Performance Assessment of New Membrane Bioreactor Systems at Average and Peak Flow Operation
To assess the operational performance and effluent water quality of five newly developed membrane bioreactor systems, MWH and City of San Diego conducted a 18-month pilot study at the Point Loma Wastewater Treatment (PLWWTP), San Diego, CA. Various configurations of MBR systems, i.e. hollow-fiber, flat-sheet and external tubular membranes, were tested during the study. Funded by the U.S. Bureau of Reclamation (USBR), the study assessed the performance of Puron™ MBR from Koch Membrane Systems (KMS), Huber® MBR from Huber Technology, Neosep™ MBR from Kruger Inc., DynaLift™ MBR from Parkson Corporation and Microza™ MBR from Pall Corporation. Each MBR pilot system was operated on municpal wastwater for a target period of 3500 hours during which the membrane performance and water quality of each system was assessed. In addition, each system was also evaluated for its ability to meet Title 22 Water Recycling Criteria for membrane systems as outlined by the California Department of Health Services (CDHS). Results obtained from the study showed that each of these MBR systems consistently produced effluent with turbidity of <0.2 NTU. As a result, all five MBR systems were granted conditional Title 22 approval by CDHS. Based on the results obtained from the pilot study, a significant difference was observed between the operating flux of the submerged and external MBR systems. The median net flux values for submerged MBR systems were measured between 12-16 gfd whereas that for external MBR system was measured at 27 gfd. The scouring air requirements per unit membrane area ranged from 0.016-0.040 scfm/ft2 whereas the scouring air requirements per unit permeate volume produced ranged from 7.6-27.1 ft3 air/ft3 permeate. During the peaking study, all five MBR systems were able to sustain the operation without any significant irreversible fouling but long-term testing at peak flux operation would be required to assess the fouling trend. The peak flux values for MBR systems ranged between 33-45 gfd and a difference in operating parameters (scouring air, backwash, recirculation flow-rate and filtration cycle time) was observed at average and peak flux operation. Results obtained from the virus seeding experiments showed 1.0 – 4.0 log removal of MS-2 phage by new MBR systems.