Incorporating catalytic ceramic membrane into the integrated process of in situ ozonation, membrane filtration and biological degradation: Enhanced performance and underlying mechanisms

The integrated process comprising of in situ ozonation, ceramic membrane filtration and biologically active carbon filtration has a bright application prospect in wastewater reclamation to confront the global water crisis. Additionally, ceramic membranes of stronger catalytic activity are highly desirable so as to further increase the process cost-efficiency. In this study, a Mn-loaded catalytic membrane was tested by conducting pilot-scale experiments of the integrated process to measure its performance in enhancing pollutant removal and in alleviating membrane fouling. Lab-scale experiments were also conducted in order to investigate the underlying mechanisms in which the conventional Al2O3 membrane was used for comparison. Results showed that the integrated process with an incorporated catalytic membrane performed very well in that at a water flux as high as 80 L/m2/h and an ozone dosage of 5 mg/L, the treated water satisfied the guideline values for indirect potable reuse and membrane fouling was minimal. Reducing the ozone dosage to 4 mg/L can still achieve significant membrane fouling control effects, and maintain good effluent quality. Catalytic ozonation could lead to the generation of hydroxyl radicals, and the catalytic ozonation effect was much stronger when the catalytic membrane was used. Catalytic ozonation took place in both the membrane tank and membrane pores, with comparable contributions to the pollutant removal and membrane fouling control. Redundancy analysis (RDA) of membrane fouling characteristics showed that residual ozone concentration in membrane tank was an essential parameter and catalytic ozonation could be more effective in abating irreversible fouling than reversible fouling. RDA also confirmed that a lower ozone dosage would be sufficient for membrane fouling control when the catalytic membrane was used. This study evidently suggested the advantage of using catalytic ceramic membrane in the integrated process for efficient while economic treatment and reclamation of wastewater.