Thames Water Utilities could have planning permission for a desalination plant revoked if London mayor Ken Livingstone has his way.
Severn Trent has estimated that the severe flooding that hit parts of England last month will cost the company between £25 million and £35 million.
The water company was forced to close its Mythe Water treatment works in Tewkesbury as a result of events it called "unprecedented in the recent history of the UK water industry".
In responding to the flooding emergency, the firm distributed 50 million litres of bottled water and sent 2,000 of its staff to help restore water supplies and help communities.
It also called in contractors including Panton McLeod Americas, a water treatment company.
The firm was hired to restore the Mythe Water works so drinkable water could be available to Gloucestershire residents out of their taps.
John Copeland, vice president of the company, said: "England has some of the toughest drinking water standards in the world. It is heavily regulated and this treatment works couldn’t be reopened until it met those exacting standards."
He added that every inch of the works, which amounts to the area of five football fields, had to be cleaned and disinfected to meet those standards.
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