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Soil washing is a well-established remediation technology for treating soil contaminated with heavy metals. It involves the separation of contaminants from the soil using acidic washing agents. Nevertheless, the application of washing agents at high concentrations may lead to soil acidification and the destruction of the clay structure. To avert this problem, recently, a soil washing variant has been presented, which solely employs high-pressure water without any chemical solvents. However, the fine soil generated from soil washing at a high-pressure contains high levels of heavy metals and requires proper treatment. This study examines the use and applicability of natural aquaculture materials as stabilizing agents for treating heavy metals (Cu, Pb, and Zn) in fine soil generated by high-pressure soil washing. Three aquaculture materials were assessed, namely, cockle shells (CKS), scallop shells (SLS), and Asterias amurensis starfish (ASF). Each material was processed to yield three types of stabilizing agents: natural type (-#10 mesh), natural type (-#20 mesh), and calcined(C) type (-#10 mesh). Each stabilizing agent was added to the contaminated soil at a ratio of 0 to 10 wt%, and then, mixed with an appropriate amount of water. After wet curing for 28 days, the stabilization efficiency of Cu, Pb, and Zn was evaluated using 0.1 N HCl solution. The elution of heavy metals showed a decreasing trend with higher dosages of stabilizing agents. The calcined type (-#10) showed the highest stabilization efficiency, followed by the natural type (-#20) and natural type (-#10). In addition, a comparison of the efficiency of the different stabilizing agents showed that calcined ASF (CASF) had the highest stabilization efficiency, followed by calcined SLS (CSLS), calcined CKS (CCKS), natural ASF (NASF), natural SLS (NSLS), and natural CKS. Finally, analysis of samples exhibiting the highest stabilization efficiency by scanning electron microscopy–energy dispersive X-ray spectrometry (SEM–EDX) confirmed that the pozzolanic reaction contributed to the stabilization treatment. The results of this study demonstrate that heavy metal-contaminated fine soil, generated by high-pressure washing, can be remediated by stabilizing Cu, Pb, and Zn using waste aquaculture materials (CKS, SLS, and ASF), which are often illegally dumped into the sea or landfills and cause environmental damage.

Recent natural disasters, such as typhoons in South Korea and other countries around the globe, have resulted in loss of human life and damage to property, often causing contamination of nearby soil environments. This study focused on the emergency recovery of soil contaminated by heavy metals following a disaster such as typhoon flooding by applying a soil washing technique that used high-pressure water rather than chemical cleaning agents. Artificially contaminated soil containing 700 mg/kg Cu, 530 mg/kg Pb and 900 mg/kg Zn, was used. All three metals were present at levels higher than the Korean Warning Standards (500 mg/kg Cu, 400 mg/kg Pb, 600 mg/kg Zn) for region 2 (miscellaneous area). A high-pressure soil washing device was designed to treat 0.6 tons/h and optimal treatment was sought for varying levels of pressure (1, 3, 5 MPa), solid to liquid ratios (S/L) (1:1, 1:3, 1:5), and number of washing cycles (1, 2, 3). The high-pressure soil washing results showed that a 5 MPa washing pressure, 1:1 solid-liquid ratio, and one washing cycle were the optimum conditions to generate the highest heavy metal removal rates. Under optimal conditions, high-pressure soil washing attained removal efficiencies of Cu (37.7%), Pb (36.6%), and Zn (45.1%), and the residual concentrations of heavy metals in the remediated soil satisfied the Korean Warning Standard (Region 2). A comparison of the changes in particle size showed that after high-pressure washing, the mass fraction of coarse sand (CS, 2–0.42 mm) decreased by 23.3%, while that of fine sand (FS, 0.42–0.074 mm), silt, and clay (SC,