Thames Water
It is the biggest water and wastewater services company in the United Kingdom.  It runs the Thames Water Ring Main around London, one of Europe's largest wastewater treatment works and the UK's first large-scale desalination plant—both at Beckton in east London—and the £4.2 billion Thames Tideway sewer currently under construction. It supplies 2.5 billion litres (550 million imperial gallons) of drinking water and treats 4.6 billion litres (1,000 million imperial gallons) of wastewater a day. It serves a population of 15.5 million people—about a quarter of the UK population—but its ageing infrastructure often leaks and causes pollution.