Chlorine to stay in Christchurch water

Wednesday, 29 November 2023

The national water regulator has officially declined to exempt Christchurch City Council from disinfectant rules, meaning low levels of chlorine are here to stay.

Brent Smith, the council’s head of three waters, said the decision was disappointing but expected, as regulator Taumata Arowai told the council in May it would likely reject the applications.

Smith on Wednesday said it would be challenging for Christchurch ever to be exempt from residual disinfection rules.

Not only because it is expensive — the city has spent almost $200 million on water supply improvements since 2018 — but also because of the complexities behind Christchurch’s water supply, most of which comes from aquifers.

Taumata Arowai’s final decision comes over seven months since it first told the council it was unlikely to approve its exemption applications, a key reason being the council’s lack of a primary treatment barrier, such as UV treatment.

At the time, the council said the necessary upgrades would cost “many millions” but would be considered in its next 10-year budget, the 2024-34 long-term plan.

The council wanted to be exempt from a requirement for continuous monitoring equipment at pump stations, which could monitor chlorine levels.

It also wanted to be exempt from ensuring there was enough chlorine contact time in the water to kill micro-organisms.

The regulator’s chief executive, Allan Prangnell, said chlorine contact time was required because some micro-organisms took time to kill.

However, the regulator suggested the council may be exempt from this rule in future if high quality research could prove those micro-organisms aren’t present in the aquifers.

Taumata Arowai offered to work with the council to get that research done.

“We know Christchurch’s drinking water supply has characteristics that make it unlike other supplies, and the research would be of immense value and hopefully a way to resolve the issue,” Prangnell said.

Prangnell met with city councillors in a closed-door briefing on November 9 and said Taumatua Arowai was willing to work with the council on a solution.

However, deputy mayor Pauline Cotter believes it’s unlikely that Christchurch will ever meet the regulator’s standards.

“In some ways, the goalposts are still moving,” she said.

Smith said it was highly unlikely the council’s entire water supply would ever meet Taumata Arowai’s standards.

However, he thought smaller and less complex supplies such as Brooklands/Kainga ora Birdlings Flat had a better chance.

Christchurch first introduced low levels of chlorine into the water supply five years ago to stave off potential contamination.

Some of the city’s well heads were found to be unsafe. A year prior, many pumps were also found to be in disrepair and vulnerable to pollution from dirty surface groundwater.

Until then, Christchurch had been the country’s only major city not to have a chlorinated water supply.

Cotter said the council believed at the time that raising the well heads was the solution.

But since then, Taumata Arowai was formed and tasked with administering the Water Services Act 2021.

The law was created in response to the 2016 campylobacter outbreak in Havelock North, which killed four people and caused more than 5000 to fall ill.

The inquiry that followed concluded that treatment, including residual disinfection, should be essential for reticulated systems.

Cotter said the issue would likely come up when council gets the chance to meet the new Local Government Minister, Simeon Brown.

As of May, the council had invested $60m in water supply improvements related to meeting drinking water standards, and $115m was spent on pipe renewals.

The council allocated $837m for drinking water infrastructure in its 2021-31 long-term plan.

The cost to chlorinate 100% of Christchurch’s water supply is about $2.8m a year.