•High prevalence of antibiotic resistance genes was influenced by human activities.•Bacteria community was the key contributing factor driving ARGs alteration.•Nutrient and mobile gene elements had positive correlation with most ARGs (P < 0.05).•Country area was a high spot for antibiotic resistome shift and pathogen breeding.The rapid human activities and urbanization exacerbate the human health risks induced by antibiotic resistance genes (ARGs). In this study, the profiling of ARGs was investigated using high-throughput qPCR from water samples of 13 catchment areas in East Tiaoxi River, China. High prevalence of ARGs indicated significant antibiotic resistance pollution in the research area (absolute abundance: 6.1 × 108–2.1 × 1010 copies/L; relative abundance: 0.033–0.158 copies/cell). Conventional water qualities (COD, TN, TP, NH3-N), bacterial communities and mobile gene elements (MGEs) were detected and analyzed as factors of ARGs shift. Nutrient and MGEs showed positive correlation with most ARGs (P < 0.05) and bacteria community was identified as the key contributing factor driving ARGs alteration. With the land-use study and field investigation, country area, especially arable, was expected as a high spot for ARGs shift and pathogen breeding. Comparing to environmental background, promotion of ARGs and marked shift of bacterial community were observed in country and urban city areas, indicating that human activities may lead to the spread of ARGs. Analysis of factors affecting ARGs in this study may shed new light on the mechanism of the maintenance and propagation of ARGs in urban rivers.Download high-res image (272KB)Download full-size image

•ARGs exponentially and linearly decreased with the increase of UV doses and chloride concentrations(p < 0.05).•Sulfa ARGs could be removed effectively by chlorination disinfection.•SMX ARB has greater tolerance to disinfection than TC or non-ARB.•Ozone and UV release free ARGs to environment resulted from apoptosis.Antibiotic resistance genes (ARGs) in environment have gradually engendered extensive concern recently due to the harm caused to environment and human beings. Wastewater treatment plants are considered as important nodes of ARGs controlling and it is of utmost importance to figure out effects and mechanisms of each process, especially disinfections. In this study, three disinfection processes (ultraviolet, chlorination, and ozone) were used to reduce levels of ARGs in secondary effluents from a municipal wastewater treatment plant. Results indicated that the abundance of ARGs decreased exponentially as the dosage increased during the ultraviolet disinfection treatment (R2 = 0.68–0.92). In the 0–5 mg/L available chlorine concentrations, with a contact time of 30 min, the abundance of ARGs decreased linearly as the chlorine concentrations increased (R2 = 0.77–0.99). In a 2 mg/L concentration of ozone (O3), the abundance of ARGs had higher removal efficiency, but the removal efficiency was not significantly enhanced by increasing the concentration of ozone. However, an experiment using the DNase I treatment showed that UV and ozone disinfection resulted in apoptosis, and the bacterial DNA was released into the environment; ARGs were mostly found as free DNA in the treated wastewater. These results provide insights into behavior of ARGs during disinfection processes in wastewater treatment plants.Download high-res image (176KB)Download full-size image

Antibiotic resistance genes (ARGs) in urban rivers are a serious public health concern in regions with poorly planned, rapid development. To gain insights into the predominant factors affecting the fate of ARGs in a highly polluted urban river in eastern China, a total of 285 ARGs, microbial communities, and 20 physicochemical parameters were analyzed for 17 sites. A total of 258 unique ARGs were detected using high-throughput qPCR, and the absolute abundance of total ARGs was positively correlated with total organic carbon and total dissolved nitrogen concentrations (P < 0.01). ARG abundance and diversity were greatly altered by microbial community structure. Variation partitioning analysis showed that the combined effects of multiple factors contributed to the profile and dissemination of ARGs, and variation of microbial communities was the major factor affecting the distribution of ARGs. The disparate distribution of some bacteria, including Bacteroides from mammalian gastrointestinal flora, Burkholderia from zoonotic infectious diseases, and Zoogloea from wastewater treatment, indicates that the urban river was strongly influenced by point-source pollution. Results imply that microbial community shifts caused by changes in water quality may lead to the spread of ARGs, and point-source pollution in urban rivers requires greater attention to control the transfer of ARGs between environmental bacteria and pathogens.

The effect of two different biochar types, rice straw biochar (RSB) and mushroom biochar (MB), on chicken manure composting was previously examined by monitoring the fate of antibiotic resistance genes (ARGs) and arsenic. The behavior of ARGs and arsenic in other kinds of manure composting with the same biochar types had not been examined. In this study, we added either RSB or MB to pig and duck manure composts to study the behavior of ARGs (tet genes, sul genes, and chloramphenicol resistance genes) and arsenic under the same experimental condition. The results showed that the average removal values of selected ARGs were respectively 2.56 and 2.09 log units in duck and pig manure compost without the addition of biochar. The effect of biochar addition on the average removal value of ARGs depended on the type of biochar and manure. For instance, in pig manure compost, MB addition increased the average removal value of ARGs, while RSB addition decreased. And both biochar additions had a negative influence on the average removal value of ARGs in duck manure compost. Analytical results also demonstrated that MB addition reduced total arsenic and the percentage of bioavailable arsenic more than RSB.

•Mixed wastewater contained high-abundant ARGs significantly differing from domestic sewage.•Normalized copy number of MGEs in IDW3 was 8.5 fold higher than in domestic wastewater.•Significant correlations were found between efflux pump genes and Streptococcus.•Six representative organic compounds remarkably promoted conjugative transfer by plasmid RP4.Domestic wastewater treatment plants as a reservoir of antibiotic resistance genes (ARGs) have received much attention, but the effect of dyes on the propagation of ARGs has rarely been investigated. In this study, we investigated the differences in distributions of ARGs and microbial communities using high-throughput qPCR and 16S rRNA gene sequencing, respectively, between mixed (dyeing and domestic) wastewater and domestic sewage. The relative abundance of ARGs in inflows of mixed wastewater (IW2 and IW3) was higher than that of domestic wastewater (IW1). The relative abundance of mobile genetic elements in the inflow of textile dyeing wastewater (IDW3) was 3- to 13-fold higher than that in other samples. Moreover, in IDW3, some distinct high abundance ARGs, particularly operons encoding efflux pumps (such as acrR-01, acrB-01 and acrF), were significantly correlated with Streptococcus of the Firmicutes. To explore why the abundance of ARGs was relatively high in mixed wastewater, six representative types of organic compounds in textile dyeing wastewater were used to test the effect on plasmid-based conjugative transfer from E. coli HB101 to E. coli NK5449. These six compounds all facilitated the transfer of resistance-carrying RP4 plasmid, and the highest transfer frequency (approximately 10−5-10−3) was over 4- to 200-fold higher than that in the control group (approximately 10−6-10−5). These results illustrated that the six common residual compounds, particularly low-dose substances in IDW3, could facilitate the dissemination of ARGs in aquatic environments. More importantly, this study revealed for the first time that dyeing contaminants influenced horizontal gene transfer (HGT) of ARGs.Download high-res image (241KB)Download full-size image

Short-chain fatty acids (SCFAs) can be produced by primary and waste activated sludge anaerobic fermentation. The yield and product spectrum distribution of SCFAs can be significantly affected by different initial pH values. However, most studies have focused on the physical and chemical aspects of SCFA production by waste activated sludge fermentation at different pH values. Information on the bacterial community structures during acidogenic fermentation is limited. In this study, comparisons of the bacterial communities during the co-substrate fermentation of food wastes and sewage sludge at different pH values were performed using the barcoded Illumina paired-end sequencing method. The results showed that different pH environments harbored a characteristic bacterial community, including sequences related to Lactobacillus, Prevotella, Mitsuokella, Treponema, Clostridium, and Ureibacillus. The most abundant bacterial operational taxonomic units in the different pH environments were those related to carbohydrate-degrading bacteria, which are associated with constituents of co-substrate fermentation. Further analyses showed that during organic matter fermentation, a core microbiota composed of Firmicutes, Proteobacteria, and Bacteroidetes existed. Comparison analyses revealed that the bacterial community during fermentation was significantly affected by the pH, and that the diverse product distribution was related to the shift in bacterial communities.

This study aimed at quantifying the concentration and removal of antibiotic resistance genes (ARGs) in three municipal wastewater treatment plants (WWTPs) employing different advanced treatment systems [biological aerated filter, constructed wetland, and ultraviolet (UV) disinfection]. The concentrations of tetM, tetO, tetQ, tetW, sulI, sulII, intI1, and 16S rDNA genes were examined in wastewater and biosolid samples. In municipal WWTPs, ARG reductions of 1–3 orders of magnitude were observed, and no difference was found among the three municipal WWTPs with different treatment processes (p > 0.05). In advanced treatment systems, 1–3 orders of magnitude of reductions in ARGs were observed in constructed wetlands, 0.6–1.2 orders of magnitude of reductions in ARGs were observed in the biological aerated filter, but no apparent decrease by UV disinfection was observed. A significant difference was found between constructed wetlands and biological filter (p < 0.05) and between constructed wetlands and UV disinfection (p < 0.05). In the constructed wetlands, significant correlations were observed in the removal of ARGs and 16S rDNA genes (R2 = 0.391–0.866; p < 0.05). Constructed wetlands not only have the comparable ARG removal values with WWTP (p > 0.05) but also have the advantage in ARG relative abundance removal, and it should be given priority to be an advanced treatment system for further ARG attenuation from WWTP.

Urbanization and industrialization in China has resulted in a dramatic increase in the volume of wastewater and sewage sludge produced from wastewater treatment plants. Problems associated with sewage sludge have attracted increasing attention from the public and urban planners. How to manage sludge in an economically and environmentally acceptable manner is one of the critical issues that modern societies are facing.Sludge treatment systems consist of thickening, dewatering, and several different alternative main treatments (anaerobic digestion, aerobic digestion, drying, composting, and incineration). Agricultural application, landfill, and incineration are the principal disposal methods for sewage sludge in China. However, sewage sludge disposal in the future should focus on resource recovery, reducing environmental impacts and saving economic costs.The reuse of biosolids in all scenarios can be environmentally beneficial and cost-effective. Anaerobic digestion followed by land application is the preferable options due to low economic and energy costs and material reuse.It is necessary to formulate a standard suitable for the utilization of sewage sludge in China.

The effect of static magnetic field on polyhydroxyalkanoates (PHAs) syntheses by activated sludge under aerobic dynamic feeding (ADF) was evaluated in sequence batch reactors (SBR), with magnetic field intensities of 42, 21, 11 and 7 millitesla (mT) exposure in the feast, feast–famine and famine periods, respectively, and one control group without magnetic field exposure. Under each level of magnetic field intensity, the effect of magnetic field exposed in the famine period to PHAs syntheses was most significant in comparison with that in the feast or feast–famine period. Maximal hydroxybutyrate (HB) and (HV) yield occurred at 21 and 11 mT, respectively, and the minimal yield occurred at 42 mT during exposure in the famine period. The maximum biodegradable rate constant of PHA was noted at 11 mT during exposure in the famine period.

•The average relative abundance of RPPs genes was higher than two other genes.•The relative abundance of 12 ARGs in wastewaters were higher than those in manures.•TetM was more diverse in duck farms than in pig farms.•sulII was conserved sequence in both duck and pig farms.Increases of antibiotic resistance genes in the environment may pose a threat to public health. The purpose of this study was to investigate the abundance and diversity of tetracycline (tet) and sulfonamide (sul) resistance genes in eight livestock farms in Hangzhou, eastern China. Ten tet genes (tetA, tetB, tetC, tetG, tetL, tetM, tetO, tetQ, tetW, and tetX), two sul genes (sulI and sulII), and one genetic element associated with mobile antibiotic resistance genes [class 1 integron (intI1)] were quantified by real-time polymerase chain reaction. No significant difference was found in the abundance of the tet and sul genes in various scales of pig, chicken, and duck farms (P > 0.05). The average abundance of ribosomal protection protein genes (tetQ, tetM, tetW, and tetO) in the manure and wastewater samples was higher than most of the efflux pump genes (tetA, tetB, tetC, and tetL) and enzymatic modification gene (tetX) (P < 0.05), except for efflux pump gene tetG, which was abundant and showed no difference from tetM. Most ARGs had higher relative abundance in the wastewater lagoon than in manures even after treatment. Although the three ribosomal protection protein genes (tetQ, tetW, and tetO) had higher relative abundance, numbers were reduced during the complete wastewater treatment process in pig farms (P < 0.05). The relative abundance of tetG, sulI, and sulII increased after the wastewater treatment and the removal of these three genes exhibited significant positive correlations with the intI1 gene (tetG: R2 = 0.60, P < 0.05; sulI: R2 = 0.72, P < 0.05; sulII: R2 = 0.62, P < 0.05), suggesting that intI1 may be involved in their proliferation. As for tetM and sulII genes, a highly significant difference was found in manure samples between pig farms and duck farms (P < 0.001). Phylogenetic analysis showed that tetM was more diverse in duck farms than in pig farms. Additionally, sulII sequence was conserved both in pig and duck farms. This is the first comprehensive study to detail the relative abundance of specific ARGs in animal manures and agricultural wastewater treatment systems, potentially providing knowledge for managing antibiotic resistance emanating from agricultural activities.Download full-size image

Antibiotic resistance genes (ARGs) are emerging environmental contaminants and pose a threat to public health. In this study, four tetracycline resistance genes (tetM, tetO, tetQ and tetW) and two sulfonamide resistance genes (sulI and sulII) were evaluated in 4 municipal wastewater and 8 rural domestic sewage treatment systems with different wastewater handling abilities and treatment processes using quantitative polymerase chain reaction (qPCR). In the influents, the relative abundance of different ARGs showed significant variations among the sampling sites. In addition, significant correlations (tetQ: R2 = 0.712, P < 0.05; tetO: R2 = 0.394, P < 0.05) between the gene copy numbers and wastewater-receiving capacity were observed. Statistical analysis revealed a positive correlation (R2 = 0.756, P < 0.05) between the gene copy numbers of sulI and intI1, whereas the gene numbers of tetM and sulI were strongly correlated with 16S rDNA. Significant reductions (1–3 orders of magnitude) in ARGs were observed in municipal wastewater treatment systems, but a smaller reduction was found in the rural domestic sewage treatment systems. These results provide insights into the occurrence and removal of ARGs in wastewater treatment systems in both rural and urban areas in eastern China.Highlights► We evaluated ARG removal in municipal and rural domestic sewage treatment systems. ► The abundance of ARGs showed significant variation among the sampling sites. ► The tetQ gene number was correlated with wastewater-receiving capacity. ► Higher removal rate of tet genes was found in municipal sewage treatment systems. ► The constructed wetland with plants may play a major role in the removal of ARGs.

In this paper, the synthesis of polyhydroxyalkanoates (PHAs) by activated sludge with aerobic dynamic feeding process was conducted in a sequencing batch reactor by using food wastes and excess sludge fermentation liquid as the carbon source. The volatile fatty acids (VFAs) in the fermentation liquid were divided into even-numbered (acetic and butyric acid) and odd-numbered (propionic and valeric acid). The experiments conducted by central-composite design (CCD) showed that the pH could significantly affect the ratio of even-numbered to odd-numbered VFAs. Statistical analysis indicated a positive correlation (R2 = 0.97, P < 0.05) between the consumption of even-numbered VFAs and the synthesized of PHB, while the consumption of odd-numbered VFAs were correlated with the synthesized PHV. By controlling the ratio of even-numbered to odd-numbered VFAs, the contents of PHV in the PHAs could be controlled within the range of 22–30%. When fermentative VFAs were used as the substrate for the synthesis of PHAs, the microbial synthesis of PHA and biomass was higher than that mixture of analytically pure acids was used. These results are of vital significance for the comprehensive utilization of solid wastes.Highlights► The ratio of even to odd-numbered fermented VFAs could controlled by pH. ► The consumption of even-numbered VFAs was correlated with PHB synthesis. ► The consumption of odd-numbered VFAs was correlated with PHV synthesis. ► The fermentation VFAs are more suitable for the synthesis of PHAs.

The effect of 7 mT (milliTesla) SMF (static magnetic field) on poly-3-hydroxybutyrate (PHB) production was studied at an acetate concentration of 260 Cmmol l−1 and temperature of 10 °C. The SMF decreased the specific acetate uptake rate by 29%, but increased the maximum PHB content and the yield of PHB on acetate by 32 and 28% respectively. The ratio qP/(qS − qP), which described specific PHB production rate over the difference between specific acetate uptake rate and specific PHB production rate, was introduced for evaluation of the ratio of carbon flux into PHB synthesis and into the TCA (tricarboxylic acid) cycle. This value reached 2.3 when activated sludge culture was exposed to magnetic field of 7 mT, which was 1.1 times higher than the qP/(qS − qP) value obtained without magnetic exposure. Therefore, the SMF promoted diversion of more acetyl-CoA towards PHB synthesis and could offset adverse effects of high acetate concentration and low temperature. These results provide evidence that SMF enhances PHB production by activated sludge.

The effect of a static magnetic field on the acclimation of activated sludge with high polyhydroxyalkanoate (PHA) storage capacity was evaluated under aerobic dynamic feeding (ADF) conditions. The acclimation processes were carried out in Sequence Batch Reactors (SBRs) with static magnetic field intensities of 42, 21, 7, or 0 mT. Static magnetic exposure significantly influenced the PHA accumulation in activated sludge. PHA content in biomass reached 66% (on a COD basis) at a magnetic field intensity of 21 mT and an organic load of 5.42 g L−1, which was 16% higher than that of the control. Analysis by PCR-DGGE showed that the underlying mechanism might involve a change in the dominant species of microorganism in each reactor in response to the static magnetic field.

Hexavalent chromium (Cr(VI)) is a priority pollutant in the USA and many other countries. This study investigated the simultaneous remediation of Cr(VI) in sediment enriched with quinone-reducing microorganisms via a closely coupled, biotic–abiotic pathway. The results showed that Cr(VI) remediation was achieved by sediment adsorption and reduction of quinone-reducing microorganism. Moreover, microorganism reduction of Cr(VI) could be continued when sediment adsorption was saturated after long-term Cr(VI) remediation. The acetate and anthraquinone-2,6-disulfonate (AQDS), which acted as exogenous carbon and electron shuttle, respectively, were two crucial factors. The optimum concentrations of acetate and AQDS were 5 mM and 1 mM when the initial Cr(VI) concentration was 10 mg/L. AQDS was recycled, and it acted in a catalytic-type manner for the bacterial reduction of Cr(VI). Thus, biological humus reduction might provide an extensive pathway for the sequestration and detoxification of Cr(VI) in anaerobic soils, water, and industrial effluents.