Integrated technology for ecological remediation of heavy metal contaminated soil based on organic solid waste

Source: B&R Working Committee

Applicating Company

Jereh Environmental Protection Technology Co.,Ltd; Qingdao University of Technology; The Second Hydro-geology&Geo-engineering Brigade of Shandong Provincial Bureau of Geology and Mineral (Shandong Lubei Geo-engineering Investigation Institute)

Technology Name

Technical principle

This technology puts forward the theory of multi source organic solid waste cooperating with FeSO₄ biochemical reduction of chromium contaminated soil. Through the self reducing substances of organic solid waste and microbial electron transfer system, the redox cycle of "Fe³+? Fe²⁺" and the directional transformation of "SO₄²^- → S^2- → S" are realized. The use of chemical agent FeSO₄ is reduced at the source to avoid secondary sulfate pollution. The S^2- produced can be used to fix other heavy metals.

This technology simultaneously realizes the reduction of hexavalent chromium and the fixation of other heavy metals. At the same time, the advantages of in-situ soil remediation technology are obvious, which can continuously produce reducing agents through biochemical reaction, and at the same time, form potential difference to accelerate the reduction of hexavalent chromium in surrounding areas and the fixation of other heavy metals.

Scope of application

This technology is applicable to the remediation of soil in heavy metal contaminated sites such as electroplating, chrome salt, tanning, mining and metallurgical industries. The organic wastes involved in this technology are soil friendly organic wastes, including biomass carbon, biogas residue, etc. The biogas residue comes from the solid residue after anaerobic fermentation, such as kitchen waste and livestock manure, and does not involve municipal sludge and industrial sludge with high heavy metals. The remediation principle of hexavalent chromium in soil involved in this technology is to reduce it to non-toxic trivalent chromium through biochemical coupling, and the remediation principle of heavy metals such as Pb, Hg, Zn, Cu is to reduce their dissolution and mobility through biological complexation and chemical precipitation. The technology has outstanding remediation effect on sites contaminated by chromium containing complex heavy metals (such as electroplating sites), and can simultaneously achieve the reduction of hexavalent chromium and the fixation of other heavy metals.

Process flow and description

The process of ex situ remediation is to excavate contaminated soil, mix ferrous sulfate and biogas residue with contaminated soil, stack them for 1-5 days, and then backfill the site after reaching the standard for remediation;

The in-situ remediation process is to first inject ferrous sulfate into the contaminated site through high-pressure rotary jet, and then inject biogas residue and waste organic nutrient for many times. The site will be remediationed in about 1-3 months;

The mode of in-situ ectopic coupling is to excavate the contaminated soil 5-10 meters deep in the surface layer, and lay a film in the excavated pit, where the film at the bottom of the pit has a certain density of mesh. The contaminated soil is mixed with reagents such as ferrous sulfate of biogas residue, and then backfilled in the excavated pit. Later, the waste organic nutrient solution and biogas residue are continuously sprayed on the surface layer to promote the regular downward penetration of the chemicals through the mesh of the lower layer, Realize the rapid remediation of the surface layer and the in-situ remediation of the points that are difficult to excavate at the bottom layer.

Promotion prospects

This technology realizes the reduction of hexavalent chromium and the solidification of other heavy metals simultaneously through the biochemical action of organic wastes such as biogas residue and the formation of ferrous sulfate. At the same time, through waste recycling, the dosage of chemical agents such as ferrous sulfate is greatly reduced, and the secondary pollution problem of sulfate is solved. The ecological and carbon emission reduction effect is outstanding. At the same time, compared with the traditional chemical method, this method has obvious ecological effect, improves the site quality, is more conducive to the use of the site as residential land, and has obvious economic benefit potential. At the same time, the in-situ disposal effect of this technology is obvious, which can realize the remediation of heavy metal pollution in some sites that cannot be excavated (such as shallow groundwater level or deep heavy metal pollution).

This technology has been applied in many sites and is relatively mature. As soil remediation has just started, this technology has just been applied, and the market scale is small, but the economic benefits of more than 100 million yuan have also been obtained. With the continuous promotion and improvement of soil laws and regulations, and the demand of national carbon emission reduction, this technology has great potential in the future.