Advances in Demonstration Research on Electric Restoration of Soil in Nanjing Institute of Soil Science, Chinese Academy of Sciences

[China Instrument Network Instrument Research and Development] To promote the research and development of contaminated site remediation technology with China's independent intellectual property rights, and to develop technology for remediation of contaminated soil at the site, Cang Long, a research fellow at the Nanjing Institute of Soil Science, Chinese Academy of Sciences, and Zhou Dongmei, a researcher, are based on the electric repair of contaminated soil for many years. Based on the research and development of the technology, an electric repair project for heavy metal-contaminated soil was carried out at a plating site in Changshu, Jiangsu Province.

Electric repair site

The basic principle of electric restoration is to apply a DC electric field on both sides of the contaminated soil. The pollutants in the soil are removed by electro-migration and electro-osmotic flow under the action of an electric field, so as to achieve the purpose of cleaning the soil. Through the investigation of the previous contaminated sites, the pollution status of the site (the main pollutant is copper with an average content of 884 mg/kg) was clearly identified. The appropriate reinforcement reagents were selected through laboratory tests and heavy-contaminated areas were selected for electric remediation at the contaminated site. demonstration. The demonstration area is 16m2 and the depth is 1m. Parallel arrangement of electrodes is adopted, and the removal rate of heavy metals in soil is improved by using biodegradable enhancement agents. External civil AC power at the test site is converted to DC by a regulated DC power supply for use in electric repair. The voltage gradient is 7.5V/m, and the operating current is 0.85-1.7A.

The main process includes civil engineering, electrode and equipment installation, electricity operation and wastewater treatment. The entire electric restoration includes a power/electrode system, an automatic monitoring/control system, an agent injection system, and a wastewater treatment system. The self-designed and installed automatic monitoring and control system can automatically acquire and control the voltage, current, and solution pH during the repair operation through the network. By regularly recovering and treating the wastewater in the two-electrolyte electrolyte, the concentration of heavy metals in the wastewater can reach the fourth-grade standard for surface water and achieve safe discharge. After 48d restoration, the total copper copper removal rate is up to 81%, and the processing energy consumption is 13.6kW?h/m3 (including the power consumption of DC power supply, various data recorders, etc.), unit volume unit removal rate The energy consumption is only 0.22-0.26 kW?h/(%?m3), and the repair cost is about 200 yuan/m3, which is superior to other repair technologies and electric repair costs in foreign reports.

The successful implementation of the demonstration project provided technical parameters and operating experience for the actual application of the electric repair site. At the same time, the in-situ electric restoration engineering mode, equipment and experience formed can be replicated and promoted, which is an application of the electric restoration technology for the contaminated sites in China. Provides reference to engineering cases.

The research was funded by the National Science and Technology Support Program and the National Natural Science Fund Project.

(Headline: Advances in the Demonstration Study of Contaminated Soil in Electric Demolition Site in Nanjing)