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Monday, November 24, 2008

Use of recycled water

(My Original Blog Post:
Chris from Toronto writes:

Hi there, I am doing a research project on the viability of implementing some rural water saving solutions in the city.  The one idea I had was to use rain barrels on top of larger buildings to supply the occupants with their water.  I figured that anything we can do to reduce the load on the city reservoirs the better, especially to conserve the electricity that our pumps use.  I was wondering if you could give me some input...Aren't apartment buildings built with an internal reservoir system already that purifies the water and distributes it onsite?  If not, do you think it could be practical to just tie into systems that don't require purifying, like toilets and washing machines?  I'd really appreciate your help.  Thanks

Hi Chris, thanks for your question.

There are two truths happening right now:

  1. An increase in population

  2. A water supply steadily decreasing in availability

As our population goes up, our ideas of housing is changing.  In larger cities, more and more condominiums are rising to the sky, housing more people in a smaller area.  In smaller cities, new housing developments are severely cutting the land around houses, packing them in closer and closer.

Working in the water treatment section of a municipality, it always amazes me how much water is being treated to tough potable standards, and how little of it is used for potable uses like drinking and cooking.  Most of it goes to washing and industrial purposes.

Currently most water is used as a once through application.  It goes down the drain and dissapears to the waste water treatment plant, for treatment and release to the environment.  But as water becomes more scarce, water will have to be recycled if we would like to continue to use water as we are.

I don't know the current status of most apartment buildings. However, sustainability projects such as you propose are feasible.  The infrastructure on older buildings would be expensive, but it would be relatively cheap to integrate into brand new apartment buildings.

Potable water from the city could still be piped in.  However, you would have a tap or taps designated as potable in your apartment, such as the kitchen sink and the bathrooms. Your drinking, cooking and other miscellaneous uses (such as brushing your teeth) would come from these taps.  To ensure that the potable water does not get cross contaminated from any other water source, the piping would have to be completely separate from other sources.

Separate from your drinking water, showers, laundry facilities and outside hose bibs could be recycled grey water mixed with rain water collected on the roof.  Simple centrifugal separators, filtration and light disinfection (U.V. and/or chlorination) could make this water clean, clear and useful for such washing applications.  The water sent to your waste water treatment plant would be a more concentrated form of the contaminants removed.

Using a system like that would mean existing water treatment plants would be able to supply cities far into the future with their potable water needs without the need for further and further expansion.

I hope that gives you a direction for your research project, Chris.  If you have any further questions or would like further detail, please do not hesitate to write in again.

0 keen observations: