Design considerations for a solar-powered desalination system for remote communities in Australia

Water in many areas of Australia is scarce and of poor quality. In some areas high levels of treatment are required either due to contamination of waters or due to high salinity. Nanofiltration (NF) and low-pressure reverse osmosis membranes are well-recognized technologies to treat waters of qualities ranging from low salinity surface water to high salinity seawater. In remote communities the operation of such facilities may be limited by the availability of electricity. Solar, or photovoltaic, energy is the ideal source of renewable energy in Australia to overcome this problem. This paper considers the various options for a small system, designed to deliver a permeate flow of 400– 1000 l/d from brackish wells. The most suitable membrane for salt retention and very high organics retention was selected and the pump energy requirements calculated. A submerged ultrafiltration (UF) membrane is used as an alternative to the traditional sand and/or prefilter cartridges. The removal of natural organics is important where disinfection of the water is required, as chlorination of waters containing natural organics may produce potentially carcinogenic by-products.

The combination photovoltaic energy and membrane processes are a great technology for remote community applications. Decreasing costs and low maintenance combined with a compact and robust design make this an ideal solution. The system is modular and transportable, and no chemicals are required, thus ensuring the safety of community members. The use of a submerged UF membrane is anticipated to enhance pretreatment performance over existing systems. NF or low pressure RO membranes, providing suitable rejection at an operating pressure of ~5 bar provide the opportunity for using solar power. The system described here is currently entering its first trial in a remote region.