A moving bed membrane bioreactor pilot plant for carbon and nutrient removal

The paper reports the main results of an experimental gathering campaign carried out on a moving bed membrane bioreactor pilot plant conceived for carbon and nutrients removal according to a University of Cape Town scheme. Organic carbon, nitrogen and phosphorus removal, biokinetic/stoichiometric constants, membrane fouling tendency and sludge dewaterability have been assessed during experiments. The achieved results showed that pilot plant was able to guarantee very high carbon removal, with average efficiency of 98%. In terms of nitrification, the system showed an excellent performance, with efficiencies higher than 98% for most of the experiments. This result might be related to the presence of biofilm in the aerobic compartment that contributed to sustain the complete nitrification of the influent ammonium. Conversely, the average P removal efficiency was quite moderate, likely due to the increase of the ammonium loading rate that could promote an increased NO3-N recycled from the anoxic to the anaerobic tank, interfering with PAOs activity inside the anaerobic tank. Referring to membrane fouling, the irreversible resistance due to superficial cake deposition was the mechanism that mostly affected the membrane filtration properties. Moreover, it was noticed the increase of the resistance due to pore blocking and a general worsening of the membrane filtration properties. This result could be due to the increase of the EPSBound fraction that could be promoted by biofilm detachment phenomena occurred during experiments.