Domestic wastewater treatment in a coupled sequential batch reactor-electrochemical reactor process

New Insights on Designing the Next-Generation Materials for Electrochemical Synthesis of Reactive Oxidative Species Towards Efficient and Scalable Water Treatment: A Review and Perspectives

Electrochemical water remediation technologies offer several advantages and flexibility for water treatment and degradation of contaminants. These technologies generate reactive oxidative species (ROS) that degrade pollutants. For the implementation of these technologies at an industrial scale, efficient, scalable, and cost-effective in-situ ROS synthesis is necessary to degrade complex pollutant mixtures, treat large amount of contaminated water, and clean water in a reasonable amount of time and cost. These targets are directly dependent on the materials used to generate the ROS, such as electrodes and catalysts. Here, we review the key design aspects of electrocatalytic materials for efficient in-situ ROS generation. We present a mechanistic understanding of ROS generation, including their reaction pathways, and integrate this with the key design considerations of the materials and the overall electrochemical reactor/cell. This involves tunning the interfacial interactions between the electrolyte and electrode which can enhance the ROS generation rate up to ~ 40% as discussed in this review. We also summarized the current and emerging materials for water remediation cells and created a structured dataset of about 500 electrodes and 130 catalysts used for ROS generation and water treatment. A perspective on accelerating the discovery and designing of the next generation electrocatalytic materials is discussed through the application of integrated experimental and computational workflows. Overall, this article provides a comprehensive review and perspectives on designing and discovering materials for ROS synthesis, which are critical not only for successful implementation of electrochemical water remediation technologies but also for other electrochemical applications.

Sequential use of the electrocoagulation-electrooxidation processes for domestic wastewater treatment

Nowadays, the decrease in useable water resources day by day necessitates studies on the protection of resources by treating wastewater. It is also one of the best options for reusing the water to be treated, and electrochemical technologies can be an alternative to existing technologies, because of the easy operation and effectiveness of pollutants treatment. The study evaluated the treatment of domestic wastewater by Electrocoagulation-Electrooxidation successive processes in continuous and batch modes. The effects of the operational parameters on the Electrocoagulation and Electrooxidation processes were determined for removals of chemical oxygen demand, ammonium-nitrogen, nitrate-nitrogen, turbidity, phosphate-phosphorus, nitrite-nitrogen, and Escherichia coli. The experiments revealed that the Electrocoagulation process effectively removed all pollutants but not ammonium-nitrogen. After the Electrocoagulation process was completed, ammonium-nitrogen from domestic wastewater treatment was removed with the Electrooxidation process for further treatment. The optimum operational conditions in the Electrocoagulation process were electrode type iron anode-carbon felt cathode, current density 100 A m^-2, initial pH original, and operation time 20 min. Under these conditions, removal efficiencies of chemical oxygen demand, turbidity, phosphate-phosphorus, nitrate-nitrogen, nitrite-nitrogen, and Escherichia coli were found to be 90.2%, 96%, 88.2%, 73.6%, and 97.9%, respectively. The removal efficiencies for the optimum operating conditions of the Electrooxidation process using Ti/SbO₂ anode and stainless steel cathode were obtained as 95.4% (chemical oxygen demand), 89.4% (ammonium-nitrogen), and 99.99% (Escherichia coli) at 100 A m^-2, 5 mm electrode distance, and 30 min operation time. Finally, the EC process is an effective process for removing chemical oxygen demand, phosphate-phosphorus, turbidity, nitrite-nitrogen, and nitrate-nitrogen. However, the Electrooxidation process is a successful process for the treatment of ammonium-nitrogen and Escherichia coli. This research revealed that the sequential processes effectively removed organic, inorganic, and Escherichia coli from domestic wastewater.