Fouling in a novel airlift oxidation ditch membrane bioreactor (AOXMBR) at different high organic loading rate

In this study membrane fouling was studied in a novel airlift oxidation ditch membrane bioreactor (AOXMBR) working under various high organic loading rates (OLRs). The results confirmed the high performance of AOXMBR in terms of Chemical Oxygen Demand (COD) removal, even at very high OLRs. The role of the membrane barrier appeared to be significant when the COD in the supernatant was high under such conditions. In addition, the study confirmed the performance of the AOXMBR was better in comparison with the conventional activated sludge as such colloid matters cannot be retained via a simple secondary settling step. Also, on-line viability measurement of the activated sludge illustrated that the fouling increased with a decrease in the viability of the activated sludge. The results showed that the qualitative change of the activated sludge affected the fouling phenomenon. The membrane fouling dynamics analysis pointed out the relationship between cause of the membrane fouling and MBR operating conditions. Adsorption in pores appeared to be the dominant cause when any biofilm or deposit was present on the membrane surface. On the other hand at high OLR in the absence of any deficiency (oxygen deficiency, large pH variations etc.) for the microbial population the biofilm played the dominant role consequent, whereas with drastic decreases of OLRs -due to significant cell lysis – external and reversible deposits appeared as the dominant cause of membrane fouling.

► A novel airlift oxidation ditch membrane bioreactor was introduced for wastewater treatment.
► Biofilm formation has a decreasing effect on membrane pore blocking and fouling.
► Reversible polysaccharide deposit due to cell lysis malfunctioning membrane performance.
► The viability of activated sludge affected on membrane fouling in MBR systems.