In 2010, USAID carried out an Environmental Assessment that analyzed conditions at Danang Airport and evaluated a number of possible dioxin remediation technologies. Thermal desorption treatment was determined to be the most effective and scientifically proven method for destroying dioxin and to have the lowest potential impact on human health and the environment given the specific conditions of the site.

The technology is an innovative dioxin destruction technology that uses conductive heating and vacuum extraction to remediate soil and sediment contaminated with dioxins. The excavated soil and sediment are placed into a completely enclosed above-ground pile structure. Heating rods operating at temperatures of approximately 750 to 800 degrees Celsius (°C) (1400 to 1500 degrees Fahrenheit [°F]) raise the temperature of the entire pile to at least 335°C (635°F).  At that temperature, the molecular bonds holding the dioxin compound together break, causing the dioxin compound to decompose into non-persistent organic and inorganic chemical constituents which are further treated to ensure final discharges comply with strict air and water emission standards.

At Danang, USAID placed contaminated soil and sediment into a pile structure in two phases.  During each phase, USAID contractors heated the soil and sediment at this high temperature for several months to destroy the dioxin. After testing confirmed the soil was no longer contaminated, USAID removed clean soil and sediment from the pile structure and provided it to airport authorities to be used as fill in airport expansion.

From a mass balance calculation performed using detailed Phase II monitoring data, USAID estimates that 99.992% of dioxin in contaminated soil was destroyed or removed by the treatment process. Treated soil had almost undetectable levels of dioxin. The process appears to have destroyed 72.8% of the dioxin through the thermal desorption heating process. The dioxin not thermally destroyed was collected in the filter media of the system’s liquid-vapor treatment plant, primarily in non-aqueous phase liquids (NAPL) (25.7%) and bag filters (1.06%).  USAID shipped these materials for hazardous waste disposal in Europe according to Basel Convention requirements administered by Vietnamese environmental regulatory authorities.