The average Canadian consumes 251 litres of water per day for residential use, according to 2011 figures. While this includes doing the dishes and laundry and taking showers and baths, it’s also the water we drink and use for cooking.
We usually assume it’s safe and clean, but with the pathogens that routinely enter rivers and other water sources, there is no room for doubt.
Until now, Nanaimo, B.C. has been drawing its water from the local supply - the South Fork of the Nanaimo River - and treating it with chlorine before it reaches peoples’ taps. Due to it being a surface water source, it didn’t meet official drinking water quality guidelines and changing regulations in the province.
But a new plant scheduled to open later in 2015 will put the city at the forefront of water treatment technology. The cutting-edge $71-million facility will make the 116 million litres of water it is capable of processing daily cleaner and safer than ever before.
The plant will also take a big bite out of the large amounts of energy traditional water treatment plants consume.
“In Canada, most membrane plants use vacuum or pressure pumps to draw water through the filters. In our case we’re using the geography of the site to draw water by gravity siphon,” says Bill Sims, Nanaimo’s Manager of Water Resources. “It’s pretty simple but it’s pretty exciting. Gravity is free − this is going to save us about $70,000 in annual energy costs.”
Working with GE Water & Process Technologies, the new plant will require only five or six operators to run. GE has advanced a membrane technology called ZeeWeed, initially developed by Oakville, Ont. based Zenon Environmental Inc. and later acquired by GE.
In the 1990s, Zenon created an innovative process where membranes are immersed directly into process tanks and need only a slight vacuum to filter water. Previously, membrane systems usually used pressurized cartridges with many components, which used a lot of energy.
The new plant will recover 99 per cent of the untreated, raw water that comes from the river and, by filtering it, deliver it for consumption. “This is unusual for a water treatment plant,” says Sims. “Oftentimes the stuff that gets left over is flushed into a sewer. We wanted to maximize our recovery so we didn’t have to waste our most precious resource.”
The technology’s strength lies partly in its simplicity, says Robert Hacking, GE Water & Process Technologies’ Regional Sales Manager. The ZeeWeed system uses hollow fibre membranes, which have microscopic pores on their polymer membrane surface. The membranes block unwanted solids, bacteria and viruses – filtering out pathogens as small as one-twentieth the thickness of a human hair − while the pores allow water molecules through. Thousands of membranes are bundled into modules, each of which is a building block for the plant. The modules are snapped into cassettes, which form units that are immersed directly into the water that will flow through to be treated.
The water flows downward into tanks, where it can be siphoned rather than pumped through the membrane fibres. Gravity is also used to move backwash water, used periodically for cleaning the membranes, into a reject tank after the cleaning is done.
In the past two decades regulations have become more stringent, public expectations about clean water have grown and we know more about pathogens such as Cryptosporidium and Giardia that can contaminate supplies and cause gastrointestinal illness. ZeeWeed membranes block such pathogens.
“As long as we know that the physical [membrane] barrier is there and that we have ways of testing it, we know that the public is going to be well protected,” Hacking says.
The rationale behind better water treatment is so simple that it’s easy to overlook, adds Hacking. “There’s always the question of why do we need this technology now,” he says. “If you talk to people who have had their immune systems compromised or have newborn babies, all of a sudden putting in water treatment that can reduce the risk of illness sounds like a good idea.”
For more innovation insights, visit www.gereports.ca
This content was produced by The Globe and Mail's advertising department, in consultation with GE. The Globe's editorial department was not involved in its creation.