Three Valleys Water is the UK's largest water-only company in England / Wales. Operating for more than 130 years it supplies parts of Bedfordshire, Buckinghamshire, Essex, Hertfordshire and Surrey and the London Boroughs of Barnet, Brent, Earling, Harrow, Hillingdon and Enfield.

Three Valleys Water supplies 877 million litres per day to 3 million customers.

Batchworth and Mill End are both critical sites for Three Valleys Water.

Batchworth originally treated 20.5 Ml/d and Mill End treated 18 Ml/d of water extracted from deep site boreholes with superchlorination and dechlorination; however the source was identified as having a cryptosporidium risk and a membrane barrier was required to meet DWI Compliance by September 2003.

VWS completed two key contracts within this scheme which have the capacity to contribute 38 and 47 Ml/d respectively to Three Valleys Water supply.

At both sites, VWS installed CMF-s Microfiltration Membrane technology, as well as refurbished the existing borehole pumps, disinfection and relift pump stations. Both sites are critical sites for Three Valleys Water and a key challenge to the project was to maintain the works supply whilst all the modifications were being made.