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The integrated process of ozonation coupled with ceramic membrane filtration has been actively utilized to alleviate membrane fouling in water/wastewater treatment, however, the effect of ozonation on protein-based ceramic membrane fouling is still contradictory. Herein, for the first time, we reported the severe protein-based ceramic membrane fouling at high ozone dosage in the integrated process of ozonation coupled with ceramic membrane filtration and the related fouling mechanism was systematically explored. Ozonation at low dosage slightly mitigated membrane fouling, whereas severe membrane fouling occurred at high ozone dosage (10 mg/L for pre-ozonation; 4 and 10 mg/L for in-situ ozonation). At high ozone dosage, the trans-membrane pressure (TMP) remarkably increased (> 40 kPa) within 90 min and both hydraulically reversible and irreversible fouling contributed to the total membrane fouling resistance. Electro kinetic potential and particle size of the bovine serum albumin (BSA) solution were not the key factors affecting the aggravated membrane fouling at high ozone dosage. The remarkably deteriorated membrane fouling at high ozone dosage can be accounted for the formation of BSA crosslinks ascribed to the oligomerization and agglomeration of BSA and the intermolecular disulfide bridge formation with the crosslinks progressively accumulating on the membrane surface and in the membrane pores during filtration. The modeling results confirmed that the BSA-based membrane fouling mechanism was changed from cake-intermediate to cake-standard with ozonation at high ozone dosage. Meanwhile, the cake layer and/or gel layer played a more important role for the aggravated membrane fouling at high ozone dosage even though the contribution of pore blocking was also significant. [ABSTRACT FROM AUTHOR]

Pre-ozonation or in-situ ozonation coupled with membrane filtration has been actively utilized for membrane fouling control in water treatment, however, the comparative analysis of these two ozonation processes on membrane fouling control has not been reported so far. In this study, the comparative effect of pre-ozonation and in-situ ozonation on mitigation of ceramic UF (ultrafiltration) membrane fouling caused by alginate was systematically investigated through characterization of TMP, fouling resistance, MW distribution, dissolved ozone concentration, the formation of hydroxyl radical and modeling. Results showed that both pre-ozonation and in-situ ozonation were effective in alleviating the cake layer fouling. Ozonation efficiently broke down the high molecular weight (MW) fractions (>150 kDa and 80–150 kDa) of alginate into the low MW fractions (6–80 kDa; 0.4–6 kDa and 0.1–0.4 kDa), reducing the membrane interception of alginate. Pre-ozonation achieved better fouling mitigation performance compared with in-situ ozonation at low ozone dosages of 2 and 4 mg/L. However, in-situ ozonation had better fouling control performance at high ozone dosage of 10 mg/L with the normalized TMP (ΔTMP) maintaining below 0.2 kPa after 60 min filtration. Besides, in-situ ozonation was more effective in hydraulically irreversible fouling control than pre-ozonation regardless of ozone dosage. Integration of in-situ ozonation and ceramic membrane filtration catalyzed ozone decomposition with the increased generation of hydroxyl radical, which further strengthened the oxidation of the accumulated foulants on the membrane surface and within the membrane pores and thus effectively alleviated the reversible and irreversible fouling. [ABSTRACT FROM AUTHOR]

The effects of in-situ ozonation on mixed liquor filterability and ceramic membrane fouling in wastewater treatment were systematically studied by evaluating the mixed liquor filterability with a factor analysis method, modeling the membrane fouling process with nine fouling models, and analyzing the mechanism of membrane fouling mitigation with a redundancy analysis method. In-situ ozonation had trade-off effects on the filterability of mixed liquor. On one hand, the filterability of mixed liquor was improved as a result of the remarkable reduction of mixed liquid suspended solids (MLSS), sludge volume after 30 min sedimentation (SV 30 ) and extractable extra-cellular polymeric substances (EPS). On the other hand, the filterability of mixed liquor deteriorated as a result of the obvious increase of dissolved organic carbon (DOC) and soluble microbial products (SMP). The contribution of sludge properties (MLSS, SV 30 , EPS) to the filterability of mixed liquor was nearly doubled compared with that of the supernatant properties (DOC, SMP). The filterability of mixed liquor was effectively improved with increase of ozone dosage (≤5 mg/L). Meanwhile, membrane fouling was effectively mitigated by in-situ ozonation with the maximum normalized TMP (ΔTMP) reduction of 55.6% achieved at ozone dosage of 5 mg/L (1.3 mg-ozone/g-MLSS). The combined intermediate-standard model excellently fitted the experimental data at different ozone dosages and the alleviation of intermediate blocking mainly contributed to the fouling mitigation by in-situ ozonation (≤5 mg/L). The cake layer resistance was maximally reduced by 61.5% at ozone dosage of 5 mg/L mainly as a result of the significantly improved filterability of mixed liquor. The gel layer resistance was maximally reduced by 32.3% at ozone dosage of 5 mg/L mainly as a result of the direct oxidation of organic foulants deposited on membrane surface. [ABSTRACT FROM AUTHOR]

The effect of mixed liquor properties changed by ozonation especially with high dosages on membrane fouling is very complex and remains unclear. In this study, the effect of mixed liquor properties changed by ozonation especially with high dosages on ceramic ultrafiltration (UF) membrane fouling in wastewater treatment and the corresponding mechanism were systematically studied by characterization of the mixed liquor properties, hydraulic performance, the fouling layers and modeling at different ozone dosages (0, 2, 5, 10 mg/L). The membrane filterability of the mixed liquor after pre-ozonation (⩽5 mg/L) was enhanced and the corresponding membrane fouling was mitigated. After pre-ozonation, activated sludge had the better settleability and larger floc size. Meanwhile, there was a remarkable reduction of dissolved organic carbon (DOC), soluble microbial products (SMP) and extractable extra-cellular polymeric substances (EPS) after pre-ozonation and the removed organics were mainly belonged to the high molecular weight (MW) (1–10 kDa) and very high MW (10–200 kDa) substances. Intermediate blocking was the main membrane fouling during the mixed liquor filtration process and the best fouling mitigation performance was achieved for the sample with an intermediate ozone dosage of 5 mg/L (1.7 mg-ozone/g-mixed liquor suspended solids (MLSS)). Meanwhile, the water quality of permeate was even better after pre-ozonation (⩽5 mg/L) with the lower DOC and total nitrogen (TN) concentrations. Severe cell lysis occurred with the significant increase of the released organics in the mixed liquor and the activated sludge had smaller floc size and worse settleability when the pre-ozonation dosage was above 10 mg/L, which in turn resulted in the deteriorated membrane fouling control performance. [ABSTRACT FROM AUTHOR]

Soluble extracellular organic matters (EOM) resulting from algal blooms in water sources can cause severe membrane fouling in water treatment. The effect of pre-ozonation on mitigation of ceramic UF membrane fouling caused by EOM released from Microcystis aeruginosa and the associated fouling mitigation mechanism were investigated through the characterization of hydraulic performance, dissolved organic carbon (DOC), fluorescence excitation–emission matrix (EEM) spectra, molecular weight (MW) distribution, hydrophilicity and model fit of five combined fouling models. Pre-ozonation achieved a remarkable effect of hydraulically reversible fouling mitigation as a result of the selective oxidation of the very high MW hydrophobic biopolymers (⩾20 kDa) to lower MW and more hydrophilic compounds. However, pre-ozonation had a very limited effect on mitigation of hydraulically irreversible fouling dominated by the high MW (1–10 kDa) hydrophilic organics. Modeling results indicated that the EOM-related membrane fouling mitigation by pre-ozonation was more likely ascribed to the alleviation of cake layer and standard pore blocking with standard pore blocking playing a more important role. [ABSTRACT FROM AUTHOR]

The presence of seasonal algal blooms with harmful algae-derived organic matters threatens the performance of ultrafiltration in drinking water treatment. The hybrid process of in-situ ozonation with ceramic ultrafiltration membrane was proposed for the treatment of algal-rich water with effective removal of algal cells and mitigation of membrane fouling. The mechanism of membrane fouling mitigation with in-situ ozonation was systematically investigated from the perspective of cake layer, gel layer and membrane pore blocking. The results showed that in-situ ozonation treatment can effectively mitigate membrane fouling. For instance, transmembrane pressure was reduced by 75.8% with in-situ ozonation at 1 mg/L. In-situ ozonation resulted in the formation of a more porous and thinner cake layer due to the disintegration of extracellular organic matters that attached on the algal surface. Besides, the portion of very high molecular weight biopolymers (around 100 kDa) and the hydrophobic fraction of algae-derived organic matters, the main component intercepted by the ceramic membrane, were reduced with in-situ ozonation and thus leaded to less severe gel layer fouling. Furthermore, in-situ ozonation induced the accelerated organics degradation within the ceramic membrane pores, alleviating the membrane pore blocking. [ABSTRACT FROM AUTHOR]

Inorganic salts (e.g., FeCl 3 and FeSO 4) are typically added to membrane bioreactor (MBR) for achieving improved total phosphorus (TP) removal and hydraulic performance. However, at the iron dose (e.g., Fe to P molar ratio of 1–4) required for effective TP removal, severe irreversible membrane fouling could become a significant concern. In this context, intermittent in-situ ozonation was provided for the first time directly in the membrane tank of Fe(II)-dosed membrane bioreactor, and its effect on membrane fouling mitigation was assessed and elucidated. The basic effluent quality remained unaffected, indicating that in-situ ozonation had no detrimental effects. In addition, concentration of foulants and the relative abundance of biofilm-forming microbes were comparable in both the Fe-MBR and Fe/O 3 -MBR. Importantly, as compared to the Fe-MBR, a 33% reduction in membrane fouling was achieved in the Fe/O 3 -MBR. The enhanced filterability of mixed liquor and the scrubbing of the membrane surface by ozone with the direct/indirect oxidation of the deposited foulants contributed to membrane fouling mitigation in the Fe/O 3 -MBR. Meanwhile, trans -membrane pressure profiles of MBRs followed cake-intermediate fouling mechanism. This study demonstrates that provision of intermittent in-situ ozonation is a simple and attractive approach to extend the operation of iron-dosed MBR. [Display omitted] • Performance of in-situ ozonation combined with Fe-MBR (Fe/O 3 -MBR) was elucidated. • Abundance of biofilm-forming bacteria was comparable in both Fe- and Fe/O 3 -MBR. • Ozonation improved mixed liquor properties and delayed the onset of severe fouling. • Increased floc size and membrane scrubbing by ozone contributed to fouling control. • Cake-intermediate fouling was the fouling mechanism in both Fe- and Fe/O 3 -MBR. [ABSTRACT FROM AUTHOR]

• Long-term performance of MBRs with and without in-situ ozonation was investigated • in-situ ozonation achieved improved (up to 26%) micropollutant removal • in-situ ozonation increased microbial diversity and favoured the growth of PAOs • Denitrifying taxa reduced in Oz-MBR, but effluent quality remained unaffected • Cake-complete model was effective to explain the fouling mechanisms in Oz-MBR In this study, impacts of in-situ ozonation applied directly in the membrane tank of a ceramic MBR (Oz-MBR) were assessed to elucidate its implications on micropollutant removal, microbial taxa and membrane fouling. The basic effluent quality (i.e. , bulk organics and nutrients) of the MBR without and with in-situ ozonation was comparable. Importantly, pollutant-specific (10-26%) improvement in micropollutant removal was achieved by the Oz-MBR, which could be attributed to the increase in the abundance of microbial taxa responsible for the removal of structurally complex pollutants and/or ozone-assisted oxidation. In-situ ozonation affected the abundance of denitrifying bacteria and functional genes but total nitrogen removal by the Oz-MBR was comparable to that achieved by the control (C)-MBR. Improved mixed liquor properties, and the reduced accumulation of foulants on the membrane surface resulted in membrane fouling alleviation (53%) in the Oz-MBR. In addition, fouling models evaluated for the first time in the case of Oz-MBR indicated that the cake-complete model was suitable to explain membrane fouling mechanism. This comprehensive study demonstrates the performance of MBR coupled with in-situ ozonation, and the obtained results would serve as a useful reference for its implementation at pilot- and/or full-scale. [ABSTRACT FROM AUTHOR]

The combined pretreatment of coagulation and ozonation is extensively adopted for water quality enhancement and membrane fouling reduction in wastewater reclamation. Herein, the integrated treatment of ferrate pretreatment and in-situ ozonation/ceramic membrane filtration on water quality improvement and fouling reduction of ceramic membrane in secondary wastewater effluent treatment was reported for the first time. The results showed that the hybrid treatment of ferrate pretreatment and in-situ ozonation greatly inhibited the generation of N-dimethyl nitrosamine (NDMA) and did not generate bromate. Meanwhile, the best removal efficiencies of low molecular weight (MW) organics (32.3%), humic-like substances (17.8%) and biopolymers (87.5%) in effluent were achieved by the combination of ferrate (0.15 mM) pretreatment and in-situ ozonation (10 mg/L). Moreover, the control sample (without any treatment) had a fouling transmembrane pressure (TMP) of 30.5 kPa after 7.0 h filtration under a constant flux of 90 L/(m2·h) while that was only 1.0 kPa by the hybrid treatment of ferrate (0.15 mM) pretreatment and in-situ ozonation (10 mg/L). Soluble microbial products (SMP)-like substances with high molecular weight (MW) of 20–2000 kDa were the main foulants and intermediate-standard fouling mechanism played a principal role during the membrane filtration process. Statistical analysis showed that dissolved organic carbon (DOC), UV 254 and protein had the greatest positive correlation (above 0.92) to the total fouling resistance, whilst turbidity displayed the greatest negative correlation (around −0.61) to the total fouling resistance. The remarkable fouling alleviation was due to the improved water quality and in-situ cleaning, which were contributed to the coagulation and oxidation by ferrate and in-situ ozonation. Image 1 • Ferrate pretreatment- in-situ ozonation greatly reduces ceramic membrane fouling. • NDMA and bromate are remarkably reduced by ferrate pretreatment- in-situ ozonation. • Intermediate-standard fouling is the main fouling mechanism. • DOC, UV 254 and protein are the most important positive factors to R t. • Fouling alleviation is due to the improved water quality and in-situ cleaning. [ABSTRACT FROM AUTHOR]