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Antibiotic resistance genes (ARGs) have been regarded as an emerging pollutant in municipal wastewater treatment plant (WWTP) effluents due to their potential risk to human health and ecological safety when reused for landscape and irrigation. Conventional wastewater treatment processes generally fail to effectively reduce ARGs, especially extracellular ARGs (eARGs), which are persistent in the environment and play an important role in horizontal gene transfer via transformation. Herein, an integrated process of pre-coagulation and microfiltration was developed for removal of ARGs, especially eARGs, from wastewater effluent. Results show that the integrated process could effectively reduce the absolute abundances of total ARGs (tARGs) (>2.9 logs) and eARGs (>5.2 logs) from the effluent. The excellent performance could be mainly attributed to the capture of antibiotic resistant bacteria (ARB) and eARGs by pre-coagulation and co-rejection during subsequent microfiltration. Moreover, the integrated process exhibited a good performance on removing common pollutants (e.g., dissolved organic carbon and phosphate) from the effluent to improve water quality. Besides, the integrated process also greatly reduced membrane fouling compared with microfiltration. These findings suggest that the integrated process of pre-coagulation and microfiltration is a promising advanced wastewater treatment technology for ARGs (especially eARGs) removal from WWTP effluents to ensure water reuse security. Image 1 • Integrated pre-coagulation and microfiltration effectively reduced tARGs and eARGs. • Capture of ARB and eARGs by Fe-coagulated flocs enhanced ARGs removal. • Pre-coagulation effectively mitigated membrane fouling. [ABSTRACT FROM AUTHOR]

Discarded face masks from the global COVID-19 pandemic have contributed significantly to plastic pollution in surface water, whereas their potential as a reservoir for aquatic pollutants is not well understood. Herein, we conducted a field experiment along a human-impacted urban river, investigating the variations of antibiotic resistance genes (ARGs), pathogens, and water-borne contaminants in commonly-used face masks. Results showed that high-biomass biofilms formed on face masks selectively enriched more ARGs than stone biofilm (0.08–0.22 vs 0.07–0.15 copies/16 S rRNA gene copies) from bulk water, which mainly due to unique microbial communities, enhanced horizontal gene transfer, and selective pressure of accumulated contaminants based on redundancy analysis and variation partitioning analysis. Several human opportunistic pathogens (e.g., Acinetobacter , Escherichia - Shigella , Bacillus , and Klebsiella), which are considered potential ARG carriers, were also greatly concentrated in face-mask biofilms, imposing a potential threat to aquatic ecological environment and human health. Moreover, wastewater treatment plant effluents, as an important source of pollutants to urban rivers, further aggravated the abundances of ARGs and opportunistic pathogens in face-mask biofilms. Our findings demonstrated that discarded face masks provide a hotspot for the proliferation and spread of ARGs and pathogens in urban water, highlighting the urgent requirement for implementing stricter regulations in face mask disposal. [Display omitted] • High-biomass biofilms were formed on discarded face masks in urban river. • Distinctive microbial community structure was detected in face-mask biofilm. • Face-mask biofilm simultaneously enriched ARGs and opportunistic pathogens. • Multiple drivers for enhanced antibiotic resistomes in face-mask biofilm were proposed. • WWTP effluents exacerbated the accumulation of pollutants in face-mask biofilm. [ABSTRACT FROM AUTHOR]

Anaerobic biological treatment technologies are one of the major hotspots of antibiotic resistance genes (ARGs). Previous studies have applied the electrochemical process to improve biogas production, however, it was challenged that high voltages might promote membrane permeability and reactive oxygen species overproduction to promote ARGs proliferation. Herein, the biogas production and ARGs proliferation in an anaerobic electrochemical membrane bioreactor (AnEMBR) were investigated at the gradient voltages of 0–0.9 V. Results show the reactor performances (average CH 4 production and current generation) were distinctly improved with the increase of applied voltage, and reached the optimum at 0.9 V. However, long-term application (>30 day) of 0.9 V deteriorated the reactor performances. Meanwhile, the relative abundances of most target ARGs in the supernatant and effluent of AnEMBR at 0.9 V increased by 0.68–1.55 and 0.42–1.26 logs compared to those before applying voltage, respectively. After disconnecting the circuit, these ARGs abundances all decreased to the original level. Significant correlations between intlI and ARGs (e.g., tetA , tetQ , sulI , and sulII) were observed, indicating horizontal gene transfer may contribute to the increased ARGs. Moreover, the shift of microbial communities caused by the applied voltage enriched potential ARGs-hosts (e.g., Tolumonas), contributing to the proliferation of ARGs. [Display omitted] • Introducing low voltage greatly improved the biogas production in AnEMBR. • Long-term application of high voltage (0.9 V) deteriorated AnEMBR performance. • Applying voltage shifted the microbial community in AnEMBR. • High voltage application increased ARGs abundances in AnEMBR. • Horizontal gene transfer and microbial community shift led to ARG proliferation. [ABSTRACT FROM AUTHOR]

Antibiotic resistance has been regarded as a global concern and biological wastewater treatment plants (WWTPs) are ideal hotbeds for the emergence and propagation of antibiotic resistance genes (ARGs). Extracellular polymeric substances (EPS), one of the primary components of activated sludge, might affect the distribution of extracellular ARGs in supernatant and EPS matrix, and thus alter their uptake potential by microbial cells. Herein, the presence and significance of EPS-associated ARGs in activated sludge from four WWTPs were assessed. Seven typical ARGs (sulI , sulII , bla TEM-1 , tetA , tetO , tetQ , tetW) and class I integron (intI1) in EPS-associated, cell-free, and intracellular DNA were quantified. Results show that the absolute abundances of EPS-associated, cell-free, and intracellular ARGs were 5.90 × 106–6.45 × 109, 5.53 × 104–4.58 × 106, and 2.68 × 108–1.79 × 1011 copies/g-volatile suspended solids, respectively. The absolute abundances of EPS-associated ARGs were 0.2–4.6 orders of magnitude higher than those of the corresponding cell-free ARGs. Considering the higher DNA contents in EPS, the transformation abilities of EPS-associated ARGs were 3.3–236.3 folds higher than those of cell-free ARGs. Therefore, EPS-associated ARGs are an important source of extracellular ARGs, and it may play a crucial role in horizontal gene transfer via transformation in WWTPs. ga1 • Presence and significance of EPS-associated ARGs in activated sludge were assessed. • EPS-associated ARG absolute abundances were 0.2–4.6 logs higher than cell-free ARGs. • EPS-associated ARGs had higher transformation potential than cell-free ARGs. • EPS-associated ARGs are an important source of extracellular ARGs. [ABSTRACT FROM AUTHOR]