Like every major city in the world, the population of London is growing straining the infrastructure in place to provide its residents with clean drinking water. Thus, the Thames Gateway Water Treatment opened this week to provide water during times of drought. This desalination plant runs off of biofuels and can quench the thirst of one million Londoners.
Desalination is often critiqued for its expense and energy consumption, but the Thames project has found a way around these problems. One part of the solution is the plant uses water from the river during the ebb tide, thus there is one-third the salt content of seawater to be removed. Thames Water explains:
We begin by taking a mixture of salty and fresh water from the tidal River Thames, then treat it using various cleaning and filtering processes, as used in all our treatment works.
We remove the salt using a process called reverse osmosis. This involves forcing the water at high pressure through very fine membranes, which hold back the salt and other molecules.
The treated water is then re-mineralised so that it has similar properties to other local supplies.
Furthermore, the plant will run on renewable energy. According to Martin Baggs, Thames Water’s Chief Executive, “Running it on biodiesel, derived from materials including used cooking oil, will also help us tread as lightly as possible on the environment, on which our core business depends.”
Former London Mayor Ken Livingstone was opposed to the desalination plant unless it was powered by renewable energy. Treehugger reports:
The desal plant was originally opposed by London’s previous Mayor, Ken Livingstone, who pointed out the primary problem with all desalination plants – it’d be too energy hungry and the benefits of more drinking water would be negated by the problems associated with more carbon dioxide from powering it. But after the operators agreed the plant would be run entirely from renewable energy sources, the construction moved forward. Though, the “renewable energy” is coming mainly from sustainably produced biofuel, which is a controversy all by itself.
Perhaps London has found the appropriate use of desalination by powering the plant with renewable biofuels and only using the plant during times of need. Not every city on the planet could afford to build a desalination plant just for times of drought, but the idea of using a tidal river rather than the ocean water is one that should seriously be considered when choosing desal sights. It only makes sense to choose water with less salt content.