Mechanical Cleaning Process for Enhanced MBR-Performance

Membrane bioreactors (MBRs) for wastewater treatment offer the advantages of superior effluent quality and a small footprint. The disadvantage is frequent membrane cleaning caused by membrane fouling that require higher labor and chemical demands when compared to conventional activated sludge process (CASP). The goal of this investigation was to operate MBR systems without chemicals, allowing a sustainable process at low costs. Microdyn-Nadir in cooperation with Darmstadt University has developed a unique non-chemical mechanical cleaning process (MCP). The MCP-process offers an operation of the MBR-Module with high flux rates up to 40 L/(m²×h) (23.6 gfd) continuous operation. For more than 20 months (test ongoing) no chemical cleanings have been performed. This process also allows for a significant flux increase of about 30 % in comparison to a standard MBR-application without MCP. The investigations showed that:
• the use of granulates
o has a positive effect on membrane permeability
o allows an operation at high flux levels
o does not negatively affect effluent quality
• the major task of a membrane in the MBR process is the rejection of biomass. This function was not affected by using granulates.
• granulates remove fouling layers via abrasive effects. The new method has a high potential for effective and economic fouling control of membranes.                                                                                                                                                    • in terms of sustainability no chemicals are required for a MBR operation using this new process technology (MCP). This makes it a sustainable operation without an impact on the environment. At the same time, costs can be reduced.
• The Mechanical Cleaning Processes is more cost efficient compared to chemical cleaning. The cost of chemicals and infrastructure can be eliminated. The membrane area can also be reduced as the membrane throughput is increased by about 28 %. These savings by far exceed the cost for granulates and granulate rejection by a screening process.                                                                                                                                                                                          Source: WEFTEC 2009 Proceedings