Impact of Diurnal Peak Flow and Pathogen Loading on MBR Performance

Two different pilot studies were conducted in Southern California over a period of several months to assess operational and water quality performance of nine different MBR systems from various manufacturers. The pilot study, conducted at the Point Loma Wastewater Treatment Plant (PLWWTP) in San Diego, CA assessed the performance of six different MBR systems on screened raw wastewater, while another study at the Inland Empire's Utilities Agency (CA) assessed the performance of three new MBR systems on primary effluent. Each of these systems was operated at peak flux for 4 hours per day for 4-6 consecutive days to assess membrane performance. Virus seeding studies were also conducted during peak flux operation to evaluate the capability of the MBRs to reject seeded MS-2 coliphage. When operating at steady state, these MBR systems achieved an effluent BOD concentration of 5.5 to >6.7 logs for fecal coliform bacteria and 2.6 to >5.4 logs for indigenous MS-2 coliphages. When operating at peak flux, seeded MS-2 coliphage removal ranged from 1.0-4.4 logs, respectively. The higher log removal values (LRVs) for indigenous MS-2 coliphage among different MBR systems were probably the result of particle association of indigenous coliphage. Differences in membrane pore size (0.04-0.2 μm) amongst the MBR systems evaluated did not have a substantial impact on indigenous MS-2 coliphage removal, but seeded MS-2 coliphage removal varied among the different MBR systems.