07 February 2011

Desalination plant at Tuas may have "a slight negative impact" on marine life

Singapore's second desalination plant at Tuas may have "a slight negative impact" on marine life, in particular, fish, reported Today Online.
The first desalination plant at Tuas, from Water Technology.
Desalination, the process of removing salt and other minerals from water to make it drinkable, is set to grow by 10 times and meet 30% of Singapore's water demand by 2060.

The article also reports:
The findings of an environmental impact assessment study include that habitat loss is expected for plants and animals living at the bottom of the sea measuring more than 0.5mm in length - known as microbenthics - but they are predicted to recover in the short term.

Regarding water quality, the study noted that iron oxides, total suspended solids and boron at the plant's offshore diffuser as well as within a 10m mixing zone will exceed the National Environment Agency (NEA) Trade Effluent Discharge Standards.

A waiver has been agreed in principle with the NEA to permit the exceeding of these standards within the 10m mixing zone.

Desalination, the process of removing salt and other minerals from water to make it drinkable, is set to grow by 10 times and meet 30% of Singapore's water demand by 2060.

The Tuas desalination plant will be constructed within a 14-hectare plot of land at Tuas View, adjacent to the western straits of Johor and lies 850m offshore from the Singapore-Malaysia International Boundary.

The surrounding Singapore coastline comprises various industrial facilities, Tuas jetty and Raffles Marina.

However, there are no nature reserves within 5km of the proposed plant.

Where is Singapore's first desalination plant?
Singapore's first desalination plant is in Tuas and began operations in 2005. It currently produces 136,000 cubic m of fresh water daily.

This is probably the location of the first desalination plant at Tuas.
First desalination plant in yellow circle.

What are some of the possible environmental impacts of desalination?
from Sydney Coastal Councils Group fact sheet on desalination
The greatest single ecological problem associated with desalination plants that use seawater is that organisms living with in the vicinity of the desalination plant are sucked into its equipment. Recent analyses have noted that the impacts to marine life associated with intake designs were greater than first considered, hard to qualify and may represent the most significant direct adverse environmental impact of seawater desalination.

Environmental impacts associated with concentrated discharge have historically been considered the major environmental concern with desalination plants. Desalination plants produce liquid wastes that may contain all or some of the following constituents:
  • High salt concentrations, chemicals used during defouling of plant equipment and pre-treatment, and
  • Toxic metals (which are most likely to be present if the discharge water was in contact with metallic materials used in construction of the plant facilities).
Liquid wastes may be:
  • Discharged directly into the ocean;
  • Combined with other discharges (e.g., power plant cooling water or sewage treatment plant effluent) before ocean discharge;
  • Discharged into a sewer for treatment in a sewage treatment plant, or
  • Dried out.
The environmental impacts of liquid waste treatment will vary depending on factors including the location of a desalination plant and method of waste disposal. Potential environmental impacts resulting from the increased turbidity, reduced oxygen levels and increased density of any discharged waste water.

Desalination plants also produce a small amount of solid waste (e.g., spent pretreatment filters and solid particles that are filtered out in the pre-treatment process) that would have to be disposed of in land fill.

In China, "to avoid the usual environmental problems associated with desalination, their desalination plant collects – and sells – the salt derived from the seawater, rather than discharging it back into the ocean." from Can the sea solve China's water crisis? Jonathan Watts guardian.co.uk 24 Jan 11;

Thanks to Hang Chong for the alert, also on the modern burrow blog:
Government Gazette, Electronic Edition, on 18th January 2011 at 5.00 pm.

ENVIRONMENTAL IMPACT ASSESSMENT REPORT FOR TUAS DESALINATION PLANT

National water agency PUB proposes to develop the Tuas Desalination Plant to provide desalinated water through a design, build, own and operate (DBOO) delivery process. The development site is located on the western coast of Tuas View, south-western Singapore. Studies have been carried out to determine the environmental impacts of the plant.

The Environmental Impact Assessment (EIA) report is available for public viewing, by appointment at Environment Building 40 Scotts Road #07-01, Singapore 228231 for four weeks with effect from 18 January 2011. To view the said report, please contact Ms Lee Zhang Er at 6731 3882 or via email at Lee_Zhang_Er@pub.gov.sg

Anyone who wishes to inspect the said report after 14 February 2011 cancontact Ms Lee Zhang Er to make arrangements to view it.


See also Tuas desalination plant: Could authorities elaborate on waiver? Keeping abreast of green issues a must Letter from Yeo Chow Khoon Today Online 11 Feb 11

And PUB response to the letter Regular monitoring at new desalination plant Letter from Tan Quee Hong Director Pollution Control Department National Environment Agency and Young Joo Chye Director, Policy and Planning PUB, the national water agency, Today Online 19 Feb 11;

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