An improved insight into the effect of powdered activated carbon (PAC) on membrane fouling is crucial to the MBR performance. Sludge key property, soluble microbial products (SMP) and transmembrane pressure (TMP) were monitored. The membrane fouling rate in the MBRs was also analyzed based on TMP profile and resistance-in-series model. PAC reduced the membrane filtration resistance and significantly decreased the fouling rate. The sludge filterability was improved by extending the filtration time by almost twofold. PAC affected the SMP release and protein/polysaccharide (carbohydrate) was in a lower ratio. Fourier transform infrared (FTIR) analysis indicated that PAC decreased the impact of organic carbon, and reduced the proteins’ and polysaccharides’ absorption and deposition on the membrane surface and in the pores. The degree of reversible and irreversible fouling was related to the PAC content added into the MBRs. At the optimum dosage of 2 g/L, the results signified the PAC potential as a mitigation strategy of membrane fouling.

Adsorption characteristics of high-silica zeolites (HSZSM-5) for two selected sulfonamide antibiotics (SAs) (sulfamethoxazole and sulfadiazine) were investigated. SAs were almost completely (>90%) removed from the water by HSZSM-5. Adsorption followed the second order kinetics with liquid-film diffusion as dominant mechanism. SAs adsorption capacity on high-silica zeolites was examined in terms of pH, temperature, and the presence of natural organic matter (NOM). HSZSM-5 had better adsorption performance in acidic conditions, and the apparent distribution coefficient indicated that SA⁰ species were the major contribution to the overall adsorption at pH of 2–10. Adsorption of SAs on HSZSM-5 was a spontaneous and exothermic physisorption process. SAs removed by HSZSM-5 were a mixed mechanism through ion-exchange and hydrophobic interaction. HSZSM-5 has a potential application prospects in removing SAs from wastewater.

Identifying the fouling degree of a membrane bioreactor (MBR) provides guidance on the determination of suitable membrane cleaning methods. There is still a lack of knowledge on the effects of powdered activated carbon (PAC) refresh ratio on the MBR fouling mechanism. Major fouling mechanisms of an MBR with constant flow rate at different PAC replenishment ratios were investigated by individual and combined mechanistic fouling models. The root mean square errors were employed to assess the prediction accuracy of the used fouling models. The combined models showed better prediction. The cake–complete model provided far better fits of the transmembrane pressure data, and provided good fits of other individual model predictions regardless of the PAC refreshment ratio. Fourier transform infrared spectroscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy confirmed that the cake layer clogging was the main fouling mechanism followed by complete blockage and standard plugging. The cake–complete model may be used to predict the fouling mechanisms in PAC/MBR systems.

Fundamental understanding on the fouling mechanism is critical to improve filtration operation. The performance of four parallel MBRs with different SRT was monitored during long-term constant flowrate filtration. Characteristics of the membrane and transmembrane pressure (TMP) profiles obtained were studied to demonstrate the fouling mechanisms. The capacity of both classical blocking models and their combined models was evaluated. The intermediate model provided a very good agreement with all the TMP data. However, the combined cake-intermediate and intermediate-standard model were more effective in the description of the experimental data. The contributions analysis indicated that the cake, intermediate and standard blocking model were the dominant fouling mechanisms. SEM-EDX observation showed that the cake blocking of organic and standard blocking of inorganic had the main contributions to membrane fouling. The combined cake-intermediate and intermediate-standard models may be applicable to systems where these two models are consistent with the experimentally observed fouling mechanisms in MBR.