United Utilities faces charges over Franklaw water bug outbreak
United Utilities is to be prosecuted over water contamination that left up to 300,000 homeowners unable to drink tap water for more than three weeks.
The cryptosporidium bug was found at Franklaw water treatment works outside Preston on 6 August 2015.
The prosecution is being brought by the Drinking Water Inspectorate (DWI), which said the outbreak affected about 700,000 people in the area.
United Utilities said it took "a full and open role" during the DWI inquiry.
The firm faces three charges alleging it supplied water unfit for human consumption, it failed to properly disinfect supplies, and it failed to design and continuously operate an adequate treatment process.
The initial hearing will take place at Preston Magistrates Court on 30 June.
A spokesman for United Utilities said it had "complied with all requests for information" but "it would be inappropriate to comment further now until after the case has been concluded".
Homeowners in Blackpool, Chorley, Fylde, Preston, South Ribble and Wyre were advised to boil their drinking water after the microbial parasite was discovered in 2015.
The bug, which was found during routine tests, can cause diarrhoea and abdominal cramps.
Robert Light, northern chair for the Consumer Council for Water, said: "We are disappointed it has taken almost two years to reach this point and customers are still waiting for answers."