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Chlorination confirmed safe for organic farming

Updated: Nov 24, 2020

The Te Mato Vai Project Management Unit (PMU) have been actively listening to community concerns about water supply chlorination, and doing their best to address them. One key concern has been from Rarotonga’s agricultural community about the impact of using chlorinated water on crops and compost. The organic farming community seem particularly worried about the potential impact on their certification.

The PMU can confidently state that chlorination is safe for use in agriculture, including organics. International standards confirm that water supplies chlorinated to the appropriate standards are approved for use in organic agriculture.

Organic farming and certification in the Cook Islands follows the Pacific Organic Standards (based upon New Zealand and international standards). Previously certification was through a third party foreign certifying body and was expensive. The new system, through the Participatory Guarantee System (PGS) means that farmers can certify themselves. Third party organisations that certify organic farming include BioGro and AsureQuality.

Organic Standards New Zealand and AsureQuality Standards state that the final rinsing of food must use ‘potable’ water. Similarly, the Pacific Organic Standards state growers must take all necessary steps to prevent contamination.

The current water supply in Rarotonga is not potable and has tested positive for E.Coli, indicating there are harmful pathogens in the water that can make people sick. This means it is unlikely organic farmers in Rarotonga are meeting the standards if they are using the public water supply to wash their crops before marketing them.

The Pacific Organic Standards allow for the use of calcium hypochlorite (the type of chlorine used to disinfect the water supply) to disinfect food preparation surfaces with no limitations outlined.

None of these standards state that chlorine is a prohibited chemical, or that a chlorinated water supply would result in the loss of organic certification.

The only mention of chlorine in Organic Standards New Zealand is the final flushing of sprouts should use water that has been through a carbon filter to remove any chlorine residue. Alternatively, farmers can allow the chlorine to evaporate off by storing the water in a mesh-covered tank before using.

BioGro, the largest and best-known certifier in New Zealand, has not listed chlorine as a prohibited chemical in their guidelines. In fact, the low levels of intake water during dry months may mean growers should avoid using the public water supply for irrigation purposes. This is because there is a specific recommendation in all standards for growers to avoid using water that may have an adverse effect on the water ecosystem. Rainwater collection for irrigation could be the best option for organic growers in Rarotonga, with the public supply as a backup only.

There have also been concerns raised about the effect of chlorinated water killing the good bacteria in soil and compost. The amount of chlorine in the water once it reaches the tap will be between the recommended 0.2 and 0.5 parts per million. Any chlorine left in the water will reduce rapidly once it hits the surface of the soil and bonds with nutrients. Microorganisms repopulate very rapidly within the compost pile, and there is no evidence to suggest there are adverse effects on the soil nutrients.

Our recommendation is that if farmers are still concerned about the effects of a chlorinated water supply on their organic farming, to collect their own rainwater. There are no restrictions placed on chlorinated water, and the chlorine can be removed very easily using a carbon filter or leaving water uncovered overnight to allow chlorine to evaporate.

Chlorination of the water supply will ensure that there is clean and reliable water for drinking, bathing and food preparation (which includes washing organic food for final sale) for the whole community.

The PMU encourages Rarotonga’s food producers to contact the PMU office with any specific concerns or questions.

References include:

New Zealand Organic Standards are available to view by purchasing here

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