The Arenales del Sol WWTP in Spain combines biological treatment with nutrient removal with a submerged MBR system fitted with flat sheet (FS) ultrafiltration membranes, with an average treatment capacity of 10,000 m3/d (10 MLD). The plant provides high quality treatment to highly variable seasonal sewage inflow due to the nature of this popular coastal region.
About two years ago, we asked for the views of a range of MBR stakeholders regarding the perceived technical challenges facing MBRs: What is the main technical problem that prevents MBRs working as they should? We received 48 responses, mainly from practitioners working in the municipal sector. About a month ago, in our 2012 MBR survey, we asked the same question.
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.