Biofouling mitigation in reverse osmosis for wastewater treatment by control of bacterial signaling

Membrane biofouling, which is the result of biofilm formation, is a main challenge in reverse osmosis (RO) based water purification systems. As a consequence, significant efforts to mitigate biofouling in RO system have been made through chemistry, material, and engineering platforms. Additionally, there is a strong desire to develop alternative fouling control strategies that are non-toxic and sustainable. Recent discoveries regarding the regulation of the biofilm life cycle by controlling signaling systems have proposed novel approaches to manipulate biofilm development and dispersal without killing the bacteria. Among the signaling molecules, N-acyl homoserine lactone (AHL) type quorum sensing molecules and nitric oxide (NO) have been identified to play an important role in the biofilm development and dispersal, respectively. In this study, we investigated novel approaches to mitigate membrane biofouling in a lab-scale RO system by controlling these two signaling molecules. First, in order to eliminate AHL signaling molecules in the bulk phase of RO system, we introduced a genetically modified Escherichia coli that expresses the AiiO lactonase, which is capable of degrading a broad-range of AHL molecules with high efficiency. Second, an NO donor with a long half-life, diethylenetriamine NONOate was injected into the RO system to disperse the biofilm on the membrane surface. Both of the approaches delayed the biofouling process significantly. Successful biofouling mitigation demonstrated that control of bacterial signaling can be an alternative solution to the membrane biofouling in RO system.