Integrated evaluation of a sequential membrane filtration system for recovery of bioreactor effluent during long space missions

Performance of an integrated membrane filtration system was investigated for treatment of the effluent from an aerated rotating membrane bioreactor system (ARMS). The ARMS is developed and operated at the Kennedy Space Center (KSC) as a potential technology for water recovery and recycling during long space missions. The 3 L bioreactor utilizes a rotating membrane module consisting of silastic hollow fibers for aeration and biofilm growth. Effluent from the ARMS contains high levels of dissolved inorganic solids. A sequential membrane filtration system consisting of prefiltration and reverse osmosis (RO) membranes was evaluated for treatment of the bioreactor effluent. To select an appropriate prefiltration membrane, a series of membrane screening experiments were conducted with two UF membranes (MWCO 10,000 and 50,000 Da) and a nanofiltration (NF) membrane using stirred filtration cells. In addition, integrated membrane filtration tests were conducted with the NF and RO membranes using a cross-flow membrane filtration unit. Effectiveness of the integrated membrane filtration system was evaluated in terms of flux and total solids rejection of the individual filtration steps as well as the overall system performance.