Efficient Anaerobic Membrane Bioreactors through Low-Fouling Membranes

Liquid fuel production from biomass in anaerobic membrane bioreactors has the potential to sup- ply the United States and the world with a large fraction of its liquid fuels from renewable biomass. The high cost and negative energy balance of such systems, however, makes the wide-spread adoption of this technology unfeasible to address energy needs. Biofouling of the membranes is at the root of these high costs and poor energy balance: a solution to reduce or eliminate fouling would make anaerobic membrane bioreactors more competitive in the energy market. The goal of the proposed work is to develop an anti-fouling coating for hollow fiber polyvinylidene fluoride filtration membranes for use in anaerobic membrane bioreactors. Many materials success- fully resist bacterial adhesion due to their superhydrophilicity, such as poly(ethylene glycol) and Zwitterionic materials. The proposed work involves development of a coating formulation – consisting of a covalent attachment chemistry and an optimized anti-fouling zwitterionic containing molecules – for polyvinylidene fluoride membranes that will be robust and highly resistant to bacterial adhesion. The Phase I effort will screen a number of attachment chemistries and copolymer compositions for low total bacterial adhesion as well as adhesion strength against C. acetobutylicum, the bacteria species used in the acetone-butanol-ethanol process for producing biobutanol. These formulations will be evaluated with respect to their resistance to cellular attachment and growth. Concurrently, we will develop a model to predict the cost and energy savings from the measured reduction in membrane fouling. Following measurements of anti-fouling efficacy and calculations of cost savings, we will select at least one candidate formulation for testing in Phase II, wherein the selected formulation(s) will be used to coat the membranes for testing in a large-scale reactor with real wastewater. Results will be used to validate and further refine the model developed in Phase I. Improving the fouling resistance of these membranes will enhance the economic viability of bio- butanol production in anaerobic membrane bioreactors by increasing membrane lifetime, increasing biofuel yields, and decreasing energy input for the mechanical and chemical counter-fouling measures. Improved performance of anaerobic membrane bioreactors will accelerate the integration of renewable liquid fuels from these reactors into the domestic and world energy supply. In addition to the application of this membrane treatment for biofuel production, such a coating could be used to treat membranes for wastewater treatment or reverse osmosis. A durable anti-fouling coating on a fluorinated polymer could also be marketed for the protection of marine craft and infrastructure.