New water-treatment model helps 700 families after Kok River metal scare

For more than 250 families in Ban Rim Kok, Chiang Rai's Muang district, heavy-metal contamination has changed daily life. Villagers stopped fishing in the Kok River and growing vegetables along its banks after metals were detected in the water.

"We are so scared. We no longer take water from the river. Now we use water from the community tap-water service to grow vegetables," said Buabhan Phomngam, 54, a resident of Ban Rim Kok. She said the change forced her to abandon commercial farming and return to household use, cutting her income by more than 70%.

The National Science and Technology Development Agency launched a clean-water pilot in Chiang Rai through its pre-Battle of Clean Water Innovation for Quality project. The programme combines water-quality monitoring, treatment systems and technology transfer so communities can operate and maintain the solutions themselves.

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We are so scared. We no longer take water from the river. Now we use water from the community tap-water service to grow vegetables.

Researchers from the agency's Nanotechnology Centre developed a community-based treatment model to remove arsenic and other heavy metals. The system uses anthracite in the first filtration stage, followed by modified biochar designed to capture heavy metals, and chlorine in the final stage. Laboratory tests showed that the biochar could remove 98% of arsenic before chlorination, while villagers test water quality each month. Results showing arsenic below 0.01 milligrams per litre meet the level recommended by Thailand's Department of Health.

The project covers about 700 families in Ban Rim Kok and Ban Muang Ngim. A community plant can produce 5,000 litres of water per hour and charge users five baht per cubic metre. The renovated plant costs about 500,000 baht, and its filters should last two to three years. A mobile version can produce 250 litres of drinking water per hour during emergencies. Researchers kept renovation costs below 25% of construction costs and worked with residents to design a simple, affordable system that is easy to maintain. They also said local materials such as bamboo and macadamia shells could reduce costs and generate income.

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Safe water means safe life.