Sustainable water
Posted on Nov 19th, 2009 by Doug Marsh VP, CR, CAPS, GBP | 0 Comments
I went to a fantastic seminar on sustainable water this week. The central thought was that water is a resource from the beginning use to the end use and back again and is not something to be used and then made to go away. Water is a closed loop resource: there is an finite amount of it on the planet. We take water from the source and we use it and then often just dump it to make it go away. There are many examples of this: surface drainage, greywater, blackwater, brownwater. The other central idea that came out of this was energy cost. It is a hidden fact, in a sense, that a treamendous amount of electricity is used to treat and move water for our uses. The facts are astounding: 19% of California's electrical use is consumed for water use. The percentages vary in different parts of the country however the issue is the same: the way we do it now will have to change. The most basic example of this is the distribution of water to users: it takes a lot of power to send water to users. Right now rainwater harvesting is a pretty large investment for a homeowner however the idea of collecting water at the point of source and using it there instead of pumping it from a central source could have major impact on electrical use. I understand this is a massive retrofit however, in Austin, consider that the Austin Green Building program is entirely funded by the savings Austin Energy reaps from the program saving energy by promoting energy efficient buildings. The upfront cost of reflective roofing (another energy saver), guttering, and storage would be offset by electrical savings over time. This is where I am headed at my place which is on a community well and it's not just a good idea but is a necessity as the aquifer water levels are plunging due to drought and population increases. This is true on the back end of water use too. The typical sewage treatment plant uses pumps to mix the sludge to break it down. This creates odours and uses alot of juice. A fantastic process called a "Vertical Shaft Bioreactor" involves drilling a deep hole (300'+) to receive the blackwater and then injecting oxygen, under pressure, into the bottom of the hole. Oxygen perculates up through the sludge without power use to mix and break down the sludge: heat is generated that can be captured, Grade A fertilizer is created, and land usage is minimized due to the vertical shaft. Another technique is called "Constructed Wetland Bioreactor" and is readily usable with your standard septic need. Dig a hole, line it, place gravel and soil, plant the right plants and then the plant's roots take oxygent to the bottom of the hole to digetst the waste that enters the hole. The odour is contained under ground. The liquid portion of the waste byproduct can be directed through sand beds and then sent to a drip system for landscaping. This technique has been installed at the Hays County precinct 4 building in Dripping Springs (see the first link below-David Venhizen is the engineer that designed the sysem)
Other interesting information that came out of this seminar: in Europe there are many instances of natural swimming pools of varing shapes and sizes that are built to naturally use plants to curtail the algae growth. This is a natural open system compared to our closed, inferently "dirty" system style of managing our pools which requires constant use of pumps and chemicals. Surface runoff is a big issue in Austin: impervious cover anyone? We normally build expensive, unsightly, concrete structures to contain runoff and then send it away. It is possible to create natural wetlands to receive this water with a beautiful effect: landscaping everywhere. It does cost money too but compare it to massive concrete projects and add in the inherent long lasting beauty and potential usage.
Here are some interesting links:
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