Membrane biotechnology

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It is estimated that by 2025, one quarter of the World's population will experience severe water scarcity (Seckler et al., 1999). Already, virtually every region of the U.S. is impacted by insufficient or contaminated supplies, and the situation is more severe in many developing countries. Moreover, the drive to increase water quality standards to safeguard health of peoples and the environment is occurring at the same time that supplies are being strained. Steps must be taken now to head off a water crisis over the next two decades. Paradoxically, the earth is awash with water, but 97% is too salty for drinking or agriculture and most of the rest is tied up as ice. Wastewater can be reclaimed, but significant energy, space, and capital are needed, and these resources are limited in many areas of the world, and particularly in the developing countries. As a result, the water crisis is joined at the hip with issues of energy and sustainability. By combining advanced membrane surface chemistry with advances in environmental biotechnology, we hope to address both issues simultaneously.

Our Objective: Sustainable Water Reuse

In a sustainable future, we envision membrane bioreactors that will permit efficient and direct conversion of sewage organics into useful fuels (methane and hydrogen) and removal of inorganic electrolytes, even at cool temperatures. Energy from the fuels would then be used to satisfy much or perhaps all of the energy demands of water purification. This would make water reuse sustainable. One key to this vision is development of non-fouling microfiltration membranes that can concentrate the microbial biomass of a wastewater treatment bioreactor to levels that are 5 to 10 times higher than those that are achieved in conventional wastewater treatment, enabling small compact bioreactors and conversion of organic wastes into fuels. A second key is development of reverse osmosis (RO) membranes that remove inorganic electrolytes with minimal energy loss due to chemical and biological fouling. Biological fouling is the number one challenge for both microfiltration and RO. In microfiltration applications, biofouling is caused by the accumulation of microbial biofilms and biological polymers at the membrane surface and by exopolysaccharide material within the membrane pores. We are working to address these issues by applying new methods for membrane surface modification together with molecular analyses of biofilm composition and structure and varied bioreactor configurations gained through these analyses will guide development of new membrane materials.

As an example of a possible application, we envision a scenario in which domestic wastewater containing complex organics, nitrogen, and sulfur, passes into a highly compact fermentor equipped with a non-fouling microfiltration membrane; complex organics are hydrolyzed and fermented, releasing an off-gas containing H2 / CO2 /H2S. Membranes remove the H2S, and CO2 leaving H2 for oxidation in a fuel cell. Liquid from the fermentor passes to a methanogenic bioreactor where short-chain fatty acids and alcohols are converted into CH4, and biomass is again separated from water using non-fouling microfiltration membranes. The CH4 is separated from CO2 by membranes then burned or oxidized in a fuel cell for energy recovery. Energy recovered by oxidation of H2 and CH4 is used to power the pumps and compressors needed for water purification. The purified water is discharged to a receiving body or treated further to remove inorganic and trace organic contaminants.

Click here for a list of researchers working on this project.