Porous poly (lactic acid)/poly (ethylene glycol) blending membrane for microorganisms encapsulation

ABSTRACTImmobilized microorganisms technology has been explored as a promising wastewater treatment method. To further increase the activity of the immobilized microorganisms, a porous membrane which was composed of poly (lactic acid) (PLA) and poly (ethylene glycol) (PEG) was designed for microorganism encapsulation. The plane membrane and the spherical membrane were prepared respectively. The morphology, mechanical properties, nitrate permeability, and biodegradability of the plane membranes were investigated to determine an optimized formulation. And then, denitrifying bacteria was encapsulated by the spherical membrane and its denitrification performance in synthetic wastewater was explored. The mean pore size of the PLA/PEG plane membranes ranged from 2.09 ± 0.63 μm to 3.15 ± 1.32 μm. PEG stimulated interconnected pore structure of the PLA/PEG plane membrane. Compare with neat PLA membrane, the tensile strength of the PLA/50%PEG plane membrane decreased by about 53.2% and elongation at break increased by about 103.5%. Nitrate permeability attained a maximum of 188.95 ± 4.59 mg·L^-1·m^-2·h^-1 for PLA/50%PEG plane membrane. The denitrifying active sludge enclosed with the spherical membrane showed good denitrification performance in a short start-up time. The nitrate removal rate reached 51.14% on the 4th day and 82.53% on the 17th day. This porous PLA/50%PEG membrane was good for the diffusion of substrates and nutrients, which enabled the encapsulated microorganism recovered activity in a short time. The spraying method made the microorganism encapsulation could be designed according to the different microorganisms and different user environments, which expanded the application scope of microorganism encapsulation technology.