Accelerated Parallel Pilot Testing of Flat Sheet and Hollow Fiber Membrane Bioreactor Technology Reduces SBR Retrofit Costs

Parallel pilot testing of flat sheet and hollow fiber submerged membrane technologies was conducted as part of a project to upgrade the industrial wastewater treatment plant (WWTP) at the Boehringer Ingelheim Chemicals (BICI) facility in Petersburg, VA. The WWTP was converted from a sequencing batch reactor (SBR) to a flow-thru membrane bioreactor (MBR) system in order to accommodate higher influent flows and loads associated with an expansion of active pharmaceutical ingredients (API) production. In order to accelerate pilot testing, the two systems were operated using a feed of mixed liquor from the existing aerated sludge storage tank. The pilot systems were operated essentially as sludge thickeners, continuously thickening the mixed liquor to the design concentration while producing permeate. The systems were run in parallel for approximately 2 months at varying flux rates to assess system performance relative to the proposed design fluxes. Short term flux tests were periodically conducted to determine the maximum operating flux rates and membrane permeability at various times during the test. Membrane flux recovery cleaning methods were also tested. The following are the key results:Both systems were able to operate for long periods of time at sustained flux rates with stable trans-membrane pressure (TMP) while producing a high quality permeate completely free of suspended solids, confirming the compatibility of the membranes with BICI wastewater.The maximum sustainable flux rate for the flat sheet membrane system was 8.5 – 9.0 gfd. The system was operated for short time periods (a few days) at flux rates as high as 13 – 15 gfd, which resulted in sustained increases in TMP.The maximum sustainable flux rate for the hollow fiber membrane system was 19 – 20 gfd. Short term flux tests indicate that sustained operation up to 25 gfd for short time periods was possible.Membrane flux recovery cleaning demonstrated that the standard cleaning solutions and procedures could be used to restore membrane permeabilityPilot testing results were used to refine proposals obtained from each supplier prior to the conduct of testing. The hollow fiber membrane supplier was able to reduce the amount of membrane area supplied, significantly reducing cost and leading to selection of the hollow fiber membrane technology for this application.