Chlorine added after E coli found in water

Drinking water in southwest Christchurch suburbs has been treated with chlorine after a supply was found to be contaminated with the bacteria E coli.

Up to 3000 homes in the Halswell, Kennedys Bush, Westmorland and Landsdowne areas are thought to have been affected.

Chlorine was added to a water supply tank yesterday after routine testing found the presence of E coli in a water sample.

Engineers have treated a tank on the corner of Dunbars Rd and Halswell Rd with a small dose of chlorine and flushed through water pipes.

City council officials warned people living in the area may notice the smell or taste of chlorine in their water for the next few days.

Council three waters and waste reticulation and maintenance manager Rob Meek said the treatment should dissipate ‘‘pretty quickly’’ and would be unnoticeable within a week. ‘‘The chlorine is harmless but if you are concerned about the taste, you can keep drinking water in a jug in the fridge. The chlorine taste will dissipate naturally over a few hours.’’

The amount of E coli discovered was the smallest detectable level and there is no suggestion of it posing any danger to the public.

John Mackie, the council’s head of three waters and waste, said: ‘‘It’s important to note the scale of the transgression is at the lowest end, with a single E coli per 100ml being identified during our routine testing. That is the lowest level of E coli that can be detected. Staff are investigating in order to identify the source. This is no cause for alarm.’’

The treatment is not part of the planned temporary chlorination of the city’s water supply, which is expected to take place next month.

Plans are still being finalised for the roll-out of the temporary treatment programme, designed to ensure the safety of the water supply until work has been completed on upgrading the city’s below-ground well heads.

Last month, the council gave the green light for water throughout the city to be temporarily chlorinated while vulnerable well heads are repaired, a project expected to take much of the year. It will be the first time such widespread treatment has happened since the February 2011 earthquake.

"The chlorine is harmless . . ." Council three waters and waste reticulation and maintenance manager Rob Meek