Investigations of fouling alleviation and permeability decline in membrane bioreactors (MBR) were carried out at two pilot plants. On the one hand, the minimization of membrane fouling via adding abrasive granulates into activated sludge (submerged operated membrane) was tested. On the other hand, the impact of truly soluble compounds released into the liquid phase of activated sludge on fouling behavior was investigated.
The first research into the impact of mechanical cleaning via adding granulates showed the unwanted formation of fouling layers was reduced as a result of abrasion processes. With this method continuous sustainable operation was achieved, without chemical cleaning and, at the same time, reaching very high flux levels up to 40 L/(m2·h) over more than 500 days (>16 months).
The investigation of the effect of truly soluble compounds on membrane fouling showed that the permeability decline during 145 days of operation resulted predominantly from wastewater or activated sludge matter larger than 0.04 μm.