Omakau/Ophir Water Supply Taste and Odour Issues
What’s happening with the water?
Since January this year, some members of the community have been noticing an unpleasant taste and odour in the Omakau-Ophir water supply; ‘muddy’, ‘earthy’, ‘musty’ or ‘swampy’ is how they’ve described it. This has continued to be an issue throughout the summer and autumn months. We had also received complaints about this in March and May 2023.
What’s causing the issue?
It is likely that the taste and odour is caused by a naturally occurring chemical called geosmin, which is produced during the breakdown of algae and other micro-organisms in raw (untreated) water sources. Geosmin has a distinct earthy or musty odour and is the cause of most taste and odour outbreaks in drinking water. It can make its presence felt after heavy rainfall, in runoff and changing river levels, as seen over the past month.
What’s the Council doing about it?
During the 2024 summer period, increased testing focused on cyanobacteria, which can produce toxins harmful to health. A change in taste and odour, along with low river flows and hot summer conditions, can be an early indicator of a cyanobacterial bloom. Testing and visual inspections of the river throughout January/March found no levels of concern. The focus has been on ensuring the safety of the water supply; removal of geosmin is difficult and can be costly, and although often unpleasant, geosmin unlike cyanobacteria, is not harmful to health.
What’s the Council going to do next?
With the issue continuing to persist, CODC has been investigating short-term options to reduce the impact. In the week ending 24 May 2024, a carbon media will be added to the treatment plant filter – effective in removing organic compounds that cause unpleasant taste and odour in water. Although success isn’t guaranteed, it is likely to remove much of the unpleasantness for the community.
What’s the long-term plan for the supply?
Council is committed to an upgrade of the Omakau Water Supply and has considered options for a new source and treatment plant.
However, following the repeal of the three waters regulation by the Government, it does require revisiting to ensure that the solution chosen is as affordable as possible for our communities while meeting the required standards.
It is intended to have an updated proposal for discussion in the 2025 Long-term Plan. CODC is committed to finding practical solutions to resolve this issue over the medium-term and asks that the community please continue to bear with us while a long-term solution is found.