Review

Taking the “Waste” Out of “Wastewater” for Human Water Security and Ecosystem Sustainability

Science  10 Aug 2012:
Vol. 337, Issue 6095, pp. 681-686
DOI: 10.1126/science.1216852

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  1. Fig. 1

    (Left) Three complementary approaches for improving the productivity of higher-quality water. The water level in each glass shows how much water is used in producing a fixed value of goods and services. Substitution uses lower-quality water in place of higher-quality water for some activities. Regeneration transforms lower-quality water into higher-quality water by treatment. Reduction achieves the same value of goods and services using less higher-quality water. In these hypothetical examples, each option cuts by half the use of higher-quality water and therefore doubles its productivity. (Right) Percent increase in water productivity associated with the 21 case studies described in the text (51). These productivity improvements are illustrative only and will vary substantially in practice. The scale at which a particular water-saving intervention was implemented is indicated. The bars are color-coded to match the three general approaches for improving water productivity.

  2. Fig. 2

    Practical examples of substitution (A), regeneration (B), and reduction (C) at the household scale. Substitution includes watering a garden with rainwater from a rainwater tank and flushing toilets and washing laundry with treated stormwater effluent from a biofilter. For regeneration, a waste stabilization pond (WSP) transforms sewage from the house into high-quality water used for irrigating an orchard. Reduction includes repairing leaks in the water distribution system, drip irrigation, a dual-flush toilet, a low-flow shower rose, and a front-loading clothes washer. Other water infrastructure elements shown include a conventional drinking water plant (DWTP); a conventional wastewater treatment plant (WWTP); and a river diversion (supplying the orchard).

  3. Fig. 3

    Wastewater reuse and water-saving schemes discussed in the text, arrayed relative to a few key attributes (A) and performance indicators (B). The color scheme matches that in Fig. 1; substituting, red; regenerating, blue; and reducing, green. Certain schemes can be classified in more than one way; for example, wastewater recycling with wastewater stabilization ponds might be considered blue or red, depending on the end use and what water is being substituted or regenerated. The adoption of water-saving schemes is influenced by policy, law, regulations, markets, and incentives.