UBC adjunct professor in engineering Troy Vassos specializes in the study and design of water recycling systems. As the unusually hot, dry summer draws to a close, he calls for governments to work together to enable the public to install water recycling systems in anticipation of future droughts.
Greywater, blackwater, harvested rainwater. What’s the difference?
Greywater is the water from baths and showers, bathroom sinks and laundry. It gets its name from its distinctive grey colour. “Blackwater” is from toilets and urinals. Whether kitchen sink and dishwater drainage, which contains food waste, is grey or black depends on the jurisdiction. Finally, harvested rainwater is typically collected from roofs and other elevated surfaces.
The general perception is that greywater is relatively clean compared to blackwater. But the fact is, both contain similar contaminants, including disease-causing microorganisms. Consequently, Health Canada doesn’t differentiate between treating the two types in its national guidelines on reclaiming wastewater for non-potable home and commercial use. Even rainwater can become contaminated and require treatment before use.
Does greywater always have to be treated before it’s reused?
Not necessarily. Although many jurisdictions require greywater to be treated and disinfected to a high water quality standard before being reused, some jurisdictions in Canada, the U.S. and Australia allow untreated greywater from individual homes to be used untreated for flushing toilets and below-the-surface irrigation of landscape plants.
Homeowners who use treated or untreated greywater to flush their toilets should know that the toilet tank and bowl will require periodic brushing to keep clean. Soaps and detergent residue can result in a buildup that can eventually cause water leakage, unless periodically cleaned.
So it sounds like greywater recycling isn’t the answer to drought conditions?
Not completely, and not without advance planning. Depending on the jurisdiction, you may need to treat the greywater first before you can reuse it, and you must comply with plumbing codes and obtain a municipal permit before modifying your household plumbing to recycle wastewater.
Of course, some homeowners simply transfer their bathwater using a bucket to flush their toilets. But however you do it, flushing using greywater alone can reduce internal household water consumption by up to 30 per cent.
How does B.C. compare to other jurisdictions in reclaiming and reusing wastewater?
B.C. has the most progressive legislation for water reclamation in Canada. Our regulations have included reclaimed water provisions since 1999. There are many ways in which wastewater is reused in B.C., including toilet and urinal flushing; landscape, playground, and green-roof irrigation; golf course irrigation; and forage crop irrigation.
Government has also updated the building code to allow water utility providers to distribute non-potable water and to allow non-potable distribution systems to be installed in buildings.
What we don’t have are municipal bylaws to adopt the new plumbing code reuse provisions and a Ministry of Health policy and regulatory framework for water reuse. There’s also a lack of harmony between the various environment, health and municipal regulations and policies regarding water reclamation and reuse. Finally, government could do a better job of providing the public with information and tools for water conservation.
A great example of an educational resource is the Building Sustainability Index, BASIX. BASIX was developed by New South Wales in Australia as an online permitting tool that requires individuals seeking residential or commercial building permits to select from a menu of water conservation options to achieve at least 40 percent reduction in water consumption. The website educates permit seekers as well as the general public, since they can also access the site.
What else can the government do?
Nowadays, most buildings have their own heating and ventilation systems. If buildings can handle their own wastewater treatment, municipalities will see significant economic benefits and our infrastructure development will be more sustainable. The technologies, codes and standards already exist to make this feasible and ensure an acceptable quality level in reclaimed water.
If every building in downtown Vancouver, for example, had its own water reclamation unit for toilet/urinal wastewater and building cooling water, up to 95 per cent of the water demands of that building could be eliminated. It’s an idea that is not without precedent. Major urban centres like Tokyo and Beijing are already decentralizing wastewater treatment to individual buildings.