(767a) Application of a New Zwitterionic Membrane Surface Chemistry for Biofouling Control

Treatment of impaired waters for beneficial use exposes the membranes to feed waters containing biological and abiotic species, which leads to fouling and loss of membrane productivity over time. Since reduction in flux due to fouling is one of the largest costs associated with membrane processes in water treatment, new coatings that limit and reverse fouling would have significant economic and societal impacts.  Developing these advanced coatings is the focus of our work.

Prior studies to control biofouling largely have focused either on preventing microorganisms from attaching or killing the microorganisms once they do attach. Based on considerable literature and experience, we know that each of these control strategies alone can be effective but not sufficient for controlling biofouling. Our hypothesis is that membranes coated with dual-mode polymer nanolayers can limit and reverse membrane biofouling by switching reversibly between passive (antifouling) and active (antimicrobial) states of biofouling control. This strategy differs fundamentally from most other surface modification strategies that rely solely on either passive control (i.e., using coatings designed only to weaken foulant adhesion and, thus, limit their accumulation) or active control (e.g., adding biocides).

In this paper, we will describe a method to minimize biofouling on ultrafiltration membranes by coating the membrane surfaces with a new type of responsive zwitterionic polymer. The effectiveness of this new chemistry will be demonstrated with data collected from bacterial deposition and membrane biofouling experiments using appropriate model systems. Bacteria deposition studies showed that the new chemistry performed better than other common anti-fouling chemistries. Biofilm studies showed that PES membranes coated with the new chemistry accumulated half the biomass volume as unmodified membranes. A unique feature of this new polymer coating is that it can switch reversibly between the anti-fouling, zwitterion mode and an anti-microbial, quaternary amine mode. We will explain the chemical switching mechanism and use FTIR to support the reversible switching of the polymer nanolayer between its antifouling and antimicrobial states. We will also explain that by slightly altering the chemistry we can adjust the pH at which the chemistry switches. These new chemistries were challenged on model substrates for biofilm growth.