Sustainable Water System Design

When undertaking projects, especially in a desert or tropical climates, it is important to consider sustainable technologies for water-system design. And anywhere a project is located, energy efficiency should be a key sustainability concern.

Domestic hot-water storage is a large energy consumer. The formerly common practice of lowering the storage temperature has proven to cause other problems, so one can be left with the need to store water at 140 degrees.

High-efficiency water heaters with improved insulation systems should be considered. Point-of-use electric heaters can reduce the quantity of stored water, simplify thermostatic mixing-valve piping and lower recirculation losses. Similarly, low-consumption fixtures can reduce the demand for hot water, and self-regulating heat-tracing reduces recirculation losses. While many of these solutions reduce energy at the meter, it is at the cost of using more global energy.

A related system is wastewater-heat recovery . This commercially available system uses a falling-film heat exchanger to extract energy from the waste stream and transfer it to incoming cold water. For buildings with high hot water usage, this can save a lot of energy. Because the drainage piping is arranged to recover the warmest water-which is close to the incoming cold water-this improves performance.

On-site biological waste treatment is also making inroads on highly sustainable projects. Turnkey solutions treat the waste stream in such a way as to have no net increase in required off-site waste treatment.

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