Hanoi (VNA) – The soil washing technology has proved to beeffective in treating dioxin-contaminated soil at Bien Hoa Airport in thesouthern province of Dong Nai, experts said at a seminar held in Hanoi onDecember 8.
The technology was trialed by the Centre for Technology EnvironmentalTreatment’s Chemical Command under the Ministry of Defence and Japan’s ShimizuCorporation during 2019-2020.
Shimizu Corporation has remediated millions of tonnes of contaminated land inJapan using this technology. However, due to the high level of dioxincontamination at Bien Hoa airbase, the company said it was necessary to try thetechnology out to evaluate its efficiency.
The firm shipped a mobile-type soil washing plant from Japan, and installed itat Bien Hoa airbase in November 2018. The plant began operation in March2019. Soil washing was piloted on varioussoil samples in different dioxin concentrations, and was successful in removing95 percent of the dioxins in feed soil.
Shimizu’s soil washing is a water-based process utilizing “physical separation”based on mining and mineral processing principles for removing a broad range oforganic and inorganic contaminants from soils. Hydrocyclone and flotation arethe most important separation methods used in soil washing process.Hydrocyclone separates the fine soil from larger sand particles by thecentrifugal force. Larger sand particles end up in the underflow; fine/light particles(silt, clay, organic) and water end up in the overflow.
As soil washing is low-cost and imposes littleenvironmental burden compared to thermal treatment, experts said it should beconsidered to be applied further in the time ahead, they said.
The area surrounding Bien Hoa airport contains high levels of the chemical andis considered one of the country’s dioxin hotspots. According to assessmentsfrom Vietnam and the US, some 500,000 cu.m of dioxin-contaminated land in theairport need to be treated, requiring a large amount of capital and technology./.
