Design and operational issues of 7 full-scale MBRs for municipal wastewater treatment
Membrane bioreactors (MBRs) represent an emerging technology for the advanced secondary treatment of municipal wastewater around the world. In this line, seven municipal MBRs facilities recently built, with capacities ranging from 1,100 m3·day-1 to 35,000 m3·day-1 (up to 100,000 m3·day-1 in total) have been diagnosed. The evaluation of the design and operational issues revealed significant improvements from the oldest to the newest MBR installed. The main operational issues surveyed have been classified and described in three different categories: i) design limitations, (ii) membranes and equipment failure and (iii) operational problems, with inter-relationships between them. The two oldest MBRs showed broken membranes after six and seven years of operation, respectively, being required its replacement. While foaming has been determined as the most common operational problem, other troubles such as clogging, reduction of denitrification process efficiency or the air in the permeate line were of more concern for the practitioners. Moreover, fouling has not been mentioned by any of the practitioners and energy consumption has been determined as the main limitation of this technology.
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