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Coagulation process is highly influenced by solution pH, floc breakage, and coagulant aid. In this work, two-stage addition of alum-based coagulants, polyaluminum chloride (PACl) and aluminum sulfate (Al2(SO4)3), was compared to their one-stage addition with the same total dosage. The dose ratio of primary and secondary addition was optimised. The effects of solution pH, floc breakage and dosing timing of coagulant aid of non-ionic polyacrylamide (NPAM) on coagulation efficiency and floc property were investigated. The results showed that two-stage addition of PACl showed less sensitivity with the variation of pH. Compared to PACl, two-stage addition of Al2(SO4)3 was more sensitive to the solution pH, especially when the pH ranged from 7 to 10. For all cases, the presence of floc breakage improved the removal of colloidal particles. The coagulation mechanism of primary coagulant was charge neutralisation, while other mechanism was involved with the secondary addition of coagulant. Compared to one-stage addition, the settling performance of aggregates and particulates removal in two-stage addition was more effective with the variation of dosage or dosing timing of NPAM. The present work provides detailed operating parameters for this coagulation strategy.

Germ cell-derived genomic structure variants not only drive the evolution of species but also induce developmental defects in offspring. The genomic structure variants have different types, but most of them are originated from DNA double-strand breaks (DSBs). It is still not well known whether DNA DSBs exist in adult mammalian oocytes and how the growing and fully grown oocytes repair their DNA DSBs induced by endogenous or exogenous factors. In this study, we detected the endogenous DNA DSBs in the growing and fully grown mouse oocytes and found that the DNA DSBs mainly localized at the centromere-adjacent regions, which are also copy number variation hotspots. When the exogenous DNA DSBs were introduced by Etoposide, we found that Rad51-mediated homologous recombination (HR) was used to repair the broken DNA. However, the HR repair caused the chromatin intertwined and impaired the homologous chromosome segregation in oocytes. Although we had not detected the indication about HR repair of endogenous centromere-adjacent DNA DSBs, we found that Rad52 and RNA:DNA hybrids colocalized with these DNA DSBs, indicating that a Rad52-dependent DNA repair might exist in oocytes. In summary, our results not only demonstrated an association between endogenous DNA DSBs with genomic structure variants but also revealed one specific DNA DSB repair manner in oocytes.

Effects of triclosan (TCS) on performance, microbial community and antibiotic resistance genes (ARGs) during partial denitrification (PD) were investigated in a sequencing moving bed biofilm reactor (SMBBR). TCS inhibited nitrite accumulation; inhibition effect was more obvious as TCS concentration increased from 1 to 5 mg/L, but it could recover. Extracellular polymeric substances contents increased with 1 mg/L TCS addition and decreased a lot at 5 mg/L TCS. Community structure in biofilm was different from that in floccular sludge, but it was similar at 5 mg/L TCS. Illumina sequencing showed that Pseudomonas, Aeromonas, Shewanella and Thauera became dominant genera. Abundance of nirS was stable and higher than that of narG and nosZ. High-throughput qPCR showed that mexF, acrA-02, fabK, etc. were screened at 5 mg/L TCS. IntI1 and tnpA-04 were abundant mobile genetic elements. The study furthers understanding of effects of TCS on PD, bacterial communities and ARGs in SMBBR.

Ammonia-oxidizing microorganisms (AOMs) play important roles in nitrogen removal, but their metabolic activity in winter months in wastewater treatment plants (WWTPs) remains unclear. Here, two full-scale WWTPs were selected, and a total of 48 DNA-based stable isotope probing (DNA-SIP) microcosms of activated sludge samples at different winter months (November-January) and temperatures (13 °C, 25 °C and 37 °C) were constructed to evaluate the temporal heterogeneity and temperature response of active AOMs. The results provided direct evidence that the temporal heterogeneity of AOMs’ activity was not obvious in winter months. In general, ammonia-oxidizing archaea (AOA) and bacteria (AOB) co-participated in the active ammonia oxidation in three winter months at in situ temperature (13 °C) in two WWTPs, and AOA were the dominant active AOMs, even though AOB outnumbered AOA in seed sludge. In contrast, higher peaks of AOA in “heavy” fractions at 25 °C and 37 °C also provided compelling evidence for the dominant contribution of AOA to active ammonia oxidation under higher temperatures. The Illumina sequencing of 13C-DNA obtained from the DNA-SIP microcosms at 13 °C in three winter months further suggest that Candidatus Nitrososphaera evergladensis and Candidatus Nitrosocosmicus exaquare were the dominant active AOA in two WWTPs, while the active AOB were dominated by Nitrosomonas oligotropha. At higher temperatures, active AOA shifted to Ca. N. evergladensis and Candidatus Nitrososphaera gargensis, and Nitrosomonas marina, Nitrosomonas europaea and Nitrosomonas communis dominated in the active AOB. Overall, AOA rather than AOB dominated the active ammonia oxidation in winter months and at higher temperatures in the full-scale WWTPs tested.

Constructed wetlands (CWs) usually exhibit limits in functional redundancy and diversity of microbial community contributing to lower performances of nutrients removal in decentralized domestic sewage treatment. To address this quandary, heterotrophic nitrification-aerobic denitrification (HN-AD) bacteria was added in tidal flow CWs (TFCWs) developing for nitrogen (N) and phosphorus (P) removal. With addition of HN-AD bacteria, TFCWs could be setup more rapidly and obtained better removal efficiencies of 66.9%-70.1% total nitrogen (TN), and 88.2%-92.4% total phosphorus (TP) comparing with control systems (TN: 53.9%; TP: 83.9%) during stable operation. Typical-cycles variations showed that TFCWs with addition of HN-AD bacteria promoted NO3--N and NH4+-N removal respectively under hydraulic retention time (HRT) of 14 h and 8 h with slight NO2--N accumulation. Activated alumina (AA) coupled with HN-AD bacteria decreased P release and relieved its poor removal performance in CWs. Based on metagenomic taxa and functional annotation, Pseudomonas and Thauera played pivotal roles in N removal in TFCWs. Furthermore, gradient oxic environments by 8 h-HRT promoted co-occurrence of heterotrophic nitrifiers (mostly Pseudomonas stutzeri) and autotrophic nitrifiers (mostly Nitrosomonas europaea. and Nitrospira sp.) which potentially accelerated NH4+-N transformation by elevated nitrification and denitrification related genes (e. g. amoABC, hao, napA and nirS genes). Meanwhile, the addition of HN-AD bacteria stimulated nirA and gltD genes of N assimilation processes probably leading to NH4+-N directly removal. The conceptual model of multi-metabolism regulation by HN-AD process highlighted importance of glk, gap2 and PK genes in glycolysis pathway which were vital drivers to nutrients metabolism. Overall, this study provides insights into how ongoing HN-AD bacteria-addition effected microbial consortia and metabolic pathways, serving theoretical basis for its engineered applications of TFCWs in decentralized domestic sewage treatment.

This study investigated the water purification function and mechanism of biofilm in storage tank, with a view to using it as a pretreatment unit for rainwater cleaner production. Shortening the hydraulic retention time (HRT) of storage tank from 12 to 4 h improved the pollutants removal performance and reduced the suspended bacteria counts. The accumulation of abundant taxa and succession of rare taxa were observed with biofilm development. Positive correlations within and across different bacterial taxa were dominant in the network, and some rare genera (Ralstonia and Micropruina) were identified as hub bacteria. Candidatus Nitrospira nitrosa and Nitrospira sp. ENR4 were two identified complete ammonia oxidizers. Denitrifying bacteria tended to enrich and formed more complex interactions over time. The main nitrogen metabolism pathways may be ammonia assimilatory, complete denitrification and dissimilatory/assimilatory nitrate reduction. HRT was negatively correlated with most dominant genera, and contributed 20.35% to the variation of functional taxa. This study highlights the self-purification function and micro-ecology of storage tank, and provides a new insight for its role in rainwater cleaner production process.

This study aimed to investigate the short-term response of abundant-rare genera and antibiotic resistance genes (ARGs) to azithromycin (AZM, 0.05–40 mg/L) and copper (1 mg/L) combined pollution in activated sludge nitrification system at low temperature. Nitrification was as expected inhibited in stress- and post-effects periods under AZM concentration higher than 5 mg/L. Abundant and rare taxa presented dissimilar responses based on full-scale classification. Conditionally rare or abundant taxa (CRAT) were keystone taxa. Relative abundance of ammonia-oxidizing archaea increased, and three aerobic denitrifying bacteria (Brevundimonas, Comamonas and Trichococcus) were enriched (from 9.83% to 68.91% in total). Ammonia nitrogen assimilating into Org-N and denitrification may be nitrogen pathways based on predict analysis. 29 ARGs were found with more co-occurrence patterns and high concentration of AZM (greater than 5 mg/L) caused their proliferation. Importantly, expect for some abundant taxa, rare taxa, potential pathogens and nitrogen-removal functional genera were the main potential hosts of ARGs.

Vacuum ultraviolet/ persulfate (VUV/PS) has been a prospective method for antibiotics removal, however, the enhanced degradation mechanism is still unclear. This study compared the sulfamethazine (SMT) degradation by VUV/PS and ultraviolet/persulfate (UV/PS) processes using a photoreaction system. Results showed that the SMT degradation rate and PS activation rate by VUV/PS was 1.36 times and 1.39 times those of the conventional UV/PS process under the same dosage of PS, respectively. VUV/PS also achieved a high SMT mineralization. SO4•− and HO• played important roles in the degradation of SMT by both processes, while the role of •O2− was little. SMT concentration changed the distributions of 185 nm and 254 nm photons absorbed by solution components and altered the initiated photolysis reaction. Both processes had faster degradation rates at low initial SMT concentrations and the optimum reaction condition was at solution pH of 5. The inhibited level of the SMT degradation in both processes by four anions was in the following order: NO3−> Cl−> HCO3−>SO42 . VUV/PS process was also more efficient than UV/PS for degrading environmental (200 μg/L) and high (5 mg/L) concentration of SMT from three kinds of typical water matrices (tap, river and lake water). Finally, ten photoproducts of SMT degradation by VUV (or UV) were identified, which were mainly the oxidized products of C-N, -NH2 and S-C on SMT molecules, and four degradation pathways were proposed. Overall, these findings could provide useful insights into the application of VUV/PS in efficient antibiotics removal from water.

For comprehensive insights into the effects of disinfection strategy on antibiotic resistance genes (ARGs) in pipe wall biofilm to ensure the biosafety of domestic hot water system (DHWS), this study investigated the occurrence, removal and interactions of ARGs, as well as their potential hosts. The shifts in biofilm community composition and microbial functions (level three) were observed under different disinfection strategies. A total of 40 ARG subtypes within seven antibiotic types were predicted. The total gene counts ranged from 6.10 × 104 to 2.31 × 105, and decreased after the chlorine, chlorine dioxide, silver ions (Ag+), ultraviolet (UV), and Ag+-UV disinfection. The ARGs in samples under different disinfection strategies were divided into four groups, and the removal and enrichment of the same ARGs in each group were almost consistent. The complex interactions among ARGs were weakened and altered by disinfection (edges decreased from 237 to 178), with yebQ and marC as the hub ARGs, but positive correlations were still dominant. Moreover, 36 nonpathogenic bacteria, including high- (Blastocatella), mid- (Ornatilinea) and low-abundant genera (Bdellovibrio), as well as 18 potential pathogens (Vibrio and Bacillus) were identified as the potential hosts harboring ARGs. Overall, this study provides some new insights into the occurrence of ARGs and their fate under eight disinfection strategies, which is of great significance for a comprehensive understanding and control of ARGs in DHWS.

This study investigated the effects of secondary chlorination on bacterial regrowth, microbial communities (abundant and rare taxa) and bacterial functions of pipe wall biofilm and bulk water in simulated secondary water supply system (SWSS). Continuous secondary chlorination was more effective than short-term secondary chlorination to control the bacterial regrowth in both biofilm and water samples. Bacterial diversity slightly reduced after continuous secondary chlorination, and 19.27% of the total operational taxonomic units (OTUs) were shared by biofilm and water samples, with Bacillus as the dominant genus. Abundant and rare taxa exhibited different community structures. Proteobacteria and candidate division WPS-1 predominated in abundant and rare phyla were sensitive to chlorine, while Firmicutes, Acidobacteria and Bacteroidetes, exhibited relative strong chlorine resistance. The abundant genera in control sample (e.g., Bosea, Sphingobium and Gemmata) exhibited poor tolerance to chlorine, while Bacillus in biofilm and Defluviimonas in water were the main chlorine-resistant genera. Moreover, the composition of rare genera in each sample was obviously different. Furthermore, a total of 18 potential pathogens were detected with Pseudomonas as the dominant genus, most of which were significantly reduced after disinfection. There were mainly positive interactions among potential pathogenic bacteria, with Enterococcus, Legionella and Vibrio as the hub genera as revealed by network analysis. Similar bacterial functions in both biofilm and water were observed with metabolism as the predominant bacterial function, while, human disease function only accounted for 1.07% of bacterial functions. These results highlighted the importance of continuous secondary chlorination for controlling biosafety of SWSS and identified the dissimilar responses of abundant and rare bacteria to the disinfection, as well as the co-occurrence patterns among potential pathogens, improving our understanding of bacterial communities in SWSS.

In a coagulation-flocculation process, optimal separation of the resultant aggregates plays a decisive role on coagulation performance and provides a lower burden for subsequent treatment units. This separation highly depends on the stability of the micro-flocs formed during the initial, rapid stage of coagulation. In this work, a two-stage addition of aluminium sulphate (alum, Al2(SO4)3) was employed by adding 0.04 and 0.08 mM Al2(SO4)3 at the beginning and the end of rapid mixing, respectively. The coagulation performance and floc characteristics were compared to conventional single addition with the same total coagulant dosage, and the effects of variable rapid-mixing speeds (160–850 rpm) and duration time (10–120 s) were investigated. The results showed that the residual turbidity of two-stage coagulant addition was 85.1% lower than single addition when applied at a mixing speed of 580 rpm and a duration time of 120 s. The underlying coagulation mechanism revealed that the two-step addition more effectively neutralized colloids and formed larger aggregates that settled better and could more easily be removed. Moreover, the aggregates were less firm, which was attributed to different interactions among the micro-flocs, the second addition of Al2(SO4)3 and destabilized colloids. The present work provides data to broaden the window of rapid-mixing environments for more effective coagulation.

This study investigated the influence of C/N ratios and tidal strategies on nitrogen removal and bacterial communities in two pilot-scale tidal flow constructed wetlands (TFCWs) with simultaneous nitrification–denitrification process. Heterotrophic nitrification aerobic denitrification (HNAD) was the main nitrogen transformation pathway in both TFCWs. High C/N ratios and effluent circulation at low temperature promoted HNAD in TFCWs with high nitrogen removal efficiencies (72.6%–95.5% for NH4+-N and 70.9%~91.8% for TN). Effluent circulation had more influence on bacterial community structure and diversity than C/N ratios. Among 16 detected genera related to nitrogen removal, HNAD bacteria (HNADB) were abundant. Especially, some dominant HNADB (e.g. Aeromonas, Hydrogenophage and Gemmobacter) were core genera, showing positive interactions with other genera related to nitrogen removal. Tidal strategies had more contribution to the shifts in these genera than C/N ratios. This study highlights the importance of HNADB in pilot-scale TFCWs and their responses to C/N ratios and tidal strategies.

This study explored the application of shale ceramsite (SC) overlaid onto active alumina (AA) to function as a double-layer substrate in tidal flow constructed wetland (TFCW, SC-AA-TFCW) for decentralized domestic sewage treatment. This was compared to AA or SC substrate alone (AA-TFCW or SC-TFCW) for nitrogen removal, variation of dissolved oxygen and porosity in TFCWs, as well as structure of bacterial communities at varied hydraulic load (HL) of 0.204–2.448 m3/m2 d with time ratio of the wet and dry phase of 3:1. The results demonstrate that SC-AA-TFCW removed 86% NH4+-N and 79% total nitrogen at HL of 0.612 m3/m2 d, which was better than AA-TFCW(76%) or SC-TFCW(49%). The higher nitrogen removal performance in SC-AA-TFCW was mainly attributed to enhanced oxygen transportation due to non-uniform flow field and irregular gap distribution in layered structure, as well as less pore blockage during long-term operation. Denitrifying bacteria including Dechloromonas, Acidovorax, Chryseobacterium and Thermomonas species took up 32% of the microbiome in SC-AA-TFCW, which was higher than in AA-TFCW (17%) and SC-TFCW (7.7%). This study highlighted the importance of layered structures and determined an optimal HL of TFCW to achieve an efficient and stable nitrogen removal for domestic sewage treatment.

In this work, the adsorption characteristics, including adsorption kinetic, isotherm and thermodynamics of chloramphenicol (CAP) onto powdered activated carbon (PAC), were carried out, and the feasibility of using ultrasound to regenerate saturated PAC in aqueous solution was evaluated. The adsorption results demonstrated that the adsorption mechanism was a complex process including surface adsorption, external liquid membrane diffusion and intraparticle diffusion as well, and the adsorption process was endothermic and non-spontaneous. The optimal conditions for PAC regeneration were as follows: acoustic density of 0.36 W/mL, saturated carbon dosage of 1.0 g/L and pH value of 10.36. The analysis of thermogravimetric analysis (TGA), Fourier transform infrared spectrometry (FTIR), Brunauer–Emmett–Teller (BET) surface area, pore size distribution and scanning electron microscopy (SEM) of PAC samples revealed that ultrasound mainly acted on surface functionalities, meso-pores and macro-pores of PAC through hydroxyl radical oxidization, high-pressure shock waves and high-speed microjets due to cavitation effect. This study highlighted that ultrasound could be efficiently desorbing CAP from saturated PAC. Practical applications of this method for PAC regeneration with complex natural matrices under environmentally realistic conditions were conducted and the adsorption capacity of the regenerated PAC decreased.

Silver-loaded stainless steel (Ag-SS) was applied in domestic hot water system (DHWS) to control the biofilm contamination. The antibacterial properties of Ag-SS, as well as the bacterial communities, potential pathogens and antibiotic resistance genes (ARGs) of pipe wall biofilm were investigated, with SS as control. Ag-SS maintained a high antibacterial efficiency on heterotrophic bacteria (70.60 ± 13.22 %) and Escherichia coli (73.56 ± 10.62 %) by contact bacteriostasis. Dominant phyla exhibited a lower relative abundance in Ag-SS than SS. The bacteria were further classified into abundant (≥ 1 %), moderately abundant (0.1∼1 %) and rare (≤ 0.1 %) taxa to investigate their responses to silver. There were 15.33 % of shared operational taxonomic units (OTUs) belonged to abundant taxa, while most unique OTUs (> 80 %) of each sample were identified as rare taxa. As the primary abundant genera, Mesorhizobium and Bradyrhizobium exhibited resistant and sensitive to silver, respectively. Most dominant moderately abundant and rare genera were resistant to silver. Moreover, among 19 detected potential pathogens, Legionella, Parachlamydia and Aeromonas were sensitive to silver, while Pseudomonas and Acinetobacter were resistant to silver. Furthermore, a total of 48 ARGs were detected and they exhibited similar distributions in both samples. The total abundance of ARGs in Ag-SS increased by 0.08 fold compared with that in SS, with efflux pumps as the main resistance mechanisms. This study highlights the different responses of abundant, moderately abundant and rare taxa to silver, and the occurrences of ARGs, confirming that Ag-SS was an effective disinfection strategy for biosafety protection of DHWS.

A novel coagulation strategy, where floc property was regulated by varying dosing sequence of dual coagulants of aluminum sulfate (AS) and chitosan (CS) with floc breakage, was applied as the pre-treatment of ultrafiltration to treat algae-laden water. The river water (TW), and TW spiked with intracellular organic matter (IOM) and extracellular organic matter (EOM) respectively (TW-IOM and TW-EOM) were tested. The results indicate that floc breakage applied in successive dosing of AS and CS in TW and TW-IOM water samples formed compact flocs through charge neutralization and bridging, generating dense cake layer to control irreversible fouling; and mitigated irreversible fouling (Rir) caused by protein-like and humic-like species in the molecular weight (MW) of 950–3000 Da. For TW-EOM water sample, the successive addition of CS and AS can relieve Rir by removing protein-like species and soluble by-products in the MW of 500–3000 Da via charge neutralization, sweeping flocculation and bridging together, while the applied breakage aggravated membrane fouling. The obtained results provide a novel coagulation strategy to control membrane fouling during algae-laden water treatment.

Ultrasonic (US) was used to activate persulfate (PS) in presence of nanoscale zero-valent iron (nZVI) to degrade chloramphenicol (CAP) in solution. Synergistic effects were observed of US and nZVI on PS activation (US-nZVI/PS) compared to US/PS, nZVI/PS, or US-nZVI alone, while replacement of nZVI with Fe(II) or Fe(III) ion was less efficient to degrade CAP. The US-nZVI/PS treatment exhibited a rapid and continuous oxidation of CAP in solution. Both OH and SO4 − were considered to be primary reactive species responsible for CAP degradation, of which SO4 − had a higher contribution than OH. Our results indicated that Fe2+ was continuously being recycled by reaction of nZVI and PS, accompanied by generation of SO4 −. US accelerated the corrosion of nZVI and removed passive films on the nZVI surface. Under optimal conditions, 98.1% of CAP was degraded during 90 min. This was established in presence of 0.5 g/L nZVI and 1.0 mM PS, with an US intensity of 0.36 W/mL at 40 kHz and a pH of 7.0. When present, inorganic anions and natural organic matter partly inhibited CAP degradation, which was mainly attributed to their scavenging effects for SO4 − and OH. The reusability of nZVI was examined in five consecutive cycles, showing a decrease in efficiency with each cycle. Seven major intermediate products were identified, and these indicated two degradation pathways. Finally, in-situ regeneration of CAP-saturated powdered activated carbon using US-nZVI/PS process was evaluated.

Commercial nanosized zero-valent copper (nZVC) was used as persulfate (PS) activator in combination with ultrasonic irradiation (US) for the oxidative degradation of typical antibiotic sulfamethazine (SMZ) in this study. Compared with other processes, the combined nZVC-PS-US process significantly enhanced SMZ removal due to a synergistic interaction between sonolysis and a heterogeneous reaction. Almost complete SMZ removal was achieved within 60 min using a PS dose of 0.5 mM and a nZVC concentration of 64 mg/L at pH 3.06, with US at 0.4 W/mL and 40 kHz. The presence of NO3–, SO42−, HCO3–, Cl− and humic acid demonstrated adverse effects on SMZ degradation. Moreover, the inhibitory effect of different inorganic anions on SMZ degradation followed the sequence of HCO3– > SO42−> NO3– > Cl− > no salt. Electron spin resonance and radical scavenging tests indicate that the primary reactive species was SO4•−, while •OH played a less important role. Cu+ is an active copper species in activating PS. The production of Cu+ and Cu2+ induced by Cu0 and US favored the continuous decomposition of PS as well as the production of SO4•− at the surface of nZVC. Nine intermediates were identified and four oxidation pathways were proposed, the aniline moiety oxidation, SO2 extrusion/smile-type rearrangement and S-N bond cleavage were the major pathways. Practicality and effectiveness of nZVC-PS-US was confirmed when other organic micro-pollutants and SMZ added to raw waters were tested. The findings reported here offer promising implications in developing the utilization of nZVC in advanced oxidation for treatment of wastewater.

A tidal flow constructed wetland (TFCW), a commonly applied system to clean wastewater, contains a substrate to assist pollutants removal, while the choice of substrate affects the formation of bacterial biofilms. Herein, activated alumina-TFCW (A-TFCW) with hydraulic load of 1.35 m3/(m2·d) parallel with shale ceramisite (S-TFCW) was investigated for treating domestic wastewater, aiming to enhance simultaneous long-term removal of organics, nitrogen and phosphorus. A-TFCW achieved significantly higher COD, NH4+-N, TN and TP removal efficiency than S-TFCW, with the removal efficiency of 85.9% COD, 85.4% NH4+-N, 72.8% TN and 96.4% TP respectively. Denitrifying bacteria dominated in both formed biofilms, with higher relative abundance of nitrifying bacteria and denitrifying bacteria in A-TFCW. These results demonstrated that AA substrate was more suitable to be applied in enhancing the removal performance in TFCW for the treatment of domestic wastewater.

Ammonia-oxidizing bacteria (AOB) and archaea (AOA) are two distinct ammonia-oxidizing microorganisms (AOMs) responsible for nitrification in wastewater treatment plants (WWTPs). However, their relative contributions to ammonia oxidation in WWTPs and short-term responses to titanium dioxide nanoparticles (TiO2 NPs) remain unclear. In this study, DNA-based stable isotope probing (DNA-SIP), quantitative polymerase chain reaction (qPCR), PCR, cloning and sequencing were applied to investigate the in situ activity of AOMs in a full-scale WWTP and to evaluate their responses to TiO2 NPs. An environmentally relevant concentration (1 mg L−1) and a higher concentration (50 mg L−1) of TiO2 NPs were chosen for laboratory microcosms. The laboratory microcosms revealed that TiO2 NPs (1 or 50 mg L−1) caused slight or no short-term inhibitions on nitrification activity and nitrification rate of activated sludge. The successful Na213CO3 assimilation of AOB rather than AOA in original sludge provided compelling evidence for the strong contribution of AOB to the in situ nitrification of the WWTP. The main AOB in original sludge, Nitrosomonas oligotropha cluster and Nitrosomonas europaea cluster, were the dominant active AOB in the WWTP. However, compared with the original sludge, the abundance and distribution of active AOB changed under 1 and 50 mg L−1 of TiO2 NPs. In particular, AOA within Nitrososphaera cluster were the active AOMs under 50 mg L−1 TiO2 NPs. These results suggested that TiO2 NPs had a potential impact on the abundance and composition of active AOMs in the WWTP. This study further provided direct evidence of the autotrophic growth of AOB within N. oligotropha cluster and N. europaea cluster, and AOA within the general Nitrososphaera cluster. Overall, AOB played an important role in the in situ nitrification of the full-scale WWTP investigated, while AOA showed a strong contribution to the active nitrification under higher concentration of TiO2 NPs.

Different from ammonia-oxidizing bacteria (AOB), the influence of ammonia levels on ammonia-oxidizing archaea (AOA) in wastewater treatment systems was poorly understood. In this study, sludge contained AOA and AOB was enriched in three sequencing batch reactors (named as R1, R2, and R3) under different ammonia levels (14, 56, and 140 mg/L) using polymerase chain reaction (PCR), cloning, sequencing, and quantitative real-time PCR (qPCR) to evaluate the effect of ammonia levels on the diversity, abundance, and contribution of AOA and AOB to ammonia oxidation. Cloning results showed that there was only one dominant AOA species (Nitrososphaera cluster) in the reactors during 140-d operation. However, AOB communities varied significantly among the reactors. After 140-d enrichment, Nitrosomonas ureae cluster, the dominant AOB cluster in seed sludge, was also dominant in R1 and R2, while Nitrosomonas europaea cluster was enriched and dominated in R3. Diversity of AOB was higher than AOA under the three ...

High-salt-induced inflammation and oxidative stress in the hypothalamic paraventricular nucleus (PVN) contribute to the pathogenesis of salt-sensitive hypertension. In this study, we hypothesized that chronic inhibition of nuclear factor-κB (NF-κB) activity in the PVN delays the progression of hypertension by upregulating anti-inflammatory cytokines, reducing NLRP3 (NOD-like receptor family pyrin domain containing 3) and IL-1β and attenuating p-IKKβ, NF-κB p65 activity and NAD(P)H oxidase in the PVN of salt-sensitive hypertensive rats. Dahl salt-sensitive rats received a high-salt diet (HS, 8 % NaCl) or a normal-salt diet (NS, 0.3 % NaCl) for 6 weeks and were treated with bilateral PVN infusion with either vehicle or pyrrolidine dithiocarbamate (PDTC, 5 μg/h), a NF-κB inhibitor via osmotic minipump. The mean arterial pressure and plasma levels of norepinephrine (NE) and epinephrine (EPI) were significantly increased in high-salt-fed rats. In addition, rats with high-salt diet had higher levels of p-IKKβ, NF-κB p65 activity, Fra-like (Fra-LI) activity (an indicator of chronic neuronal activation), NOX-4 (subunits of NAD(P)H oxidase), NLRP3 and IL-1β, and lower levels of IL-10 in the PVN than normal diet rats. Bilateral PVN infusions of PDTC attenuated these high-salt-induced changes. These findings suggest that high-salt-induced NF-κB activation in the PVN caused hypertension via sympathoexcitation, which are associated with the increases of NLRP3, IL-1β and oxidative stress in the PVN; PVN inhibition of NF-κB activity attenuates NLRP3, IL-1β and oxidative stress in the PVN and thereby attenuates hypertension.

Shifts in bacterial community composition and abundance of nitrifiers during aerobic granulation, and the effects of wastewater composition on them were investigated using Illumina sequencing and quantitative PCR. The bacterial diversity decreased sharply during the post-granulation period. Although cultivated with different wastewater types, aerobic granular sludge (AGS) formed with similar bacterial structure. The bacterial structure in AGS was completely different from that of seed sludge. The minor genera in seed sludge, e.g., Arcobacter, Aeromonas, Flavobacterium and Acinetobacter, became the dominant genera in AGS. These genera have the potential to secrete excess extracellular polymer substances. Whereas, the dominant genera in seed sludge were found in less amount or even disappeared in AGS. During aerobic granulation, ammonia-oxidizing archaea were gradually washed-out. While, ammonia-oxidizing bacteria, complete ammonia oxidizers and nitrite-oxidizing bacteria were retained. Overall, in this study, the bacterial genera with low relative abundance in seed sludge are important for aerobic granulation.

Increasing ammonia emissions could exacerbate air pollution caused by fine particulate matter (PM2.5). Therefore, it is of great importance to investigate ammonia oxidation in PM2.5. This study investigated the diversity, abundance and activity of ammonia oxidizing archaea (AOA), ammonia oxidizing bacteria (AOB) and complete ammonia oxidizers (Comammox) in PM2.5 collected in Beijing-Tianjin-Hebei megalopolis, China. Nitrosopumilus subcluster 5.2 was the most dominant AOA. Nitrosospira multiformis and Nitrosomonas aestuarii were the most dominant AOB. Comammox were present in the atmosphere, as revealed by the occurrence of Candidatus Nitrospira inopinata in PM2.5. The average cell numbers of AOA, AOB and Ca. N. inopinata were 2.82 × 104, 4.65 × 103 and 1.15 × 103 cell m−3 air, respectively. The average maximum nitrification rate of PM2.5 was 0.14 μg (NH4+-N) [m3 air·h]−1. AOA might account for most of the ammonia oxidation, followed by Comammox, while AOB were responsible for a small part of ammonia oxidation. Statistical analyses showed that Nitrososphaera subcluster 4.1 was positively correlated with organic carbon concentration, and Nitrosomonas eutropha showed positive correlation with ammonia concentration. Overall, this study expanded our knowledge concerning AOA, AOB and Comammox in PM2.5 and pointed towards an important role of AOA and Comammox in ammonia oxidation in PM2.5.

High-orderly TiO2 nanotube arrays were fabricated by anodic oxidation of pure titanium substrate in organic electrolyte containing fluoride. Different morphological nanotubes of titania were obtained through controlling the different anodization voltages and durations. The length of the longest nanotubes was approximately 60 m and the length-to-width aspect ratio was about 600. The nanotube layers were then annealed at different temperatures (450, 550, and 650C) in air for 2 h. The samples were characterized by scanning electron microscopy, X-ray diffraction (XRD), energy dispersive X-Ray (EDS) and UV-Vis spectrometer. The XRD results demonstrated that the as-anodized samples were amorphous and the structure changed to antanse and rutile when the samples were annealed at higher temperature. The EDS microanalysis indicated the presence of carbon in the TiO2 nanotubes. The result of degradation of methylene blue showed clearly that the photocatalytic activity of C-doped TiO2 nanotubes increased by 10%.

High-orderly nanotubes of titania were fabricated by anodic oxidation of pure titanium substrate in different electrolytes containing fluoride. Different morphological nanotubes of titania were obtained through controlling the different pH value of inorganic electrolytes, and it was found that nanotubes of titanium oxide would not formed when pH value was above 6. The morphological and structural properties of nanotublar products were characterized by SEM. The synthesized nanotubes of titania in organic electrolytic solutions containing fluoride was of 60 μm in length. The experiments demonstrated the length and orderliness of nanotubes of titanium oxide in organic solutions were much better than those in inorganic solutions.

In this study, GelGreen™ was investigated as a replacement for SYBR® Safe to stain DNA in cesium chloride (CsCl) density gradients for DNA-stable isotope probing (SIP) experiments. Using environmental DNA, the usage of GelGreen™ was optimized for sensitivity compared to SYBR® Safe, its optimal concentration, detection limit for environmental DNA and its application in environmental DNA-SIP assay. Results showed that GelGreen™ was more sensitive than SYBR® Safe, while the optimal dosage (15X concentration) needed was approximately one-third of SYBR® Safe, suggesting that its sensitivity was three times more superior than SYBR® Safe. At these optimal parameters, the detection limit of GelGreen™-stained environmental DNA was as low as 0.2 μg, but the usage of 0.5 μg environmental DNA was recommended to produce a more consistent DNA band. In addition, a modified needle extraction procedure was developed to withdraw DNA effectively by fractionating CsCl density gradients into four or five fractions. The successful application of GelGreen™ staining with 13C-labeled DNA from enriched activated sludge suggests that this stain was an excellent alternative of SYBR® Safe in CsCl density gradients for DNA-SIP assays.