WHO guides definition of ‘potable’

Thursday January 03, 2019 Written by Published in Health

"Potable water” is a term commonly used to describe water that is considered safe for human consumption whether through drinking, cooking or personal bathing. It has either been treated, cleaned, or filtered and meets established drinking water standards.


Examples of potable water would be tap water from treated water supply systems or water that has been UV filtered, or distilled.

Non-potable water is generally raw water that is untreated for example from lakes, rivers, rainwater, groundwater, natural springs, and ground wells. Such water is not considered safe to drink or use in cooking or personal bathing.

Te Mato Vai Project Management Unit (PMU) is using World Health Organization (WHO) drinking water quality specifications as a guide to achieving the project’s potable water objective. WHO specifications state that “drinking water available at the tap shall be microbiologically safe, wholesome and potable.” This standard addresses drinking water quality from the holistic perspective of taste, smell, and turbidity (cloudiness) as well as safety.

All water intakes on Rarotonga are untreated and do not provide potable water. Community and school drinking water stations as well as privately-owned accommodation establishments undergo some form of treatment, whether by physical filtering or ultraviolet (UV) treatment.

The Ministry of Health has conducted two to three drinking water safety surveillance tests every year at community and school water stations, and up to monthly in the latter half of 2018. Over the past five years, most community and school water stations have produced variable results, especially after heavy rain, with a select few continuing to fail to meet the required microbiological standards for acceptable drinking water.

This has required public health officers to temporarily place red stickers on those stations which have failed, until remedial action has been taken.  

The Ministry of Health public health department has become increasingly concerned with the poor water safety surveillance test results in 2018.

“The endorsement of the National Drinking water standards last month provides an important benchmark for the Cook Islands in moving forward to ensuring the provision of microbiologically safe, wholesome, and potable water and thus reducing the risk of a water-borne disease outbreak” says  Health secretary, Dr Aumea Herman

The Ministry of Health, the PMU and other government agencies are investigating water disinfection options in preparation for water quality discussions during community consultations in 2019. Factors under consideration include safety, complexity, reliability, capital cost, and ongoing operational and maintenance costs.

Disinfection options include:

• UV - A complex system that uses ultraviolet (UV) energy. Maintenance costs are high, and specialist skills are required

• Ozone - Used for niche applications where good technical support is available. Maintenance costs are high, and specialist skills are required

•  Chemical disinfection – Safe, cost-effective and easier to manage effectively. The most commonly used option, including in New Zealand and Australian water supply networks.

Separate discussions include consideration to minimise the environmental impact of single-use plastic bottles and other non-biodegradable plastic products that hold drinking water. The Water, Waste and Sanitation (WATSAN) Division of Infrastructure Cook Islands (ICI)  has  highlighted the mounting burden that plastic bottles and other non-biodegradable products have on the economy, human health and the environment of the Cook Islands.

By providing potable drinking water at the tap for all properties connected to the public water supply network, the Te Mato Vai project would contribute to reducing not only drinking water-related public health risks, but also support waste minimisation and healthier environmental efforts.       

   - TMV

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