Electrocoagulation in Wastewater Treatment: A Comprehensive Review of Heavy Metal and Pollutant Removal

Abstract

Population explosion, urbanization, and industrialization have resulted in the generation of many types of wastewaters. One of the most crucial aspects of water treatment is the elimination of pollutants/contaminants from wastewaters, as numerous industries cause environmental pollution. The rising scarcity of freshwater quality and quantity is a global concern. Discharging untreated wastewater into water bodies causes bad odour, nuisance and adverse impacts on human health, ecosystem and the world economy. Electrocoagulation (EC) is gaining ground as a potential electrochemical technique to treat wastewater due to its versatility, environmental compatibility and several other advantages. It is evident from the thorough literature review that electrocoagulation is the most frequently used and proficient process for the treatment of wastewaters containing pollutants/contaminants. During electrocoagulation in the electrochemical reactor, sacrificial anodes dissolute to release active coagulant flocs into the water/wastewater. During electrolytic reactions hydrogen gas evolves at the cathode. Many treatment methods, including adsorption, membrane filtration, coagulation/flocculation, and ion-exchange, advanced oxidation process, Moving Bed Bio-reactor, Sequencing Batch Reactor, Upflow Anaerobic Sludge Blanket, Trickling Filter, Rotating Biological Contactors are used to remove pollutants/contaminants from water/wastewater. These aforementioned methods are capital intensive, require large areas, chemicals, and a high level of instrumentation and generate secondary sludge, which poses a risk to the environment without proper disposal. To overcome these drawbacks, Electrocoagulation to treat water/wastewater can be considered. This review article focuses on understanding the role of electrochemical coagulation technique in treating wastewater and the effects of different system characteristics and operating parameters. The first few sections of this article help readers quickly understand the adverse impacts of untreated wastewater and the importance of electrochemical coagulation in water/wastewater treatment. The later sections discuss the chemical reactions, mechanisms, and effects of different operating parameters in the electrochemical reactor, which contribute to the potential removal of pollutants/contaminants from water/wastewater. It also includes a section snippet about microplastics removal and three-dimensional electrocoagulation technique which is the latest and attention gaining technique in wastewater treatment. This article includes facts and findings considered from the published research and/or review articles.