Abstract

In this study, a composite bioactive membrane was developed and tested to generate and capture hydrogen ( H-2) during the process of wastewater treatment. Hollow fiber membranes were coated with encapsulated acetogenic bacteria to simultaneously produce and capture H-2 from waste feedstocks. Acetogens were encapsulated with cast poly(vinylalcohol) or electrospun microfibers. Under anaerobic conditions the poly(vinylalcohol) and electrospun composite membranes produced an average of 44.6 +/- 11.3 mL H-2 g(-1) hexose ( 0.33 +/- 0.08 mol H-2 mol(-1) hexose) and 21.2 +/- 4.8 mL H-2 g(-1) hexose ( 0.16 +/- 0.04 mol H-2 mol(-1) hexose), respectively, and captured 73 +/- 12% and 57 +/- 11%, respectively, of the total H-2 produced in bioreactors fed synthetic high strength wastewater. The H-2 capture efficiency of the electrospun composite membrane was improved by coating the modules with a thin film of polymeric silica gel, improving the H-2 production to 28.3 +/- 2.3 mL H-2 per hexose ( 0.21 +/- 0.02 mol H-2 mol(-1) hexose) and the H-2 capture efficiency to 73 +/- 15%. Final composite membranes were built by immobilizing bacteria directly onto the membrane surface, again improving H-2 yields from high strength synthetic wastewater to a maximum of 48.4 +/- 9.4 mL H-2 g(-1) hexose ( 0.36 +/- 0.07 mol H-2 mol(-1) hexose) with a maximum H-2 capture efficiency of 86 +/- 9%. The optimized composite membranes were also capable of generating and capturing H-2 from real wastewaters, with yields and capture efficiencies of 19.2 +/- 3.0 mL H-2 g(-1) hexose ( 0.14 +/- 0.02 mol H-2 mol(-1) hexose) and 99.1 +/- 0.2%, and 46.0 +/- 15.5 mL H-2 g(-1) hexose ( 0.34 +/- 0.12 mol H-2 mol(-1) hexose) and 79 +/- 19% when tested with a feed of sugar beet wastewater and dairy production wastewater, respectively. After further optimization, the composite membrane system could allow the extraction of high-quality energy from wastewater.