Andy Kirkwood: Sludge!

Saturday May 02, 2020 Published in Letters to the Editor

Dear editor,

Cook Islands News has identified a challenge (“Cook Islands waste worsens in Covid-19 slowdown,”April 18) that faces many small island states on the path to developed status.


With access and reliance on imported, processed foods comes the processed food packaging.

Similarly, the chemical treatment method proposed for Te Mato Vai system generates chemical waste.

A March 2020 expert review estimates the scale of the issue. The use of polyaluminum chloride (PACl) – a chemical that helps to remove dirt during rain – will generate 4,000 cubic metres of chemical sludge each year.

This sludge has a jelly-like consistency. It is not suitable for agricultural re-use. Dissolved aluminium strips nutrients from the soil that are essential for plant growth.

The septic vacuum trucks used to clear household tanks hold around three cubic metres. Due to the risk of overflow to the streams, the sludge cannot remain at the intakes. That means 1300 to 1400 return trips along narrow, steep, and unsealed access roads to clear the sludge.

With reports that solid and liquid storage at the Arorangi landfill is at capacity, Diane Charlie-Puna's challenge will be making space to contain large volumes of chemical sludge, to prevent leaching into the streams and the environment.

Andy Kirkwood,
Te Vai Ora Maori.

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