Upcycling Contaminated Soil into Artificial Aggregates
Soil Remediation Methods
Due to increased industrialization activities worldwide, soil pollution has become a greater concern. Soil remediation is undertaken to contain further contamination of the area and possibly use the contaminated site again.
Soil remediation often starts with site investigation to assess the extent of remediation required, entailing determination of the volume of soil needing remediation, the prevailing regulatory requirements, identifying pollutants of concern and their concentrations, and evaluating the technical feasibility and economics of different treatment options. Polluted soil remediation technologies can be broadly categorized as physical, chemical, and biological techniques.
Physical techniques employ physical treatment processes, including dilution, soil washing, and incineration. Dilution involves the mixing of polluted soil with other materials that are relatively clean. However, simple dilution of contaminated soil can increase the total waste volume and does not change the total leaching of contaminated soil. In soil washing, an aqueous solution is mixed with contaminated soil to dissolve pollutants from the soil. However, this method can produce a large amount of wastewater that needs to be treated. Incineration is effective in decomposing organic pollutants, and some volatile metals are vaporized and captured from the flue gas, but incineration requires large energy consumption, and the treatment cost could be high.
Solidification involves adding a binder material to the polluted soil through mixing, which is then allowed to cure to form a solid product. The material acts to prevent pollutant exposure and migration by physically encapsulating the pollutants.
Chemical techniques involve the use of chemical reagents, such as chemical stabilization, to react with pollutants. In chemical stabilization, chelating agents, lime, soluble phosphate compounds, and adsorbents such as zeolite can be used to induce the formation of insoluble precipitates of pollutants. The stabilized pollutants do not leach out to the soil under natural conditions.
ZA’s SIL Process is a combination of physical solidification and chemical stabilization technologies that chemically immobilize pollutants and physically harden the soil containing the pollutants. This technology is effective in treating contaminated soil to meet disposal or waste utilization standards and generates no waste byproducts. The contaminated soil can be transformed into artificial aggregate products for different construction applications, including backfilling, road construction, land reclamation, and nonstructural concrete.
The SIL technology has been applied in China since 2015 and in Singapore at the Changi East depot construction site to treat contaminated soil for utilization as backfill material on site since 2023.