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Energy Provision

Environmental Impact

Reverse Osmosis Desalination

Risk to Marine organisms

(Mitchell et al. 2008)

  • Energy will be supplied by Victoria's coal-burning power plants
  • 933, 820 tonnes of CO2 per year are estimated to be produced in the operation of the plant
  • Offsetting CO2 emissions by buying renewable energy credits will occur but this doesn't stop the emissions.
  • Co-generation, where waste heat from electrical power generation is used to enhance reverse osmosis, can lower energy consumption by the plant.
  • Co-generation would be true off-setting but this is not used by the Wonthaggi plant.

(Madden 2009)

  • Water is pumped against its osmotic gradient through a semi-permeable membrane.
  • This membrane allows passage of water but not of dissolved substances
  • To overcome osmotic gradient, high pressure is required to move the water. This requires energy.

Before construction of the plant, there was consideration of the most appropriate location in terms of the environment. It was identified that:

(Shannon et al. 2008)

  • Models constructed suggested little risk to population numbers because of entrainment (Madden 2009)
  • It was noted (Independent Expert Group 2008) that the models were probably not accurate for species with short larval stages.
  • Species with short lived or poorly dispersive larvae are at greatest risk of population reduction because of entrainment.
  • These species are also thought to be most at risk from the brine discharge
  • Particularly at risk were reef-associated species, such benthic invertebrates: sponges, bryozoans

Costs

Increases to water prices 2013-2014 period

Fritzmann et al. 2006

  • There is little data on long term effects of larval entrainment, particularly for Victorian species.
  • The pipes will be located on moderate relief reef.
  • Discharge from the plant is highly saline brine but may also contain pre- and post-treatment chemicals that can affect marine life
  • Modeling showed increased salinity extending 500m from outlet but in some cases could extend 1-2km

(Independent Expert Group 2008)

Adapted from Melbourne Water (2013).

Thickness of arrows indicates relative energy consumption of different processes

Least sensitive to most sensitive

(Sadhwani et al. 2005)

  • Consumers will face prices rises on their water bills so that Melbourne Water can pay for the desalination plant
  • Melbourne water attributes 90% of their price increases to the desalination plant (Melbourne Water 2013).
  • Retail water company Yarra Valley water attributes 70% of their increase to the desalination plant (Yarra Valley Water 2012).

Brine Produced

(Independent Expert Group 2008)

Location

  • Located in Wonthaggi, the plant will provide drinking water to the city of Melbourne, 135km away
  • Situated on 264ha of land (Mitchell et al. 2008)
  • Water is transferred 84km, via a specifically constructed pipeline, to Berwick and from there, via the existing network, to Cardinia Reservoir.
  • Future extensions could see the plant supplying South-Gippsland as well.
  • 87km of underground cable brings electricity to the plant (AquaSure, 2010).
  • After salt has been removed from the seawater, a highly concentrated salt solution is created called brine.
  • The Wonthaggi desalination plant will dispose of the brine back into the ocean via outtake pipes
  • Rosette diffusers will help to dilute highly saline water, mixing it quickly into the seawater when it's released (Madden 2009).
  • However, brine is denser than seawater and therefore sinks. Salinity of seawater is generally around 35,000mg/L whereas brine is 65,000-85,000 mg/L
  • Since RO desalinated water sinks, the benthic zone organisms are the most likely to be adversely affected by higher salinity (Fritzmann et al. 2008).

Black - Seawater Intake; White - Pre-treatment; Blue - Reverse Osmosis; Red - Post-treatment

Comparative Cost of Water Supplies

Cost

Source: Elimelech & Philip, 2011

(Department of Environment and Primary Industries 2012)

Intake and Outlet Pipelines

  • The Victorian State Government has contracted the plant out for 30yrs to AquaSure
  • The plant was constructed and designed for a capital cost of $3.5bn
  • Melbourne Water must pay for any water provided by the desalination plant
  • Even if no water is ordered, an annual $610m security charge must be paid
  • Prices charged to retail water companies will be adjusted yearly to reflect water ordered.
  • Cost of running the plant depends a lot on intake water, increased salt concentration means more electricity consumed.

Energy Consumption

Source: Marsden Jacob Associates (2006)

(Melbourne Water 2013)

Location

  • Intake pipe: 1.25km; Outlet pipe: 1.5km into the ocean
  • Entrainment and impingement can kill marine organisms
  • Entrainment - organisms drawn into plant
  • Impingement - organisms trapped against screen as water is drawn into intake pipe
  • The screen across intake pipe to prevent entrainment of larger organisms does not prevent larvae and eggs from being pulled in with the water (Madden 2009).

Seawater desalination is certainly not the most expensive option but there are a number of cheaper options that could have been considered before constructing a desalination plant.

  • Reverse osmosis desalination is an energy intensive process
  • Osmotic pressure of seawater determines energy required to push water across membrane.
  • Pressure put on seawater must be greater then the osmotic pressure.
  • The more concentrated the salts in the water, the more energy is required to get water to correct pressure for reverse osmosis

Cardinia Reservoir

Chemical Waste

Location of pipeline

Process May be present in effluent Impact

  • Additional energy usage occurs at the pre- and post-treatment stages.

Desalination plant

Image Source: http://victoriasdesalinationplant-present.blogspot.com.au/

How entrainment and impingement occur (Steinbeck et al. 2007).

Elimelech & Philip 2011

Adapted from Lettemann & Hopner, 2008

Processes listed are used in desalination pre-treatment, post-treatment and cleaning of the membrane. These products may end up in the water discharged to the ocean unless they are actively removed(Lettemann & Hopner 2008).

Pre-treatment waste, from cleaning pre-treatment filters, will be disposed of to landfill (Independent Expert Group 2008)

Chemicals used, those listed under 'Cleaning' in table above, to clean reverse osmosis membranes will be disposed of to the ocean after neutralization.

(Mitchell et al. 2008).

The Plant

  • Current capacity of 150GL/year or 411 million litres per day
  • Uses reverse osmosis desalination
  • Available for use since 2012
  • Not currently supplying water
  • Located in Wonthaggi

Summary

Image Source: http://www.heraldsun.com.au/news/victoria/wonthaggi-desalination-plant-produces-its-first-drops-of-drinking-water/story-e6frf7kx-1226466517254

The desalination plant will:

  • use a lot of energy
  • be expensive for water customers
  • be a comparatively expensive way of producing water
  • be a risk to marine organisms because of brine production and larval entrainment
  • produce chemical waste that needs to be safely disposed of

Wonthaggi Desalination Plant

Reference List

Aquasure 2010, AquaSure Pty Ltd, Melbourne viewed 27 April 2013, <http://www.aquasure.com.au/project_description.php>.

Department of Environment and Primary Industries 2013, Victorian Government, Melbourne viewed 27 April 2013, <http://www.water.vic.gov.au/initiatives/desalination>.

Elimelech, M & Philip, W 2011, 'The future of seawater desalination: energy, technology and the environment', Science, vol. 333, pp. 712-717.

Fritzmann, C, Lowenberg, J, Wintgens, T & Melin, T 2007, 'State-of-the-art reverse osmosis desalination', Desalination, vol. 216, pp. 1-76.

Independent Expert Group 2008, 'Advice on the desalination project environment effects statement', October.

Lattemann, S & Hopner, T 2008, 'Environmental impact and impact assessment of seawater desalination', Desalination, vol. 220, pp. 1-15.

Madden, J 2009, 'Victorian desalination project assessment', January.

Marsden Jacob Associates 2006, 'Securing Australia's urban water supplies: opportunities and impediments'.

Mitchell, K, Wimbush, N, Harty, C, Lampe, G & Sharpley, G 2008 'Victorian desalination project environment effects statement: report of the inquiry', December.

Melbourne Water 2013, '2013 Water Plan', Victorian Government, Melbourne, viewed 27 April 2013, <http://www.melbournewater.com.au/content/library/about_us/customers_and_prices/wp_draft_2013/WP3%20Fact%20sheet%20Desalination%20Plant.pdf>.

Sadhwani, J, Veza, J & Santana, C 2005, 'Case studies on environmental impact of seawater desalination', Desalination, vol. 185, pp. 1-8.

Shannon, M, Bohn, P, Elimelech, M, Georgiadis, J, Marinas, B & Mayes, A 2008, 'Science and technology for water purification in the coming decades', Nature, vol. 452, pp. 301-310.

Steinbeck, J, Hedgepeth, J, Raimondi, P, Cailliet, G & Mayer, D 2007, 'Assessing power plant cooling water intake system entrainment impacts', California Energy Commission, Sacramento viewed 3 May 2013 <http://www.energy.ca.gov/2007publications/CEC-700-2007-010/CEC-700-2007-010.PDF>.

Yarra Valley Water 2012, 'Yarra Valley future water', Yarra Valley Water, Mitcham, viewed 26 April 2013, <http://yoursayyvw.com.au/document/show/20>.

An argument against

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