Remediation of emerging contaminated sites due to uncontrolled e-waste recycling

Abstract

• Uncontrolled e-waste recycling produces multiple toxic pollutants. • Highly essential to prohibit illegal imports, and centralize up-to-standard recycling. • Small and efficient gas treatment plants are recommended before air emission. • Low-cost pollutant barriers and ex-situ water treatment are encouraged. • Soil washing with biodegradable agent and microbe-assisted vegetation are suggested. The use of primitive techniques in recycling electronic waste (e-waste) has led to severe soil pollution in recent decades, posing great threats to environmental and human health. It is urgently needed to remediate e-waste-contaminated sites effectively. This is especially true for the new e-waste-receiving countries/regions, after China has banned import of e-waste since 2016. The major aim of this article is to provide a comprehensive review of the policy, management, and remediation techniques (of contaminated sites) related to e-waste recycling, based on the information gained in two mega e-waste recycling sites in China (i.e., Guiyu town and Taizhou city). The article focuses on the remediation techniques developed to decontaminate soil/sediment/water contaminated by mixtures of toxic metals and persistent organic pollutants. Recommended innovative remediation technologies include: 1) integrating the techniques of spray tower, electronic precipitation, and photocatalysis significantly reduces health risk (e.g., VOC: ∼39%; bromomethane: ∼46%) due to the gas emitted by e-waste recycling; 2) enhanced ex-situ soil washing (using biodegradable vegetable oil) with pollutant removal efficiencies of 30–97%, depending on types of agents and pollutants; 3) enhanced phytoremediation using suitable plants, microbes, and/or soil amendments. Hyperaccumulators can extract metals, e.g., cadmium up to 14.8 kg/km 2 . Proper vegetation further extracts, stabilizes, and degrades pollutants and restores soil functions and health. Approximately 25–90% of the residual organic pollutants can be degraded depending on types of pollutants and plant species. Since the primary principle of remediation is universal, it is hoped that remediation techniques are applicable to emerging e-waste sites in other countries/regions.