Photovoltaic powered operational scale Membrane Capacitive Deionization (MCDI) desalination with energy recovery for treated domestic wastewater reuse

Abstract

An operational scale Membrane Capacitive Deionization (MCDI) desalination system was trialled for water reuse applications in Western NSW, Australia. The 6 electrode module system had an average current efficiency of 74 %, water recovery of 84 % (77 % including pre-treatment) and delivered 1.0 m3/h of treated water with an electrode energy consumption of 0.35 kWh/m3 (including energy recovery) and total energy consumption of 1.28 kWh/m3 (using mains power) or 1.05 kWh/m3 (using photovoltaics to power the electrodes). No performance decline was noted over an operational period of 3 months that included reverse current stopped flow desorption and regular cleaning with sodium hypochlorite. The use of photovoltaics for the electrode power supply enabled an average power saving of 27 %. The inclusion of energy recovery devices on the electrode control system facilitated a 40 % reduction in electrode energy consumption. The system demonstrated that MCDI desalination is a feasible option for treated domestic wastewater reuse and can be easily coupled with photovoltaics supply to the electrodes. As one of the first larger scale MCDI operations, we demonstrate that performance trends found in bench scale studies do translate to larger units, however control constraints of the operational units may require optimisation trade-offs between performance parameters.