Combined sieving and washing of multi-metal-contaminated soils using remediation equipment: A pilot-scale demonstration

This study mainly examines the effects of combined sieving and washing process by remediation equipment for heavy metal decontamination at a historically contaminated site. The laboratory results showed that the optimum parameters for the washing process were pH 2, 30 degrees C, and 10:1 liquid/soil ratio. The results from field remediation proved that the overall removal of arsenic (As), cadmium (Cd), lead (Pb), and zinc (Zn) could reach 37.1-51.1%, 44.3-78.1%, 21.2-64.3% and 29.2-59.4%, respectively, in various particle fractions. To prevent secondary pollution, coagulating sedimentation and adsorption processes were used to treat the wastewater, with removal rates of 99.4% As, 99.9% Cd, 93.5% Pb and 99.1% Zn. A composite material was adopted to solidify the fine clay that was enriched with a large amount of metals and form it into non-fired bricks. As seen from the mass balance, 23 kg of stone and 140 kg of gravel were separated, and 367 kg of fine clay with a 45% soil moisture content was treated by solidification and stabilization, achieving a volume reduction of approximately 36.5%. In conclusion, the presented method can be applied to heavy-metal-contaminated sites to greatly reduce the amount of pollutants in soils while at the same time minimizing the environmental risk. (C) 2018 Elsevier Ltd. All rights reserved.