Treatment of flue gas desulfurization wastewater by bipolar membrane electrodialysis and its optimization by response surface methodology

Abstract

Flue gas desulfurization (FGD) wastewater is a terminal wastewater in power plant which seriously restricts the realization of zero-liquid discharge. Bipolar membrane electrodialysis (BMED) is a sustainable and eco-friendly technology widely applied in wastewater treatment. In this study, response surface methodology is employed to optimize the three key independent operating parameters: feed concentration, current density and initial acid and base concentration in order to increase desalination rate and by-product yield. The optimum condition was obtained as feed concentration 0.675 mol/L, current density 25 mA/cm2 and initial acid and base concentration 0 mol/L. In this optimum condition, the mean value of alkali conversion rate could be higher than 89.99%. The process cost for the regeneration of 1 kg NaOH from the FGD wastewater was $0.84. Increasing current density is an effective method to enhance by-product yield and shorten operation time, but it can cause a higher energy consumption, which means that the performance of the BMED system should be improved by optimizing operational conditions. Therefore, BMED is a new technology to realize the resource utilization and reuse of FGD wastewater.