Viral Communities Contribute More to the Lysis of Antibiotic-Resistant Bacteria than the Transduction of Antibiotic Resistance Genes in Anaerobic Digestion Revealed by Metagenomics.

Ecological role of the viral community on the fate of antibiotic resistance genes (ARGs) (reduction vs proliferation) remains unclear in anaerobic digestion (AD). Metagenomics revealed a dominance of Siphoviridae and Podoviridae among 13,895 identified viral operational taxonomic units (vOTUs) within AD, and only 21 of the vOTUs carried ARGs, which only accounted for 0.57 ± 0.43% of AD antibiotic resistome. Conversely, ARGs locating on plasmids and integrative and conjugative elements accounted for above 61.0%, indicating a substantial potential for conjugation in driving horizontal gene transfer of ARGs within AD. Virus-host prediction based on CRISPR spacer, tRNA, and homology matches indicated that most viruses (80.2%) could not infect across genera. Among 480 high-quality metagenome assembly genomes, 95 carried ARGs and were considered as putative antibiotic-resistant bacteria (pARB). Furthermore, lytic phages of 66 pARBs were identified and devoid of ARGs, and virus/host abundance ratios with an average value of 71.7 indicated extensive viral activity and lysis. The infectivity of lytic phage was also elucidated through laboratory experiments concerning changes of the phage-to-host ratio, pH, and temperature. Although metagenomic evidence for dissemination of ARGs by phage transduction was found, the higher proportion of lytic phages infecting pARBs suggested that the viral community played a greater role in reducing ARB numbers than spreading ARGs in AD.

Temporal variations in micropollutant inlet concentrations matter when planning the design and compliance assessment of stormwater control measures.

Stormwater Control Measures (SCMs) contribute to reducing micropollutant emissions from separate sewer systems. SCM planning and design are often performed by looking at the hydrological performance. Assessment of pollutant removal and the ability to comply with discharge concentration limits is often simplified due to a lack of data and limited monitoring resources. This study analyses the impact of using different time resolutions of input stormwater concentrations when assessing the compliance of SCMs against water quality standards. The behaviour of three indicator micropollutants (MP - Copper, Diuron, Benzo[a]pyrene) was assessed in four SCM archetypes, which were defined to represent typical SCM removal processes. High resolution MP data were extrapolated by using high resolution (2 min) measurements of TSS over a long period (343 events). The compliance assessment showed that high resolution input concentrations can result in a different level of compliance with water quality standards, especially when discharged concentrations are close to the limit values. This study underlines the importance of considering the high temporal variability of stormwater micropollutants when planning and designing SCMs to identify the most effective solutions for stormwater pollution management and to ensure a thorough consideration of all the environmental implications.

Effects and Mechanisms of Different Types of Biochar on Heavy Metal Passivation during Sludge Composting.

The effects and mechanisms of the different types of biochar on heavy metal passivation are still not fully understood. This study compared the effects of three types of biochar on heavy metal passivation during sludge composting. Compared with composting without biochar, rice husk biochar was most effective for the passivation of Zn and Pb, with increased passivation rates of 1.90% and 20.43%, respectively. In contrast, sludge biochar was the most effective for the passivation of Cr and Hg, with increased passivation rates of 28.30% and 3.09%, respectively. Coconut shell biochar showed the best performance for the passivation of Cu, Ni, As, and Cd, and was enriched with micropore structures, which possibly led to the adsorption and reaction of heavy metals, organic matter, and microorganisms. The improved passivation effect of the rice husk and sludge biochar on heavy metals can be attributed to the improved humification of organic matter. This study suggests that specific types of biochar should be considered for the passivation of different types of heavy metals for practical applications.

Sustainable wastewater treatment and reuse in space.

Exploring the vast extraterrestrial space is an inevitable trend with continuous human development. Water treatment and reuse are crucial in the limited and closed space that is available in spaceships or long-term use space bases that will be established in the foreseeable future. Dedicated water treatment technologies have experienced iterative development for more than 60 years since the first manned spaceflight was successfully launched. Herein, we briefly review the related wastewater characteristics and the history of water treatment in space stations, and we focus on future challenges and perspectives, aiming at providing insights for optimizing wastewater treatment technologies and closing the water cycle in future.

Changes of composition and antibiotic resistance of fecal coliform bacteria in municipal wastewater treatment plant.

The dynamics of the composition and antibiotic resistance of the fecal coliform bacteria (FCB) in a typical wastewater treatment plant (WWTP) were investigated concerning the seasonal changes. Results showed that WWTP could remove the FCB concentration by 3∼5 logs within the effluent of 104∼105 CFU/L, but the antibiotic resistant rate of FCB species increased significantly after WWTP. The dominant FCB changed from Escherichia coli in the influent (∼73.0%) to Klebsiella pneumoniae in the effluent (∼53.3%) after WWTP, where the Escherichia coli was removed the most, while Klebsiella pneumoniae was the most persistent. The secondary tank removed the most of FCB (by 3∼4 logs) compared to other processes, but increased all the concerned antibiotic resistant rate. The potential super bugs of FCB community showing resistance to all the target antibiotics were selected in the biological treatment unit of WWTP. The FCB showed the highest multiple antibiotic resistance (92.9%) in total which even increased to 100% in the effluent. Klebsiella has the highest antibiotic resistant rate in FCB, with a multiple antibiotic resistance rate of 98.4%. These indicated that the Klebsiella pneumoniae not just Escherichia coli should be specially emphasized after WWTP concerning the health risk associated with FCB community.

Chemical characteristics and water stability evaluation of groundwater in the CKDu Zone of Sri Lanka.

Groundwater is the main source of drinking water for the rural population in the chronic kidney disease of unknown etiology (CKDu) zone of the North Central Province (NCP) in Sri Lanka. In this study, a total of 334 groundwater samples (311 dug wells, 21 tube wells and 2 springs) during the wet season from two aquifers in the NCP were collected, and investigated their chemical characteristics and evaluate their water quality, including groundwater chemistry, main ion sources, the corrosion and scaling potential of groundwater. The results showed that the two hydrochemical types of groundwater in the NCP were mainly of the Ca-HCO3, Na·Ca-HCO3 types, with the main HCO3-, Na+ and Ca2+ ions in both types of groundwater originating from silicate and evaporite salt dissolution and influenced by alternating cation adsorption, while the presence of NO3- was mainly anthropogenic. Evaluation of water stability using namely Langelier saturation index (LSI), Ryznar stability index (RSI), Puckorius scaling index (PSI) and Larson-Skold index (LS), indicated that most groundwater presents corrosion potential and has corrosion behavior tendency of metals to some degrees. The water quality of Polonnaruwa was better than that of Anuradhapura in the NCP, and when the groundwater was worse than the "good" grade, which must be properly treated before it is used as drinking water.

Rational Construction of Protein-Mimetic Nano-Switch Systems Based on Secondary Structure Transitions of Synthetic Polypeptides.

The manipulation of the flexibility/rigidity of polymeric chains to control their function is commonly observed in natural macromolecules but largely unexplored in synthetic systems. Herein, we construct a series of protein-mimetic nano-switches consisting of a gold nanoparticle (GNP) core, a synthetic polypeptide linker, and an optically functional molecule (OFM), whose biological function can be dynamically regulated by the flexibility of the polypeptide linker. At the dormant state, the polypeptide adopts a flexible, random-coiled conformation, bringing GNP and OFM in close proximity that leads to the "turn-off" of the OFM. Once treated with alkaline phosphatase (ALP), the nano-switches are activated due to the increased separation distance between GNP and OFM driven by the coil-to-helix and flexible-to-rigid transition of the polypeptide linker. The nano-switches therefore enable selective fluorescence imaging or photodynamic therapy in response to ALP overproduced by tumor cells. The control over polymer flexibility represents an effective strategy to manipulate the optical activity of nano-switches, which mimics the delicate structure-property relationship of natural proteins.

Swine-manure composts induce the enrichment of antibiotic-resistant bacteria but not antibiotic resistance genes in soils.

Composting is a common and effective strategy for reducing antibiotic resistance genes (ARGs) and antibiotic-resistant bacteria (ARB) from animal manure. However, it is unclear whether the advantages of composting for the control of ARGs and ARB can be further increased in land application. This study investigated the fate of ARB and ARGs after land application of swine-manure composts (SMCs) to three different soil types (red soil, loess and black soil). The results showed that although the SMCs caused an increase in the abundance of total ARGs in the soil in the short period, they significantly reduced (p < 0.01) the abundance of total ARGs after 82 days compared to the control. The decay rate of ARGs reflected by the half-life times (t1/2) varied by soil type, with red soil being the longest. The SMCs mainly introduced ermF, tetG and tetX into the soils, while these ARGs quickly declined to the control level. Notably, SMCs increased the number of ARB in the soils, especially for cefotaxime-resistant bacteria. Although SMCs only affected the microbiome significantly during the early stage (p < 0.05), it took a much longer time for the microbiome to recover compared to the control. Statistical analysis indicated that changes in the microbial community contributed more to the fate of ARGs during SMCs land application than other factors. Overall, it is proposed that the advantages of ARGs control in the composting process for swine manure can be further increased in land application, but it can still bring some risks in regard to ARB.

Response of prokaryotic, eukaryotic and algal communities to heavy rainfall in a reservoir supplied with reclaimed water.

The global climate change made the heavy rainfall happen more frequently, and the non-point source pollution caused by it would exacerbate the risk to the water ecological environment. In this study, we took a reservoir (Shahe reservoir, Beijing, China) supplied with reclaimed water as an exapmle to investigate how spatiotemporal changes in the quantity and diversity of prokaryotic, eukaryotic, and algal communities respond to heavy rainfall. Results showed that heavy rainfall could directly impact the composition of the prokaryotic community by introducing amounts of runoff closely associated bacterium especially for the human potential pathogens such as Aliarcobacter, Aeromonas and Pseudomonas in the Shahe reservoir area. While the eukaryotic community was rather stable, and the development and changes in algal communities occurred in the last few days after heavy rainfall. The microbial source tracking through FEAST indicated that Nansha river (S) was the major contributor to the development of all the three concerned communities in the reservoir. The co-occurrence analysis showed that the modules with the highest cumulative abundance in each community were all strongly and positively connected with Chl-a, pH, turbidity, COD and TOC, but negatively correlated with NO3-N (p < 0.01). The network analysis showed that the eukaryotes played a key role in the interaction network among the three communities, and were more likely to interact with algae and prokaryotes. It was suggested that the controlling of human potential pathogens associated with prokaryotic community should be emphasized at the beginning of the heavy rainfall, but the prevention of the eutrophication bloom should be another focus after the heavy rainfall. This study provided valuable information concerning the role of heavy rainfall on the water ecological environment from the perspective of microbial community.

Fluorescence characteristics and source analysis of DOM in groundwater during the wet season in the CKDu zone of North Central Province, Sri Lanka.

The dissolved organic matter (DOM) should be purified for safe drinking water due to disinfection by-products (DBPs) produced by disinfectants reaction with DOM. Current research on groundwater in the chronic kidney disease with unknown etiology (CKDu) zone of the North Central Province (NCP) in Sri Lanka has focused mainly on aquatic chemistry, with limited attention paid to the spatial distribution, compositional sources and factors of DOM. Therefore, the structure, composition, source and spatial distribution of the DOM of two kinds of groundwater samples collected from dug well and tube well in the NCP during the wet season were determined, compared and analyzed by analytical tools such as parallel factor analysis (PARAFAC). Results show that the average concentrations of TOC in these two groundwater samples are generally higher than 5.0 mg/L, and the concentration of TOC in the groundwater of the shallow weathered aquifer is higher than that of the deep hard rock aquifer, while its distribution of the two aquifers are on contrary. The DOM in the dug well has three types and four components, including humus-like component C1 (33.36%) and C2 (38.60%), protein-like component C3 (13.09%) and heterogeneous organic component C4 (14.95%). In the tube well, two types and two components of the DOM are determined, including humus-like component CⅠ (69.80%) widely existing in natural water and soluble microbial by-product CⅡ (30.20%) produced by microbial community activities. In the dug well, DOM is mainly exogenous input, the higher ion concentration in water affected the fluorescence intensity of humus and protein components. And in the tube well, DOM has obvious endogenous characteristics, and higher pH value may inhibit the production of protein like fluorescent substances to a certain extent.

Effect of rainfall characteristics on the sewer sediment, hydrograph, and pollutant discharge of combined sewer overflow.

Significant management needs raised in urban sewer system to facilitate urban resilience to rainstorm. The work investigated the effects of temporal evolution of rainfall on hydrograph and pollutant discharge of CSO over an intensive observation period of 12 months, with special attention to differences in temporal scale for supporting management decision making. The characteristics of rainfall in different temporal scales helped overflow-risk identification and assessment. Prolonged dry seasons over 112 days in the CSO monitored year 2018 increased the sediment buildup in the pipes. The built sediment was mostly flushed out to overflow (and the treatment facility) by initial rainfall during 47 h. Following CSO hydraulics and pollutant discharge follows initial peak patterns which responded to rainfall patterns. Results of Redundancy analysis and network analysis showed that the combined effects of rainfall, urbanization, and sediments as "CSO troika" are the driving forces for CSO pollutants in the long-term. The improved characterization of CSO events and the associated pollutants has refined our understanding of how overflow hydrograph and pollutant discharge responds to rainfall temporally, which methodology supported decision making in the combining source/process control with terminal management for facilizing urban resilience.

Water environment protection and sustainable development in townlet of China: A case study in Taicang.

The Environmental Kuznets Curve (EKC) model was applied to investigate the relationship between economic growth and water environment quality based on panel data of Taicang during 2010-2017. The typical inversed-U shaped relationship has been obtained between GDP (gross domestic product) and indicators of ammonia, total nitrogen (TN) and total phosphorus (TP), respectively. The EKC turning point appeared when the GDP per capita was around US$2270, which was much lower than those in some developed countries (US$11,200). However, the decoupling between chemical oxygen demand (COD) and GDP per capita occurred even before this period, which should be attributed to the strict COD emission regulation being implemented since 2010. Further, analysis based on the Tapio decoupling coefficient elasticity model analyzed the ammonia nitrogen and economic development of each industry. We found that the agriculture no-point was strong decoupling in 2011-2014, then came to Recessive decoupling. The domestic wastewater had been in a strong decoupling state; Both urban non-point and industry experienced expansive negative decoupling, due to strict policy that prioritizes the environment over development and the investment in improvement of environment and techniques, both of them gradually came to strong decoupling. The result demonstrated that the EKC turning point could be appear in earlier economic stage and the decoupling coefficient elasticity could be improved through taking strong regulation measures.

Optimized pre-treatment of high strength food waste digestate by high content aluminum-nanocluster based magnetic coagulation.

Coagulation-based pre-treatment efficiency of high strength digestate of food waste (HSDFW) anaerobic digestion is negated by organic ligand-catalyzed decomposition of coagulants. In this study, an efficient HSDFW pre-treatment method, magnetic seeds (MS) coagulation, was employed by using highly stable Keggin Al30 nanocluster (PAC30), MS and polyacrylamide (PAM), and its operation was optimized by evaluating the performance of removing turbidity, total suspended solids (TSS), chemical oxygen demand (COD), and total phosphorous (TP) phosphate. Results showed that at the optimum dosage of 4.82 g/L, PAC30 demonstrated excellent removals as high as 98.93% ± 0.1% of turbidity, 98.04% ± 0.1% of TSS, 58.28% ± 0.3% of total COD, 99.98% ± 0.01% of TP and 99.50% ± 0.01% of dissolved phosphate, respectively. Apparent molecular weight (AMW) and three-dimensional excitation-emission matrix (3D-EEM) fluorescence spectroscopy analyses demonstrated more efficient removal of dissolved organic matter (DOM), particularly non-biodegradable and hydrophobic components by PAC30 than commercial coagulant. The sedimentation was much improved from 40 min by coagulation/flocculation to about 5 min settling by MS coagulation. The PAC30 based magnetic coagulation (MC) presents theoretical guidance on a cost-effective and much less footprint pre-treatment alternative for high strength wastewater.

Ca2+ and SO42- interactions with dissolved organic matter: Implications of groundwater quality for CKDu incidence in Sri Lanka.

It has recently been proposed that recalcitrant dissolved organic carbon (DOC) in groundwater plays a potent etiological role in the peculiar distribution of chronic kidney disease of unknown etiology (CKDu). This study aims to elucidate the interactions of Ca2+ and SO42- with a model organic fraction of humic acid (SHA) to determine the possible relationship of CKDu incidence with the DOC in drinking water. XPS and FT-IR methods respectively determined the surface functional groups and chemical composition of protonated dissolved organic carbon (HDOC) in a CKDu high-risk zone (HR) of Sri Lanka and in SHA. Higher surface C composition (87.9%) and lower O (11.4%) were observed for HDOC from the HR region than for SHA (C: 73.8%, O: 24.7%). Aromatic C with less O-containing functional groups was observed in HDOC. The IR band at 1170 cm-1 confirms the formation of organic sulfonate (C-SO3-) on SHA. A band at 1213 cm-1 due to organic sulfonate in HDOC from the CKDu HR region was also identified. The IR band at 866 cm-1 evidenced the formation of CaCO3 on SHA above pH 7.4. XPS data confirmed the presence of sulfur oxidation states corresponding to SO32- and SO42- at 168.9 eV and 170.1 eV binding energies, respectively. The binding energies at 347 eV and 351 eV for Ca 2p3/2 and Ca 2p1/2 eV, respectively, confirmed the bidentate complexation of Ca2+ with COO- and sulfonate groups on SHA. The organic sulfonate formed is postulated as a uremic toxicant.

Hypoxia-Induced Pro-Protein Therapy Assisted by a Self-Catalyzed Nanozymogen.

The success of intracellular protein therapy demands efficient delivery and selective protein activity in diseased cells. Therefore, a cascaded nanozymogen consisting of a hypoxia-activatable pro-protein, a hypoxia-inducing protein, and a hypoxia-strengthened intracellular protein delivery nanovehicle was developed. RPAB, an enzymatically inactive pro-protein of RNase, reversibly caged with hypoxia-cleavable azobenzene, was delivered with glucose oxidase (GOx) using hypoxia-responsive nanocomplexes (NCs) consisting of azobenzene-cross-linked oligoethylenimine (AOEI) and hyaluronic acid (HA). Upon NC-mediated delivery into cancer cells, GOx catalyzed glucose decomposition and aggravated tumoral hypoxia, which drove the recovery of RPAB back to the hydrolytically active RNase and expedited the degradation of AOEI to release more protein cargoes. Thus, the catalytic reaction of the nanozymogen was self-accelerated and self-cycled, ultimately leading to a cooperative anti-cancer effect between GOx-mediated starvation therapy and RNase-mediated pro-apoptotic therapy.

Effects of chlortetracycline, Cu and their combination on the performance and microbial community dynamics in swine manure anaerobic digestion.

Swine manure was typical for the combined pollution of heavy metals and antibiotics. The effects of widely used veterinary antibiotic chlortetracycline (CTC), Cu and their combination on swine manure anaerobic digestion performance and microbial community have never been investigated. Thus, four 2L anaerobic digestion reactors were established including reactor A (control), B (CTC spiked by 0.5g/kg dry weight, dw), C (Cu spiked by 5g/kg dw) and D (combination of CTC, 0.5g/kg dw, and Cu, 5g/kg dw), and dynamics of bacterial and archaeal community structure was investigated using high throughput sequencing method. Results showed that addition of CTC and Cu separately could increase the total biogas production by 21.6% and 15.8%, respectively, while combination of CTC and Cu severely inhibited anaerobic digestion (by 30.3%). Furthermore, corresponding to different stages and reactors, four kinds of microbes including bacteria and archaea were described in detail, and the effects of CTC, Cu and their combination mainly occurred at hydrolysis and acidification phases. The addition of Cu alone changed the dynamics of archaeal community significantly. It was genus Methanomassiliicoccus that dominated at the active methane production for A, B and D, while it was genus Methanobrevibacter and Methanoculleus for C.

Who contributes more to N2O emission during sludge bio-drying with two different aeration strategies, nitrifiers or denitrifiers?

Global warming effects have drawn more and more attention to studying all sources and sinks of nitrous oxide (N2O). Sludge bio-drying, as an effective sludge treatment technology, is being adopted worldwide. In this study, two aeration strategies (piles I and II) were compared to investigate the primary contributors to N2O emission during sludge bio-drying through studying the evolution of functional genes involved in nitrification (amoA, hao, and nxrA) and denitrification (narG, nirS, nirK, norB, and nosZ) by quantitative PCR (qPCR). Results showed that the profile of N2O emission can be divided into three stages, traditional denitrification contributed largely to N2O emission at stage I (days 1-5), but N2O emission mainly happened at stage II (days 5-14) due to nitrifier denitrification and NH2OH accumulation by ammonia-oxidizing bacteria (AOB), accounting for 51.4% and 58.2% of total N2O emission for piles I and II, respectively. At stage III (days 14-21), nitrifier denitrification was inhibited because sludge bio-drying proceeded mainly by the physical aeration, thus N2O emission decreased and changed little. The improved aeration strategy availed pile I to reduce N2O emission much especially at stages II and III, respectively. These results indicated that nitrifier denitrification by AOB and biological NH2OH oxidation due to AOB made more contribution to N2O emission, and aeration strategy was crucial to mitigate N2O emission during sludge bio-drying.

Multiple effects of trace elements on methanogenesis in a two-phase anaerobic membrane bioreactor treating starch wastewater.

For enhancing anaerobic membrane bioreactor (AnMBR) treating food processing wastewater due to speed-limited methanogenesis step, multiple effects of trace element (TE) supplementation on methanogenesis of a two-phase AnMBR were firstly investigated in batch tests. TE supplementation included individual element, combination and recovery of Fe, Ni, Co, Cu and Zn supplementation. Multiple effects of TE supplementation were highest stimulated by 22.4 ± 5.6 % (TE313) for chemical oxygen demand (COD) removal, 43.1 ± 12.5 % (TE303) for specific methanogenic activity (SMA) and 13.9 ± 3.7 % (TE405) for biomass growth, respectively, although only 7.5 ± 0.6 % (TE106) for methane production. Dosage of TEs played a critical role in methane production, COD removal and biomass growth of the AnMBR's methanogenesis. Low dosages of TE supplementation improved the COD removal and slightly stimulated the COD bioconverting to methane and biomass, but their specific methanation activities were inhibited in the initial rapid methanogenesis stage. Several methanation functional species were increased in abundance like Methanosarcina and Methanoculleus.

The color removal and fate of organic pollutants in a pilot-scale MBR-NF combined process treating textile wastewater with high water recovery.

A combination of membrane bioreactor (MBR) and nanofiltration (NF) was tested at pilot-scale treating textile wastewater from the wastewater treatment station of a textile mill in Wuqing District of Tianjin (China). The MBR-NF process showed a much better treatment efficiency on the removal of the chemical oxygen demand, total organic carbon, color and turbidity in comparison with the conventional processes. The water recovery rate was enhanced to over 90% through the recycling of NF concentrate to the MBR, while the MBR-NF showed a stable permeate water quality that met with standards and could be directly discharged or further reused. The recycled NF concentrate caused an accumulation of refractory compounds in the MBR, which significantly influenced the treatment efficiency of the MBR. However, the sludge characteristics showed that the activated sludge activity was not obviously inhibited. The results of fluorescence spectra and molecular weight distribution indicated that those recalcitrant pollutants were mostly protein-like substances and a small amount of humic acid-like substances (650-6,000 Da), which contributed to membrane fouling of NF. Although the penetrated protein-like substances caused the residual color in NF permeate, the MBR-NF process was suitable for the advanced treatment and reclamation of textile wastewater under high water yield.

Comparison of NF membrane fouling and cleaning by two pretreatment strategies for the advanced treatment of antibiotic production wastewater.

The nanofiltration (NF) membrane fouling characteristics and cleaning strategies were investigated and compared for treating membrane bioreactor (MBR) effluent and MBR-granular activated carbon (GAC) effluent of an antibiotic production wastewater by DK membrane. Results showed that the fouling of treating MBR effluent was more severe than that of treating MBR-GAC effluent. After filtering for 216 h, the difference of membrane flux decline was obvious between MBR effluent and MBR-GAC effluent, with 14.9% and 10.3% flux decline, respectively. Further study showed that organic fouling is the main NF membrane fouling in the advanced treatment of antibiotic production wastewater for both of the two different effluents. Soluble microbial by-product like and tyrosine-like substances were the dominant components in the foulants, whereas humic-like substances existing in the effluents had little contribution to the NF membrane fouling. A satisfactory efficiency of NF chemical cleaning could be obtained using combination of acid (HCl, pH 2.0-2.5) and alkali (NaOH + 0.3 wt% NaDS, pH 10.0-10.5). The favorable cleaning strategy is acid-alkali for treating the MBR-GAC effluent, while it is alkali-acid for treating the MBR effluent.