Increased MBR MLSS
Membrane bioreactors (MBR) have been widely applied at industrial facilities to provide pretreatment of wastewater prior to discharge to the collection system. One of the advantages of an MBR system is that it provides a high degree of treatment in a compact footprint, in part because it is operated at high mixed liquor suspended solids (MLSS) concentrations ranging from 8,000 to 18,000 mg/L. A common problem encountered with industrial MBRs is the inability to maintain the target dissolved oxygen (DO) level during peak loading events. This is partially attributed to the nature of industrial wastewater, which is typically inconsistent in water quality and flow, resulting in periods of low influent loading followed by high influent loading. This dramatic change in loading may cause a sudden spike in oxygen uptake rate in the aeration basin immediately followed by a sustained decline in DO. If the oxygen-transfer system is not able to recover by supplying the DO required to support the biological system, BOD removal across the MBR will decline. The capital expenditure required to expand or upgrade an undersized aeration system can be substantial, often with limited to no return on investment across the expected useful life of the equipment. However, the application of nanobubbles in wastewater treatment provides cost-effective supplemental aeration for MBRs.