BACKGROUND Anoxic brain injury is a potentially lethal condition characterized by cerebral hypoperfusion and irreversible neuronal injury.Arterial spin-labeling(ASL)perfusion and diffusion-weighted imaging(DWI)magneti...BACKGROUND Anoxic brain injury is a potentially lethal condition characterized by cerebral hypoperfusion and irreversible neuronal injury.Arterial spin-labeling(ASL)perfusion and diffusion-weighted imaging(DWI)magnetic resonance imaging(MRI)have been proposed as tools to detect cerebral ischemic changes and may aid in the assessment of anoxic injury.AIM To explore the relationship between regional ASL perfusion patterns and clinical outcomes following cardiac arrest.METHODS We performed a retrospective review to identify patients with clinical suspicion of anoxic brain injury who underwent MRI within 15 days of cardiac arrest.Receiver operator characteristic(ROC)analysis and univariate logistic regression were used to evaluate associations between ASL perfusion scores,DWI signal intensity,and the following clinical features:(1)Myoclonus status epilepticus(MSE)within 24 hours;(2)Absent extensor or motor reflexes(EMR)at day 3 post-arrest;and(3)Absent brainstem reflexes(BSR)within 15 days.RESULTS Twenty-eight patients met inclusion criteria.Increased ASL signal in the left occipital lobe was significantly associated with MSE(P=0.038),while a trend was observed between right frontal ASL signal and EMR(P=0.078).ROC analysis showed that ASL scores≥7 were associated with higher odds of absent BSR(OR 2.14,P=0.53),though this did not reach statistical significance.DWI signal intensity did not show significant associations with clinical outcomes.The overall discriminatory performance of ASL for predicting outcomes was limited(AUC≈0.52).CONCLUSION This exploratory study suggests that regional ASL hyperperfusion,particularly in the left occipital and right frontal lobes,may be associated with adverse clinical signs following cardiac arrest.However,most findings did not reach statistical significance,and the study was underpowered to detect small-to-moderate effects.These preliminary results should be interpreted with caution and considered hypothesis-generating.Larger,prospective studies are warranted to clarify the prognostic value of ASL perfusion imaging in anoxic brain injury.展开更多
[Objective] The aim of this study was to provide a fast, stable and efficient piggery wastewater processing technology. [Method] The start-up process was studied through the experiment of piggery anaerobic fermentatio...[Objective] The aim of this study was to provide a fast, stable and efficient piggery wastewater processing technology. [Method] The start-up process was studied through the experiment of piggery anaerobic fermentation slurry treated by Anoxic/Oxic （A/O） reactor. The process was divided into two stages： at the first stage, dominant micro flora were cultivated in Anoxic and Oxic reaction tanks respectively; at the second stage. Anoxic and Oxic reaction tanks were initiated jointly to gradually enhance water load and continued to cultivate and domesticate microorganisms, and finally the start-up process was completed. [ Result] The results showed that return mixture ratio and return sludge ratio was 2 and 1 respectively when the temperature reached 32 ±2 ℃. However. when aeration rate of Oxic reaction amounted to 0.5 m^3/h, the re- moval rate of COD and NH4^＋ -H were 89.87% and 89.31% respectively through practical operation within 50 days, which indicated that the start- up process through A/O reactor was successful. Conclusion This study can provide a scientific basis and reference for innocuous technique of piggery anaerobic fermentation slurry treatment.展开更多
Kinetics models of COD degradation,biomass growth of the anoxic-oxic ( A/O) system as well as NH3-N degradation in aerobic phase were presented according to the mass balance theory,reaction-diffusion theory and Fick l...Kinetics models of COD degradation,biomass growth of the anoxic-oxic ( A/O) system as well as NH3-N degradation in aerobic phase were presented according to the mass balance theory,reaction-diffusion theory and Fick law. Then these models were testified by comparson with experimental results. It is demonstrated that the variation trends of theoretical and experimental values for COD degradation and biomass growth are similar. The deviation rate between theoretical and experimental values is always under 20% even it increases along with the fluctuation of influent organic loading. In terms of NH3-N degradation,nitrification can also be well simulated by the model as the substrates of influent are sufficient. It indicates that the model can accurately reflect the reaction in hybrid A/O process. Models presented herein provide a theoretical basis for the design, operation and control of hybrid A/O process.展开更多
Introduction.The study of catastrophic events that affected past marine ecosystems provides us the unique opportunity to establish models which can be applied to ongoing environmental changes and to understand future ...Introduction.The study of catastrophic events that affected past marine ecosystems provides us the unique opportunity to establish models which can be applied to ongoing environmental changes and to understand future evolution of the biotas.The growing interest of the society for the ongoing and potential future environmental changes attests for the value represented by the analysis of past climatic changes.In the case of the Toarcian Oceanic Anoxic Event(T-OAE,Early Jurassic;~182 Ma),a dramatic change of marine ecosystems related to massive extinction has been documented in several areas around the world.The Pliensbachian–Toarcian transition and the T-OAE are two global episodes recording worldwide palaeoenvironmental perturbations(Jenkyns,1988;Jenkyns and Clayton,1997;Hesselbo et al.,2007).The end of the Pliensbachian regression is followed by a transgression occurring in the Early Toarcian(Haq et al.,1987;de Graciansky et al.,1999).This transgression was also coeval with a widespread deposition of black shales(Jenkyns,1988),a global warming(Garcia Joral et al.,2011;Korte and Hesselbo,2011;Suan et al.,2011),and perturbations of the carbon cycle indicated by a negative carbon isotopic excursion(CIE)documented in both marine and terrestrial material(Jenkyns and Clayton,1986;Schouten et al.,2000;Hesselbo et al.,2007;Al-Suwaidi et al.,2010;Caruthers et al.,2011;Izumi et al.,2012;Reolid,2014).展开更多
In order to enhance phosphorus removal in traditional step-feed anoxic/oxic nitrogen removal process,a modified pilot-scale step-feed anaerobic/anoxic/oxic(SFA 2/O) system was developed,which combined a reactor simila...In order to enhance phosphorus removal in traditional step-feed anoxic/oxic nitrogen removal process,a modified pilot-scale step-feed anaerobic/anoxic/oxic(SFA 2/O) system was developed,which combined a reactor similar to UCT-type configuration and two-stage anoxic/oxic process.The simultaneous nitrogen and phosphorus removal capacities and the potential of denitrifying phosphorus removal,in particular,were investigated with four different feeding patterns using real municipal wastewater.The results showed that the feeding ratios(Q1)in the first stage determined the nutrient removal performance in the SFA 2/O system.The average phosphorus removal efficiency increased from 19.17% to 96.25% as Q1 was gradually increased from run 1 to run 4,but the nitrogen removal efficiency exhibited a different tendency,which attained a maximum 73.61%in run 3 and then decreased to 59.62%in run 4.As a compromise between nitrogen and phosphorus removal,run 3 (Q1=0.45Qtotal) was identified as the optimal and stable case with the maximum anoxic phosphorus uptake rate of 1.58 mg·(g MLSS)-1 ·h-1.The results of batch tests showed that ratio of the anoxic phosphate uptake capacity to the aerobic phosphate uptake capacity increased from 11.96% to 36.85% with the optimal influent feeding ratio to the system in run 3,which demonstrated that the denitrifying polyP accumulating organisms could be accumulated and contributed more to the total phosphorus removal by optimizing the inflow ratio distribution.However,the nitrate recirculation to anoxic zone and influent feeding ratios should be carefully controlled for carbon source saving.展开更多
This paper presents new geological and geochemical data from the Shuanghu area in northern Tibet, which recorded the Early Toarcian Oceanic Anoxic Event. The stratigraphic succession in the Shuanghu area consists most...This paper presents new geological and geochemical data from the Shuanghu area in northern Tibet, which recorded the Early Toarcian Oceanic Anoxic Event. The stratigraphic succession in the Shuanghu area consists mostly of grey to dark-colored alternating oil shales, marls and mudstones. Ammonite beds are found at the top of the Shuanghu oil shale section, which are principally of early Toarcian age, roughly within the Harplocearas falciferrum Zone. Therefore, the oil shale strata at Shuanghu can be correlated with early Toarcian black shales distributing extensively in the European epicontinental seas that contain the records of an Oceanic Anoxic Event. Sedimentary organic matter of laminated shale anomalously rich in organic carbon across the Shuanghu area is characterized by high organic carbon contents, ranging from 1.8% to 26.1%. The carbon isotope curve displays the δ 13C values of the kerogen (δ 13Ckerogen) fluctuating from –26.22 to –23.53‰ PDB with a positive excursion close to 2.17‰, which, albeit significantly smaller, may also have been associated with other Early Toarcian Oceanic Anoxic Events (OAEs) in Europe. The organic atomic C/N ratios range between 6 and 43, and the curve of C/N ratios is consistent with that of the δ 13Ckerogen values. The biological assemblage, characterized by scarcity of benthic organisms and bloom of calcareous nannofossils (coccoliths), reveals high biological productivity in the surface water and an unfavorable environment for the benthic fauna in the bottom water during the Oceanic Anoxic Event. On the basis of organic geochemistry and characteristics of the biological assemblage, this study suggests that the carbon-isotope excursion is caused by the changes of sea level and productivity, and that the black shale deposition, especially oil shales, is related to the bloom and high productivity of coccoliths.展开更多
A novel modified pilot scale anaerobic oxidation ditch with additional internal anoxic zones was operated experimentally, aiming to study the improvement of biological nitrogen and phosphorus removal and the effect of...A novel modified pilot scale anaerobic oxidation ditch with additional internal anoxic zones was operated experimentally, aiming to study the improvement of biological nitrogen and phosphorus removal and the effect of enhanced denitrifying phosphorus removal in the process. Under all experimental conditions, the anaero- bic-oxidation ditch with additional internal anoxic zones and an internal recycle ratio of 200% had the highest nutrient removal efficiency. The effluent NH4 -N, total nitrogen （TN）, PO3 -P and total phosphorus （TP） contents were 1.2 mg.L-1, 13 mg.L 1, 0.3 mg.L -1 and 0.4 mg.L-1, respectively, all met the discharge standards in China. The TN and TP removal efficiencies were remarkably improved from 37% and 50% to 65% and 88% with the presence of additional internal anoxic zones and internal recycle ratio of 200%. The results indicated that additional internal anoxic zones can optimize the utilization of available carbon source from the anaerobic outflow for denitrification. It was also found that phosphorus removal via the denitrification process was stimulated in the additional internal anoxic zones, which was beneficial for biological nitrogen and phosphorus removal when treating wastewater with a limited carbon source. However, an excess internal recycle would cause nitrite to accumulate in the system. This seems to be harmful to biological phosphorus removal.展开更多
The early Albian Oceanic Anoxic Event 1 b(OAE 1 b) is well documented in the Tethys, Pacific and North Atlantic, but few studies have evaluated whether or not terrestrial records of OAE 1 b exist. In order to identify...The early Albian Oceanic Anoxic Event 1 b(OAE 1 b) is well documented in the Tethys, Pacific and North Atlantic, but few studies have evaluated whether or not terrestrial records of OAE 1 b exist. In order to identify terrestrial records of the early Albian OAE 1 b and to infer possible driving mechanisms, an integrated multi-proxy study from the late Aptian to Albian in the Fuxin lacustrine basin was conducted,including thick, organic-rich black mudstones, total organic carbon(TOC), organic carbon isotopes(d13 Corg), mercury concentration(Hg) and results from pyrolysis analyses(S2, Tmaxand HI). Results show three distinct short-term negative d13 Corgexcursions corresponding with relatively high TOC values,which could be counterparts of the Kilian, Paquier and Leenhardt sub-events of the early Albian OAE1 b. Atmospheric CO2 concentration(p CO2) recovered from C3 plant d13 Corgcompositions indicates an increasing trend in Unit C during the early Albian, and there are three short-term increases of p CO2 corresponding to the three sub-events of OAE 1 b at this time interval. We infer that a trend of increasing p CO2 during the Kilian sub-event in the study area is closely related to volcanism. Continental weathering calculated using chemical weathering indices(CIA, WIP and MIA(O)) show an increasing trend during the OAE 1 b interval, likely resulting from warmer and more humid conditions. Mixed sources of terrestrial plants and lacustrine plankton demonstrated by pyrolysis analyses(HI vs. Tmaxand S2 vs. TOC), indicate a terrestrial contribution to the organic-rich sediments of the Kilian, Paquier and Leenhardt sub-events of OAE 1 b. We suggest that a CO2-forced greenhouse effect during the early Albian might have triggered the relatively warm and humid palaeoclimatic conditions, and intensified chemical weathering that combined to create high nutrient and organic matter levels that were flushed into lakes contributing to eutrophication and anoxia in lacustrine and in contemporaneous oceanic systems.展开更多
Removal of denitrifying phosphorus was verified in a laboratory anaerobic/anoxic sequencing batch reactor (A/A SBR). The results obtained demonstrated that the anaerobic/anoxic strategy can enrich the growth of denitr...Removal of denitrifying phosphorus was verified in a laboratory anaerobic/anoxic sequencing batch reactor (A/A SBR). The results obtained demonstrated that the anaerobic/anoxic strategy can enrich the growth of denitrifying phosphorus removing bacteria (DPB) and take up phosphate under anoxic condition by using nitrate as the electron acceptor. The phosphorus removal efficiency was higher than 90% and the effluent phosphate concentration was lower than 1 mg·L-1 after the A/A SBR was operated in a steady-state. When the chemical oxygen demand(COD) of influent was lower than 180mg· L-1, the more COD in the influent was, the higher efficiency of phosphorus removal could be attained under anoxic condition. However, simultaneous presence of carbon and nitrate would be detrimental to denitrifying phosphorus removal. Result of influence of sludge retention time (SRT) on denitrifying phosphorus removal suggested that the decrease of SRT caused a washout of DPB and consequently the enhanced biological phosphorus removal decreased with 8 days SRT. When the SRT was restored to 16 days, however, the efficiency of phosphorus removal was higher than 90%.展开更多
To achieve stable and efficient nitrogen and phosphorus removal and to investigate the characteristics of the A/A SBR enriched with denitrifying phosphorus removal bacteria(DPB),the whole course of startup was studied...To achieve stable and efficient nitrogen and phosphorus removal and to investigate the characteristics of the A/A SBR enriched with denitrifying phosphorus removal bacteria(DPB),the whole course of startup was studied with two reactors operated in different mode.The reactor I was operated under anaerobic/settling/anoxic/settling mode,and the reactor II was operated under anaerobic/anoxic/settling mode.Differences between the two reactors in removal efficiency of COD,nitrogen and phosphorus were examined.The results indicated that efficient performance could be achieved in both reactors with different startup operation mode,while the phosphorus removal efficiency was improved sooner in reactor I than in reactor II,which suggested that reactor I would supply a more favorable condition for DPB proliferation.Meanwhile,it was observed that the amount of organic substrates consumption had a linear correlation to that of phosphorus release in anaerobic phase when DPB was accumulated in the A/A SBR denitrifying phosphorus removal system.展开更多
The anaerobic/anoxic/oxic（A2O） process is globally one of the widely used biological sewage treatment processes. This is the first report of a metagenomic analysis using Illumina sequencing of full-scale A2O sludge ...The anaerobic/anoxic/oxic（A2O） process is globally one of the widely used biological sewage treatment processes. This is the first report of a metagenomic analysis using Illumina sequencing of full-scale A2O sludge from a municipal sewage treatment plant.With more than 530,000 clean reads from different taxa and metabolic categories, the metagenome results allow us to gain insight into the functioning of the biological community of the A2O sludge. There are 51 phyla and nearly 900 genera identified from the A2O activated sludge ecosystem. Proteobacteria, Bacteroidetes, Nitrospirae and Chloroflexi are predominant phyla in the activated sludge, suggesting that these organisms play key roles in the biodegradation processes in the A2O sewage treatment system.Nitrospira, Thauera, Dechloromonas and Ignavibacterium, which have abilities to metabolize nitrogen and aromatic compounds, are most prevalent genera. The percent of nitrogen and phosphorus metabolism in the A2O sludge is 2.72% and 1.48%, respectively. In the current A2O sludge, the proportion of Candidatus Accumulibacter is 1.37%, which is several times more than that reported in a recent study of A2O sludge. Among the four processes of nitrogen metabolism, denitrification related genes had the highest number of sequences（76.74%）, followed by ammonification（15.77%）, nitrogen fixation（3.88%） and nitrification（3.61%）. In phylum Planctomycetes, four genera（Planctomyces, Pirellula, Gemmata and Singulisphaera） are included in the top 30 abundant genera, suggesting the key role of ANAMMOX in nitrogen metabolism in the A2O sludge.展开更多
The optimal operation conditions in an anoxic sulfide oxidizing (ASO) bioreactor were investigated. The maximal removal rates for sulfide and nitrate were found to be 4.18 kg/(m3·d) and 1.73 kg/(m3·d), respe...The optimal operation conditions in an anoxic sulfide oxidizing (ASO) bioreactor were investigated. The maximal removal rates for sulfide and nitrate were found to be 4.18 kg/(m3·d) and 1.73 kg/(m3·d), respectively. The volumetrical volumetric loading rates (LRs) observed through decreasing hydraulic retention time (HRT) at fixed substrate concentration are higher than those by increasing substrate concentration at fixed HRT. The sulfide oxidation in ASO reactor was partially producing both sulfate and sulfur; but the amount of sulfate produced was approximately one third that of sulfur. The process was able to tolerate high sulfide concentration, as the sulfide removal percentage always remained near 99% when influent concentration was up to 580 mg/L. It tolerated relatively lower nitrate concentration because the removal percentage dropped to 85% when influent con- centration was increased above 110 mg/L. The process can tolerate shorter HRT but careful operation is needed. Nitrate conversion was more sensitive to HRT than sulfide conversion since the process performance deteriorated abruptly when HRT was decreased from 3.12 h to 2.88 h. In order to avoid nitrite accumulation in the reactor, the influent sulfide and nitrate concentrations should be kept at 280 mg/L and 67.5 mg/L respectively. Present biotechnology is useful for removing sulfides from sewers and crude oil.展开更多
The potential for degradation of five nitrogenous heterocyclic compounds（NHCs）, i.e.,imidazole, pyridine, indole, quinoline, and carbazole, was investigated under anoxic conditions with acclimated activated sludge. ...The potential for degradation of five nitrogenous heterocyclic compounds（NHCs）, i.e.,imidazole, pyridine, indole, quinoline, and carbazole, was investigated under anoxic conditions with acclimated activated sludge. Results showed that NHCs with initial concentration of 50 mg/L could be completely degraded within 60 hr. The degradation of five NHCs was dependent upon the chemical structures with the following sequence：imidazole 〉 pyridine 〉 indole 〉 quinoline 〉 carbazole in terms of their degradation rates.Quantitative structure-biodegradability relationship studies of the five NHCs showed that the anoxic degradation rates were correlated well with highest occupied molecular orbital.Additionally, the active sites of NHCs identified by calculation were confirmed by analysis of intermediates using gas chromatography and mass spectrometry.展开更多
Manganese ion(Mn^(2+))generated from metallurgical,steel making and chemical industries enters sewage treatment plants and affects the sludge activity and flocculation.The effect of Mn^(2+)on the removal of chemical o...Manganese ion(Mn^(2+))generated from metallurgical,steel making and chemical industries enters sewage treatment plants and affects the sludge activity and flocculation.The effect of Mn^(2+)on the removal of chemical oxygen demand(COD)and total phosphorus(TP)and sludge activity were investigated in anoxic zone of an anaerobic/anoxic/oxic(A2O)process.The compositions and structures of extracellular polymeric substances(EPS)were charac-terized using three-dimensional excitation emission matrix fluorescence spectroscopy(3D-EEM),X-ray photoelectron spectroscopy(XPS)and Fourier transform infrared spectroscopy(FTIR)to reveal the relationship among Mn^(2+),EPS and sludge flocculation.The results showed thatlow concentration of Mn^(2+)(<5 mg/L)improved removal efficiencies of COD and TP and increased the activity of alkaline phosphatase,acid phosphatase and dehydrogenase.Meanwhile,the addition of Mn^(2+)increased total EPS,sludge contact angle,Zeta potential and sludge particle size,and thus enhanced sludge flocculation.However,high concentration of Mn^(2+)(>10 mg/L)hindered microbial flocculation and reduced removal efficiencies of the pollutants.When Mn^(2+)was 5 mg/L,removal efficiencies of COD and TP reached 65%and 90%,respectively.Sludge flocculation was the best and SVI was 70.56 mL//g.The changes of Mn^(2+)concentration caused deviation of groups'compositions in LB-EPS and TB-EPS,where the main components were always protein(PN)and polysaccharide(PS).The addition of Mn^(2+)resulted in the degradation of humic acids.However,it did not give rise to significant morphology changes of EPS.展开更多
Membrane fouling limits the effects of long-term stable operation of membrane bioreactor （MBR）. Control of membrane fouling can extend the membrane life and reduce water treatment cost effectively. A pilot scale ano...Membrane fouling limits the effects of long-term stable operation of membrane bioreactor （MBR）. Control of membrane fouling can extend the membrane life and reduce water treatment cost effectively. A pilot scale anoxic/aerobic-membrane bioreactor （A/O- MBR, 40 L/hr） was used to treat the hyperhaline municipal sewage from a processing zone of Tianjin, China. Impact factors including mixed liquid sludge suspension （MLSS）, sludge viscosity （Ix）, microorganisms, extracellular polymeric substances （EPS）, aeration intensity and suction/suspended time on membrane fouling and pollution control were studied. The relationships among various factors associated with membrane fouling were analyzed. Results showed that there was a positive correlation among MLSS, sludge viscosity and trans-membrane pressure （TMP）. Considering water treatment efficiency and stable operation of the membrane module, MLSS of 5 g/L was suggested for the process. There was a same trend among EPS, sludge viscosity and TMP. Numbers and species of microorganisms affected membrane fouling. Either too high or too low aeration intensity was not conducive to membrane fouling control. Aeration intensity of 1.0 m3/hr （gas/water ratio of 25：1） is suggested for the process. A long suction time caused a rapid increase in membrane resistance. However, long suspended time cannot prevent the increase of membrane resistance effectively even though a suspended time was necessary for scale off particles from the membrane surface. The suction/suspended time of 12 min/3 rain was selected for the process. The interaction of various environmental factors and operation conditions must be considered synthetically.展开更多
To achieve advanced nitrogen removal from actual municipal sewage,a novel multistage anoxic/aerobic process with sludge regeneration zone(R-MAO)was developed.The reactor was used to treat actual domestic sewage and th...To achieve advanced nitrogen removal from actual municipal sewage,a novel multistage anoxic/aerobic process with sludge regeneration zone(R-MAO)was developed.The reactor was used to treat actual domestic sewage and the nitrogen removal capacity of the sludge regeneration zone(R zone)was investigated during the long-term operation.The best performance was obtained at the R zone’s Oxidation-Reduction Potential(ORP)of-50±30 mV and hydraulic residence times(HRT)of 1.2 hr.The average effluent COD,TN,NH_(4)^(+)-N and NO_(3)^(−)-N of the R-MAO process were 18.0±2.3,7.5±0.6,1.0±0.5 and 4.6±0.4 mg/L,respectively,with the corresponding removal efficiency of COD,TN and NH_(4)^(+)-N were 92.9%±1.0%,84.1%±1.5% and 97.5%±1.1%.Compared to the sole MAO system,the TN removal efficiency of the R-MAO increased by 10.1%.Besides,under the optimal conditions,the contribution of the R zone in the R-MAO that removal COD,TN,NH_(4)^(+)-N and NO_(3)^(−)-N were 0.36,0.15,0.032 and 0.82 g/day.High-throughput sequencing results showed that uncultured_bacterium_f_Burkholderiaceae(5.20%),OLB8(1.04%)and Ottowia(1.03%)played an important role in denitrification in the R zone.This study provided effective guidance for the design and operation of the R-MAO process in domestic sewage treatment.展开更多
The effects of nitrate concentration in the main anoxic zone on denitrifying dephosphatation capability were conducted based on modified University of Cape Town （MUCT） process. Meanwhile the relation between optimal...The effects of nitrate concentration in the main anoxic zone on denitrifying dephosphatation capability were conducted based on modified University of Cape Town （MUCT） process. Meanwhile the relation between optimal nitrate concentration （Nopt） and influent C/N ratio was evaluated, in which the influont chemical oxygen demand （COD） concentration was stabilized at （2905：10）mg/L, the influent total phosphorus （TP） concentration was stabilized at （7.0±0. 5）mg/L. The results indicated that： （1） the nitrate concentration in the main anoxic zone had an effect on denitrifying dephosphatation capability, and the average percentages of anoxic phosphorus uptake in total phosphorus uptake （ηa） increased with nitrate cancentration increasing, i.e., increasing from 62.1% at2.0 mg/L to63.7%, 65.6%, 68.1%, and 72.3% at 2.2, 2.4, 2.6 and 2.8mg/L, respectively; （2） the Nopt as function of influent C/N ratio could be calculated by the equation： y = 0.67x^2-7.79x ＋ 22. 21; the maximum percentages of anoxic phosphorus uptake in total phosphorus uptake （ηa,max） as function of the Nopt could be calculated by the equation： y=0.77-0.33e^-（x/1.52）. The Nopt was the important control parameter that must be optimized for operation of conveational biological nutrieat removal activated sludge （BNRAS） system.展开更多
Nitrogen is the most important component for living beings while the excessive discharge of organic and inorganic nitrogen may create severe environmental problems.In this study,a continuous anoxic/oxic(A/O)reactor ad...Nitrogen is the most important component for living beings while the excessive discharge of organic and inorganic nitrogen may create severe environmental problems.In this study,a continuous anoxic/oxic(A/O)reactor adopting activated sludge and sludge biofilms in the anoxic and oxic zones was applied for total nitrogen(TN)and chemical oxygen demand(COD)removal,and the efficiencies of nitrification and denitrification were compared as well.Results showed that when using activated sludge,the effluent concentrations of NH_(4)^(+)-N,NO_(3)^(-)-N,NO_(2)^(-)-N,TN and COD were inconsistent and fluctuated greatly,and the removal efficiencies of corresponding nitrification,denitrification and TN were also unstable;the obtained average COD removal efficiency was 85%.While using sludge biofilms,the acquired effluent concentrations of NH^(+)_(4)-N,NO^(-)_(3)-N,NO_(2)^(-)-N,TN and COD became stable and constant.The nitrification,denitrification,TN and COD removal efficiencies were 96%,84%and 65%and 94%,respectively.Bacterial community analysis of sludge biofilms indicated that the genus Arcobacter was the major denitrifiers in the anoxic zone with relative abundance of 76.1%,and in the oxic zone the abundances of Acinetobacter,Hydrogenophaga and Nitrospira responsible for complete nitrification were 20.05%,7.6%and 3.7%respectively.The high abundance of nitrifying bacteria and denitrifiers were related with the high and stable nitrogen and COD removal.展开更多
Nitrous oxide（N_2O） is a potent greenhouse gas that can be emitted during biological nitrogen removal. N_2O emission was examined in a multiple anoxic and aerobic process at the aeration rates of 600 m L/min sequenc...Nitrous oxide（N_2O） is a potent greenhouse gas that can be emitted during biological nitrogen removal. N_2O emission was examined in a multiple anoxic and aerobic process at the aeration rates of 600 m L/min sequencing batch reactor（SBRL） and 1200 m L/min（SBRH）.The nitrogen removal percentage was 89% in SBRLand 71% in SBRH, respectively. N_2O emission mainly occurred during the aerobic phase, and the N_2O emission factor was 10.1%in SBRLand 2.3% in SBRH, respectively. In all batch experiments, the N_2O emission potential was high in SBRLcompared with SBRH. In SBRL, with increasing aeration rates, the N_2O emission factor decreased during nitrification, while it increased during denitrification and simultaneous nitrification and denitrification（SND）. By contrast, in SBRHthe N_2O emission factor during nitrification, denitrification and SND was relatively low and changed little with increasing aeration rates. The microbial competition affected the N_2O emission during biological nitrogen removal.展开更多
Introduction,A better understanding the functioning of Earth System in the context of past climatic upheavals is essential for predictions about the fate of the diversity of life and the future of our society.The Inte...Introduction,A better understanding the functioning of Earth System in the context of past climatic upheavals is essential for predictions about the fate of the diversity of life and the future of our society.The International Geoscience Program(IGCP),a joint initiative of UNESCO and IUGS,serves as a knowledge hub to facilitate international scientific cooperation in the geosciences.One of the strategical themes of the IGCP is Global Change:evidence from the geological record,which perfectly applies to the project IGCP-655,Toarcian Oceanic Anoxic Event:Impact on marine carbon cycle and ecosystems.展开更多
文摘BACKGROUND Anoxic brain injury is a potentially lethal condition characterized by cerebral hypoperfusion and irreversible neuronal injury.Arterial spin-labeling(ASL)perfusion and diffusion-weighted imaging(DWI)magnetic resonance imaging(MRI)have been proposed as tools to detect cerebral ischemic changes and may aid in the assessment of anoxic injury.AIM To explore the relationship between regional ASL perfusion patterns and clinical outcomes following cardiac arrest.METHODS We performed a retrospective review to identify patients with clinical suspicion of anoxic brain injury who underwent MRI within 15 days of cardiac arrest.Receiver operator characteristic(ROC)analysis and univariate logistic regression were used to evaluate associations between ASL perfusion scores,DWI signal intensity,and the following clinical features:(1)Myoclonus status epilepticus(MSE)within 24 hours;(2)Absent extensor or motor reflexes(EMR)at day 3 post-arrest;and(3)Absent brainstem reflexes(BSR)within 15 days.RESULTS Twenty-eight patients met inclusion criteria.Increased ASL signal in the left occipital lobe was significantly associated with MSE(P=0.038),while a trend was observed between right frontal ASL signal and EMR(P=0.078).ROC analysis showed that ASL scores≥7 were associated with higher odds of absent BSR(OR 2.14,P=0.53),though this did not reach statistical significance.DWI signal intensity did not show significant associations with clinical outcomes.The overall discriminatory performance of ASL for predicting outcomes was limited(AUC≈0.52).CONCLUSION This exploratory study suggests that regional ASL hyperperfusion,particularly in the left occipital and right frontal lobes,may be associated with adverse clinical signs following cardiac arrest.However,most findings did not reach statistical significance,and the study was underpowered to detect small-to-moderate effects.These preliminary results should be interpreted with caution and considered hypothesis-generating.Larger,prospective studies are warranted to clarify the prognostic value of ASL perfusion imaging in anoxic brain injury.
基金Supported by National Eleventh Five-Year Science and TechnologySupport Program(1-1-12-0661)~~
文摘[Objective] The aim of this study was to provide a fast, stable and efficient piggery wastewater processing technology. [Method] The start-up process was studied through the experiment of piggery anaerobic fermentation slurry treated by Anoxic/Oxic （A/O） reactor. The process was divided into two stages： at the first stage, dominant micro flora were cultivated in Anoxic and Oxic reaction tanks respectively; at the second stage. Anoxic and Oxic reaction tanks were initiated jointly to gradually enhance water load and continued to cultivate and domesticate microorganisms, and finally the start-up process was completed. [ Result] The results showed that return mixture ratio and return sludge ratio was 2 and 1 respectively when the temperature reached 32 ±2 ℃. However. when aeration rate of Oxic reaction amounted to 0.5 m^3/h, the re- moval rate of COD and NH4^＋ -H were 89.87% and 89.31% respectively through practical operation within 50 days, which indicated that the start- up process through A/O reactor was successful. Conclusion This study can provide a scientific basis and reference for innocuous technique of piggery anaerobic fermentation slurry treatment.
基金Sponsored by the National Water Plan (2008ZX07207-005-03)
文摘Kinetics models of COD degradation,biomass growth of the anoxic-oxic ( A/O) system as well as NH3-N degradation in aerobic phase were presented according to the mass balance theory,reaction-diffusion theory and Fick law. Then these models were testified by comparson with experimental results. It is demonstrated that the variation trends of theoretical and experimental values for COD degradation and biomass growth are similar. The deviation rate between theoretical and experimental values is always under 20% even it increases along with the fluctuation of influent organic loading. In terms of NH3-N degradation,nitrification can also be well simulated by the model as the substrates of influent are sufficient. It indicates that the model can accurately reflect the reaction in hybrid A/O process. Models presented herein provide a theoretical basis for the design, operation and control of hybrid A/O process.
基金This is a contribution of the IGCP-655 project of the IUGS and UNESCO.
文摘Introduction.The study of catastrophic events that affected past marine ecosystems provides us the unique opportunity to establish models which can be applied to ongoing environmental changes and to understand future evolution of the biotas.The growing interest of the society for the ongoing and potential future environmental changes attests for the value represented by the analysis of past climatic changes.In the case of the Toarcian Oceanic Anoxic Event(T-OAE,Early Jurassic;~182 Ma),a dramatic change of marine ecosystems related to massive extinction has been documented in several areas around the world.The Pliensbachian–Toarcian transition and the T-OAE are two global episodes recording worldwide palaeoenvironmental perturbations(Jenkyns,1988;Jenkyns and Clayton,1997;Hesselbo et al.,2007).The end of the Pliensbachian regression is followed by a transgression occurring in the Early Toarcian(Haq et al.,1987;de Graciansky et al.,1999).This transgression was also coeval with a widespread deposition of black shales(Jenkyns,1988),a global warming(Garcia Joral et al.,2011;Korte and Hesselbo,2011;Suan et al.,2011),and perturbations of the carbon cycle indicated by a negative carbon isotopic excursion(CIE)documented in both marine and terrestrial material(Jenkyns and Clayton,1986;Schouten et al.,2000;Hesselbo et al.,2007;Al-Suwaidi et al.,2010;Caruthers et al.,2011;Izumi et al.,2012;Reolid,2014).
基金Supported by the Project of Beijing Science and Technology Committee (D07050601500000)the National Key Science and Technology Special Projects (2008ZX07317-007-105)
文摘In order to enhance phosphorus removal in traditional step-feed anoxic/oxic nitrogen removal process,a modified pilot-scale step-feed anaerobic/anoxic/oxic(SFA 2/O) system was developed,which combined a reactor similar to UCT-type configuration and two-stage anoxic/oxic process.The simultaneous nitrogen and phosphorus removal capacities and the potential of denitrifying phosphorus removal,in particular,were investigated with four different feeding patterns using real municipal wastewater.The results showed that the feeding ratios(Q1)in the first stage determined the nutrient removal performance in the SFA 2/O system.The average phosphorus removal efficiency increased from 19.17% to 96.25% as Q1 was gradually increased from run 1 to run 4,but the nitrogen removal efficiency exhibited a different tendency,which attained a maximum 73.61%in run 3 and then decreased to 59.62%in run 4.As a compromise between nitrogen and phosphorus removal,run 3 (Q1=0.45Qtotal) was identified as the optimal and stable case with the maximum anoxic phosphorus uptake rate of 1.58 mg·(g MLSS)-1 ·h-1.The results of batch tests showed that ratio of the anoxic phosphate uptake capacity to the aerobic phosphate uptake capacity increased from 11.96% to 36.85% with the optimal influent feeding ratio to the system in run 3,which demonstrated that the denitrifying polyP accumulating organisms could be accumulated and contributed more to the total phosphorus removal by optimizing the inflow ratio distribution.However,the nitrate recirculation to anoxic zone and influent feeding ratios should be carefully controlled for carbon source saving.
文摘This paper presents new geological and geochemical data from the Shuanghu area in northern Tibet, which recorded the Early Toarcian Oceanic Anoxic Event. The stratigraphic succession in the Shuanghu area consists mostly of grey to dark-colored alternating oil shales, marls and mudstones. Ammonite beds are found at the top of the Shuanghu oil shale section, which are principally of early Toarcian age, roughly within the Harplocearas falciferrum Zone. Therefore, the oil shale strata at Shuanghu can be correlated with early Toarcian black shales distributing extensively in the European epicontinental seas that contain the records of an Oceanic Anoxic Event. Sedimentary organic matter of laminated shale anomalously rich in organic carbon across the Shuanghu area is characterized by high organic carbon contents, ranging from 1.8% to 26.1%. The carbon isotope curve displays the δ 13C values of the kerogen (δ 13Ckerogen) fluctuating from –26.22 to –23.53‰ PDB with a positive excursion close to 2.17‰, which, albeit significantly smaller, may also have been associated with other Early Toarcian Oceanic Anoxic Events (OAEs) in Europe. The organic atomic C/N ratios range between 6 and 43, and the curve of C/N ratios is consistent with that of the δ 13Ckerogen values. The biological assemblage, characterized by scarcity of benthic organisms and bloom of calcareous nannofossils (coccoliths), reveals high biological productivity in the surface water and an unfavorable environment for the benthic fauna in the bottom water during the Oceanic Anoxic Event. On the basis of organic geochemistry and characteristics of the biological assemblage, this study suggests that the carbon-isotope excursion is caused by the changes of sea level and productivity, and that the black shale deposition, especially oil shales, is related to the bloom and high productivity of coccoliths.
基金Supported by Major Science and Technology Program for Water Pollution Control and Treatment(2008ZX07316)
文摘A novel modified pilot scale anaerobic oxidation ditch with additional internal anoxic zones was operated experimentally, aiming to study the improvement of biological nitrogen and phosphorus removal and the effect of enhanced denitrifying phosphorus removal in the process. Under all experimental conditions, the anaero- bic-oxidation ditch with additional internal anoxic zones and an internal recycle ratio of 200% had the highest nutrient removal efficiency. The effluent NH4 -N, total nitrogen （TN）, PO3 -P and total phosphorus （TP） contents were 1.2 mg.L-1, 13 mg.L 1, 0.3 mg.L -1 and 0.4 mg.L-1, respectively, all met the discharge standards in China. The TN and TP removal efficiencies were remarkably improved from 37% and 50% to 65% and 88% with the presence of additional internal anoxic zones and internal recycle ratio of 200%. The results indicated that additional internal anoxic zones can optimize the utilization of available carbon source from the anaerobic outflow for denitrification. It was also found that phosphorus removal via the denitrification process was stimulated in the additional internal anoxic zones, which was beneficial for biological nitrogen and phosphorus removal when treating wastewater with a limited carbon source. However, an excess internal recycle would cause nitrite to accumulate in the system. This seems to be harmful to biological phosphorus removal.
基金supported by the Yue Qi Scholar Project of China University of Mining and Technology(Beijing)Chinathe National Natural Science Foundation of China(41572090+1 种基金42002128)Shandong Key Laboratory of Depositional Mineralization&Sedimentary Mineral Shandong University of Science and Technology China(DMSM20190015)。
文摘The early Albian Oceanic Anoxic Event 1 b(OAE 1 b) is well documented in the Tethys, Pacific and North Atlantic, but few studies have evaluated whether or not terrestrial records of OAE 1 b exist. In order to identify terrestrial records of the early Albian OAE 1 b and to infer possible driving mechanisms, an integrated multi-proxy study from the late Aptian to Albian in the Fuxin lacustrine basin was conducted,including thick, organic-rich black mudstones, total organic carbon(TOC), organic carbon isotopes(d13 Corg), mercury concentration(Hg) and results from pyrolysis analyses(S2, Tmaxand HI). Results show three distinct short-term negative d13 Corgexcursions corresponding with relatively high TOC values,which could be counterparts of the Kilian, Paquier and Leenhardt sub-events of the early Albian OAE1 b. Atmospheric CO2 concentration(p CO2) recovered from C3 plant d13 Corgcompositions indicates an increasing trend in Unit C during the early Albian, and there are three short-term increases of p CO2 corresponding to the three sub-events of OAE 1 b at this time interval. We infer that a trend of increasing p CO2 during the Kilian sub-event in the study area is closely related to volcanism. Continental weathering calculated using chemical weathering indices(CIA, WIP and MIA(O)) show an increasing trend during the OAE 1 b interval, likely resulting from warmer and more humid conditions. Mixed sources of terrestrial plants and lacustrine plankton demonstrated by pyrolysis analyses(HI vs. Tmaxand S2 vs. TOC), indicate a terrestrial contribution to the organic-rich sediments of the Kilian, Paquier and Leenhardt sub-events of OAE 1 b. We suggest that a CO2-forced greenhouse effect during the early Albian might have triggered the relatively warm and humid palaeoclimatic conditions, and intensified chemical weathering that combined to create high nutrient and organic matter levels that were flushed into lakes contributing to eutrophication and anoxia in lacustrine and in contemporaneous oceanic systems.
文摘Removal of denitrifying phosphorus was verified in a laboratory anaerobic/anoxic sequencing batch reactor (A/A SBR). The results obtained demonstrated that the anaerobic/anoxic strategy can enrich the growth of denitrifying phosphorus removing bacteria (DPB) and take up phosphate under anoxic condition by using nitrate as the electron acceptor. The phosphorus removal efficiency was higher than 90% and the effluent phosphate concentration was lower than 1 mg·L-1 after the A/A SBR was operated in a steady-state. When the chemical oxygen demand(COD) of influent was lower than 180mg· L-1, the more COD in the influent was, the higher efficiency of phosphorus removal could be attained under anoxic condition. However, simultaneous presence of carbon and nitrate would be detrimental to denitrifying phosphorus removal. Result of influence of sludge retention time (SRT) on denitrifying phosphorus removal suggested that the decrease of SRT caused a washout of DPB and consequently the enhanced biological phosphorus removal decreased with 8 days SRT. When the SRT was restored to 16 days, however, the efficiency of phosphorus removal was higher than 90%.
基金Sponsored by the National Natural Science Foundation of China(Grant No.50778052)Development Program for Outstanding Young Teachers in Harbin Institute of Technology(Grant No.NQQQ92324547)
文摘To achieve stable and efficient nitrogen and phosphorus removal and to investigate the characteristics of the A/A SBR enriched with denitrifying phosphorus removal bacteria(DPB),the whole course of startup was studied with two reactors operated in different mode.The reactor I was operated under anaerobic/settling/anoxic/settling mode,and the reactor II was operated under anaerobic/anoxic/settling mode.Differences between the two reactors in removal efficiency of COD,nitrogen and phosphorus were examined.The results indicated that efficient performance could be achieved in both reactors with different startup operation mode,while the phosphorus removal efficiency was improved sooner in reactor I than in reactor II,which suggested that reactor I would supply a more favorable condition for DPB proliferation.Meanwhile,it was observed that the amount of organic substrates consumption had a linear correlation to that of phosphorus release in anaerobic phase when DPB was accumulated in the A/A SBR denitrifying phosphorus removal system.
基金supported by the National Natural Science Foundation of China (No. 41430643)
文摘The anaerobic/anoxic/oxic（A2O） process is globally one of the widely used biological sewage treatment processes. This is the first report of a metagenomic analysis using Illumina sequencing of full-scale A2O sludge from a municipal sewage treatment plant.With more than 530,000 clean reads from different taxa and metabolic categories, the metagenome results allow us to gain insight into the functioning of the biological community of the A2O sludge. There are 51 phyla and nearly 900 genera identified from the A2O activated sludge ecosystem. Proteobacteria, Bacteroidetes, Nitrospirae and Chloroflexi are predominant phyla in the activated sludge, suggesting that these organisms play key roles in the biodegradation processes in the A2O sewage treatment system.Nitrospira, Thauera, Dechloromonas and Ignavibacterium, which have abilities to metabolize nitrogen and aromatic compounds, are most prevalent genera. The percent of nitrogen and phosphorus metabolism in the A2O sludge is 2.72% and 1.48%, respectively. In the current A2O sludge, the proportion of Candidatus Accumulibacter is 1.37%, which is several times more than that reported in a recent study of A2O sludge. Among the four processes of nitrogen metabolism, denitrification related genes had the highest number of sequences（76.74%）, followed by ammonification（15.77%）, nitrogen fixation（3.88%） and nitrification（3.61%）. In phylum Planctomycetes, four genera（Planctomyces, Pirellula, Gemmata and Singulisphaera） are included in the top 30 abundant genera, suggesting the key role of ANAMMOX in nitrogen metabolism in the A2O sludge.
基金Project supported by the National Natural Science Foundation of China (No. 30070017)the Science and Technology Foundation for Key Project of Zhejiang Province (No. 2003C13005), China
文摘The optimal operation conditions in an anoxic sulfide oxidizing (ASO) bioreactor were investigated. The maximal removal rates for sulfide and nitrate were found to be 4.18 kg/(m3·d) and 1.73 kg/(m3·d), respectively. The volumetrical volumetric loading rates (LRs) observed through decreasing hydraulic retention time (HRT) at fixed substrate concentration are higher than those by increasing substrate concentration at fixed HRT. The sulfide oxidation in ASO reactor was partially producing both sulfate and sulfur; but the amount of sulfate produced was approximately one third that of sulfur. The process was able to tolerate high sulfide concentration, as the sulfide removal percentage always remained near 99% when influent concentration was up to 580 mg/L. It tolerated relatively lower nitrate concentration because the removal percentage dropped to 85% when influent con- centration was increased above 110 mg/L. The process can tolerate shorter HRT but careful operation is needed. Nitrate conversion was more sensitive to HRT than sulfide conversion since the process performance deteriorated abruptly when HRT was decreased from 3.12 h to 2.88 h. In order to avoid nitrite accumulation in the reactor, the influent sulfide and nitrate concentrations should be kept at 280 mg/L and 67.5 mg/L respectively. Present biotechnology is useful for removing sulfides from sewers and crude oil.
基金supported by the Harbin Institute of Technology (No. 2013DX10)the Sino-Dutch Research Program (No. zhmhgfs2011-001)the Sino-American Coal Chemical Industry Program (No. ZMAGZ 2011001)
文摘The potential for degradation of five nitrogenous heterocyclic compounds（NHCs）, i.e.,imidazole, pyridine, indole, quinoline, and carbazole, was investigated under anoxic conditions with acclimated activated sludge. Results showed that NHCs with initial concentration of 50 mg/L could be completely degraded within 60 hr. The degradation of five NHCs was dependent upon the chemical structures with the following sequence：imidazole 〉 pyridine 〉 indole 〉 quinoline 〉 carbazole in terms of their degradation rates.Quantitative structure-biodegradability relationship studies of the five NHCs showed that the anoxic degradation rates were correlated well with highest occupied molecular orbital.Additionally, the active sites of NHCs identified by calculation were confirmed by analysis of intermediates using gas chromatography and mass spectrometry.
基金This work was supported by the National Natural Science Foundation of China(No.51678119)the Science and Technology Development Program of Jilin Province(No.20180201016SF).
文摘Manganese ion(Mn^(2+))generated from metallurgical,steel making and chemical industries enters sewage treatment plants and affects the sludge activity and flocculation.The effect of Mn^(2+)on the removal of chemical oxygen demand(COD)and total phosphorus(TP)and sludge activity were investigated in anoxic zone of an anaerobic/anoxic/oxic(A2O)process.The compositions and structures of extracellular polymeric substances(EPS)were charac-terized using three-dimensional excitation emission matrix fluorescence spectroscopy(3D-EEM),X-ray photoelectron spectroscopy(XPS)and Fourier transform infrared spectroscopy(FTIR)to reveal the relationship among Mn^(2+),EPS and sludge flocculation.The results showed thatlow concentration of Mn^(2+)(<5 mg/L)improved removal efficiencies of COD and TP and increased the activity of alkaline phosphatase,acid phosphatase and dehydrogenase.Meanwhile,the addition of Mn^(2+)increased total EPS,sludge contact angle,Zeta potential and sludge particle size,and thus enhanced sludge flocculation.However,high concentration of Mn^(2+)(>10 mg/L)hindered microbial flocculation and reduced removal efficiencies of the pollutants.When Mn^(2+)was 5 mg/L,removal efficiencies of COD and TP reached 65%and 90%,respectively.Sludge flocculation was the best and SVI was 70.56 mL//g.The changes of Mn^(2+)concentration caused deviation of groups'compositions in LB-EPS and TB-EPS,where the main components were always protein(PN)and polysaccharide(PS).The addition of Mn^(2+)resulted in the degradation of humic acids.However,it did not give rise to significant morphology changes of EPS.
基金supported by the Special Projects of Major National Science and Technology of China (No. 2008ZX07314-003)the National Natural Science Foundation of China (No. 50708063)
文摘Membrane fouling limits the effects of long-term stable operation of membrane bioreactor （MBR）. Control of membrane fouling can extend the membrane life and reduce water treatment cost effectively. A pilot scale anoxic/aerobic-membrane bioreactor （A/O- MBR, 40 L/hr） was used to treat the hyperhaline municipal sewage from a processing zone of Tianjin, China. Impact factors including mixed liquid sludge suspension （MLSS）, sludge viscosity （Ix）, microorganisms, extracellular polymeric substances （EPS）, aeration intensity and suction/suspended time on membrane fouling and pollution control were studied. The relationships among various factors associated with membrane fouling were analyzed. Results showed that there was a positive correlation among MLSS, sludge viscosity and trans-membrane pressure （TMP）. Considering water treatment efficiency and stable operation of the membrane module, MLSS of 5 g/L was suggested for the process. There was a same trend among EPS, sludge viscosity and TMP. Numbers and species of microorganisms affected membrane fouling. Either too high or too low aeration intensity was not conducive to membrane fouling control. Aeration intensity of 1.0 m3/hr （gas/water ratio of 25：1） is suggested for the process. A long suction time caused a rapid increase in membrane resistance. However, long suspended time cannot prevent the increase of membrane resistance effectively even though a suspended time was necessary for scale off particles from the membrane surface. The suction/suspended time of 12 min/3 rain was selected for the process. The interaction of various environmental factors and operation conditions must be considered synthetically.
基金supported by a project of Shenzhen Science and Technology Plan (No. KCXFZ202002011006362)Project of Central and Southern China Municipal Engineering Design & Research Institute Co.,Ltd. (Technology Development 2019)
文摘To achieve advanced nitrogen removal from actual municipal sewage,a novel multistage anoxic/aerobic process with sludge regeneration zone(R-MAO)was developed.The reactor was used to treat actual domestic sewage and the nitrogen removal capacity of the sludge regeneration zone(R zone)was investigated during the long-term operation.The best performance was obtained at the R zone’s Oxidation-Reduction Potential(ORP)of-50±30 mV and hydraulic residence times(HRT)of 1.2 hr.The average effluent COD,TN,NH_(4)^(+)-N and NO_(3)^(−)-N of the R-MAO process were 18.0±2.3,7.5±0.6,1.0±0.5 and 4.6±0.4 mg/L,respectively,with the corresponding removal efficiency of COD,TN and NH_(4)^(+)-N were 92.9%±1.0%,84.1%±1.5% and 97.5%±1.1%.Compared to the sole MAO system,the TN removal efficiency of the R-MAO increased by 10.1%.Besides,under the optimal conditions,the contribution of the R zone in the R-MAO that removal COD,TN,NH_(4)^(+)-N and NO_(3)^(−)-N were 0.36,0.15,0.032 and 0.82 g/day.High-throughput sequencing results showed that uncultured_bacterium_f_Burkholderiaceae(5.20%),OLB8(1.04%)and Ottowia(1.03%)played an important role in denitrification in the R zone.This study provided effective guidance for the design and operation of the R-MAO process in domestic sewage treatment.
基金Water Pollution Control and Management of Science and Technology Majon Projects (No.2008ZX07207005)The Programs for Development of Science and Technology of Jilin Province of China (No.20071105)
文摘The effects of nitrate concentration in the main anoxic zone on denitrifying dephosphatation capability were conducted based on modified University of Cape Town （MUCT） process. Meanwhile the relation between optimal nitrate concentration （Nopt） and influent C/N ratio was evaluated, in which the influont chemical oxygen demand （COD） concentration was stabilized at （2905：10）mg/L, the influent total phosphorus （TP） concentration was stabilized at （7.0±0. 5）mg/L. The results indicated that： （1） the nitrate concentration in the main anoxic zone had an effect on denitrifying dephosphatation capability, and the average percentages of anoxic phosphorus uptake in total phosphorus uptake （ηa） increased with nitrate cancentration increasing, i.e., increasing from 62.1% at2.0 mg/L to63.7%, 65.6%, 68.1%, and 72.3% at 2.2, 2.4, 2.6 and 2.8mg/L, respectively; （2） the Nopt as function of influent C/N ratio could be calculated by the equation： y = 0.67x^2-7.79x ＋ 22. 21; the maximum percentages of anoxic phosphorus uptake in total phosphorus uptake （ηa,max） as function of the Nopt could be calculated by the equation： y=0.77-0.33e^-（x/1.52）. The Nopt was the important control parameter that must be optimized for operation of conveational biological nutrieat removal activated sludge （BNRAS） system.
基金National Natural Science Foundation of China(No.52070040,No.51878136,and No.51878135)Shanghai Rising-Star Program,China(No.19QC1400300)the Fundamental Research Funds for the Central Universities,China(DHU Distinguished Young Professor Program)。
文摘Nitrogen is the most important component for living beings while the excessive discharge of organic and inorganic nitrogen may create severe environmental problems.In this study,a continuous anoxic/oxic(A/O)reactor adopting activated sludge and sludge biofilms in the anoxic and oxic zones was applied for total nitrogen(TN)and chemical oxygen demand(COD)removal,and the efficiencies of nitrification and denitrification were compared as well.Results showed that when using activated sludge,the effluent concentrations of NH_(4)^(+)-N,NO_(3)^(-)-N,NO_(2)^(-)-N,TN and COD were inconsistent and fluctuated greatly,and the removal efficiencies of corresponding nitrification,denitrification and TN were also unstable;the obtained average COD removal efficiency was 85%.While using sludge biofilms,the acquired effluent concentrations of NH^(+)_(4)-N,NO^(-)_(3)-N,NO_(2)^(-)-N,TN and COD became stable and constant.The nitrification,denitrification,TN and COD removal efficiencies were 96%,84%and 65%and 94%,respectively.Bacterial community analysis of sludge biofilms indicated that the genus Arcobacter was the major denitrifiers in the anoxic zone with relative abundance of 76.1%,and in the oxic zone the abundances of Acinetobacter,Hydrogenophaga and Nitrospira responsible for complete nitrification were 20.05%,7.6%and 3.7%respectively.The high abundance of nitrifying bacteria and denitrifiers were related with the high and stable nitrogen and COD removal.
基金supported by the Shenzhen Overseas High-Level Talents Innovation Funds Peacock Plan Project (No. KQCX20120814155347053)the National Natural Science Foundation of China (No. 51108242)
文摘Nitrous oxide（N_2O） is a potent greenhouse gas that can be emitted during biological nitrogen removal. N_2O emission was examined in a multiple anoxic and aerobic process at the aeration rates of 600 m L/min sequencing batch reactor（SBRL） and 1200 m L/min（SBRH）.The nitrogen removal percentage was 89% in SBRLand 71% in SBRH, respectively. N_2O emission mainly occurred during the aerobic phase, and the N_2O emission factor was 10.1%in SBRLand 2.3% in SBRH, respectively. In all batch experiments, the N_2O emission potential was high in SBRLcompared with SBRH. In SBRL, with increasing aeration rates, the N_2O emission factor decreased during nitrification, while it increased during denitrification and simultaneous nitrification and denitrification（SND）. By contrast, in SBRHthe N_2O emission factor during nitrification, denitrification and SND was relatively low and changed little with increasing aeration rates. The microbial competition affected the N_2O emission during biological nitrogen removal.
文摘Introduction,A better understanding the functioning of Earth System in the context of past climatic upheavals is essential for predictions about the fate of the diversity of life and the future of our society.The International Geoscience Program(IGCP),a joint initiative of UNESCO and IUGS,serves as a knowledge hub to facilitate international scientific cooperation in the geosciences.One of the strategical themes of the IGCP is Global Change:evidence from the geological record,which perfectly applies to the project IGCP-655,Toarcian Oceanic Anoxic Event:Impact on marine carbon cycle and ecosystems.
