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Abstract The comparison of long-term ceramic membrane bioreactors (MBRs) without and with in-situ ozonation was investigated in this study in terms of membrane fouling, activated sludge, effluent quality and microbial community in wastewater treatment. The optimal dosage of in-situ ozonation for long-term MBR operation was firstly determined as 5 mg/L (0.66 mg-ozone/g-mixed liquor suspended solid (MLSS)) with the optimal filterability of mixed liquor. During the long-term filtration experiment, MBR-ozone with in-situ ozonation demonstrated its significantly alleviated ceramic membrane fouling performance compared with MBR-control without in-situ ozonation as a result of the enhanced filterability of mixed liquor and organic foulants removal from membrane surface by in-situ ozonation oxidation. Furthermore, ozonation was beneficial to phosphorus removal and the total phosphorus (TP) concentration in effluent of MBR-control (0.82 ± 0.63 mg/L) was >2-fold higher than that of MBR-ozone (0.29 ± 0.41 mg/L). The improved phosphorus removal performance by ozonation was due to the increased abundance of phosphate accumulating bacteria of Candidatus Accumulibacter in activated sludge. However, ozonation was detrimental to nitrogen removal mainly as a result of the inhibition of denitrification with the decreased relative abundance of denitrification genus of Dechloromonas in activated sludge. Overall, ceramic MBR with in-situ ozonation had not only significantly alleviated membrane fouling but also remarkably improved phosphorus removal performance. Graphical abstract Unlabelled Image Highlights • Long-term ceramic MBRs without and with in-situ ozonation were compared. • The optimal filterability of mixed liquor was achieved at ozone dosage of 5 mg/L. • In-situ ozonation significantly alleviated ceramic membrane fouling. • Ozonation was beneficial to phosphorus removal but detrimental to nitrogen removal. • Microbial community of activated sludge was significantly changed by ozonation. [ABSTRACT FROM AUTHOR]

Integration of an electrochemical process with membrane bioreactor (MBR) has attracted considerable attention in the last decade for simultaneous improvement in pollutant removal and hydraulic performance of MBR. Electrochemical MBR (eMBR) with sacrificial anodes has been observed to achieve enhanced phosphorus (up to 40%) and micropollutant removal (5–60%). This is because direct anodic oxidation, indirect oxidation by reactive oxygen species and electrocoagulation can supplement the biological process. The application of an electric field can substantially reduce membrane fouling by 10% to 95% in the eMBR as compared to the conventional MBR. Sacrificial electrodes (e.g., iron or aluminium) have been reported to be more suitable for fouling mitigation than non-sacrificial electrodes (e.g., titanium). However, during prolonged operation, metal ions released from sacrificial electrodes can adversely affect microbial activity and could accumulate in activated sludge. Depending on the current density and electrode material (sacrificial or non- sacrificial), anodic oxidation, electrocoagulation, electrophoresis and/or electroosmosis mechanisms are responsible for suppressing membrane fouling propensity. This paper critically reviews the current status of the electrochemical MBR technology and presents a concise summary of eMBR configurations and electrode materials. Comparative removal of bulk organics, nutrients and micropollutants in the eMBR and conventional MBR is discussed, and performance governing factors are elucidated. Impacts of operating conditions such as current density on mixed liquor properties (e.g., floc size and zeta potential) and microbial activity are elucidated. The extent of membrane fouling mitigation along with associated mechanisms as well as energy consumption is explained and critically analysed. Future research directions are suggested to fast track the scalability of eMBR, which include but are not limited to electrode lifetime, development of self-cleaning conductive membranes, optimisation of operating parameters, removal of emerging micropollutants, accumulation of toxic metals in activated sludge, and degradation by-products and ecotoxicity. Unlabelled Image • Electrochemical membrane bioreactor (eMBR) is an emerging alternative of MBR • eMBR can achieve enhanced pollutant removal and membrane performance • Electric current affects sludge properties, microbial activity and diversity • Electrode lifetime and toxic metals accumulation in sludge are the major drawbacks [ABSTRACT FROM AUTHOR]

Abstract Ferrous dosing is used to reduce phosphorus concentration and alleviate polymeric membrane fouling in membrane bioreactor (MBR). However, limited studies have been conducted to investigate the impacts of ferrous dosing on ceramic membrane fouling, nutrient removal efficiency and microbial community. Accordingly, the aim of this study was to investigate the effect of intermittent ferrous dosing with Fe/P molar ratios of 2 and 1 (with a dosing frequency of every two days) on the overall nutrient removal, functional microbial changes and membrane fouling in ceramic membrane bioreactors (CMBR) in treatment of wastewater. TP concentration of 10 mg/L in influent decreased to 1.94 ± 0.62 mg/L (control), 0.38 ± 0.22 mg/L (Fe/P = 1) and 0.31 ± 0.18 mg/L (Fe/P = 2) in the effluent, respectively. Meanwhile, the effluent total nitrogen (TN) concentrations with Fe/P = 1 treatment (6.80 ± 2.02 mg/L) and Fe/P = 2 treatment (5.12 ± 2.28 mg/L) were lower than that of the control (7.72 ± 2.36 mg/L). Compared to Fe/P = 1, the TN removal performance was better for Fe/P = 2 mainly due to the increased abundance of denitrifying bacteria (Zoogloea and Acinetobacter). In addition, excess iron dose might have toxic effects on bacterial physiology, however the Fe concentrations that cause cell damage vary for different bacteria. The relative abundance of Zoogloea (aerobic denitrifying bacteria) continuously increased with ferrous addition (Fe/P = 2), while other bacteria including Dechloromonas , Hyphomicrobium and Thauera (anoxic denitrifying bacteria), Nitrospira (nitrifying bacteria) and Candidatus Accumulibacter (phosphorus accumulating organism) decreased sharply. Furthermore, membrane fouling was effectively moderated by ferrous dosing and Fe/P = 1 treatment showed improved membrane fouling mitigation than Fe/P = 2. Overall, intermittent ferrous addition in CMBR with Fe/P molar ratio of 1 was beneficial to the removal of nutrients (TP, TN and organics), enhanced succession of microbial community and membrane fouling mitigation. Graphical abstract Unlabelled Image Highlights • Ferrous dosing (Fe/P = 1) is beneficial to phosphorus and nitrogen removal. • Microbial community of activated sludge is significantly changed by ferrous dosing. • Excess iron dose has toxic effects on bacterial physiology. • The optimal fouling control performance is achieved at Fe/P molar ratio of 1. [ABSTRACT FROM AUTHOR]

The occurrence, bioaccumulation and risk assessment of lipophilic pharmaceutically active compounds (LPhACs), such as antibiotics (roxithromycin, erythromycin and ketoconazole), anti-inflammatories (ibuprofen and diclofenac), β-blockers (propranolol), antiepileptics (carbamazepine) and steroid hormones (17α-ethinylestradiol), were investigated in the downstream rivers of sewage treatment plants in Nanjing, China. The results indicate that these LPhACs were widely detected in the surface water and fish samples, with the mean concentrations of the total LPhACs (ΣLPhACs) being in the range of 15.4 and 384.5 ng/L and 3.0 and 128.4 ng/g (wet weight), respectively. The bioaccumulation of the ΣLPhACs in wild fish tissues was generally in the order the liver > brain > gill > muscle. Among the target LPhACs, however, an interspecies difference in tissue distribution was evident for erythromycin. The bioaccumulation factors of LPhACs in the liver and brain, the two major targeted storage sites for toxicants, exhibited an obvious negative correlation with the aquatic concentrations ( P < 0.05). Finally, risk quotients posed by pharmaceuticals were assessed by comprehensive and comparative methods for different aquatic organisms (algae, daphnids and fish). The overall relative order of susceptibility was estimated to be algae > daphnids > fish. However, the results indicate that diclofenac, ibuprofen and 17α-ethinylestradiol each posed chronic risks for high trophic level organisms (fish). In all of the risk assessments, erythromycin was found to be the most harmful for the most sensitive algae group. In this work, however, the total BAF and toxicological interactions of pharmaceuticals were not performed due to the lack of metabolite information and combined toxicity data, which represents a major hindrance to the effective risk assessment of pharmaceuticals. [ABSTRACT FROM AUTHOR]

In this study, the tissue distribution, bioconcentration, metabolism and biological effects of the macrolide antibiotic erythromycin (ERY) were investigated in fish using crucian carp ( Carassius auratus ) as a model. Crucian carp were exposed to various concentrations of ERY (4, 20, and 100 μg/L) for 28 days. The UPLC/MS/MS analysis of both water and tissue provided the bioconcentration of ERY and its metabolites in the fish body. The results from tissue samples showed that a maximum tissue concentration occurred in the muscle and that the bioconcentration factor (BCF) of 72.2 was lower than the theoretical BCF of 90.4 calculated from the octanol-water coefficient of ERY. A significant portion of the absorbed ERY was metabolized via demethylation and dehydration and observed in the form of descladinose in fish. In addition, the relevant biomarkers, including acetylcholinesterase in the brain, as well as 7-ethoxyresorufin O-deethylase and superoxide dismutase in the liver, changed significantly during 28 days of exposure ( P < 0.05). These results clearly indicated that ERY accumulated in fish and that similar metabolites as those observed in mammals were produced, resulting in the biochemical disturbance of biological systems. [ABSTRACT FROM AUTHOR]

In this study, the effect of a high concentration of powdered activated carbon (PAC) on pollutant removal and microbial communities was systematically investigated. Micropollutant removal by the 'control' MBR (without PAC addition) was pollutant-specific and was mainly controlled by their molecular properties. The PAC-MBR achieved enhanced removal of micropollutant by 10% (ofloxacin) to 40% (caffeine). Analysis of the microbial communities in the sludge samples collected from both MBRs indicated an increase in the abundance of 24 (out of 31) genera following PAC addition. Notably, bacterial diversity enriched, particularly in the anoxic zone of the PAC-MBR, indicating a positive impact of recirculating mixed liquor containing PAC from the aerobic to the anoxic zone. In addition, PAC improved the abundance of Comamonas and Methanomethylovorans (up to 2.5%) that can degrade recalcitrant micropollutants. According to the quantitative PCR (qPCR) analysis, the copies of functional genes (nirS , nosZ and narG) increased in PAC-MBR. This study demonstrated that MBR could be operated at a high PAC concentration without compromising the pollutant removal and microbial community evolution during wastewater treatment. Unlabelled Image • Micropollutant removal in MBR was influenced by their molecular properties. • PAC addition favoured the growth of more than 20 genera in the PAC-MBR. • Diversity and richness of denitrifying bacteria particularly increased with PAC. • PAC addition was favourable for nitrifying and denitrifying functional genes. [ABSTRACT FROM AUTHOR]

In biological wastewater treatment systems, extracellular polymeric substances (EPS) are continuously excreted as a response to environmental changes and substrate conditions. It could severely affect the treatment efficacy such as membrane fouling, dewaterability and the formation of carcinogenic disinfection by-products (DBPs). The heterogeneous dissolved organic matter (DOM) with varying size and chemical nature constitute a primary proportion of EPS. In the last few decades, fluorescence spectroscopy has received increasing attention for characterizing these organic substances due to the attractive features of this low-cost spectroscopic approach, including easy sample handling, rapid, non-destructive and highly sensitive nature. In this review, we summarize the application of fluorescence spectroscopy for characterizing EPS and provide the potential implications for online monitoring of water quality along with its limitations. We also link the dynamics of fluorescent dissolved organic matter (FDOM) in EPS with operational and environmental changes in wastewater treatment systems as well as their associations with metal binding, membrane fouling, adsorption, toxicity, and dewaterability. The multiple modes of exploration of fluorescence spectra, such as synchronous spectra with or without coupling with two-dimensional correlation spectroscopy (2D-COS), excitation-emission matrix (EEM) deconvoluted fluorescence regional integration (FRI), and parallel factor analysis (PARAFAC) are also discussed. The potential fluorescence indicators to depict the composition and bulk characteristics of EPS are also of interest. Further studies are highly recommended to expand the application of fluorescence spectroscopy paired with appropriate supplementary techniques to fully unravel the underlying mechanisms associated with EPS. Unlabelled Image • Fate of fluorescence moieties in EPS of WWTPs is elucidated. • Modes of fluorescence spectra: 2D-COS, EEM, and PARAFAC, are broadly discussed. • Membrane fouling and sludge properties are linked with the FDOM in EPS analyzed. • Intensity of protein– and humic–like fluorescence indicates sludge properties. • On-line fluorescence sensors are urgently needed for wide scale applications. [ABSTRACT FROM AUTHOR]