INVESTIGATING MEMBRANE BIOREACTOR OPERATION FOR DOMESTIC WASTEWATER TREATMENT: A CASE STUDY

The City of McAllen Texas, with the assistance of CH2M HILL and the co-sponsorship of United States Bureau of Reclamation, Electric Power Research Institute, and the Texas Water Development Board, pilot tested the ZenoGem® internal (immersed) design membrane bioreactor (MBR) for an extended period (∼6,000 hours) to optimize its operation relative to the major requirements of nutrient removal and membrane flux stability. The pilot-scale study was conducted from March through October 1999 at the City of McAllen South Wastewater Treatment Plant.The results from this case study indicate that (1) mixed liquor concentration and sludge dewatering characteristics dominate the degree of membrane permeability rather than membrane pore size, (2) oxygen transfer limitations at the higher mixed liquor concentrations used in this study (13 g/L) established conditions favorable for simultaneous nitrification/denitrification and bio-phosphorus uptake, and (3) controlled cycled aeration produced the greatest degree of nitrogen removal. These results will be of value to those interested in MBR use for domestic wastewater treatment, particularly where nutrient removal is required.