Verifying MBR Membrane Integrity with Pressure Decay Testing; Implications and Interpretation of Test Pressure

The question of pathogen Log-Removal Value (LRV) credits for the MBR process still looms over next-generation wastewater reuse plants. Based on the Membrane Filtration Guidance Manual, the Pressure Decay Test (PDT) is the benchmark of regulatory compliance for LRV credits from UF systems. The value of the PDT is that it evaluates the integrity of the membrane barrier directly, rather than the overall system performance. The MBR PDT methodology described in this paper is based on the 3 ?m defect resolution already in place for UF processes in advanced treatment trains meeting 12/10/10 log removal of virus, Giardia, and Cryptosporidium, respectively. Results from a demonstration-scale MBR in California show an average LRV of 3.7 by a PDT with 3 ?m defect resolution, corresponding to a 14 psi start pressure. This paper presents the MBR PDT procedure, the LRV calculation, and data from an operating demonstration-scale MBR.