There is little doubt that, of the challenges faced in MBR operation, recovery of permeability is arguably the most critical. When the routine maintenance membrane clean fails to achieve the required recovery and more aggressive recovery cleans are also found wanting, then ex-situ cleaning becomes necessary. This invariably incurs extensive manual intervention, not always with guaranteed success.
The German river association Erftverband has been into MBRs for municipal wastewater treatment for more than a decade, installing the first such system in Germany and commissioning what was the largest membrane bioreactor in the world. The company’s experience in MBR operation provides a valuable insight into the technology.
Aquapolo is the largest wastewater reuse project in the Southern Hemisphere, and the fifth largest of its kind in the world. Upon completion, this facility will free up enough drinking water to continuously supply a population of 350,000 inhabitants, with the potential capacity to reach 600,000.
It is widely recognised by MBR practitioners that membrane bioreactors, and specifically those treating municipal wastewater, are subject to what is sometimes referred to as ‘ragging’. When the membrane module is removed, characteristic thick strands of material can be seen hanging from the bottom of the module.
In October 2009, we received a list of what was thought to be the 20 largest MBRs in the world at that time. The peak daily flow capacities on that list ranged from 30 to 100 MLD, with the total capacity being just over 1,000 MLD. 16 of the top 20 installations were fitted with GE’s Zeeweed technology, though the largest – Origin Water’s Wenyu river plant in Beijing – was based on Asahi Kasei membranes.
Membrane bioreactor (MBR) systems are becoming more accepted in the wastewater industry as an alternative to traditional conventional treatment systems. A number of factors have been instrumental in the acceptance of the MBR technology. Victoria Kippax explains the MemPulse MBR system.