Large-scale “bio-sand” filters have been found to be among the most cost-effective water cleaning methods in the Kingdom, according to a recent evaluation by the Trailblazer Foundation, which hopes to start installing them in villages soon.

Thousands of families in Cambodia already use household-size bio-sand filters, in which water is cleaned by passing through copper tubes and a stack of sand, gravel and a natural layer of micro-organisms. However, larger village-size filters, which cost about $1,000, are more efficient, the NGO found.

The filters reduce pathogens by 97 to 99 per cent and remove over 80 per cent of dirt particles in the water, according to the test run of one such filter in Siem Reap, performed by Jason Hahn, a researcher from the University of Alaska Anchorage, who worked with Trailblazer. “This project demonstrated that community-scale biosand filters are a viable and effective solution to rural clean water challenges in Cambodia,” Hahn wrote.

A family-size filter can clean 40 to 60 litres per day, while the larger filters can produce thousands of litres per day and require less maintenance.

Hang Hybunna, a sanitation expert with Plan International, which was not involved in the study, said that irregular maintenance was the largest drawback of the family-size devices.

There are only a handful of community-size filters in the country, though Trailblazer is seeking boost adoption by meeting with commune chiefs in Siem Reap, many of whom seem receptive, said Scott Coats, a project director with Trailblazer.

According to Hybunna, while bio-sand filters are good at cleaning river and lake water, they are less useful for groundwater, as they don’t do as good a job at removing iron and arsenic.