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The high-frequency pulse flow, equivalent to the natural frequency of rocks, is generated by a self-excited oscillating cavity to achieve resonance rock-breaking. The flow field and oscillating mechanism of the self-excited oscillating cavity were simulated using the large eddy simulation method of Computational Fluid Dynamics (CFD). A field-scale testing apparatus was developed to investigate the impulse characteristics and verify the simulation results. The results show that the fluid at the outlet at the tool is deflected due to the pulse oscillation of the fluid. The size and shape of low-pressure vortices constantly change, leading to periodic changes in fluid impedance within the oscillating cavity. The impulse frequency reaches its highest point when the length–diameter ratio is 0.67. As the length–diameter ratio increases, the tool pressure loss also increases. Regarding the cavity thickness, the impulse frequency of the oscillating cavity initially decreases, then increases, and finally decreases again. Moreover, both the impulse frequency and pressure loss increase with an increase in displacement. The numerical simulation findings align with the experimental results, thus confirming the validity of the theoretical model. This research provides theoretical guidance for the practical application of resonance rock-breaking technology. [ABSTRACT FROM AUTHOR]

Abstract Dibenzothiophene (DBT) degradation mechanisms and the transformation of pathways during the incubation of three types of coastal sediments with C/N ratios ranging from 1 to 9 were investigated. The DBT degradation efficiencies were clearly improved with increasing C/N ratio in reed wetland sediments, tidal wetlands sediments and estuary wetland sediments. The quantitative response relationships between DBT degradation rates and related functional genes demonstrate that the Kodama pathway-related gene groups were dominant factors at low C/N ratios, while the 4S-related gene groups mainly determined the degradation rate when the C/N ratio was up to 5. Network analysis also shows that the pathway shifts from the Kodama pathway to the 4S pathway occurred through changes in the connections between functional genomes and rates. Furthermore, there were competition and collaboration between the Kodama and 4S pathways. The 4S pathway-related bacteria were more active in estuary wetland sediments compared with reed wetland sediments and tidal wetland sediments. The higher degradation efficiency in estuary wetland sediments may indicate the greater participation of the 4S pathway in the DBT biodegradation reaction. And the effects of ring cleavage of Kodama pathway caused more complete metabolizing of DBT. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

Abstract Nitrification and denitrification are important to nitrogen balance in agricultural ecosystems. However, the molecular drivers and limiting steps for these microbial processes in rice paddy soils are not well understood. Here, we assessed soil properties and abundances of functional genes affiliated with nitrification (amoA and nxrA), denitrification (nirS , nirK and nosZ), nitrate reduction (narG and napA) processes, and measured potential nitrification and denitrification rates (PNRs and PDRs) at 15 sites in Xiamen, China. The soil properties imposed indirect impacts on the potential rates by mediating the relative abundances of microbial communities. No significant relationships between the size of microbial communities and the potential rates were observed. Instead, we found the variables that best explained the variations in the PNRs and PDRs were AOB/nirS and (nirK + nirS) /nosZ , respectively. The PNRs were mainly limited by the relative strength of two steps, namely bacterial ammonium oxidation and nitrite into nitric oxide reduction, whereas the PDRs were mainly limited by the relative strength of the second and last denitrification steps. These results indicated that the dynamics of microbial communities based on the relative gene abundances are valuable in integrating fluctuations in soil physicochemical properties and are indictive of potential rates in paddy soils. Results of this study contribute to our quantitative understanding of the relative importance of soil physicochemical and biological factors in driving microbial potential in paddy soils. Graphical abstract Image 1 Highlights • Soil properties affected potential rates through relative gene abundances. • Soil pH was indicative of the ecological patterns of nitrifiers and denitrifiers. • No significant relationship was found between community size and potential rates. • Relative gene abundances were indictive of nitrification and denitrification rates. [ABSTRACT FROM AUTHOR]

Increased nitrous oxide (N 2 O) in the atmosphere is of global concern. Biofiltration has been studied for gaseous nitrogen treatments in drinking water environments; however, the molecular mechanisms mediating N 2 O accumulation in denitrification biofilters have not been quantified. Five denitrification biofilters were developed in this study and all achieved high removal efficiencies for total nitrogen (TN: 72.4–92.7%), nitrate nitrogen (NO 3 − -N: 88.6–98.2%) and chemical oxygen demand (COD: 79.3–90.0%) across a low-temperature gradient (5–25 °C). Denitrification coupling with anaerobic ammonium oxidation (ANAMMOX) and dissimilatory nitrate reduction to ammonium (DNRA) processes yielded the presently robust treatment performance. Nitrite availability limited TN removal at 5–15 °C. Our findings indicate that temperature affected N 2 O accumulation indirectly by controlling the balance of nitrite versus N 2 O reductase carrying microorganisms. In addition, our results demonstrated that genetic association was an important index reflecting the relative intensity of N 2 O accumulation at low temperatures. [ABSTRACT FROM AUTHOR]

Heterotrophic denitrification is usually inhibited by insufficient carbon sources; however, the underlying mechanisms responsible for nitrous oxide (N 2 O) accumulation within denitrification at low carbon:nitrogen (C/N) ratios have not been quantified from a molecular level. In this study, five denitrification biofilters were developed and exhibited efficiency (total nitrogen: 18.5%–92.2%; nitrate nitrogen: 42.9%–99.5%; chemical oxygen demand: 50.5%–93.7%) in remediating micro-polluted water with C/N ratios ranging between 0.65 and 3.0. A combined analysis revealed that the coupling of anaerobic ammonium oxidation (ANAMMOX) and denitrification accounted for N 2 O accumulation in the biofilters, and the key drivers of the N 2 O accumulation rates were qnorB/nirK , nosZ/(narG + napA) , amx/(nirS + nirK) , narG/bacteria and qnorB/bacteria . Our study demonstrated that genetic association was indicative of microbial processes relative to nitrogen cycling and reflected N 2 O flux within denitrification biofilters at low C/N ratios. [ABSTRACT FROM AUTHOR]

The present study explored the distribution patterns of nitrogen micro-cycle genes and the underlying mechanisms responsible for nitrogen transformation at the molecular level (genes) in a biotrickling filter (biofilter). The biofilter achieved high removal efficiencies for ammonium (NH 4 + -N) (80–94%), whereas nitrate accumulated at different levels under a progressive NH 4 + -N load. Combined analyses revealed the anammox, nas , napA , narG , nirS , and nxrA genes were the dominant enriched genes in different treatment layers. The presence of simultaneous nitrification, ammonium oxidation (anammox), and dissimilatory nitrate reduction to ammonium (DNRA) were the primary factors accounted for the robust NH 4 + -N treatment performance. The presence of DNRA, nitrification, and denitrification was determined to be a pivotal pathway that contributed to the nitrate accumulation in the biofilter. The enrichment of functional genes at different depth gradients and the multi-path coupled cooperation at the functional gene level are conducive to achieving complete nitrogen removal. [ABSTRACT FROM AUTHOR]

A denitrification biofilter (DB), developed for the remediation of groundwater in this study, operated with increased removal efficiencies of total nitrogen (TN, 35.1–93.2%), nitrate ( N O 3 − – N , 61.6–97.7%), and chemical oxygen demand (COD, 43.2–82.4%) as hydraulic retention time (HRT) increased from 0.5 h to 4.0 h. Declined denitrification rates of N O 3 − – N (123.1–24.9 g/(m 3 h)), N O 2 − – N (52.6–1.5 g/(m 3 h)), NO (22.9–3.2 mg/(m 3 h)) and N 2 O (64.8–11.1 g/(m 3 h)), were observed with increased HRTs from 0.5 h to 4.0 h. Gene abundances (total bacterial 16S rRNA, anaerobic ammonium oxidation (anammox) bacterial 16S rRNA, archaeal 16S rRNA, narG, napA, nirK, nirS, qnorB and nosZ ) were estimated and their relative importance in denitrification rates were quantified based on path analyses. As a result, the ratio ( napA + narG )/( nirK + nirS ), followed by nosZ /bacterial 16S rRNA were the main drivers for the transformation of N O 3 − – N and N O 2 − – N , while ( napA + narG )/( nirK + nirS ), followed by nosZ / narG dominated the accumulation of NO and N 2 O. In the content of environmental changes, this study suggests that gene associations integrating denitrification rates and recent environmental changes are valuable index reflecting variations in denitrification processes in groundwater restoration. [ABSTRACT FROM AUTHOR]

The multimedia biofilter achieved high and stable removal efficiencies for chemical oxygen demand (COD, 62–98%) and NH 4 + (68–98%) without costly aeration. Results revealed that lower CL (less than 13.9 g COD/m 3 d) and ACL (less than 2.8 g NH 4 + -N/m 3 d) or a C/N ratio exceeding five was required to reduce NO 3 − -N accumulation and NO/N 2 O emission. Integrated analyses indicated that the coupling of simultaneous nitrification, anammox and denitrification processes (SNAD) were the primary reason accounted for the enhanced NH 4 + -N treatment performance. NH 4 + -N removal pathways can be ranked as follows: nitrification ( amoA , archaeal) (54.6%) > partial denitrification ( nirS , nirK ) and anammox (37.8%) > anammox and partial denitrification ( narG , napA ) (12.6%). Specifically, NH 4 + -N removal was significantly inhibited by NO 2 − -N accumulation in the system (−21.6% inhibition). Results from stepwise regression analysis suggested that the NH 4 + removal rate was collectively controlled by amoA , archaeal, anammox, nirS , nirK , narG and napA . [ABSTRACT FROM AUTHOR]

An aerobic denitrification biofilter (ADB) for groundwater remediation was developed with high removal efficiencies (total nitrogen (TN): 82.3–95.8%; NO 3 − -N: 93.2–98.2%). Nitrate (NO 3 − -N) transformation rates stabilized between 21.0 and 23.4 g/(m 3 h), whereas nitrite (NO 2 − -N) and ammonium (NH 4 + -N) transformation rates remained less than 6.0 g/(m 3 h) as the dissolved oxygen (DO) level increased from 1.0 mg/L to 6.0 mg/L. Nitric oxide (NO) and nitrous oxide (N 2 O) accumulated with great fluctuations (NO: 0–1.6 × 10 −3 g/(m 3 h); N 2 O: 0.1–1.1 g/(m 3 h)) throughout the experiment. This study suggested that gene associations reflect quantitative relationships with aerobic denitrification rates and can provide useful information regarding aerobic denitrification processes in groundwater. Especially, the qnorB / nosZ ratio acts as the main driver for NO 3 − -N and NH 4 + -N transformation, while the qnorB / nosZ ratio followed by the ( nirS + nirK )/ nosZ ratio serve a dominant role in the accumulation of N 2 O and NO. [ABSTRACT FROM AUTHOR]

The present study explored the treatment performance and nitrogen removal pathways in a multimedia biofilter treating micro-polluted source water under hydraulic loading rate (HLR) constraints, ranging from 0.5 to 3.0 m 3 /m 2 d. High and stable chemical oxygen demand (COD) (97.7–99.1%) and ammonium (NH 4 + -N) (76.3–90.9%) removal efficiency were simultaneously achieved. Results showed that an HLR exceeding 2.5 m 3 /m 2 d was required to achieve complete denitrification without NO 3 − -N accumulation in the biofilter. Molecular biological analyses showed that nitrification and anaerobic ammonium oxidation were the dominant NH 4 + -N removal pathways in the biofilter. Quantitative analysis demonstrated that the key functional gene groups for NH 4 + -N transformation process rate were amoA /archaea, nxrA /archaea, and ( nirS + nirK )/anammox. Furthermore, nxrA /archaea contributed the most to the NH 4 + -N transformation rate, followed by ( nirS + nirK )/anammox, and amoA /archaea. The results support that archaea potentially play vital roles in the nitrogen removal pathways, and nitrogen transformation pathways are coupled at the molecular level (i.e., the functional gene level). [ABSTRACT FROM AUTHOR]

A study was conducted of treatment performance and nitrogen transformation processes in a trickling filter (TF) used to treat micro-polluted source water under variable hydraulic loading rates (HLRs), ranging from 1.0 to 3.0 m 3 /m 2 d. The TF achieved high and stable COD (97.7–99.3%) and NH 4 + -N (67.3–92.7%) removal efficiencies. Nitrification and anaerobic ammonium oxidation were the dominant nitrogen removal processes in the TF. Path analysis indicated that amoA /anammox and amoA /( narG + napA ) were the two key functional gene groups driving the major processes for NH 4 + -N and NO 2 − -N, respectively. The analysis also revealed that anammox/ amoA and nxrA /( nirK + nirS ) were the two key functional gene groups affecting processes associated with the NO 3 − -N transformation rate. The direct and indirect effect of functional gene groups further confirmed that nitrogen transformation processes are coupled at the molecular level, resulting in a mutual contribution to nitrogen removal in the TF. [ABSTRACT FROM AUTHOR]

The present study explored treatment performance and nitrogen removal mechanisms of a novel tidal flow constructed wetland (TF CW) under C/N ratios ranging from two to 12. High and stable COD (83–95%), NH 4 + − N (63–80%), and TN (50–82%) removal efficiency were simultaneously achieved in our single-stage TF CW without costly aeration. Results showed that a C/N ratio exceeding six was required to achieve complete denitrification without NO 2 − − N and NO 3 − − N accumulation in the system. Molecular biological analyses revealed aerobic ammonia oxidation was the dominant NH 4 + − N removal pathway when the C/N ratio was less than or equal to six. However, when the C/N ratio was greater than six, anammox was notably enhanced, resulting in another primary NH 4 + − N removal pathway, in addition to the aerobic ammonia oxidation. Quantitative response relationships between nitrogen transformation rates and nitrogen functional genes were established, and these relationships confirmed that different nitrogen transformation processes were coupled at the molecular level (functional genes), and collaboratively contributed to nitrogen removal in the TF CW. Specifically, NH 4 + − N transformation rates were collectively determined by amoA , nxrA , anammox, narG , nirS , nirK , and nosZ ; and TN removal was influenced primarily by amoA and anammox. [ABSTRACT FROM AUTHOR]

Abstract: Real-time PCR was fist used to quantitatively study the spatial distribution of the absolute abundance, relative abundance, and relative richness of amoA, nxrA, narG, napA, nirK, qnorB, nosZ, nas, and nifH genes and anaerobic ammonium oxidation (anammox, or ANO) bacteria in four multimedia biofilters. The results showed that these multimedia biofilters could provide NH4 + and total nitrogen (TN) average removal efficiencies of 88%. Except for nifH, ANO and the other nitrogen removal functional genes all were dominantly enriched in different zones. In fact, ANO, napA, qnorB, nosZ, and nxrA were enriched by 5.6–330.1 times; and nirK, narG, amoA, and nas were enriched by 1.4–2.1 times. In addition, ANO, napA, qnorB, and nosZ showed partially or mutually beneficial cooperation. The nxrA and nirK genes showed protocooperation, and the amoA and narG genes showed partially beneficial cooperation. [Copyright &y& Elsevier]

The current study determined the carboxymethyl cellulose (CMC) degradation efficiency, dominant microbial flora, eubacteria and archaebacteria characteristics, and expression levels of genes cel5A, cel6B, and bglC in an anaerobic/aerobic bio-reactor consisting of two-stage UASB (U1 and U2) and two-stage BAF (B1 and B2). The results showed that under three CMC loads, the CMC degradation efficiency of the UASB-BAF system was 91.25 %, 80.44 %, and 78.73 %, respectively. At higher CMC loads, the degradation of cellulose and transformation to cellobiose in U1 was higher, while the transformation to glucose was lower. The results of DGGE and real-time PCR indicated that cellulose degradation bacteria are dominant in U1, cellulose degradation bacteria and cellulose degradation symbiosis bacteria are dominant in B1, and non-cellulose degradation symbiosis bacteria are dominant in both U2 and B2. The rate-limiting enzyme gene of cellulose degradation in U1, B1, and B2 is cel6B, but it is cel5A in U2. [ABSTRACT FROM AUTHOR]

Abstract: This study explores a bibliometric approach to quantitatively evaluate global scientific constructed wetlands research, and statistically assess current trends, and future directions using the Science Citation Index Expanded (SCI-EXPANDED) database from 1991 to 2011. Articles referencing constructed wetlands were analyzed by accessing the following: publication language, output characteristics, publication performance by country and institution, author keywords, title words, and KeyWords Plus. Synthetically analyzing three keyword types, we concluded that the dominant constructed wetlands research hotspots from 1991 to 2011 included water, nutrients, plants, and flow. These four hotspots remained the most dominant research areas throughout our study period, and are predicted to remain the top research emphases in the near future. “Soil” also exhibited a notable increase since 2005, and is likely to become another notable area of research interest in the future. “Phytoremediation” and “horizontal” were not identified in 1991–1995, but exhibited marked increases from 136th (0.5%) and 169th (0.7%) in 1996–2000, to 9th (3.8%) and 11th (4.3%) in 2006–2011, respectively. Therefore, given the heightened attention during the last 15years, these topics are likely to become a primary research focus in upcoming years. [Copyright &y& Elsevier]

Abstract: A two-stage UASB and 2-stage BAF series bioreactor was used for treating the microcrystalline cellulose (MCC) wastewater. The treating efficiency, dominant microbes, eubacterial and archaebacterial composition and cel5A, cel6B and bglC gene expression levels were examined using combined PCR-DGGE and real-time PCR technology. The results showed that under three MCC loads (1000, 2000 and 3000mgL−1), the total MCC degradation efficiency of the UASB-BAF system was 82.0%, 83.5% and 70.5%, respectively. In different MCC load cases, the first stage UASB and BAF formed an approximate full-value cellulase system where cellulolytic microorganisms were the dominant flora, while the second stage UASB and BAF formed a low-value cellulase system where non-cellulolytic microorganisms were the dominant flora. Eubacteria were dominant in every UASB-BAF unit. The rate-limiting enzyme gene for MCC degradation in every unit was cel6B. These results will support the development of high efficiency bio-reactors for the degradation of MCC. [Copyright &y& Elsevier]

Abstract: We examined the effects of power and treatment time on the ultrasonically enhanced ozonation of carbazole dissolved in APG1214 surfactant solutions, including an analysis of the mechanism of l formation, the zeta potential of the colloidal suspension, the influence of ultrasound on micellar morphology, and the degradation kinetics for carbazole and APG1214. A 30min ultrasound treatment at 28kHz and 20W improved the degradation of carbazole by 5–10%, while power levels of 40W and 80W provided improvements only during the first 5min and resulted in reduced degradation after 15min. The tration was inversely proportional to ultrasound power, and directly proportional to the irradiation time. The absolute value of the APG1214 micelle zeta potential was inversely proportional to power and decreased with increasing irradiation time. The relationships of l concentration in APG1214 micelles, the zeta potential, and the micellar dynamic radius (R h) to ultrasonic power and time are the key factors affecting carbazole degradation in this system. [Copyright &y& Elsevier]

Abstract: The distribution patterns of amoA, nxrA, narG, napA, nirK, qnorB, nosZ, nas, nifH, and 16S rRNA of anammox bacteria (ANO) were quantitatively studied in four subsurface wastewater infiltration systems (SWIS). Furthermore, the ecological groups of nitrogen transformation functional genes and key nitrogen transformation pathways were investigated. The results indicated that ANO, qnorB, nifH, and other dominant genes were mainly enriched in the up-flow area of the SWIS; amoA, nxrA, nirK, narG, napA, and other rare genes together with the nosZ dominant gene community were mainly enriched in the infiltration area. The key mechanism of denitrification in the up-flow area was the coupled collaboration between anammox and reduction of NO to N2O catalyzed by the qnorB gene codase, while the key mechanisms of denitrification in the infiltration area included: anammox, nitrification, and the coupled collaboration between aerobic denitrification and reduction of N2O to N2 catalyzed by the nosZ gene codase. [Copyright &y& Elsevier]

Abstract: The present study, a quantitative investigation of distribution patterns of functional gene communities, including Anammox bacteria 16S rRNA, amoA, nxrA, narG, napA, nirK, qnorB, nosZ, nas, and nifH in two multimedia constructed wetland systems (CWs) was conducted. DGGE results showed similar distribution patterns in two constructed wetland groups. Lactococcus sp. and Moraxella sp. were the dominant organic nitrogen and denitrification flora; Acinetobacter sp. were the dominant NO3 − to NH4 + transformation flora; and Bacillus sp. and β-Proteobacteria sp. were the dominant NH4 + removal flora in the two constructed wetland groups. Quantitative real-time PCR results showed the qnorB and nas functional genes were predominantly enriched in the 15cm and 60cm layers of the CW, which was prepared by multi-media packing of 1% zero-valent iron. The nirK was predominantly enriched in the 60cm layer of the CW, which was prepared by multi-media packing of 2% zero-valent iron. Other functional nitrogen transformation genes were predominantly enriched in the 15cm layer of CWs. [Copyright &y& Elsevier]

Abstract: An ultrasound-enhanced five-stage gradient elution system employing mixed solutions of Triton X-100 (TX100), sodium dodecyl benzenesulfonate (SBDS), and salt (abbr. MSTS) was used to elute super heavy oil from weathered soils. The use of ultrasound increased the elution of super heavy oil by 13–14% and improved first-stage dissolution and dispersion by 62%. However, the amount of super heavy oil dissolved or dispersed in the second through fifth elution stages was unchanged by the application of ultrasound. Saturated hydrocarbons were more quickly eluted in the first two stages. During the final three stages the order of elution for the four identified super heavy oil fractions was: asphaltenes>saturated hydrocarbons>aromatics>resins. A large number of elution stages aided in eluting markers containing a large number of C atoms in the absence of ultrasound. The elution at each stage was higher when ultrasound was employed, and ultrasound-enhanced elution is a potentially useful method for removing super heavy oil from weathered soils. [ABSTRACT FROM AUTHOR]

Bacterial communities, taxonomic functional groups, and chemical characteristics of granular sludge were assessed in an ultrahigh-temperature (70°C) upflow anaerobic sludge blanket reactor (UASB) used to treat super heavy oil-containing wastewater. The UASB, with an organic loading rate of 3.0 kg COD m−3 day−1, achieved an average chemical oxygen demand removal of 48%, with 52% oil removal from the wastewater. It was also found to successfully degrade two typical biomarkers of super heavy oil, C26-34 17α 25-norhopanes and C26-28 triaromatic steroid. Scanning electron microscope, Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction results showed that the granular sludge became more compact with an increased quantity of extracellular polymeric substances, Fe2O3, FeS, and CaCO3 crystals in the reactor. Polymerase chain reaction-denaturing gradient gel electrophoresis and real-time polymerase chain reaction results indicated that after 90 days of operation, the density of total bacteria in the UASB dropped while Pseudomonas density increased, making it a dominant bacterium in the reactor. Data obtained from this research will provide useful information and insights with respect to effective treatment for super heavy oil wastewater under ultrahigh-temperature conditions. [ABSTRACT FROM AUTHOR]

Abstract: A multi-media biological aerated filter (MBAF) with clinoptilolite media was used to treat synthetic wastewater. Coal ash bioceramsite with supplemental metallic iron was added to the clinoptilolite media of MBAFs in a brick-wall embedded design. Performance parameters, such as hydraulic, organic, N and P loading capacity and microbial community composition were studied for different quantity of supplemental metallic iron contained in three MBAFs. The MBAFs with more metallic iron were found to have superior hydraulic and organic loading, and higher N and P capacities. COD, NH3–N and TP removal dropped by 7–10%, 6–7% and 4–5%, respectively, with when hydraulic loading was raised from 2.8 to 7.5 m3 m−2 d−1. NH3–N removal also decreased 8–9% when ammonia loading was elevated from 0.078 to 0.156kg NH3–Nm−3 d−1. Real-time PCR revealed a relatively stable bacterial community composed primarily of eubacteria that formed after an initial 120d operational period. Doubling the amount of metallic iron in the bioceramsite media resulted in a twofold increase of eubacteria in the MBAF, but a decrease in the ratio of anaerobic ammonia-oxidizing bacteria to total bacteria. [ABSTRACT FROM AUTHOR]

Abstract: A sequencing batch reactor (SBR) employing a low superficial gas velocity was used to produce aerobic granular sludge for wastewater treatment. At a gas velocity of 0.0056ms−1 sludge containing a mixture of light yellow and black granules with similar functional groups was quickly formed. The black granules contained crystals of CaCO3, FeS, and Fe2O3 as well as filamentous bacteria that strengthened the particles and reduced the mass transfer resistance. No inorganic crystals were detected in the yellow sludge granules, and their structure was maintained through cohesion mediated by extracellular polymeric substances (EPS). The light yellow granules were denser and offered better settling performance than the black granules, enhancing the settling properties of the mixed sludge. During a 12-h cycle, the maximum reductions in chemical oxygen demand (COD), NH3–N, and total nitrogen (TN) occurred at 240, 480, and 360min with removal efficiencies of 90%, 90%, and 54%. When the cycle time was limited to 480min, self-dissolution of the granules was avoided while sill maintaining removal efficiencies for COD, NH3–N, and TN of 88%, 90%, and 53%. [ABSTRACT FROM AUTHOR]

Ceramsite materials made from coal ash and modifiers such as sawdust, clinoptilolite, clay, and CaCO3 were prepared by pelletizing and high-temperature sintering to improve the adsorption to nitrogen and phosphorus. To incorporate Fe/C and Fe/Fe3C microelectrochemical cells, materials were also modified by the addition of metallic iron during the preparation process. Addition of more iron increased the Brunauer, Emmett, and Teller surface area and average pore diameter while decreasing the packing density and acid and alkali solubility. Examination using X-ray diffraction and X-ray fluorescence revealed that metallic iron modification also increased the abundance of Fe3C and FeC8 particles and electrochemical effects. Time required to reach adsorption equilibrium decreased with addition of iron. Ammonia nitrogen and phosphorus adsorption isotherms and kinetics for each ceramsite composition followed the Langmuir isotherm model in a similar second-order manner with respect to the amount of iron. Results provide useful information for preparing ceramsites with enhanced nitrogen and phosphorus adsorption capacity and thus improved biofilter efficiency. [ABSTRACT FROM AUTHOR]

Abstract: An ultrasound-enhanced elution system with Triton X-100 solution was used to remediate aging soils contaminated with super heavy oil. We used GC/MS, SEM, and X-ray diffraction (XRD) to analyze the effect of ultrasonic time (0–1800s) on the elution of super heavy oil and its three characteristic biomarkers (C26–34 17α 25-norhopanes, C26–28 triaromatic steroid [TAS], and C27–29 methyl triaromatic steroid [MTAS]). The oil and biomarkers remaining in the treated soils followed similar second-order functions with increasing ultrasonication times. Biomarker elution was closely related to carbon numbers in the marker. For C26–34 17α 25-norhopanes, the smaller molecules were more readily eluted during 0–360s ultrasound. This trend was reversed upon application of ultrasound during 1080–1800s, with improved elution of larger molecules and elution followed a similar second-order function. For C26–28 TAS, smaller molecules were more readily eluted but the elution of larger molecules followed a similar second-order function. For C27–29 MTAS, elution of larger molecules was close to that of C26–34 17α 25-norhopanes. Results of SEM and XRD indicated that the mineral and chemical compositions of soils eluted at ultrasonication times of 1080–1800s closely resembled clean soils. [Copyright &y& Elsevier]

Abstract: An ultrasound-enhanced elution system employing water at a temperature of 70°C was used to remedy weathered soils contaminated with severely biodegraded heavy oil (SBHO). The effect of varying the ultrasonic irradiation time from 0 to 1800s on the elution of SBHO and three characteristic biomarkers (C26–34 17α 25-norhopanes, C26–28 TAS, and C27–29 MTAS) was analyzed using GC/MS, scanning electron microscopy (SEM), and X-ray diffraction (XRD). Elution of the three biomarkers was closely related to the carbon number of the marker. C26–34 17α 25-norhopanes and C26–28 TAS species with higher carbon numbers and C27–29 MTAS species with lower carbon numbers were more readily eluted using sonication times of 1080–1800s, while smaller TAS homologs were more readily eluted after sonication times of 0–360s. SEM images of samples treated for longer periods revealed larger “bare patches” on the soil surface. The results of XRD and energy spectroscopy experiments indicated that ultrasound irradiation for 1080s negatively affected the deposition of CaCO3, but overall improved the mineral and chemical compositions of treated soils and removal of SBHO. [Copyright &y& Elsevier]

Abstract: An ultrasound-enhanced elution system employing Triton X-100 solutions was used for remedying aging soils contaminated with super heavy oil. The effect of varying the ultrasonic power density on the elution of the oil and three characteristic biomarkers was analyzed using GC/MS and FTRS. The oil and biomarkers remaining in treated soils decreased as a similar first-order function of increasing ultrasonic power density. Elution of the three biomarkers in the absence of ultrasound was closely related to carbon numbers in the marker: smaller molecules were more readily eluted. This trend was reversed upon application of ultrasound at higher power densities, with improved elution of molecules containing a greater carbon numbers. The two ratios, both 22S/(22S +22R) of C26–34 17α 25-norhopanes and 20S/(20S +20R) of C26–28 triaromatic steroids, in treated soils decreased with increasing power density from 20 to 100WL−1. The results of SEM, FTRS, XRD, and energy spectroscopy experiments indicated that the mineral and chemical compositions of soils eluted at power densities greater than 60WL−1 closely resembled clean soils. [Copyright &y& Elsevier]

Abstract: An ultrasound-enhanced elution system using water at a temperature of 70°C was employed to remove severely biodegraded heavy oil (SBHO) from weathered soil. The effect of varying the ultrasonic power density from 0 to 100WL−1 on the elution of SBHO and three characteristic biomarkers (C26–34 17α 25-norhopanes, C26–28 triaromatic steroids (TAS), and C27–29 methyl triaromatic steroids (MTAS) was analyzed using GC/MS, scanning electron microscopy (SEM), and X-ray diffraction (XRD). The amount of SBHO and biomarkers present in the treated soils and eluent had significant negative correlation with increasing ultrasonic power density. Elution of the three biomarkers was closely related to the number of C atoms in the marker: C26–34 17α 25-norhopanes with more carbon numbers and MTAS homologs with less carbon numbers were more readily eluted at higher power densities. The smaller TAS species were more readily eluted at a power density of less than 60WL−1, while larger TAS species displayed improved elution at power densities greater than 60WL−1. SEM images of samples treated at higher power densities revealed a more compact SBHO accumulation layer at the water–soil interface. The results of XRD and energy spectroscopy experiments indicated that ultrasound at a power density of 20WL−1 was helpful for the formation and sedimentation of calcite, although this effect disappeared at higher power of greater than 60WL−1. [Copyright &y& Elsevier]

Abstract: Status of, and changes in, the bacterial communities at two acclimation stages (with- and without-ultrasound) in a small 70°C ultrasound-enhanced anaerobic reactor for treating carbazole-containing wastewater reactor were analyzed by PCR–DGGE and real-time PCR techniques. PCR–DGGE results indicated that a large number of bands occurred in the whole sludge samples. Pseudomonas sp., Comamonas sp., and Diaphorobacter sp. were identified as being able to utilize carbazole as a carbon source, survive in an anaerobic and ultra-high-temperature environment and become dominant bacterial taxa during the with-ultrasound stage in the reactor. Total bacterial density in the with-ultrasonic stages was 10×higher than in the without-ultrasonic treatment. The proportion of Pseudomonas was relatively stable at 0.13%–0.15% in both acclimation stages, which indicates that Pseudomonas can flourish and promote carbazole degradation either with or without-ultrasound. These studies provide information on carbazole degradation under ultra-high-temperature conditions in an anaerobic environment. [Copyright &y& Elsevier]

Abstract: An up-flow fixed-bed (UFB) bioreactor with patented functional polyurethane foam (FPUF) carriers was used to treat sulfide in hydrocarbon wastewater. Community compositions of autotrophic and heterotrophic bacteria were analyzed by polymerase chain reaction–denaturing gradient gel electrophoresis (PCR–DGGE). DGGE results showed that a relatively stable bacterial community composed of heterotrophic and autotrophic bacteria formed in the bioreactor by the end of experiment, which ensured 92–100% sulfide removal efficiencies. Furthermore, autotrophic genera of Thiobacillus and Thiomonas, as well as those of the heterotrophic genus of Acinetobacter survived and exhibited high sulfide oxidation activity under all three operational conditions. Different special genera were also observed under each operational condition, such as the halophilic genus of Nesterenkonia. In addition, a new genus of sulfide oxidation bacteria was found in the bioreactor, which had the ability to synthesize cytoplasm from organic compounds. These genera have wide applications for the treatment of sulfide in hydrocarbon wastewater. [Copyright &y& Elsevier]

Abstract: Weathered crude oil contaminated soils (COCSs), which are much more difficult to remediate than those freshly contaminated, are widespread especially at the sites of oil fields and industries. Surfactant enhanced ex situ soil washing could be used to remediate COCSs, but surfactant toxicity becomes one of the major concerns. In this study, a class of green surfactants, alkyl polyglucosides (APGs), were tested in washing the field weathered COCS with relatively high oil concentration (123mgg−1 dry soil) from Jilin Oilfield, Northeastern China. APG1214, characterized with longer alkyl chain, was more effective than APG0810 in crude oil removal. Adding inorganic sodium salts into APG1214 solution further improved the crude oil removal efficiency (CORE). Washing parameters (temperature, washing time, agitation speed and solution/soil ratio) were investigated and further optimized integratedly with an orthogonal design. At the optimum conditions, the CORE reached 97%. GC/MS analysis showed that the proportion of small n-alkanes (C16–C23) in residual crude oil gradually increased, which was helpful to interpret the oil removal mechanism. Moreover, eminent effect on removal of large n-alkanes was achieved from the synergy between APG1214 and inorganic salts, which was opposite to the effect when they were added separately. This study demonstrated a promising way to remediate COCS with ecologically compatible surfactant and provided guidelines for its practical application. [Copyright &y& Elsevier]

Abstract: The impacts of heavy oil-contaminated soils on a reed wetland were studied during a 3-year field experiment in China''s Liaohe Oilfield. Contaminated soils with a 30% heavy oil concentration were spread in the reed wetland in April of the first 2 years with 0.2, 2, 6, 18, and 0kg of oil-polluted soil m−2 for 4 reed beds and a control. In the third year no polluted soil was spread in the wetland. Results indicated that removal efficiencies in 0–80cm soil layers were between 88 and 92% in the first 2 years, and up to 96% in the third year. The soil profile analysis pointed out that in the third harvest season, there was little residual heavy oil in soil layers 60–80cm deep, with most of heavy oils removed in the 0–20cm surface layer, thus avoiding additional pollution of the deep soil layer. Furthermore, contaminated soils had beneficial impacts on soil physiochemical indices of chloride (Cl−), pH, and organic matter in the 0–20cm surface layer, as well as allowing total nitrogen (TN) and total phosphorus (TP) in the 0–20cm surface layer to recover within the last 2 years of operation. At the end of this experiment, all these indices in the soil profile (0–80cm) followed the same trend as those in normal soil. During the first harvest season, reed biomass in the wetland increased with increasing heavy oil pollution loading. In the last two harvest seasons, reed biomass followed the same trend, i.e., at the highest and lowest contaminated soil levels (18 and 0.2kg oil-polluted soil m−2 soil, respectively), reed biomass in reed beds increased with time, and resulted in levels higher than in the control. In contrast, at middle contaminated soil levels (2 and 6kg oil-polluted soil m−2 soil) reed biomass followed an inverse trend similar to that experienced by the control. Reed health results suggested that contaminated soils had no obvious adverse effects on reed height and number of leaves, and no significant effect on the eco-physiological indices of reeds, including cellulose, pentose, lignose, length and width ratio of cellulose, and width of cellulose. There was also no effect on germination percentages from below-ground rhizomes, but some inhibition on the germination process. In order to analyze heavy oil uptake and distribution within reeds, a 14C-hexadecane tracer experiment was conducted in 2003. Results indicated that after a growing season, heavy oil concentrated mainly in the below-ground root of reeds. [Copyright &y& Elsevier]

A pilot subsurface flow constructed wetland (CW) has been constructed in the Liaohe Delta, China to treat heavy oil-produced water with large amounts of dissolved recalcitrant organic compounds. Pollutant concentrations and change of wetland plants were periodically monitored. Treatment effectiveness was evaluated and indicated high mean removal efficiencies, 81% for chemical oxygen demand (COD), 89% for biochemical oxygen demand (BOD5), 89% for mineral oil, and 81% for total Kjeldahl nitrogen (TKN) achieved in reed bed#2, to produce wetland effluent average concentrations with COD 77 mg l−1, BOD5 3.5 mg l−1, TKN 2.2 mg l−1, and mineral oil 2.9 mg l−1. We observed that during the vegetation growth period there was no influence of heavy oil-produced water on the numbers of leaves of reeds in CW, whereas, the biomasses and heights of reeds showed significant loss with increasing hydraulic loading. The heavy oil-produced water had no obvious effect on the reed indices of cellulous, lignin, pentose and the length/width ratio of cellulose. [Copyright &y& Elsevier]

Nitrate pollution in fresh water is becoming increasingly serious. In this study, the effects of temperature and graphene oxide materials on the potential functions of denitrification communities in lake sediments were investigated by metagenome. The addition of graphene oxide significantly affected the abundance of denitrification genes such as Nap , Nos , and enhanced the contribution of Pseudomonas , making low temperature and material addition conducive to the denitrification process. Module network implied that low temperature increased the centrality of denitrification in community functions. At low temperatures, graphene oxide enhanced community anabolism by stimulation organic carbon consumption and regulating the gene abundance in the citric acid cycle and the semi-phosphorylation Entner-Doudoroff, thus possibly stimulating extracellular polymeric substances (EPS) synthesis and secretion. In addition, graphene oxide may also regulate the transfer of reducing electrons from NADH to denitrifying enzymes by affecting the gene abundances of complex I and complex IV. [Display omitted] • Graphene oxide led to an increase in the proportion of denitrification genes at 8 °C. • Graphene oxide enhanced community anabolism at 8 °C. • Graphene oxide stimulated EPS synthesis and secretion at 8 °C. • Graphene oxide regulated the transfer of electrons to denitrifying enzymes. [ABSTRACT FROM AUTHOR]

The stable isotope technique has been used in tracking nitrogen cycling processes, but the isotopic characteristics are influenced by environmental conditions. To better understand the variability of nitrate isotopes in nature, we investigated the influence of organic carbon sources on isotope fractionation characteristics during microbial denitrification. Denitrifying cultures were inoculated with freshwater samples and enriched with five forms of organic compounds, that is, acetate, citrate, glucose, cellobiose, and leucine. Though the isotope enrichment factors of nitrogen and oxygen (15ε and 18ε) changed with carbon sources, 18ε/15ε always followed a proportionality near 1. Genome‐centred metagenomics revealed the enrichment of a few populations, such as Pseudomonas, Enterobacter, and Atlantibacter, most of which contained both NapA‐ and NarG‐type nitrate reductases. Metatranscriptome showed that both NapA and NarG were expressed but to different extents in the enrichments. Furthermore, isotopic data collected from a deep reservoir was analysed. The results showed δ18O‐ and δ15N‐nitrate did not correlate in the surface water where nitrification was active, but 18ε/15ε followed a proportionality of 1.05 ± 011 in deeper waters (≥ 12 m) where denitrification controlled the nitrate isotope. The independence of 18ε/15ε from carbon sources provides an opportunity to determine heterotrophic denitrification and helps the interpretation of nitrate isotopes in freshwaters. [ABSTRACT FROM AUTHOR]

Sulphur‐driven denitrification is a low‐cost process for the treatment of nitrate‐contaminated water. However, a comprehensive understanding of core populations and microbial interactions of a sulphur‐based denitrifying system is lacking. This study presents results from three replicated denitrifying systems amended with thiosulphate and operated under a low C/N ratio. Amplicon sequencing revealed gradual enrichments of a few abundant denitrifiers. Based on genome‐centred metagenomics and metatranscriptomics, a core set of microbes was identified in the systems, with Pseudomonas 1 and Thauera 2 being the most abundant ones. Although the replicates showed different enrichments, generalized observations were summarized. Most core populations conserved energy from denitrification coupled with sulphur. Pseudomonas 1 and Thauera 2 were able to finish complete denitrification. Surprisingly, they were also able to synthesize almost all amino acids and vitamins. In contrast, less abundant members, including Pseudomonas 2, were relatively auxotrophic and required an exogenous supply of amino acids and vitamins. The high expression of enzymes involved in biosynthesis and transport systems indicated their syntrophic relationships. The genomic findings suggested life strategies and interactions of the core thiosulphate‐based denitrifying microbiome, with implications for nitrate‐polluted water remediation. [ABSTRACT FROM AUTHOR]

The dominance of different nitrate-reducing pathways determines nitrogen cycling patterns. Denitrification (DNF) has been widely studied, but assimilatory nitrate reduction (ANR) and dissimilatory nitrate reduction to ammonium (DNRA) have received much less attention. Their ecological patterns and responsible microbes are poorly understood. Here, we studied the structure and function succession of the three functional groups in the middle route of the South-to-North Water Diversion Project, which is a 1230 km canal spanning 8 degrees of latitude. The results reflected a nitrogen-removing pattern dominated by DNF in the summer and a nitrogen-retaining pattern dominated by ANR and DNRA in the winter. Stenotrophomonas , a typical denitrifier, was the keystone species in the summer and contributed to N 2 O production. Clostridium , a genus able to conduct ANR and DNRA, was the keystone species in the winter. Notably, a significant zonation pattern was discovered. According to the community structure, the system could be separated into two biogeographic zones, and the Yellow River (about latitude 35°N) is an important cut-off line. This bacterial biogeography followed different water characteristics and ecological processes. ANR was found to be an important process and seasonally transformed its habitat from the northern zone to the southern zone. DNRA bacteria were acclimated to the northern zone and favored at this region in both seasons. The generation of N 2 O, a strong greenhouse gas, also exhibited this zonation pattern. This is the first study to consider assimilatory and dissimilatory nitrate reducers together at a molecular level, and provides new insights into the underlying patterns of a nitrate-reducing bacterioplankton community. [ABSTRACT FROM AUTHOR]

Hulun Lake is the largest lake in northeastern China, and its basin is located in China and Mongolia. This research aims to analyze the dynamic changes in the water volume of Hulun Lake and to estimate the groundwater recharge of the lake during the past 60 years. Multi-source data were used, and water-level-data-interpolation extrapolation, water-balance equations, and other methods were applied. The proportion of the contribution of each component to the quantity of water in Hulun Lake during the last 60 years was accurately calculated. Evaporation loss was the main component in the water loss in Hulun Lake. In the last 60 years, the average annual runoff into the lake was about 1.202 billion m3, and it was the factor with the largest variation range and the leading factor affecting the changes in the quantity of water in Hulun Lake. There was groundwater recharge in Hulun Lake for a long period, and the average annual groundwater recharge was about 776 million m3 (excluding leakage). The contribution ratio of the river water, groundwater, and precipitation to the recharging of Hulun Lake was about 5:3:2. The changes in the quantity of water in Hulun Lake are affected by climate change and human activities in China and Mongolia, especially those in Mongolia. [ABSTRACT FROM AUTHOR]

• A link between substrates, performance, isotopes and functional microbes was built. • δ18O was another indicator to discern carbon sources in addition to site preference. • Glucose led to the least N 2 O production due to the lowest abundance of NorB. • Glucose produced N 2 O with the highest site preference due to Thiobacillus -type cNorB. • Cellobiose led to the lowest δ18O due to cNorB and qNorB carried by Alicycliphilus. Denitrification is one of the major sources of N 2 O in freshwaters. Diverse forms of organic compounds act as the electron donors for microbial denitrification. However, the influences of carbon sources on N 2 O production, N 2 O reduction, isotope fractionation and functional microbes during denitrification were largely unknown. In this study, five forms of carbon sources (i.e. acetate, citrate, glucose, cellobiose and leucine) were used to enrich denitrifiers in freshwater sediments. N 2 O conversion in the enrichments was investigated by a combination of inhibition technique, natural stable isotope method and metagenomics. Acetylene was effective in inhibiting N 2 O reduction without influencing the isotopic characteristics during N 2 O production. Glucose led to the least N 2 O production and reduction, in accordance with the lowest abundance of both NO and N 2 O reductases in this enrichment. δ18O and site preference value (SP, =δ15Nα-δ15Nβ) of N 2 O were sensitive to discriminate the five carbon sources, except when comparing acetate and leucine. Isotopic values of N 2 O were not significantly different in these two enrichments due to the similarity of NO reductases - Pseudomonas -type cNorB. Specifically, the enrichment with cellobiose produced N 2 O with the lowest δ18O values (39.4‰±1.1‰), due to Alicycliphilus with both cNorB and qNorB. The enrichment with glucose led to the highest SP values (8.9‰±8.6‰), caused by Thiobacillus -type cNorB. Our results demonstrated the link between carbon sources, N 2 O production and reduction, isotopic signatures, microbial populations and enzymes during denitrification in freshwaters. [Display omitted] [ABSTRACT FROM AUTHOR]

Microbial nitrate reduction can be driven by organic carbon oxidation, as well as by inorganic electron donors, such as reduced forms of sulfur and iron. An apparent inverse oxygen isotope fractionation effect was observed during nitrate reduction in sediment incubations from five sampling sites of a freshwater lake, Hongze Lake, China. Incubations with organic and inorganic electron donor additions were performed. Especially, the inverse oxygen isotope effect was intensified after glucose addition, whereas the incubations with sulfide and Fe2+ showed normal fractionation factors. Nitrate reductase encoding genes, napA and narG, were analysed with metagenomics. Higher napA/narG ratios were associated with higher oxygen fractionation factors. The most abundant clade (59%) of NapA in the incubation with glucose was affiliated with Rhodocyclales. In contrast, it only accounted for 8%–9% of NapA in the incubations with sulfide and Fe2+. Differences in nitrate reductases might explain different oxygen isotope effects. Our findings also suggested that large variance of O‐nitrate isotope fractionations might have to be considered in the interpretation of natural isotope records. [ABSTRACT FROM AUTHOR]

The adsorption of organic pollutants from super heavy oil wastewater (SHOW) by lignite activated coke (LAC) was investigated. Specifically, the effects of LAC adsorption on pH, BOD 5 /COD Cr (B/C), and the main pollutants before and after adsorption were examined. The removed organic pollutants were characterized by Fourier transform infrared spectroscopy (FTIR), Boehm titrations, gas chromatography–mass spectrometry (GC–MS), and liquid chromatography with organic carbon detection (LC–OCD). FTIR spectra indicated that organic pollutants containing COOH and NH 2 functional groups were adsorbed from the SHOW. Boehm titrations further demonstrated that carboxyl, phenolic hydroxyl, and lactonic groups on the surface of the LAC increased. GC–MS showed that the removed main organic compounds are difficult to be degraded or extremely toxics to aquatic organisms. According to the results of LC–OCD, 30.37 mg/L of dissolved organic carbons were removed by LAC adsorption. Among these, hydrophobic organic contaminants accounted for 25.03 mg/L. Furthermore, LAC adsorption was found to increase pH and B/C ratio of the SHOW. The mechanisms of adsorption were found to involve between the hydrogen bonding and the functional groups of carboxylic, phenolic, and lactonic on the LAC surface. In summary, all these results demonstrated that LAC adsorption can remove bio-refractory DOCs, which is beneficial for biodegradation. [ABSTRACT FROM AUTHOR]

Effects of Cu(II) and Cr(III) ions on the binding of Al(III) onto Dissolved Organic Matter (DOM) exemplified by Suwannee River Humic Acid (SRHA) at pH 6.0 were quantified in this study using linear and log-transformed SRHA absorbance spectra acquired at varying Al 3+ concentrations and Cu 2+ or Cr 3+ levels. The competition between Al 3+ and Cu 2+ /Cr 3+ for the binding sites in DOM was ascertained by examining the intensity and shapes of the metal-specific differential spectra of DOM. The results indicated that the binding of Al 3+ onto SRHA is little influenced in the cases of in presence of 1.0 and 10.0 μM background Cr 3+ and in presence of 1.0 μM background Cu 2+ , but it is significantly depressed in presence of 10.0 μM Cu 2+ . Changes of the spectral slope of the log-transformed absorbance spectra in the 350–400 nm wavelength range (S 350-400 ) were unambiguously correlated with the total amount of DOM-bound metals. The concentrations of Me-DOM complexes were determined using the NICA-Donnan Model. The results demonstrate that differential absorbance measurements provide quantitatively interpretable information concerning the nature and mechanisms of metal-DOM interactions and effects of metal cations competition on these processes. [ABSTRACT FROM AUTHOR]

The present study explored treatment performance and nitrogen removal mechanisms of a single-stage tidal flow constructed wetland (TFCW) under flooded time ranging from 12 to 48 h. The TFCW achieved high and stable COD (77–94%), NH 4 + –N (55–82%), and TN (60–84%) removal efficiencies simultaneously, without costly aeration. Quantitative response relationships between nitrogen transformation rates and nitrogen functional genes were established, and these relationships confirmed that, under the FT constraints, the anammox 16S rRNA was the key factor of the NH 4 + –N transformation rates, whereas, ( napA + narG ) was the key factor regulating the NO 3 − –N transformation rate. The analysis also revealed that the simultaneous nitrification, anammox, and denitrification (SNAD) process was the dominant nitrogen removal pathway in the TFCW. [ABSTRACT FROM AUTHOR]

Nitrate contamination in aquatic systems is a widespread problem across the world. The isotopic composition (δ15N, δ18O) of nitrate and their isotope effect (15ε, 18ε) can facilitate the identification of the source and transformation of nitrate. Although previous researches claimed the isotope fractionations may change the original δ15N/δ18O values and further bias identification of nitrate sources, isotope effect was often ignored due to its complexity. To fill the gap between the understanding and application, it is crucial to develop a deep understanding of isotopic fractionation based on available evidence. In this regard, this study summarized the available methods to determine isotope effects, thereby systematically comparing the magnitude of isotope effects (15ε and 18ε) in nitrification, denitrification and anammox. We found that the enzymatic reaction plays the key role in isotope fractionations, which is significantly affected by the difference in the affinity, substrate channel properties and redox potential of active site. Due to the overlapping of microbial processes and accumulation of uncertainties, the significant isotope effects at small scales inevitably decrease in large-scale ecosystems. However, the proportionality of N and O isotope fractionation (δ18O/δ15N; 18ε/15ε) associated with nitrate reduction generally follows enzyme-specific proportionalities (i.e., Nar, 0.95; Nap, 0.57; eukNR, 0.98) in aquatic ecosystems, providing enzyme-specific constant factors for the identification of nitrate transformation. With these results, this study finally discussed feasible source portioning methods when considering the isotope effect and aimed to improve the accuracy in nitrate source identification. [Display omitted] • Ignorance of isotope fractionations impedes the nitrate source identification. • Enzymatic reaction is the fundamental factor to drive isotope fractionations. • 18ε/15ε provides specific constant factors for nitrate source identification • Appropriate practices of isotopic effect improves the accuracy of identification. [ABSTRACT FROM AUTHOR]

Nitrate contamination in aquatic systems is a widespread problem across the world. The isotopic composition (δ15N, δ18O) of nitrate and their isotope effect (15ε, 18ε) can facilitate the identification of the source and transformation of nitrate. Although previous researches claimed the isotope fractionations may change the original δ15N/δ18O values and further bias identification of nitrate sources, isotope effect was often ignored due to its complexity. To fill the gap between the understanding and application, it is crucial to develop a deep understanding of isotopic fractionation based on available evidence. In this regard, this study summarized the available methods to determine isotope effects, thereby systematically comparing the magnitude of isotope effects (15ε and 18ε) in nitrification, denitrification and anammox. We found that the enzymatic reaction plays the key role in isotope fractionations, which is significantly affected by the difference in the affinity, substrate channel properties and redox potential of active site. Due to the overlapping of microbial processes and accumulation of uncertainties, the significant isotope effects at small scales inevitably decrease in large-scale ecosystems. However, the proportionality of N and O isotope fractionation (δ18O/δ15N; 18ε/15ε) associated with nitrate reduction generally follows enzyme-specific proportionalities (i.e., Nar, 0.95; Nap, 0.57; eukNR, 0.98) in aquatic ecosystems, providing enzyme-specific constant factors for the identification of nitrate transformation. With these results, this study finally discussed feasible source portioning methods when considering the isotope effect and aimed to improve the accuracy in nitrate source identification. [Display omitted] • Ignorance of isotope fractionations impedes the nitrate source identification. • Enzymatic reaction is the fundamental factor to drive isotope fractionations. • 18ε/15ε provides specific constant factors for nitrate source identification • Appropriate practices of isotopic effect improves the accuracy of identification. [ABSTRACT FROM AUTHOR]

[Display omitted] • Iron-based denitrification improved nitrogen removal at low C/N ratio in freshwaters. • Microbially mediated denitrification dominated rather than chemodenitrification. • Five fast-growing microbes accounted for over 99% of the community. • Amino acids and vitamins needed by an organism could be satisfied by another member. • The two-partner relationships increased community stability without limiting activity. Iron-dependent denitrification is a safe and promising technology for nitrogen removal in freshwaters. However, the understanding of microbial physiology and interactions during the process was limited. Denitrifying systems inoculated with freshwater samples were operated with and without iron(II) at a low C/N ratio for 54 days. Iron addition improved nitrogen removal. Batch experiments confirmed that microbially mediated reaction rather than abiotic reaction dominated during the process. Metagenomics recovered genomes of the five most abundant microorganisms, which accounted for over 99% of the community in every triplicate of the iron-based system. Based on codon usage bias, all of them were fast-growing organisms. The total abundance of fast-growing organisms was 38% higher in the system with iron than in the system without iron. Notably, the most abundant organism Diaphorobacter did not have enzymes for asparagine and aspartate biosynthesis, whereas Rhodanobacter could not produce serine and cobalamin. Algoriphagus and Areminomonas lost synthesis enzymes for more amino acids and vitamins. However, they could always obtain these growth-required substances from another microorganism in the community. The two-partner relationship minimized the limitation on microbial reproduction and increased community stability. Our results indicated that iron addition improved nitrogen removal by supplying electron donors, promoting microbial growth, and building up syntrophic interactions among microorganisms with timely communications. The findings provided new insights into the process, with implications for freshwater remediation. [ABSTRACT FROM AUTHOR]

Abstract The present study characterized the distribution and sources of polycyclic aromatic hydrocarbons (PAHs) in 57 sediment cores collected from estuary and tidal flat wetlands in the Bohai coast region and investigated the molecular degradation mechanism of PAHs. The results showed that the PAH concentrations in estuary sediments were significantly higher than in tidal flat sediments. PAH patterns and pollutant sources were more complicated in estuary sediments. Quantitative response relationships showed that in estuary sediments, the key factors affecting PAH degradation changed from initial dioxygenase genes and C23O to salicylate hydroxylase genes and C23O with an increase in the PAH ring number. In contrast, for tidal flat sediments, the initial dioxygenase genes remained the key factors (nidA and nahAc / nagAc , except only nidA for 5-ring PAHs) related to PAHs with different ring numbers. Non-metric multidimensional scaling (NMDS) analysis revealed that the lower catechol dioxygenase pathway coupled with the upper pyrene dioxygenase pathway. The total polycyclic aromatic hydrocarbon (TPAH) level across the Bohai coast region was most affected by catechol dioxygenation (catA + C23O). Catechol dioxygenation was directly affected by naphthalene dioxygenation/ nahG ((nahAc + nagAc)/ nahG), indicating that the interaction within the upper pathway coupled with the lower pathway. In addition, TOC had direct positive effects on catechol dioxygenation and nidA. This study improves our understanding of the biodegradative pathway of PAHs with different ring numbers and the response of PAHs to biotic and abiotic factors. Graphical abstract Image 1 Highlights • Initial dioxygenase genes were key factors for 2–6 ring PAHs in tidal flat sediments. • The lower pathway was dominant in the degradation of HMW PAHs in estuary sediments. • Lower catechol dioxygenase pathway coupled with upper pyrene dioxygenase pathway. • Catechol dioxygenation contributes to TPAH most and is directly affected in Bohai rim. [ABSTRACT FROM AUTHOR]

Abstract In this study, the spatial and seasonal bacterioplankton community dynamics were investigated in the main channel of the Middle Route of the South-to-North Water Diversion Project (MRP) using Illumina HiSeq sequencing. Water samples were collected in spring and summer from south to north at eight water quality monitoring stations, respectively. The results showed that seasonal changes had a more pronounced effect on the bacterioplankton community compositions (BCCs) than spatial variation. The diversity analysis results indicated that samples of summer have more operational taxonomic units (OTUs), higher richness and diversity than those in spring. The main phyla, Proteobacteria , Actinobacteria , Bacteroidetes , Cyanobacteria and Chloroflexi , displayed significant differences (P < 0.05) between spring and summer in the main channel. The Redundancy analysis (RDA) targeting all samples indicated that specific conductivity (SPC), dissolved oxygen (DO), pH and temperature (T) might be key factors in driving BCCs, while trophic status showed no significant correlation (P > 0.05). The present study provides important insights into the potential ecological roles of specific taxa in the new artificial ecosystem and it offers reference for studies on ecosystem succession of other giant interbasin water diversion project in the world. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Adding an external source under low C/N can significantly improve nitrogen removal efficiency. • N transformation processes were coupled at the functional genes level. • The vertical distribution of the microbial community in CWs was a remarkable discrepancy. • Adding rice husk as a carbon source could be conducive to the complete nitrification process. Abstract The effect of adding rice husk as an electron donor on the genetic and metabolic diversity of denitrifying communities in a long-term flooded constructed wetland (D1) was compared with the control group without external carbon source addition (D2). The underlying molecular mechanisms responsible for nitrate removal were quantified under different nitrate loading rates. The results showed that D1 achieved higher and more stable removal efficiencies for NO 3 −-N (90–97%) and total nitrogen (73–87%) under different nitrate loading rates, which were approximately 10 times higher than those of D2. This corresponded with much higher absolute abundances of bacterial and nitrogen functional genes in D1 than D2. Additionally, the vertical distribution of microbial communities in D1 and D2 showed significant differences. This pattern suggested that adding rice husk in flooded CWs had beneficial effects on the denitrifying community. Quantitative response relationships and network analysis indicated that denitrification was the dominant nitrogen removal pathway. Moreover, the present study indicated that using rice husk as an external carbon source could be conducive to completing the nitrification process, which was first confirmed at the molecular level. The present study indicated that using rice husk as an external carbon source can significantly enhance denitrification rates and thus improve nitrogen removal in CWs for wastewater treatment process. [ABSTRACT FROM AUTHOR]

The widely applied aromatic nitration in modern industry leads to toxic p -nitrophenol (PNP) in environment. Exploring its efficient degradation routes is of great interests. In this study, a novel four-step sequential modification procedure was developed to increase the specific surface area, functional group, hydrophilicity, and conductivity of carbon felt (CF). The implementation of the modified CF promoted reductive PNP biodegradation, attaining 95.2 ± 0.8% of removal efficiency with less accumulation of highly toxic organic intermediates (e.g., p -aminophenol), compared to carrier-free and CF-packed biosystems. The constructed anaerobic-aerobic process with modified CF in 219-d continuous operation achieved further removal of carbon and nitrogen containing intermediates and partial mineralization of PNP. The modified CF promoted the secretion of extracellular polymeric substances (EPS) and cytochrome c (Cyt c), which were essential components to facilitate direct interspecies electron transfer (DIET). Synergistic relationship was deduced that glucose was converted into volatile fatty acids by fermenters (e.g., Longilinea and Syntrophobacter), which donated electrons to the PNP degraders (e.g., Bacteroidetes_vadinHA17) through DIET channels (CF, Cyt c, EPS) to complete PNP removal. This study proposes a novel strategy using engineered conductive material to enhance the DIET process for efficient and sustainable PNP bioremediation. [Display omitted] • Four-step sequential modification for carbon felt (CF) was conducted. • Modified CF promoted PNP biodegradation, with less accumulation of PAP. • DIET was enhanced between fermenters and PNP degraders. • Contents of EPS and Cyt c facilitating DIET increased. [ABSTRACT FROM AUTHOR]