Revealing the membrane fouling mechanism caused by the denitrification filter effluent during ozonation by model assessment

Membrane fouling has been a major obstacle for stable operation of ultrafiltration. In this study, prevailing fouling models were applied to assess the fouling behavior of the denitrification filter (DNF) effluent during ozonation. In order to clarify the fouling mechanism, correlation analysis and redundancy analysis (RDA) were conducted to investigate the correlations among model parameters, fouling potential and water features of the DNF effluent. The combined intermediate-standard model exhibited superior determination coefficients (R2 > 0.99). Based on analytical results, the model parameter of intermediate blocking (Ki) and standard blocking (Ks) was fairly applicable to describe the fouling of higher molecular weight (F1, MW >4,000 Da) and lower molecular weight fractions (F2, MW = 2,000–4,000 Da and F3, MW < 2,000 Da), respectively. In comparison, F1 played a predominant role in the fouling behavior of the DNF effluent. Increased ozone dosage resulted in decreased membrane fouling contribution of F1 and increased fouling contribution of F2 and F3 during ozonation. The change of fouling contributions was attributed to the transformation of high MW fractions into lower MW fractions by ozonation. This study clarified the relationships between model parameters and the membrane fouling process caused by organic fractions with specific molecular weight, thus demonstrating the membrane fouling mechanism of the DNF effluent during ozonation.