In-situ Remediation of Contaminated Groundwater Using Permeable Reactive Barrier at the 16th Lum Nam Jone Reservoir, Chachoengsao, Thailand

The 16th Lum Nam Jone reservoir is located in Chachoengsao Province, Thailand. Since 2019, water has become highly acidic with a pH of 2.5-3.5 and contaminated by heavy metals. The groundwater plume is associated with high concentrations of Iron (60 – 3,327 mg/L), Manganese (38 – 803 mg/L), Copper (5 –500 mg/L), Zinc (11 –340 mg/L), and high Total Dissolved Solids (2,600 –23,000 mg/L). The hydrogeochemical assessment confirmed that the contamination is related to the molybdenum ore processing plant located upgradient. The industrial wastewater was illegally discharged underground and flowed to the reservoir due to a hydraulic gradient. The main objective of this research is to evaluate the efficiency of different reactive materials for In-situ remediation using a permeable reactive barrier (PRB). The experiment column setup showed that marl has the highest efficiency in elevating pH by 3.6 units. The Fe, Cu, and Zn removal rates by crushed shells were 100, 98, and 60%, respectively. The Fe, Cu, and Zn removal rates by limestone were 100, 73, and 32%, respectively. The Fe, Cu, and Zn removal rates by marl were 100, 100, and 48%, respectively. Regarding the laboratory-scale experiment, the pilot PRB was installed upstream of the reservoir. The PRB was filled with marl at the bottom, overlain by limestone, and then covered with the uppermost rice straw layer. The pH increased by 2.6 units inside PRB (from pH 3.1 to 5.7). A reduction of about 50% in Fe, 85% in Cu, and 50% in Zn had been achieved.