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Sustainable Urban Waterfutures: A Vision
Citation:
ASHBOLT, N. Sustainable Urban Waterfutures: A Vision. Presented at Federal Subcommittee on Water Availability and Quality Executive Office of the President, Washington, DC, October 16, 2008.
Impact/Purpose:
Presentation given at a meeting with the Federal Subcommittee on Water Availability and Quality Executive Office of the President in Washington, DC, October 16, 2008
Description:
Background: Urban growth is seriously limited by water scarcity on every continent, and trying to house more people that aspire to current developed region water services is simply impossible due to lack of available water, let alone the cost. Furthermore, traditional water/sanitation services are net users of energy (e.g. 10% of US energy production is used in drinking and wastewater services), whereas the biodegradable organic matter within wastewater contains over nine times as much energy as typically used to treat wastewater in developed regions. However, an often overlook third key point here is the finite nature of agriculturally-required phosphorus (P, mined from rock phosphate reserves) that is expected to be fully exploited in 60-150 years time (variability depending on global food/biofuel production increases). Hence, it should be obvious that ‘wastewater’ nutrients, and in particular P need to be recycled for agriculture to be sustainable, not to mention the energy savings that would result from co-recycling nitrogen and potassium. Why do we have unsustainable water services? Despite our centralized water services being engineered to meet public health protection, there has been a series of misinformed decisions that provide us with today’s legacy – starting in the mid 1800’s when London’s engineer Sir Joseph Bazalgette instituted major sewers systems on the basis that bad air (miasma) resulting from human wastes fouling the Thames River were the causes of cholera and typhoid. The word Sewer means "seaward" in Old English, and that was the start of the ‘solution to pollution was dilution’ instituted by Queen Victoria and used by many sanitary engineers to this day. The large-scale introduction of the flushing toilet from the 1890’s only exacerbated the need for larger sewers and waterworks, with the latter primarily articulated throughout cities for fire fighting (=reduced house insurance premiums), with only some 10% required for drinking water purposes. Also lost was the concept of ‘night soil’ for nutrient recycling to agriculture. A more sustainable path for water services: Using the sustainability principle of source-separation of waste streams, there is a range of options with household sanitary streams for nutrient and energy recovery (Figure 1). However, such changes require different incentives and institutional structures/relationships to flourish. For example, peoples’ recent enthusiasm for hybrid/electric cars is sadly not for altruistic reasons, but simply due to the sudden increase in fuel costs. In many situations, more decentralized water systems (possibly still centrally managed) may not only provide the means for local energy recovery ‘stations’, but also household greywater reuse that would reduce drinking water demand by over 70% and reduce the need for large water mains, sewers and pumping stations. Hence, incentives need to be abundant to aid in this translation to more sustainable urban water systems. Experience from projects in Sweden and Australia that are based on participatory, iterative processes of agreement for more sustainable systems will be discussed.