Hazardous events in membrane bioreactors – Part 1: Impacts on key operational and bulk water quality parameters

• MBR shock conditions significantly decreased organic matter removal.
• Organic matter removal could be used for monitoring impacts of shock loads.
• Turbidity was an effective indicator for online monitoring of membrane damage.
• Increased fouling rate from ammonia shock was easily reversible through relaxation.
• An increasing fouling layer formed by other shock loads was of an irreversible nature.

In this series of articles, the potential impacts of a number of operational ‘hazardous events’ on membrane bioreactors (MBRs) removal performance were investigated. The hazardous events assessed included salinity shock, 2,4-dinitrophenol (DNP) shock, ammonia shock, organic carbon shock, feed starvation, loss of power supply, loss of aeration, complete wash out of biomass, defective fibres, and physical membrane damage. This initial study focuses on the removal of key bulk water quality and operational parameters, i.e. changes in pH, turbidity, chemical oxygen demand (COD), dissolved organic carbon (DOC), biomass concentrations, capillary suction time (CST) and membrane fouling rate. DNP, salinity and organic carbon shock conditions were shown to significantly impact removal of organic matter (in terms of COD and DOC). These findings suggest that changes in COD and DOC concentrations were determined to be effective parameters for monitoring the impacts of these shock load events. Feed starvation significantly impacted biomass concentrations but the overall system performance remained relatively resilient, as it continued to achieve effective COD and DOC removals. The results from physical membrane damage experiment confirm that turbidity is an effective indicator for online monitoring of physical membrane damage. The results of this study can assist with validation of MBR processes.