SEAWATER DESALINATION: A SUSTAINABLE SOLUTION TO WORLD WATER SHORTAGE
PLANNING, DESIGN, CONSTRUCTION AND OPERATION OF THE ADELAIDE DESALINATION PLANT
JE Blesing, C Pelekani
Publication Date (Web): 12 February 2016
There are many parts of the world currently experiencing drought conditions combined with a water supply that is unfit for human consumption. Scarcity of water also results in reduced availability for food production. Alternative water sources are necessary for sustainable development.
Seawater desalination provides a climate-independent source of drinking water. However, community perception that the process is energy intensive and environmentally damaging still exists.
This paper addresses the methodology adopted for the design, construction and operation of the Adelaide Desalination Plant (ADP) in South Australia, based on robust sustainable planning principles. South Australia is the driest state in the driest inhabited continent in the world, and Adelaide, with a population of 1.2 million, has a catchment storage capacity that equates to approximately 12 months of average annual demand. Natural catchment run-off is augmented by water pumped from the Murray River, which can vary from 40% in an average rainfall year to more than 90% during drought periods.
In 2006–2007, the state was experiencing a severe drought, with the water level in the Murray River at record low levels. In 2007, the South Australian government established a Desalination Working Group (DWG) to consider a range of water supply options including increasing reservoir capacity, stormwater reuse and wastewater recycling. Seawater desalination was identified as the only viable climate-independent source of water.
From the DWG’s report and subsequent work by SA Water, the plant design brief included strict criteria including low energy consumption, minimal impact to marine and terrestrial environments, positive social and cultural heritage outcomes for the local community, and renewable energy sources for the plant’s electricity requirements. A plant capacity of 50 GL/year, expandable to 100 GL/year (50% of Adelaide potable water demand) was required.
The ADP uses reverse osmosis to produce up to 300 ML/day (100 GL/ year at full capacity) of drinking quality water, equivalent to 50% of metropolitan Adelaide’s average daily demand. Plant design incorporates the key criteria from the DWG report as well as the recommendations from extensive environmental studies and latest technology in seawater desalination, including the large-scale use of ultrafiltration, a unique RO membrane array, energy recovery systems that reduce maximum power demand by more than 40%, and the ability to operate at capacities from 30 ML/day up to 300 ML/day without energy penalty.
The ADP has been operating since December 2012, with the following key performance indicators:
- Specific power consumption ranging from 3.47–3.70 kWh/kL of water produced;
- Silt density index (SDI) of permeate from the ultra-filtration plant ranging from 1.4 to 3.0 (average 2.4);
- Permeate recovery range of 47.3% to 49.9% (average of 48.8%);
- Average salinity measured 100m from the outfall is 0.4 ppt above ambient, measured 15km from the outfall (EPA license condition maximum 1.3 ppt) with no discernible impact on marine biota; and,
- Power supply for the plant is fully sourced from renewable energy sources.
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