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It is becoming clear that the wastewater treatment plants (WWTPs) is a key repository for antibiotic resistance genes (ARGs), and WWTPs also represent an important node for limiting ARGs spreading via altering the magnitude and distribution of ARGs in environment. This review provides an overview of the ARGs degradation performance both in sewage sludge and wastewater in WWTPs. The ARGs reduction behaviors during sludge treatment processes including anaerobic digestion (AD), composting, aerobic digestion, bio-drying and air-drying were reviewed, and parameters affecting ARGs reducing efficiency and the probable mechanisms were concluded. In particular, pretreatment approaches such as microwave, thermal hydrolysis and ozone before sludge AD are found to provide the extra benefits for ARGs removal. Additionally, ARGs fates and reduction mechanisms during sewage biological treatments such as anaerobic, aerobic, anaerobic combined with aerobic process and physical-chemical treatment including coagulation, advanced oxidation and disinfection processes were appraised. Furthermore, problems or doubts of previous study are proposed, and some in-depth mechanism researches are anticipated to elucidate the ARGs decay in sewage and sludge treatment process. This can help further enhance the ARGs removal efficiency in WWTPs. [ABSTRACT FROM AUTHOR]

Wastewater treatment systems are considered as hotspots for release of antibiotic resistance genes (ARGs) into the environment. Anaerobic-aerobic sequential (AAS) bioreactors now are intensively used for wastewater treatment worldwide. However, the occurrence of ARGs in wastewater treatment systems exposed to low-level (i.e., sub-inhibitory) antibiotic is poorly known. Here, we studied the distribution patterns of seven tetracycline resistance genes ( tet genes) including tet (A), tet (C), tet (G), tet (X), tet (M), tet (O), and tet (W), as well as one mobile element [class 1 integron ( intI1 )] in AAS bioreactors under exposure to tetracycline from 50 μg/L to 500 μg/L. Additionally, effect on the removal performance of nutrients and tetracycline in both anaerobic and aerobic units was also investigated. A tetracycline concentration gradient selected for bacterial resistance in the anaerobic reactor, with the exception of tet (A) and tet (W), and the tetracycline removal deteriorated by 47%. However, the abundance of tet and intI1 genes reduced in the subsequent aerobic unit, and the removal of tetracycline, soluble COD, and NH 4 + -N maintained at average efficiencies of 91%, 90%, and 93%, respectively. The level of tet (X) was largely unaffected by AAS treatment. It is notable that intI1 genes probably played a crucial role on the horizontal dissemination of tet genes. The tetracycline levels and intI1 genes appear to be the primary factors influencing the occurrence of tet genes in AAS bioreactors. Nonetheless, AAS treatments still show promise for reducing antibiotics, ARGs and mobile elements without affecting nutrient removal, and need further research for practical applications. [ABSTRACT FROM AUTHOR]

Activated sludge system is an important process of domestic and industrial wastewater treatment containing highly diverse microbial communities. In this study, high-throughput sequencing was applied to examine the microbial community composition and diversity of activated sludge samples from four full-scale municipal wastewater treatment plants (WWTPs) in Shanghai. A relationship between microbial communities and environmental variables was examined. Proteobacteria was the most dominant phylogenetic group, followed by Bacteroidetes and Firmicutes. A total of 166 genera were commonly shared by all seven sludge samples, including Zoogloea, Dechloromonas, Thauera, Nitrospira, Arcobacter, etc. Besides these shared populations, certain unique bacterial populations were found abundant in individual sludge sample. Canonical correspondence analysis (CCA) indicated that influent COD and pH had the greatest influence on microbial community compositions, whereas dissolved oxygen (DO) exhibited the least influence. The operating process was likely to foster diversity of the microbial communities inhabiting the wastewater treatment facilities. Alternative operation methods including a fluctuation of anoxic, oxic, and anaerobic conditions were favorable for promoting the growth of diverse microbial populations in activated sludge systems. [ABSTRACT FROM AUTHOR]

Antibiotic resistance is a global challenge and represents a growing threat on human health worldwide. Wastewater treatment plants (WWTPs) are generally considered as hotspots for control and/or dissemination of antibiotic resistance. The role of antibiotics, antibacterial residues, and heavy metals played on the evolution and spread of antibiotic resistance is still not well understood. Here, the occurrence of antibiotics (i.e., macrolides, tetracyclines, sulfonamides, and quinolones), antibacterial residues (i.e., triclosan), as well as heavy metals (i.e., cadmium, chromium, copper, zinc, lead, and nickel) in urban wastewater was investigated. Also, the abundances of erythromycin resistance genes (ERY-ARGs) including ere(A), ere(B), mef(A)/ mef(E), erm(A), erm(B), erm(C), and msr(A)/ msr(B) genes were screened. A relationship between certain antibiotics, antibacterial residues, and heavy metals and ERY-ARGs was demonstrated. ERY presented significant correlations (0.883 < r < 0.929, P < 0.05) with ere(A), ere(B), and mef(A)/ mef(E) genes, while tetracycline exhibited a significant correlation ( r = 0.829, P < 0.05) with erm(B) genes. It is noteworthy that triclosan correlated significantly (0.859 < r < 0.956, P < 0.05) with ere(A), ere(B), mef(A)/ mef(E), and erm(B) genes. In addition, significantly positive correlations (0.823 < r < 0.871, P < 0.05) were observed between zinc and lead and certain ERY-ARGs (i.e., ere(B), mef(A)/ mef(E), erm(B), etc.). Further investigations should be involved to elucidate the co-selection and/or cross-selection mechanisms due to co-existence of these selective factors in urban wastewater. [ABSTRACT FROM AUTHOR]

Abstract: Occurrence and removal efficiencies of fifteen pharmaceuticals were investigated in a conventional municipal wastewater treatment plant in Michigan. Concentrations of these pharmaceuticals were determined in both wastewater and sludge phases by a high-performance liquid chromatograph coupled to a tandem mass spectrometer. Detailed mass balance analysis was conducted during the whole treatment process to evaluate the contributing processes for pharmaceutical removal. Among the pharmaceuticals studied, demeclocycline, sulfamerazine, erythromycin and tylosin were not detected in the wastewater treatment plant influent. Other target pharmaceuticals detected in wastewater were also found in the corresponding sludge phase. The removal efficiencies of chlortetracycline, tetracycline, sulfamerazine, acetaminophen and caffeine were >99%, while doxycycline, oxytetracycline, sulfadiazine and lincomycin exhibited relatively lower removal efficiencies (e.g., <50%). For sulfamethoxazole, the removal efficiency was approximately 90%. Carbamazepine manifested a net increase of mass, i.e. 41% more than the input from the influent. Based on the mass balance analysis, biotransformation is believed to be the predominant process responsible for the removal of pharmaceuticals (22% to 99%), whereas contribution of sorption to sludge was relatively insignificant (7%) for the investigated pharmaceuticals. [Copyright &y& Elsevier]

• Photocatalytic membrane was prepared with aCN and PDA in a facile way. • The membrane coupled the effect of filtration and photocatalysis. • The membrane exhibited excellent removal ratio for dye and antibiotic. • The removal mechanism of the membrane was investigated. Graphite carbon nitride (gCN) has attracted extensive attention due to excellent 2D structure and photocatalytic performance since it was discovered. In this work, the novel membrane was fabricated with acidified graphite carbon nitrogen (aCN) as a selective layer and dopamine (DA) as a cushion layer on a polysulfone (PS) membrane. The removal effect of aCN membrane on methyl blue and ciprofloxacin has improved with the excellent photocatalytic property of aCN. Meanwhile, SEM, XRD, FTIR spectra and DLS was performed to investigate the morphology, structure and property of the obtained membranes. The results showed that dopamine not only provided adhesion for aCN, but also enhanced photoelectron transfer. The membrane with optimized conditions aided by the structure and photocatalytic performance of aCN exhibited great removal rates for both methyl blue (97.2%) and ciprofloxacin (99.4%). The above experiments proved the advantages of aCN in the removal of dyes and antibiotics in coupling filtration and photocatalysis. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cr, Cu, Zn and Cd could be removed simultaneously by nZVI@SBC. • NO 3 – and HA promote the removal of Cr, Cu, Zn and Cd. • Cr and Cu were reduced by nZVI and then removed through co-precipitation. • The removal of Cd and Zn were driven by alkali precipitation and complexation. Cr, Cu, Zn, and Cd commonly coexisted in the electroplating wastewater with high salinity and organics, while their removal was often investigated individually. In this study, the simultaneous removal of Cr, Cu, Zn, and Cd was investigated by nano zero-valent iron modified sludge biochar (nZVI@SBC). The results showed that nZVI@SBC could significantly improve the removal efficiency of the four heavy metals (HMs) in high salinity wastewater. NO 3 – (N-NO 3 –) and humic acid (HA) could promote the removal of Cr, Cu, Zn, and Cd, and PO 4 3- (P-PO 4 3-) could enhance the removal of Cd. EPR analysis demonstrated the generation of 1O 2 in different water matrices. The 1O 2 intensity increased in the presence of NO 3 – and HA, which indicated the acceleration of the nZVI corrosion and the promoted electron transfer in the system. To further understand the reaction mechanism, the variation of nZVI@SBC structures and compositions during the treatment process were characterized by SEM-EDS, XRD, BET, and XPS. Cr and Cu were removed through adsorption and co-precipitation after reduction by nZVI, while Cd and Zn were removed by alkali precipitation and complexation. This work improves the understanding of simultaneous removal of HMs by nZVI@SBC and provides a cost-effective approach for the electroplating wastewater treatment. [ABSTRACT FROM AUTHOR]

[Display omitted] • Recent advances on wastewater recovery of high value-added products are reviewed. • Optimized OLR, temperature, SRT, and COD/N enhance alginate-like polymer recovery. • P can be recovered as struvite by regulating ratios of Mg, N, and P, and pH value. • Various streams can be used for polyhydroxyalkanoate recovery via factor adjustment. • Sulfated polysaccharides as new value-added products in wastewater merit attention. Wastewater resource recovery not only allows the extraction of value-added products and offsets the operational costs of wastewater treatment, but it is also conducive to alleviating adverse environmental issues due to energy and chemical inputs and associated emissions. A number of attractive compounds such as alginate-like polymers, struvite, polyhydroxyalkanoates, and sulfated polysaccharides, were found and successfully obtained from wastewater and have a wide range of application prospects. The aim of this work is to provide a comprehensive review of recent advances in recovery of these popular products from wastewater, and their physicochemical properties, main sources, and current recovery status are summarized. Various factors influencing the recovery performance of these materials are thoroughly discussed. Moreover, the research needs and future directions towards wastewater resource recovery are highlighted. This study can provide valuable insights for future research endeavors aiming to improve wastewater resource recovery through the retrieval of high value-added products. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • ZVI coupled with H 2 O 2 could remove aniline, Sb and Cr simultaneously. • Aniline was degraded by OH but Sb, Cr removal did not depend on Fenton. • Fe(0) corrosion promoted by H 2 O 2 and in-situ generated nano iron(hydr)oxides. • Nano iron(hydr)oxides had abundant adsorption and co-precipitation sites. • Sb and Cr was mainly removed as the states of Sb(III) and Cr(III). Abstract Aniline, antimony (Sb) and chromium (Cr) are typical and regulated co-contaminants in textile wastewater, but their removal was often investigated individually. In this work, simultaneous removal of aniline, Sb and Cr by ZVI coupled with H 2 O 2 was studied. With the dosage of 0.5 g L−1 ZVI and 2 mM H 2 O 2 , aniline, Sb and Cr can be removed completely at pH 3. Experiment with iso -propanol as the radical scavenger confirmed that OH derived from Fenton reaction accounts for aniline degradation, but not for Sb and Cr removal. H 2 O 2 accelerated Fe(0) corrosion and generated the nanoscale iron(hydro)oxides. Aniline was degraded by OH first and then the degradation products were removed by iron(hydro)oxides via adsorption and co-precipitation. Both Fe(0) and iron(hydro)oxides were responsible for Sb and Cr removal, yet iron(hydro)oxides were identified as the major contributor. X-ray photoelectron spectroscopy analysis demonstrated that Sb and Cr were removed mainly as the states of Sb(III) and Cr(III). The real textile wastewater investigation confirmed that ZVI coupled with H 2 O 2 can eliminate aniline, Sb and Cr effectively, which has important implications for the advanced treatment of textile wastewater. [ABSTRACT FROM AUTHOR]

Abstract: An iopromide (IOPr)-degrading bacterium was isolated from activated sludge of a wastewater treatment plant in Shanghai. Based on its morphology, physiological-biochemical characteristics and a phylogenetic analysis of its 16S rRNA sequence, the bacterium was identified and named as Pseudomonas sp. I-24. The optimum condition for degrading IOPr was at 30°C and pH 7.0. After 5days, strain I-24 could degrade 30mg/L IOPr by 99% in a basal salts medium with a 5% (V/V) inoculum and 200mg/L starch as the primary substrate. When applied to an Anaerobic-Anoxic/Aerobic (A2/O) process, with the coexistence of other bacteria, the strain I-24 got lower (61.3%) IOPr removal, but in two A2/O systems (with and without I-24 inoculation), the CODcr removal were both approximately 95%. The trial dosed with strain I-24 showed better IOPr removal than the un-dosed one. I-24 sustained its abundance in the A2/O system during the experiment. [Copyright &y& Elsevier]

Wastewater treatment plants (WWTPs) serve as an important source of microplastics into the environment, but the factors affecting the distribution of microplastics remain unknown. To address this knowledge gap, four WWTPs in Guilin City, Guangxi Province, China were selected to analyze the dynamic distribution of microplastics in each wastewater treatment stage, of which, one used A/O process and the other three used A/A/O process. Results showed that the microplastic content in the WWTP influent was 0.70–8.72 items/L, in which 41.2–47.1% were removed during the pretreatment stage. Compared with the influent, the microplastic content in the final effluent decreased by 89.2–93.6%, dropping to 0.07–0.78 items/L. Microplastics in the size range from 500 μm to 5 mm dominated in the influent of each WWTP, and the proportion was even higher in the effluent. Fiber, fragment, and film were the main microplastic types found in the influent, but fibers were predominated in the effluent. Fragments and films were mainly composed of polypropylene (PP) and polyethylene (PE), while fibers had a more diverse compositions including PP, polyethylene terephthalate (PET), and polyacrylonitrile (PAN). Microplastics were also widely present in the sludge, with an abundance of 234.7–6908.3 items/kg dry weight. Correlation analysis showed that the tertiary industry is the main contributor of microplastics to WWTPs in Guilin City, providing direction for the future prevention and control of microplastics. Image 1 • MPs in wastewater were reduced by 89.2–93.6% through treatment. • The removal rate of fiber was significantly lower than that of fragment and film. • Fibers could bypass and escape through WWTPs. • MPs may cause environmental risks in the process of sludge resource utilization. [ABSTRACT FROM AUTHOR]