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Chemical Contamination in Household Water Supply

Ōhakea, New Zealanmd

Chemical Contamination in Household Water Supply

Ōhakea, New Zealanmd

Manawatu District Council
Plant Capacity
Plant Capacity
1,500 m3p]/d
Greensand Filtration
Water Source
Water Source
Ground Water
Water Quality Issue
Quality Issue
PFAS Contamination

Customer Need

Chemical Contamination in Drinking Water Supply

Sanson, a small settlement adjacent to the Royal New Zealand Air Force (RNZAF) base in Ōhakea, faced severe water contamination issues. For four years, residents relied on bottled water due to toxic firefighting foam runoff, which had contaminated the local groundwater with PFAS and PFOS chemicals.

The Manawatu District Council required an urgent upgrade to the Ōhakea water scheme to eliminate chemical contamination in household water supply and provide safe drinking water to the affected residences and farms in rural Ōhakea and Sanson, along with the RNZAF base.

Chemical Contamination in Household Water Supply

What We Did

Provided a New Water Treatment Plant with Greensand Filtration

FILTEC designed and constructed a new 1,500 m³/day water treatment plant for the Ōhakea rural water scheme, starting with the development of a new deep bore to replace the contaminated water source.

Three greensand filters were installed to effectively remove iron and manganese. Pre-chlorine dosing oxidized these elements, which were then captured by the greensand media, ensuring cleaner water. Each filter has the ability to backwash individually while the other filters stay in operation. The filtered water is passed through to a 3M cartridge filtration system which filters the remaining solids from the water.

These filters provided a robust solution by capturing oxidised particles, preventing them from passing through, and significantly enhancing water clarity and safety.

Installed a Robust UV Disinfection System

After filtration, the water passes through a Trojan UV Swift SC disinfection system. This advanced UV system not only inactivates microorganisms, making the water free of harmful pathogens, but also enhances the breakdown of certain chemical contaminants like PFAS.

The consistent UV dose of at least 40 W/cm2 is meticulously monitored and controlled, maintaining high water quality standards and providing an additional layer of protection against chemical contaminants.

Implemented Post-Chlorine Dosing for a Residual Disinfect

The final purification stage involves post-chlorine dosing, which maintains a low level of chlorine in the water supply network. This step eradicates any remaining biological organisms, ensuring the water remains safe as it travels through the piping system.

FILTEC also provided construction support including building the treatment building and installing essential infrastructure.

The Result

Safe and Compliant Drinking Water to the Rural Communities

The new water scheme, rolled out in August 2022, provided safe, compliant drinking water to 80 houses, farms, and the Ōhakea air force base. The upgrades eliminated chemical contamination in household water supply, alleviating community health concerns. The plant produces up to 1,500 m³/day of water, with the capacity to expand to 4,000 m³/day, ensuring future growth needs are met.

FILTEC’s successful implementation restored reliable drinking water access, significantly benefiting the rural Ōhakea and Sanson communities. Our team attended the opening of the new Ōhakea rural water scheme where the plant was switched on by the Manawatū District mayor and Environment Minister.


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