Unsustainable Water for London

Thames Water switched on their desalination plant at Beckton in London for the first time a couple of months ago in anticipation of a drought this summer. London’s first desalination plant cost £250m and can produce 140-150 million litres of water per day, which is enough for one million people. Desalination has been used in hot dry countries for many decades but in cloudy wet UK, it seems odd to be using this technology. The reason is that the population of London continues to expand beyond the capacity of the local water supplies.

Let us take a look at a range of possible solutions (all of which are being used or under consideration):

1. Desalination

2. Pump water from other parts of the country

3. Buy water from Norway

 These three possible solutions need energy input. The reverse osmosis process used at the Beckton plant typically requires about 4KwH per cubic metre of waters produced [1]. Pumping water across the country from the exceedingly wet west is also an energy-hungry activity. Shipping water from Norway in tankers or towed across in large plastic bags is, surprisingly, also an option being considered. In a world facing the challenge of increasing energy prices and the need to hold carbon dioxide emissions in check, energy intensive solutions should be avoided. None of these three options therefore look very attractive. Three more options are:

1. Fix leaks in London’s delivery network

2. Alter plumbing systems to use less water

3. Cap population growth in the Greater London Area.

First, fix the leaks in London’s old creaking supply system which leaks a staggering 26% of the water supplied [2]. Halving the leaks would increase supply to consumers by 13%. Second, alter plumbing systems to use less water. This could include the installation of water harvesting systems to collect rainwater. This could be envisaged to reduce water demand by 10-20%. Third, a logical option would be to hold the population of the greater London area (about 8 million) from further increase so capping the need for additional supplies. The idea that population should, of even could, be held down is not considered seriously by policy makers, so this option is off the table.

That leaves the two best options:

1. Fix leaks in London’s delivery network;

2. Alter plumbing systems to use less water including water harvesting.

Thames Water may be proud to show off their desalination plant at Beckton sewage works. They presumably worked out the figures and concluded that it would be a good investment. From the narrow perspective of the water supply company this may be logical. It is hard to find the cash to invest massively in long-term network improvements; and customer plumbing solutions are outside their control. We therefore get Beckworth desalination plant, a shiny new memorial to unsustainable policy.

Notes:

1. Energy Requirements of Desalination processes, Encyclopedia of Desalination and Water Resources (DESWARE), UNESCO Encyclopedia of Life Support Systems (EOLSS).

2. BBC News, 5th April 2012. How much does your water company leak?