While there is no quick fix for the brown-tinted drinking water periodically on tap in the Hauraki Plains, the Hauraki District Council is investigating a possible long-term solution.
Caused by high levels of manganese, the discoloured water looks unappealing but is safe to drink.
Manganese also builds up on the inside of water pipes and clogs filters during treatment, resulting in extra maintenance costs for the council. The water is sourced from the Waihou River and treated at the Kerepehi Water Treatment Plant. Testing over the last few years has shown this river has high levels of manganese and iron, particularly over summer.
Hauraki District Council group manager engineering services Adrian de Laborde says manganese is soluble in water and the levels fluctuate daily, which makes it difficult to remove.
“We've been trialling different options since 2016 and have only found one possible solution, which the council has now agreed to investigate further.”
The proposed solution involves a special type of filter that causes a chemical change in the manganese turning it into particles that don't dissolve and can be filtered out of the water using conventional methods.
Plains ward chair Gill Leonard says although the colour of the water is off-putting for many and can cause problems on white-sheet-washing day, health and safety has never been an issue,
“Economically, we have to weigh up the cost of this potentially expensive solution against the potential benefits, including lower maintenance costs at our end, and that's what this more detailed investigation is all about,” she says.
“I'd like to thank everyone for their ongoing patience and understanding while we look into this further.”
New reservoirs cater for growing Hauraki Plains
The council is installing two new 4015m3 drinking water reservoirs at the Kerepehi Water Treatment Plant. The existing reservoir holds 2000m3, which is not enough to keep Hauraki Plains taps running for long in the event of an unexpected plant shutdown.
Adrian says the addition of the new tanks will allow the storage of 10,000m3, or four Olympic swimming pools, of clean drinking water.
“This is good news for the community and enough to keep everyone hydrated for about 24 hours should we experience something unexpected like a temporary plant shutdown.
“There is a lot of business and residential growth in this area and we need to make sure have the capacity to keep up with demand.”
The project will cost an estimated $2 million overall.