Microbial Electrolysis Cell for Heavy Metal Removal from Wastewater

Heavy metals find their applications in various industries like medical, agriculture, textile, cosmetic, etching and microfabrication, electroplating, tanneries, pharmaceutical and other technological industries. This wide application had resulted in presence or accumulation of these heavy metals in the environment. Though they are naturally occurring elements with a greater density and higher atomic weight, their toxicity to human is a major concern. These heavy metals are carcinogens and causes systemic damage to human. Release of these heavy metals in the wastewaters of such industries lead to water pollution. Wastewaters are now a major source of water due to water scarcity and population growth. In India, water demand from domestic and industry will be 85%. Demand of water will increase from 22 to 32% in 2025 and 2050, respectively. Sustainable clean water and sanitation is a major challenge across the globe. Recycling and reuse of wastewater can meet 50% of the water requirements for domestic and industrial applications. Without the reuse of treated wastewater, it is impossible to meet the demands of the present and future generations. Untreated wastewater leads to environmental pollution and human health hazard. Thus, heavy metal removal from industrial wastewaters plays a major role in achieving sustainability. The conventional treatment methodologies are insufficient in removing trace amounts of heavy metals in wastewaters, where they are present in trace amounts. Thus, innovative wastewater treatment methods are required to remove and recover these elements. Microbial Electrolysis Cells (MECs) are a promising technology to remove and recover heavy metals. These MECs use microorganisms either as single culture or a consortium of microorganisms. Microbial metabolism with electrodeposition and precipitation is the mechanisms used in MECs. Several factors influence the removal and recovery of heavy metals in such systems. This review summarizes the need for heavy metal removal, the types of MECs used for removal, their significance, efficacy and the challenges in implementing this technology at the large scale.