East Anglia the driest part of the UK - will we need to consider desalination?

East Suffolk - the coastal district in the driest part of the UK with average rainfall below 600mm each year

Oceans cover 71% of the Earth's surface and contain 97% of the Earth's water.

Less than one percent of the Earth's water is fresh water and 2-3% is contained in the glaciers and ice caps.

66% of the worlds inhabitants could live in water-stressed conditions by 2025

For many arid areas of the world ensuring a viable alternative water supply has resulted in the growth of desalination plants. Desalination plants operate in more than 120 countries in the world producing over 3.5 billion gallons of potable water a day. Even though there is a very strong environmental and economic case against this technology; population growth, climate change and drought could force more nations including our own to consider investing in seawater desalination technology.

The Department for International Trade say, 'the South East England is already using 41% of its renewable resources and must develop further sustainable solutions in order to meet growing demand. As the global search for new freshwater supplies intensifies, UK companies are at the forefront of successfully accessing new water sources and has developed pioneering new technologies to help identify new sources of water, as well as cutting-edge methods in desalination'.

Here in East Anglia, the 'bread basket' of the country we live in the driest part of the UK, (Woodbridge average annual rainfall is a mere 554mm -21.8"). With our meagre rainfall we still manage to waste a lot of water each year through leakages in our system. (Anglian Water claims to spend 14million each year repairing around 30,000 leaks). So if we can let gallons go down the drain and still manage we must be safe for the foreseeable future and not need to consider turning to our close neighbour, the sea for an alternative water supply? Or should we be having a hard look at the technology and the case for and against?

In a reply to a recent letter from one of our readers Charles Mugleston, the Chief Executive of Anglian Water, Peter Simpson said,

'We face four pressing and interlinked challenges - climate change, environmental protection, population growth and the risk of drought. We have to act now or we will move from a strong position of a surplus of 150 million litres of water daily to a deficit of 30 million litres daily by 2025'.

As Mr Simpson explains, 'We will focus on the demand side first and reduce the amount of water used by installing smart meters, reducing leakage and investing in water efficiency. But we will also invest in the supply-side to increase the amount of water available. This includes investing in a series of interconnecting pipes to better join up our network and ensure we make best use of available resources before developing new ones. In the medium to long-term, we are likely to need additional resources. This could include winter storage reservoirs, re-circulation of recycled water, or desalination'.

What then is Desalination?

Most of the water on earth is salty and brackish. Desalination has evolved into a viable water supply alternative allowing nations to tap the largest water reservoir in the world - the ocean. Seawater desalination technology, has been available for decades.

There are three principle methods of desalination: thermal, electrical, and pressure. The oldest method, thermal distillation, has been around for thousands of years. In thermal distillation, the seawater is sucked in, heated it up to get the pure vapor, and the remaining brine is pumped back out to sea. A cheaper method involves distilling the water using solar power and directly heating the water to boiling from sunlight instead of the usual fuels.

The least energy intensive method is a semi- permeable membrane process, referred to as Reverse Osmosis (RO). With membranes, seawater is pushed at great pressures through a series of filters, which pull out all the salt and other contaminants. Typical brackish water RO desalination uses a fraction of the energy required for seawater desalination.

Freezing is another potential method involving the removal of the dissolved salts from the ice crystals in the frozen seawater. In 1971 the Government approved a feasibility study for the construction of a pilot plant near Ipswich to produce 1million gallons of fresh water per day from the sea by freeze desalination.

In the face of strong opposition from the then London mayor Ken Livingston, the first large-scale plant in the United Kingdom, the Thames Water Desalination Plant, was built in Beckton, east London for Thames Water by Acciona Agua in 2010 at a cost of £250m. The plant treats water from the brackish waters of the River Thames, turning into clean, fresh drinking water and can provide up to 150 million litres of drinking water each day - enough for nearly one million people. The plant is mainly used in times of drought or to support existing supplies if needed.

One of the strongest argument against desalination is the tremendous amount of energy in takes to process seawater. New technologies including the use of solar power do mean that the amount of energy required in some processes is reduced thereby enabling some plants to claim to be carbon neutral.

Energy consumption is not the only concern for environmentalists.

According to wired.com 'a less chattered-about problem is the effect on the local environment: The primary byproduct of desalination is brine, which facilities pump back out to sea. The stuff sinks to the seafloor and wreaks havoc on ecosystems, cratering oxygen levels and spiking salt content'.

The point of disposal of heavily slated brine back into sea/can damage sealife. The brine is devoid of dissolved oxygen as a result of the desalination process. If it is released into calm water it can sink to the bottom as a plume of salty water that can kill organisms on the sea bed from a lack of oxygen.

A final word on the subject from Mr Peter Simpson, Chief Executive Anglian Water in his reply to Mr Mugleston,

'We have looked at the feasibility of de-salination plants in the past, and will continue to consider them in the future. Although they seem like a straight-forward solution to potential water shortages, they are expensive in terms of both building and running and are carbon intensive. In the meantime we are pursuing less expensive and carbon intensive solutions to keep our supplies safe and secure.

Anglian Water is incredibly proud of our industry-leading action on carbon reduction. This year we have not just met, but exceeded the hugely ambitious 2020 carbon reduction goals we unilaterally set for the business at a time when reducing carbon was not on most utility firms' agendas. We have reduced the capital carbon embodied in our construction projects by a remarkable 61%, based on our 2010 baseline, and reduced our operational carbon by 29% since 2014/15. We recognised early both the need to take carbon out of our operations and the opportunity that doing so would afford in terms of reducing costs.

Sources:

Solar Desalination Technology, edited by Anil Kumar, Om Prakash Published by Springer

Department for International Trade

Thames Water Desalination Plant

Seawater Desalination - hbfreshwater.com Damage to sealife

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