The Process and Water Quality Specialists

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Sludging Phenomenon

Although there are many variations of membrane manufacturers and products for MBR applications, all of these systems require an intense shear force at the membrane surface to resuspend the rejected solids and transferring them back to the bulk solution. Today, the most common means of resuspending the rejected solids are large coarse aeration bubbles that are applied intermittently to increase efficiency and reduce power. If the coarse aeration system is compromised (e.g. plugged or obstructed, not supplied with enough pressure/flow, or valve failures), the MBR system will fail due to a “sludging” phenomenon. Sludging occurs as rejected material accumulates near the membrane surface and becomes increasingly concentrated (e.g. dewatered) as there is inadequate force to resuspend this solids to the bulk solution. Sludging will cause a loss of production and cannot be adequately restored by in-situ chemical cleans. The module or cassette will need to be pulled and physically cleaned to restore performance. Sludging becomes more of a potential issue with inadequate pre-screening (e.g. too much hair, rags or inert debris that can clog up aeration system and restrict fiber movement) and with increasing MLSS concentrations.