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By
Elizabeth Cutright
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| Elizabeth Cutright |
The public sewer system in Germany is over 100 years old and rapidly deteriorating. Experts warn it could take years and several billion dollars to rehabilitate the centralized systems currently in place. The high cost associated with maintaining the existing centralized systems has prompted the exploration of alternative solutions. “As with an old car,” explains Harald Hiessl, Ph.D., of the Fraunhofer Institute for Systems and Innovation Research ISI (Fraunhofer-ISI), “if the costs for repairs and renovations start to increase, you should think about whether to make further investments in the old system or whether a new system would be more sensible in the long term”
In April 2003, Fraunhofer-ISI initiated the AKWA 2100 project in order to “investigate alternative water infrastructure systems.” AKWA 2100 applied three different treatment methodologies to examples based on the current situations in two German cities: Dortmund-Asseln (a heavily developed urban environment) and Selm-Bork (a rural environment with a dense center development). The three different scenarios included continuation (rehabilitating the current centralized system), municipal water recycling (employing water reuse on a municipal scale), and local water recycling (abandoning a centralized system altogether in favor of a combination of decentralized water treatment and water reuse). The study concluded that although the continuation scenario was the least expensive, the local water recycling scenario was the better option. According to Hiessl, the sustainable aspects of combining onsite water treatment with water recycling far outweighed the 5%–15% increase in cost.
Although this study was conducted in Europe, it has international implications. The conclusion drawn by the study—that decentralized systems in an urban environment are “technologically and economically feasible”—should serve as a clarion call to municipalities around the world.
There are several reasons for a municipality to encourage onsite water treatment. A decentralized system allows for greater flexibility when it comes to growth and development. Onsite water treatment facilities also allow for the development of previously inaccessible areas, opening up development opportunities for communities bursting at the seams. Of course, as cities expand, the strain on water resources increases. What better way to mitigate increased water demand than to combine water treatment with water recycling?
Many cities have already turned to water reuse to mitigate the push-pull tension of exponential growth and diminishing natural resources. One of the oldest of these projects is New York City’s Battery Park residential development. The project, initiated in 1960, involved state land leased to private developers required to meet New York State’s sustainable construction mandates as well as the city’s Residential Environmental Guidelines. As a result, the Battery Park project has incorporated several onsite treatment systems, including stormwater reuse for green roof irrigation and an immersed ultrafiltration membrane system. The treated water is then reused in the buildings’ restrooms and cooling tower and irrigates a nearby park.
When an onsite system operates at near perfection, the water discharged is just about as pure as anything coming out of your tap. No one doubts that our planet has stumbled into nothing short of a full-blown water crisis. It only makes sense to take the water that’s been treated onsite and put it to non-potable uses.
OW - July/August 2007 |
