Te Vai Ora Maori: Non-chemical Water Treatment Methods

Water Treatment Process: Catchment. Intake. Sedimentation. Filtration. Storage.

Te Vai Ora Maori: Non-chemical Water Treatment Methods.
Released by Te Vai Ora Maori, Nov 2019.


Masthead Te Mato Vai System showing proposed non-chemical water treatment methods.


This info sheet was produced by Te Vai Ora Maori for the Koutu Nui Vaka Meetings, Sept-Oct 2019.


Language: Maori | English

Community group Te Vai Ora Maori has researched ways to ensure clean and safe drinking water without using chemicals. These methods require only minor changes to the new Te Mato Vai water treatment system. Non-chemical methods are culturally and environmentally appropriate, sustainable, and cost-effective.

Water Treatment

  1. SLOW WATER: Planting vegetation such as vetiver grass up the valley and along banks slows water flow and stop leaves and soil from entering streams.
  2. DIVERT: At the intake point, a device monitors water clarity (turbidity) and only collects clear water. Cloudy or muddy water will be diverted back into the stream. Stored water will be used until the water clears.
  3. COAGULANT: A coagulant helps smaller particles in the water clump-together and fall to the bottom of the Sedimentation tank. The proteins and oils in ground moringa seed work in a similar way to chemical coagulants. FILTER: Vetiver grass grown on floating rafts filters and disinfects through the action of beneficial bacteria (biofiltration). Both plants have been cleared by the Ministry of Agriculture and are grown in Rarotonga.
  4. SEDIMENTATION: It takes three hours for water to move through the Sedimentation tank. Larger particles settle to the bottom of the tank and lighter material floats to the surface for separation. Even without the use of coagulants, this is an effective way of cleaning (already clear) water.
  5. FILTRATION: The new AVG Sand Filters trap fine particles at the top of a deep filter bed. Large AVG filters can process up to 125,000L/hr. No chemicals needed.

Household Disinfection

Water quality is affected by breaks in network pipes or substandard plumbing. Household disinfection is the most reliable method of assuring the safety of drinking-water ‘at the tap’. A combined filtration and UV irradiation system is preferred by most residents and is used at village filling stations.

Commissioning and Cleaning

Anolyte solution is an alternative that can be used to sterilise storage tanks and network pipes prior to use. Anolyte achieves the same level of disinfection without the environmental impact of shock-chlorination.

If biofilm or sediment build-up slows water flow, then pipes can be cleaned using ice-slurry (ice-pigging).


Download Te Vai Ora Maori: Non-chemical Water Treatment Methods


References and Further Reading


Classification/subjects: Te Mato Vai, To Tatou Vai, chlorination, coagulation, biocoagulants, biofiltration, disinfection, drinking-water, commissioning, surface water, non-chemical water treatment, filtration, vetiver grass, moringa oleifera, Rarotonga, Cook Islands, South Pacific.

Acknowledgements / Meitaki ma’ata

Te Mato Vai engineers David Sloan and Ross Dillon for technical detail on the new Te Mato Vai System. Evan Mayson and Tangi Taoro from the Project Management Unit for access to the Turangi Water Treatment Plant. Dr Ian Calhaem for information on anolyte and oice-piggin’. Maori translation by Julie Taripo Shedden and Tauraki Rongo. Info-graphic: Island Booth Information Design.

Published 7 Nov 2019. .


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