Desalination and water security
Water security and sustainable use are crucial elements for future development. Agricultural use represents seventy per cent of water use in Victoria and Australia, with the remainder consumed by industry and urban usage. The drought and broader environmental concerns necessitate that Victoria develop alternative water sources to traditional surface reserves and rain-fall.
Desalination is an alternative water source to ensure water supplies for Melbourne, and reduce pressure on traditional water sources.
Reverse osmosis (RO) is the preferred method in Australia (64% of national capacity) and worldwide, and is being utilised in the NSW desalination plant. This technology can be used for both salt-water desalination and waste-water reclamation (irrigation water or treated effluent).
Environmental impacts are of great concern to the public. Of particular concern are any affect desalination may have on:
- Marine water quality and biota â€“ disposal of concentrated salty effluent, and traces of chemicals used in reverse osmosis process;
- Vegetation â€“ potential effects of construction and operation of desalination plant on near by vegetation;
- Atmospheric emissions (especially greenhouse emissions and nitrogen oxides) â€“ most greenhouse gas emissions come from construction and ongoing use, while other potentially toxic emissions originate from the RO process; and
- Noise â€“ protecting amenity of nearby residents caused by high pressure pumps.
RO plants have lower energy consumptions than other desalination technology, which means less atmospheric emissions. It also converts a greater percentage of intake brine into water, which results in greater amounts of drinking water for the same volume of chemicals needed for other desalination technologies.
The reliance on fossil fuels makes renewable energy an attractive investment. Solar powered RO plants exist in rural areas in Australia.
Membrane technology, especially RO is widely considered to have lower costs than other technologies, particularly in construction and production of drinkable water.
RO is economical for both large and small scale desalination. Flow rates can be increased or decreased, and plants can be expanded by adding extra modules.
Energy costs represent approximately 33% of total life-cycle costs. Commonly cited energy sources considered globally are RO plant with electric power from the local network and RO plant with solar energy. Renewable energy powered plants reduces carbon emissions caused by power generation, but increase water costs.
Reverse osmosis is the preferred desalination option given the drought conditions and the uncertainty of traditional water sources.
RO is the most widely used, can be utilised for salt and waste water desalination, and its environmental impact is relatively low. RO plants can also be expanded to meet future demand.