Recycling of aged RO membranes as NF/UF membranes: Biosafety evaluation and aging process

With dramatic growth of reverse osmosis (RO) in water treatment, more than 1.5 million waste RO membrane modules will be generated worldwide annually, which will lead to waste of resources and environmental pollution if not properly disposed. The present study aims at evaluating the feasibility of using aged RO membranes in NF/UF process. And ultraviolet (UV) irradiation was used to simulate the aging process. In addition to the conventional separation performance, virus (bacteriophage MS2) removal rate was used to evaluate the ability that membranes ensure the biosafety of the permeate. After 48 h continuous UV irradiation (313 nm, 1 W/m2), the membrane maintained high Na2SO4 rejection (88%) and phage MS2 removal rate (>4 log), which was comparable to NF-like membrane. After 96 h, the membrane manifested sound virus removal rate (>3.4 log) and high pure water permeability (122.6 L·m−2·h−1·bar−1), but the ability for salt rejection was rather weak, which approximated to a UF-like membrane. It was noteworthy that the aged membrane maintained a high virus removal rate within 0–96 h, which ensured the biosafety of the permeate. The results provided a basis for direct recycling of aged membranes.