With different C/N rate of wastewater treatment in membrane bioreactor

The use of membrane bioreactors (MBR) increases in our country due to some advantages such as low sludge production, low space requirements and high removal efficiency. Due to the effective separation in MBRs quite good results for the treatment of domestic and industrial wastewaters are obtained. In this study, synthetic wastewater with different C/N ratios of 6,21 and 40 was treated in a lab-scale MBR at two different sludge ages (20 and 40 days). Changes in the wastewater having different C/N ratios which was treated in 3 different MBRs operated simultaneously were investigated. C/N ratios of 6, 21 and 40 represent dairy industry wastewater, domestic wastewater and paper industry wastewater, respectively. It was observed that as C/N ratio increased, membrane fouling and extracellular polymeric substances in the reactor also increased. Thus, the maximum fouling was observed in the reactor treating wastewater with a C/N ratio of 40, whereas the minimum fouling was observed in the reactor treating wastewater with a C/N ratio of 6. Various parameters such as EPS, SRT are known affect the behaviour of sludge in an MBR system. Flocculation increased by increasing sludge age and therefore, improvement was observed in the precipitation properties of the sludge. In this study, with increasing sludge age EPS increased in the reactor treating wastewater with a C/N ratio of 6, on the other hand EPS decreased in the reactors having C/N ratio of 21 and 40. MLSS, COD and NH3 removal efficiencies increased in each reactor, with increasing sludge age. There are many studies in the literature about the effects of SRT on membrane fouling. Some of the results reported that membrane fouling decreased as SRT increased, others reported that membrane fouling increased with increasing SRT values. There are also some studies reporting that no significant change was noted with increasing SRT values. In this study, however, it was observed that membrane fouling increased with increasing SRT values.