Up to 300,000 people in the area could not drink tap water for more than three weeks after cryptosporidium was found.
The bug was discovered by United Utilities at Franklaw water treatment plant near Preston on 6 August.
Temporary ultraviolet light rigs were set up to kill the bug. A permanent one is due to be operational by April 2016.
The Drinking Water Inspectorate is continuing an investigation into the cause of the contamination.
A United Utilities spokesman said a "brand new ultraviolet rig... is currently being constructed and should be up and running by April 2016.
"In the meantime, we will continue to use the temporary UV rigs which were installed at strategic points on the local network back in August."
Cryptosporidium, a microscopic bug that can cause diarrhoea and cramps, was found during routine tests by the utility firm and resulted in households being told to boil drinking water.
The alert affected residents in Blackpool, Chorley, Fylde, Preston, South Ribble and Wyre.
Those who were affected were given up to Â£60 in compensation.
A permanent ultraviolet light rig is being fitted at a water treatment works in Lancashire after a parasite contaminated supplies.