DESALINATION

360 Environmental provides leading practice environmental management services and advice to governments and private organisations utilising desalination to provide sustainable water supplies. We provide proven environmental management services from conception through to design, construction to operation for large scale infrastructure projects. We have worked successfully in alliances and joint ventures to deliver outstanding environmental results.

360 Environmental has developed significant expertise in the desalination field and is recognised as one of the foremost providers of environmental management services to the rapidly expanding desalination industry in Australia. Key projects have included:

Western Australia

• Burrup Peninsula Industrial Seawater Supplies Project – (Project Environmental Manager). A 280ML/day intake with thermal desalination technology.
  
• Perth Seawater Desalination Plant (Project Environmental Management for overall Scheme). A 45GL/annum reverse osmosis desalination plant.
  
• Southern Source Desalination Plant (Project Environmental Management). A proposed 50GL/annum, with expansion capacity to 100GL/annum using reverse osmosis technology.
  
• Support forthe proposed Esperance Seawater Desalination Plant.

New South Wales

• Sydney Desalination Plant. Coordinating an international benchmarking study into the environmental impacts of large scale desalination plants and mitigation options and the provision of technical advice.

Victoria

• Victorian Desalination Plant (Expert Advice and peer review role for the Department of Sustainability and Environment and the Victorian Environmental Protection Authority). A proposed 150GL/annum plant using reverse osmosis technology.

Queensland

• Tugan Desalination Plant (Advice to the Queensland Environmental Protection Authority).
  
• Provision of environmental and financial advice to assist in the feasibility assessment of a second Queensland Seawater Desalination Plant.

Perth Seawater Desalination Plant (Western Australia)

360 Environmental provided overall project environmental management on behalf of the Water Corporation for the award winning Perth Seawater Desalination Plant, the largest in the southern hemisphere (at the time of building).

At a peak capacity of 144ML/day the Perth Seawater Desalination Plant is the world’s third largest seawater reverse osmosis plant. It was the first large scale desalination facility to be constructed in Australia and as such was subject to intense scrutiny from both the public and government agencies. Major concerns included energy management and the management of seawater concentrate. With one of the most complex environmental approvals experienced in Western Australia for large scale infrastructure projects, the environmental studies undertaken successfully meet the strict requirements of the Western Australian Environmental Protection Authority.

The approach adopted for the management of environmental issues associated with large scale desalination has set a new benchmark for large-scale desalination facilities of this kind.

Construction of the plant was fast tracked on an exceptionally short time frame and was successfully completed on schedule and on budget in just 18 months. Managing the environmental impacts of construction works, as part of a team delivering a plant the size of the Perth Seawater Desalination Plant, in such a short time frame, provided many challenges. Construction works were audited on several occasions by the environmental regulator and found to be complying with strict environmental management standards.

The detailed marine investigations and monitoring undertaking prior to, and during construction and the continuous monitoring undertaken during operations are unsurpassed internationally. To ensure that the local marine environment was protected, an extensive array of studies were commissioned.

These included:

• Intensive baseline water and sediment quality program
  
• Sediment oxygen demand tests
  
• International literature review of dissolved oxygen levels and historic levels within Cockburn Sound
  
• Ecological investigation and literature review – regional study focusing on fauna life cycles and their likely seasonal positions within Cockburn Sound
  
• Whole Effluent Toxicity testing - simulated brine and actual seawater concentrate
  
• Diffuser Modelling and Design Peer Review
  
• Diffuser tank testing - seawater concentrate is returned via a 40-port diffuser, with nozzles spaced at four metre intervals, to ensure total mixing of seawater concentrate within 50 metres
  
• Macrobenthic fauna investigations prior and post operations
  
• International benchmarking exercise to understand global trends for marine investigations Marine models, for far and near field monitoring include:
  
• 3 dimensional (3D) hydrodynamic Environmental Fluid Dynamics Code Model
  
• 1D box model (University of New South Wales)
  
• 3D hydrodynamic and dispersion model Mike 3 (Danish Hydraulics Institute)
  
• 3D numerical model Estuary, Lake and Coastal Ocean Model (CWR University of Western Australia)
  
• 3D Computation Aquatic Ecological Dynamics Model (CWR University of Western Australia); and
  
• Field checks confirming dilutions (salinity checks and rhodamine die tests).

Field checks during the first year of operations (during summer and autumn) included tracing an environmentally benign dye added to the plant discharge, validated the modelling undertaken and showed that the desalination discharge rapidly mixes with the surrounding waters.

The baseline marine investigations led to the establishment of a real-time telemetered monitoring system positioned to take readings (dissolved oxygen, temperature, conductivity, current, wind speed and direction) from three positions in Cockburn Sound from throughout the water column. Management responses have been agreed with the regulator in the event agreed trigger levels are reached.

Desalination is an energy intensive process. High energy use and consequent high greenhouse gas emissions are an aspect of desalination that needs to be addressed from an environmental perspective.
 
The energy requirements of the Perth Seawater Desalination Plant are met through the 82MW Emu Downs wind farm located to the north of Perth city, which was completed in 2007. The wind farm supplies over 272 GWhrs of energy per year to Perth’s electricity grid, more than off setting the Perth Seawater Desalination Plant consumption and thereby making the Perth Seawater Desalination Plant the worlds largest desalination plant using renewable energy. Coupling this energy source with the low specific energy consumption achieved from the plants novel design, incorporating isobaric energy recovery devices (PX) from ERI, also ensures that it is the world’s most energy conscious plant.