Liquid crystal display electrode assisted bio-reactor for highly stable and enhanced biofilm attachment for wastewater treatment – A sustainable approach for e-waste management

Abstract

Abstract Existing conventional attached growth wastewater systems are greatly hampered by long start-up times, frequent biofilm sloughing and/or erosion which lead to poor or inconsistent performance. In this study, a novel electrically bound biofilm process has been developed, and its efficacy in achieving an improved bacterial adhesion for the removal of organic waste has been demonstrated. An electrically bound biofilm reactor (EBBR) was developed, consisting of a conductive nematic liquid crystal electrode (NLCE) as the anode, obtained from an inutile desktop monitor. Three metal electrodes, namely, Al, Cu and Pt were evaluated as candidate cathodes. Electric potential and choice of the cathode were chosen as the two optimization parameters for enhancing biofilm attachment. At the optimized condition (corresponding to 1\u202fV and Pt-NLCE electrode combination), enhanced biofilm attachment was observed, with reduction in suspended solids up to 79.3% and a bio degradation rate of 71.2%, within a reaction time of 28\u202fh. The presence of active functional groups and chromophores (containing C N, NH2 and C O functional groups) were confirmed using Cyclic Voltammetry (CV), Fluorescence spectroscopy, Raman and Fourier transform infrared (FTIR) spectroscopy. High biofilm stability (over 120\u202fh) and rapid start-up times (of the order of few hours) were observed, which can be attributed to (a) the presence of these functional groups on NLCE, and (b) electrostatic attractive forces in the EBBR, unlike in conventional attached growth systems. Enhanced biofilm attachment combined with rapid start-up times paves way for a sustainable approach towards future wastewater treatment efforts.