Scales, Impingement and Entrainment: Know Desalination’s Negative Side

desalination plantDesalination’s negative environmental risks can outweigh the benefits, argues our environmental lawyer blogger Josh.

Israel will quadruple its output of desalinated water by 2050, according to a report released by the country’s Water Authority Council. The government will also encourage construction of new desalination facilities on manmade islands. These measures will ensure a continuous stream of desalted water without developing coastal lands in the tiny country.

Water experts have sung desalination’s praises far and wide lately. It provides a reliable, secure water supply. It reduces our reliance on natural waterways. And not least importantly it has become cheaper as desalting companies develop more cost-effective technology.

Desalination’s critics have, in equal measure, leveled their own concerns at the industry. The process requires exorbitant amounts of energy, they say, is too expensive, and poses potential health risks.

But these concerns only tell a partial story of desalination’s environmental impacts. It affects the marine environment in an important way: through seawater intakes. Decision makers often ignore or downplay this impact. When desalination facilities suck in huge amounts of water, scores of fish and even marine mammals become stuck to the grates. Scientists call this phenomenon “impingement”.

Additionally, millions of marine larvae and eggs are pulled into the pipes – referred to as “entrainment”. Together, impingement and entrainment may account for spectacular losses of marine life. High volume intake systems are the worst culprits.

Experts often focus their cost-benefit analysis on energy use and brine disposal. Desalination facilities use reverse-osmosis membranes, pushing seawater through tiny pores at high pressures. This removes the salts and other harmful chemicals. It also leaves behind minerals on the membranes, referred to as “scales”, which require chemicals to remove. And operators must dispose of brine either by burial, incineration or discharge to the ocean.

These factors give us only a partial idea of desalination’s costs. Its effect on marine life through impingement and entrainment rounds out the picture. And when we look at this cost in its entirety, we might be motivated to consider alternatives.

For example, researchers in Israel recently developed a methodology for effectively desalinating brackish groundwater. Brackish groundwater is found in aquifers and typically contains less salt than ocean water. Scientists from the University of Colorado, Ben Gurion University, and the Hashemite University were able to desalinate groundwater using less energy and producing less brine. Because the source water is in the ground, not in the ocean, impingement and entrainment are not a concern.

But perhaps we need not survey the horizons of new technology for alternatives. Conservation techniques can be extremely effective at reducing water demand. Israel is already a leader in conservation, having pioneered dual flush toilets and drip irrigation systems. But local governments should convince their constituents to use less water for washing and install “greywater” systems for irrigating gardens and fields.

Irvine Ranch Water District, in Southern California, uses a tiered rate structure to encourage conservation. As customers consume more, the rate increases. In its first year, this system reduced consumption by 19%. Demand side solutions work.

Recycled water is also crucial for Israel. Its source, wastewater, will never be in short supply. Some countries have used recycled water as a potable supply. After a particularly intense drought, suppliers in Queensland, Australia began pumping highly treated recycled water to households. But Israelis need not go that far. The country would do well to simply ramp up agricultural and industrial applications of recycled water.

Desalination has a place in Israel’s water portfolio. But it is no panacea. The Water Authority Council’s plan to quadruple its capacity should be a wake-up call. The country is likely to see exponential growth in the desalination industry.

Alternative sources such as brackish groundwater should be considered. And if seawater desalination continues to expand, its growth must be balanced by water conservation and recycling.

Water means security and prosperity. Israel and its neighbors are acutely aware of this. But in their haste, they must not concede precious energy resources and healthy marine environments to the cause of seawater desalting. They must diversify. And in doing so they will succeed.

Image via lancecheungmedia

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3 thoughts on “Scales, Impingement and Entrainment: Know Desalination’s Negative Side”

  1. umm says:

    hi, i’m interested in learning about desalination because we get our water from a plant about 1/2 hour away. can you recommend any books on the topic. also children’s books.

    re: brine, why don’t they evaporate it and sell the sea salt?

    thanks for the article.

  2. Aviva Weisgal says:

    Finally, an explanation that shows the danger of the “one solution for each issue” of our policy makers.

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