Evaluating the electrokinetic effect on microbial signaling molecules in activated sludge systems

Quorum sensing is a communication system that plays a critical role in biofilm formation. Several studies have explored quorum-sensing inhibitors as an anti-biofouling approach. Recently, studies on the effects of an electric field on biofouling reduction have indicated that the electric field also disrupts the QS system, although the exact mechanism remains unclear. This study has investigated the effect of the electrokinetic process on QS and its possible mechanisms. The results showed that applying an electric field reduced AHL signals in both the sludge mixture and the supernatant without microbial cells, indicating a direct effect of the electric field on the signaling system. Given the high efficiency and rapid kinetics of signal removal (>90% removal within 5 min in cell-free supernatant), indirect electrochemical oxidation-potentially mediated by reactive oxygen species (ROS) such as H₂O₂-is proposed as a plausible mechanism for AHL degradation under the applied electric field. Moreover, the concentration of extracellular polymer compounds (EPS & SMP) has decreased due to the electric field, resulting from a decrease in AHL signal concentration.