Electrokinetic and Electrochemical Methods for Microbial and Organic Fouling Mitigation at Liquid-Solid Interfaces

Abstract

Organic and microbial fouling are the initial steps for biofilm formation, resulting in severe fouling problems in many environmental and engineered applications including membrane water filtration. Electro-active methods are proposed to mitigate microbial as well as organic fouling via electrokinetic and/or electrochemical mechanisms. In the first part of this thesis, a parallel-electrode configuration was adopted and the cathode antifouling was evaluated. A carbon nanotube-polyvinylidene fluoride (CNT-PVDF) porous non-Faradaic cathode was first fabricated on top of an ultrafiltration (UF) membrane to produce negative surface charges via capacitive charging at 2 V, which reduced energy requirements (up to 2-fold) in comparison to the unmodified control. A semi-quantitative study was then completed on cathode coatings of different nanomaterials (CNM) to reduce microbial fouling. The bacterial attachment and inactivation were correlated to the electric potential and cathodic H2O2 generation, respectively. Next, a CNT and carbon black (CB) composite cathode was made on a forward osmosis (FO) membrane surface and challenged with synthetic and actual wastewater, which reduced fouling in regard to initial flux loss (~60%) for the actual wastewater and fouling rate (~50%) for both solutions at 2 V in 84 h. In the other part of the thesis, the electrode configuration was improved by fabricating interlaced surface electrodes on a substrate or membrane surface instead of only using a cathode. Insulated interlaced Ag electrodes resulted in optimal bacterial inactivation (84%) and detachment (94% after 15 h biofilm growth) with 2 min treatment at 50 V AC (10 kHz). Interlaced CNT electrodes on a microfiltration (MF) membrane altered the bacterial density and morphology at 2 V DC and reduced the fouling rate by up to 75% under the optimal filtration conditions at 2 V AC.