Silica Entrapment of Biofilms in Membrane Bioreactors for Water Regeneration

Abstract : Habitat systems for long-term resource recovery must be reliable, safe and highly efficient, while providing potable water, oxygen, and edible biomass. Water makes up a large portion of the daily mass input into habitat systems. Considerations for water recycling technologies include shelf life, resupply-return logistics, maintenance time, power requirements, and footprint. Water recovery via physicochemical processes is limited by resupply, which can be alleviated by incorporation of an autonomous bioregenerative core, utilizing innate metabolic activity of cells to recover useable water from various wastestreams. Major components of bioregenerative core systems include plant/crop production systems and microbial bioreactors. One of the microbial bioreactor technologies currently under consideration for use within closed loop water recovery systems is the membrane-aerated bioreactor (MABR). Although many advancements have been made regarding the optimization of MABR biotechnologies, problems that persist include: slow startup time, shock loading/reduction of processing efficiency, uncontrolled detachment of sessile bacteria, and the ability to control microniche community formation for degradation of complex wastestreams. To improve bioreactor design in these areas, we have demonstrated a technique linking advanced cell immobilization to hollow fiber membrane bioreactor. Porous silica immobilization of cells (biosilification) is a biocompatible, optically transparent encapsulation method used for high quality thin film deposition. Results indicate that encapsulated membrane-bound cells within biofilms are viable, retain their morphology, are metabolically active, and are physically trapped following biosilification. The resultant thin silica membrane is evenly distributed over the biofilm surface, reducing molecular diffusion limitations, and reinforcing the matrix.