Blenheim’s water to be chlorinated

Blenheim’s water supply is to be chlorinated to ensure it meets national regulator Taumata Arowai’s standards.

The water regulator requires a residual disinfectant, which is typically provided by chlorine, and while Blenheim’s water is currently treated for protozoa and bacteria, there is no chlorine dosing.

Council’s Planning and Development Engineer Stuart Donaldson told July’s Assets and Services Committee meeting that chlorination would initially be done on a temporary basis at the Central Water Treatment Plant (CWTP) until a permanent dosing plant is built. There is sufficient space to install permanent chlorine dosing at the secondary water treatment plant in Springlands.

“There is currently not enough room for a permanent chlorine dosing plant at the CWTP,” Mr Donaldson said. “Chlorine dosing would initially be at a temporary plant until the sodium hydroxide dosing plant is complete and there is sufficient space for a permanent dosing plant.”

Chlorine is a safe, simple and inexpensive way to disinfect drinking water, capable of killing most common bacteria including campylobacter and norovirus. It’s generally used alongside other processes such as protozoa barriers which remove single-celled parasites such as cryptosporidium and giardia.

Provision has been made in the Long Term Plan for chlorinating the supply.

Mr Donaldson said Taumata Arowai had reinforced the need for Blenheim’s water supply to be chlorinated from 31 December this year. This was to ensure it met the Water Services Act and the Drinking Water Quality Assurance Rules.

The committee recommended upgrading the existing CWTP site, which has been developed over time with the pH correction plant built in 2000 and disinfection, a reservoir and pump station added in 2012. Changing the pH correction plant from hydrated lime to sodium hydroxide will free up space for a permanent chlorine dosing plant.

Mr Donaldson added that existing equipment would be re-used as much as possible to save money.