SUMMARY

Water and wastewater treatment systems are significant energy consumers. The exact cost of energy use can vary widely from one utility to the next, with estimates ranging from 2%–60% of total operating costs. Since most water treatment plants are not primarily designed and operated with energy efficiency in mind, the usage of energy in these systems is high. Also, conventional methods for removing contaminants are either becoming inadequate to meet stricter regulatory effluent limits or are increasing in cost. As a result, alternative, cost effective technologies are needed which are cost effective, efficient in removing the contaminants as well as using lesser energy.

Methods using electric field which uses direct electricity have recently gained interests in treatment of variety of waste waters including industrial waste waters with heavy metals, organic contaminants as well as groundwater and municipal waste waters. They do not require adding of chemicals into the wastewater for treatment and thus produce less waste. The low energy methods investigated in this study include electrically conductive 2D membranes, specifically transition metal carbides, carbonitrides, and nitrides or MXene membranes and electrically dissolved aluminum electrodes for ion removal from aqueous solutions.

The overarching aim of this PhD proposal and dissertation is to evaluate two methods for contaminant removal using low energy. For the MXene membranes the electrical resistance of these membranes was calculated in monovalent and divalent ion solutions to understand the transport of ions through these membranes under electric field. The ion transport and selectivity was also measured under a diffusion and acid gradient to optimize for faster transport as well as better selectivity based on the type of ions in the solution. For the electrically dissolved aluminum electrodes, the aim of the study is to evaluate the electrocoagulation performance for silica and hardness removal from synthetic groundwater solution and compare this performance to chemical coagulation. To understand the mechanism of the removal, nanoscale characterization of the electrodes was carried out using XPS, EDS and EIS. Lastly, to reduce the energy required for the dissolution of aluminum, porous electrodes of different porosity were evaluated to treat the same synthetic groundwater and the energy required was calculated.