all go to the toilet basically at the same time,” says Kiely.

It’s one of the reasons Kiely founded Sentry. His company’s biosensors are designed to measure bacterial activity in wastewater treatment plants and help spot patterns so operators can dial up or down the oxygen flows as needed. “We can now show very clearly the pattern of when the high strength wastewater is coming in and when it’s a lot more diluted. We can provide operators with that information in real time.”

Where there’s waste there’s wattage

To the average person, there’s nothing valuable in the stench of wastewater. But to microbiologists, it can mean renewable power. When microbes are put to work digesting organic waste matter in a low-oxygen environment, they produce methane. This valuable biogas can be collected and sent to the natural gas grid, or burned to generate electricity on site.

Montreal’s wastewater treatment plant, which is the third largest in the world and treats nearly half of Quebec’s wastewater, is being outfitted with this technology, as part of a $682-million refurbishment. It is expected to cut the plant’s emissions by 92 per cent as well as creating energy.

Not every plant captures these methane emissions, nor can most generate electricity with complete efficiency, but Elizabeth Edwards, a bioengineering professor at the University of Toronto says that in theory, “there’s enough energy in the organic matter in wastewater to power the treatment facility.”

There is even a technology in the early stages of development that can directly harness energy generated by microbes as they break down industrial wastewater to produce small amounts of electricity. These microbial fuel cells, as they’re called, are already in use at a Pepsi facility in California.

Our water is getting harder to treat

When it comes to clean water, new problems are emerging. Recent studies suggest that wastewater is high in microplastics — everything from polyester fibres from clothing to the microbeads in facial scrubbers. We also have to contend with PFAFs, or forever chemicals, which are used to dispel grease or oil stains in consumer products. And then there’s pharmaceuticals — anywhere from 30 to 90 percent of the medication you take passes right through you. There is much we still don’t know about the effect of drugs and personal care products on the environment, but studies in the last decade have proven they’re harmful to fish.

While technologies exist to remove some of these — such as special filters and chemicals that cause microplastics to clump together — and they are already deployed in some treatment plants, their use needs to be expanded. “There’s great technology out there,” says Edwards. “It’s a matter of finding ways of incentivizing municipalities to invest in them.”

Hear more from Patrick Kiely about the hidden potential of wastewater on the MaRS podcast Solve for X: Innovations to Change the World.

 
Photography: iStock (main image); Sentry.