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1.
Bioresour Technol ; 322: 124570, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-33384203

RESUMO

Weak magnetic field (WMF) and aerobic granular sludge (AGS) technology were both robust technologies in wastewater treatments. In this study, the AGS characteristics and nutrient removal performances were all estimated at the load of 20 to 40 mg/L ammonia nitrogen (NH4+-N) and 0 to 40mT magnetic field. Results showed that 10mT was beneficial for keeping stable structure of granules when increasing NH4+-N load, accompanied with increasing protein (PN) secretion in EPS. Besides, all the total nitrogen (TN) removal rate under 10mT reached above 90%, while they were all less than 80% under other WMF strength when loading with 40 mg/L NH4+-N. Moreover, the simultaneous nitrification and denitrification (SND) efficiency could be enhanced by WMF of 10mT. Illumina MiSeq sequencing showed that NH4+-N load changed the bacterial richness and diversity when the magnetic strength was 10mT. And Candidatus_Competibacter was identified as the main functional genes for effective operation in this system.


Assuntos
Amônia , Purificação da Água , Reatores Biológicos , Desnitrificação , Fenômenos Magnéticos , Nitrificação , Nitrogênio , Esgotos , Eliminação de Resíduos Líquidos , Águas Residuárias
2.
Water Res ; 189: 116557, 2021 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-33220610

RESUMO

Denitrifying phosphorus removal is a cost and energy efficient treatment technology that relies on polyphosphate accumulating organisms (DPAOs) utilizing nitrate or nitrite as terminal electron acceptor. Denitrification is a multistep process, but many organisms do not possess the complete pathway, leading to the accumulation of intermediates such as nitrous oxide (N2O), a potent greenhouse gas and ozone depleting substance. Candidatus Accumulibacter organisms are prevalent in denitrifying phosphorus removal processes and, according to genomic analyses, appear to vary in their denitrification abilities based on their lineage. Denitrification kinetics and nitrous oxide accumulation in the absence of inhibition from free nitrous acid is a strong indicator of denitrification capabilities of Accumulibacter exposed long-term to nitrate or nitrite as electron acceptor. Thus, we investigated the preferential use of the nitrogen oxides involved in denitrification and nitrous oxide accumulation in two enrichments of Accumulibacter and a competitor - the glycogen accumulating organism Candidatus Competibacter. We modified a metabolic model to predict phosphorus removal and denitrification rates when nitrate, nitrite or N2O were added as electron acceptors in different combinations. Unlike previous studies, no N2O accumulation was observed for Accumulibacter in the presence of multiple electron acceptors. Electron competition did not limit denitrification kinetics or lead to N2O accumulation in Accumulibacter or Competibacter. Despite the presence of sufficient internal storage polymers (polyhydroxyalkanoates, or PHA) as energy source for each denitrification step, the extent of denitrification observed was dependent on the dominant organism in the enrichment. Accumulibacter showed complete denitrification, whereas Competibacter denitrification was limited to reduction of nitrate to nitrite. These findings indicate that DPAOs can contribute to lowering N2O emissions in the presence of multiple electron acceptors under partial nitritation conditions.


Assuntos
Desnitrificação , Óxido Nitroso , Reatores Biológicos , Elétrons , Cinética , Nitritos , Fósforo
3.
Water Res ; 189: 116619, 2021 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-33232815

RESUMO

Wetland ecosystems play an important role in nitrogen cycling, yet the role of anaerobic ammonium oxidation (anammox) in tropical wetlands remains unclear. In the current study the anammox process accounted for 29.8 ~ 57.3% of nitrogen loss in ex situ activity batch tests of microcosms established from anoxic sediments of different tropical wetlands, with the highest activity being 17.95±0.51 nmol-N/g dry sediment/h. This activity was most likely driven by sulfide oxidation with dissimilatory nitrate reduction to ammonium (sulfide-driven DNRA). Microbial community analyses revealed a variety of anammox bacteria related to several known lineages, including Candidatus Anammoximicrobium, Candidatus Brocadia and Candidatus Kuenenia, at different wetlands. Metagenome predictions, batch tests, and isotope-tracing suggested that the high level of anammox activity was due to sulfide-driven DNRA. This was corroborated by a strong correlation (through Pearson's analysis) between the abundance of anammox bacteria and the nrfA (a dissimilatory nitrate reduction to ammonium gene) and dsrA (a sulfate reductase gene) genes, as well as sulfate, ammonium and nitrate concentrations. These correlations suggest syntrophic interactions among sulfate-reducing, sulfide-driven DNRA, and anammox bacterial populations. A better understanding of the role of sulfur in nitrogen loss via the anammox reaction in natural systems could inform development of a viable wastewater treatment strategy that utilizes sulfate to minimize the activity of denitrifying bacteria and thus to reduce nitrous oxide emissions from wastewater treatment plants.


Assuntos
Compostos de Amônio , Áreas Alagadas , Anaerobiose , Desnitrificação , Nitrogênio , Oxirredução , Enxofre
4.
Sci Total Environ ; 758: 143580, 2021 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-33223174

RESUMO

Phosphorus (P) and nitrogen (N) pollution are the worldwide challenging problem. In the present study, a new salt-tolerant phosphate-accumulating organism (PAO) was isolated and identified as Bacillus subtilis GHSP10. Strain GHSP10 did not produce hemolysin and showed high susceptibility to antibiotics. The favorable phosphorus removal C/N ratios, P/N ratios, temperature, salinities, pH values and shaking speeds of strain GHSP10 were 10-20, 0.1-0.2, 28 °C, 0-3%, 7.5-8.5 and 100-250 r/min. Besides, strain GHSP10 could conduct heterotrophic nitrification-aerobic denitrification and the maximal removal efficiencies of ammonium, nitrite and nitrate were 99.52%, 81.10% and 95.84% respectively. Moreover, the phosphorus removal process of strain GHSP10 was achieved under entirely aerobic conditions, and glycogen and poly-ß-hydroxybutyrate could provide energy source for the phosphorus removal process of strain GHSP10. The amplification of ppk, hao, napA, narG, nirK genes as well as the expression of polyphosphate kinase helped to reveal the removal pathways of phosphorus and nitrogen, providing theoretical support for the phosphorus removal, nitrification and aerobic denitrification abilities of strain GHSP10. Furthermore, efficient removal of phosphorus and nitrogen from both domestic sewage and aquaculture sewage could be accomplished by strain GHSP10. This study may provide a hopeful candidate strain for simultaneous removal of phosphorus and nitrogen pollution from both freshwater sewage and saline sewage.


Assuntos
Nitrogênio , Fósforo , Aerobiose , Aquicultura , Reatores Biológicos , Desnitrificação , Nitrificação , Nitritos , Fosfatos , Esgotos
5.
Sci Total Environ ; 758: 143594, 2021 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-33246723

RESUMO

Constructed wetlands are efficient in removing nitrogen from water; however, little is known about nitrogen-cycling pathways for nitrogen loss from tidal flow constructed wetlands. This study conducted molecular and stable isotopic analyses to investigate potential dissimilatory nitrate reduction to ammonium (DNRA), denitrification, nitrification, anaerobic ammonium oxidation (anammox), and their contributions to nitrogen removal by two tidal wetland mesocosms, PA (planted with Phragmites australis) and NP (unplanted), designated to treat Yangtze River Estuary water. Our results show the mesocosms removed ~22.6% of TN from nitrate-dominated river water (1.19 mg·L-1), with better performance obtained in PA than that in NP, which was consistent with the molecular and stable isotopic data. The potential activities of DNRA, anammox, denitrification and nitrification varied between 0.6 and 1.6, 4.6-37.3, 36.4-305.7, and 463.7-945.9 nmol N2 g-1 dry soil d-1, respectively, with higher values obtained in PA than NP. Nitrification accounted for 94.3-99.4% of NH4+ oxidation, with the rest through anammox. Denitrification contributed to 77.9-90.3% of NOx- reduction, compared to 9.2-21.6% and 0.5-1.5% via anammox and DNRA, respectively; 78.4-90.9% of N2 was produced through denitrification, with the rest via anammox. Pearson correlation analyses suggest NH4+ was the major factor regulating nitrification, while NO3- played an important role in the competition between denitrification and DNRA, and NO2- was a key restrictive factor for anammox. Overall, this study reveals the importance of nitrification, denitrification, anammox and DNRA in nitrogen removal, providing new insight into the nitrogen-cycling mechanisms in natural/artificial tidal wetlands.


Assuntos
Compostos de Amônio , Áreas Alagadas , Desnitrificação , Nitrificação , Nitrogênio , Oxirredução
6.
Sci Total Environ ; 758: 143677, 2021 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-33288255

RESUMO

Removal of nitrogen compounds is particularly important domestic wastewater treatment. Our recent study reported the successful removal of nitrogen in single-chamber electroactive biofilm reactors (EBRs) under aeration-free conditions. We hypothesized that the oxygen diffused from the air-cathode is a key factor in the removal of nitrogen in the EBR. If so, the effect of the penetrated oxygen would vary according to the ratio of the air-cathode surface area to the reactor volume (AV ratio) and the hydraulic retention time (HRT). In this study, single-chamber EBRs with three different AV ratios: 125 m2/m3 (EBR-125), 250 m2/m3 (EBR-250), and 500 m2/m3 (EBR-500) were evaluated for the removal of nitrogen under different HRTs of 0.5-6 h. The higher the AV ratio, the greater the increase in nitrification. The total nitrogen (TN) removal efficiency of EBR-125 and EBR-250 decreased as the HRT decreased, while that of EBR-500 increased. EBR-250 showed the highest TN removal (62.0%) with well-balanced nitrification (83.9%) and denitrification (75.1%) at an HRT of 6 h. However, EBR-500 appeared to be superior for practical application because it showed a comparable TN removal (59%) at a substantially short HRT of 1 h. The microbial communities that were involved in the nitrogen cycle varied according to whether the biofilms were located on the anodes, separators, and cathodes but were similar among EBRs with different AV ratios. Nitrifying bacteria were detected in the biofilms that were presented on the cathodes (approximately 7.8% of the total phylotypes), while denitrifying bacteria were mainly found in biofilm that were located on the anodes (approximately 23.3%). Anammox bacteria were also detected on the anode (approximately 3.7%) and in the separator biofilms (approximately 1.9%) of all the EBRs. These results suggest that both the A/V ratio and the HRT could affect the counter diffusion of substrates (NH4+ and organic compounds) and oxygen in the biofilms and allow interactions between a diversity of microorganisms for the successful removal of nitrogen in EBRs. These findings are expected to aid in the development of new applications using EBR for energy-saving wastewater treatment.


Assuntos
Microbiota , Nitrogênio , Biofilmes , Reatores Biológicos , Desnitrificação , Eletrodos , Nitrificação , Águas Residuárias
7.
J Environ Manage ; 280: 111783, 2021 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-33349513

RESUMO

Wetlands play an important role in reducing the impact of nitrogen pollution on natural aquatic environments. However, during the plant wilting period (winter) there will inevitably be a reduction in nitrogen removal from wetlands. Understanding optimum harvest time will allow the use of management practices to balance the trade-off between nitrogen removal and the sustainability of wetlands. In this study, we investigated wetland nitrogen removal and reed (Phragmites australis) nutrient responses for two years [first year: influent total nitrogen (TN) 17.6-34.7 mg L-1; second year: influent TN 3.2-10.0 mg L-1] to identify the optimal harvest time: before wilting, mid-wilting, or late wilting. Harvesting decreased wetland nitrogen removal in both years, with later harvest time producing a smaller decrease in TN and ammonium-nitrogen (NH4+-N) removal. In addition to harvest before wilting, aboveground reed harvest at mid-wilting harvested more nutrients [carbon (C) 7.9%, nitrogen (N) 46.6% and phosphorus (P) 43.6%] in the first year, while harvest at late wilting harvested more nutrients (C 4.9%, N 7.8% and P 24.1%) in the second year, although this was not statistically significant. The late wilting harvest caused fewer disturbances to root stoichiometric homeostasis in the first year, while mid-wilting harvest promoted root nutrient availability in the second year. In addition, redundancy analysis (RDA) showed that root stoichiometry was interrelated with wetland nitrogen removal. Our results suggest that optimal harvest time was late wilting on the basis of wetland nitrogen removal, or either mid- or late wilting according to reed nutrient response to influent nitrogen concentration in some years. Our results provide crucial information for winter wetlands management.


Assuntos
Nitrogênio , Áreas Alagadas , Desnitrificação , Nutrientes , Fósforo , Poaceae
8.
J Environ Manage ; 280: 111859, 2021 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-33352382

RESUMO

This study assesses bacterial denitrification at alkaline pH, up to 12, and high nitrate concentration, up to 400 mM. Two types of electron donors organic (acetate) and inorganic (dihydrogen) were compared. With both types of electron donors, nitrite reduction was the key step, likely to increase the pH and lead to nitrite accumulation. Firstly, an acclimation process was used: nitrate was progressively increased in three cultures set at pH 9, 10, or 11. This method allowed to observe for the first time nitrate reduction up to pH 10 and 100 mM nitrate with dihydrogen, or up to pH 10 and 400 mM nitrate with acetate. Nitrate reduction kinetics were faster in the presence of acetate. To investigate further the impact of the type of electron donor, a transition from acetate to dihydrogen was tested, and the pH evolution was modelled. Denitrification with dihydrogen strongly increases the pH while with acetate the pH evolution depends on the initial pH. The main difference is the production of acidifying CO2 during the acetate oxidation. Finally, the use of long duration cultures with a highly alkaline pH allowed a nitrate reduction up to pH 11.5 with acetate. However, no reduction was possible in hydrogenotrophy as it would have increased the pH further. Instead, bacteria used organic matter from inoculum to reduce nitrate at pH 11.5. Therefore, considering bacterial denitrification in a context of alkaline pH and high nitrate concentration an organic electron donor such as acetate is advantageous.


Assuntos
Nitratos , Nitritos , Acetatos , Bactérias/genética , Reatores Biológicos , Desnitrificação , Elétrons , Concentração de Íons de Hidrogênio , Oxirredução
9.
Sci Total Environ ; 755(Pt 1): 142477, 2021 Feb 10.
Artigo em Inglês | MEDLINE | ID: mdl-33039892

RESUMO

The sustainability of rural sanitation includes the long-term welfare of both rural and urban societies. As a commonly used rural sanitation technology, operation of intermittent sand filters (ISF) is impacted by biofilm clogging inside the ISF. In this study ISF performance is studied at low hydraulic loading rates (HLR) to explore the interaction between biofilm growth and wastewater treatment efficiency. CW2D/HYDRUS, a simulation model which does not include media hydraulic property changes caused by biofilm growth, is utilized as a numerical control to contrast the effects of biofilm growth inside an experimental ISF. A paired experiment with simulation demonstrate that biofilm clogging comprised dominantly of heterotrophs occurred in the top layers of the ISF. Lowered HLR slows clogging development but not final clogging extent. The biofilm clogging development zone offers adequate removal of applied biodegradable COD and NH4+ - N. However, the spatial distribution of heterotrophs and biodegradable COD does not match the denitrification requirement of the resulting NO3- - N. A simultaneous nitrification and denitrification (SND) potential is manifested in the clogging development zone, but lowered HLR reduces media moisture level to a less favorable level for denitrification. Furthermore, slowed water movement under lower HLR aggravates the accumulation of NO3- - N, which can potentially result in counterproductive salt accumulation. Since biofilm growth is a natural and self-adaptive response to wastewater application, this study suggests accepting limited, managed biofilm growth and clogging in ISFs. In addition, this study calls for further research to manage biofilm growth and clogging for long-term ISF sustainability.


Assuntos
Filtração , Areia , Biofilmes , Reatores Biológicos , Desnitrificação , Nitrogênio , Dióxido de Silício , Eliminação de Resíduos Líquidos , Águas Residuárias
10.
Water Res ; 189: 116626, 2021 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-33249306

RESUMO

A novel 'anammox' in the absence of anammox bacteria was confirmed to occur in an anaerobic sludge slurry system, in which Fe(II)/Fe(III) cycle driven by NO2--induced Fe(II) oxidation and subsequent NH4+-induced Fe(III) reduction (Feammox) pushed the nitrogen removal. Results showed that Fe(II) contents significantly (p<0.05) decreased and Fe(III) accordingly increased with NO2- addition, indicating that Fe(II) was anaerobically oxidized to Fe(III). With depletion of NO2-, the Fe(II) content began to increase which was a result of Feammox. Consequently, 96.0% NH4+-N of the NO2--added reactor was removed during 18 days operation, while NH4+-N content remained essentially unchanged in the control in which NO2- was not added. X-ray diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS) analysis indicated that FeOOH was produced from chemical Fe(II) oxidation with NO2-. During the treatment, anammox bacteria was not detected, but the relative abundance of Geobacter of the NO2--added group increased by 13 folds. Isotope experiment in 15NH4+-containing reactors found that much more 30N2 and 29N2 in the 14NO2--added group were produced than those in the control (without 14NO2-), confirming that 14NO2- induced Fe(II) oxidation to participate in Feammox for 15NH4+ removal. Also, NO2- could be produced from partial denitrification of NO3-, meaning that NO3- as a more common species might substitute NO2- to trigger this new anammox process.


Assuntos
Desnitrificação , Compostos Férricos , Anaerobiose , Bactérias , Reatores Biológicos , Compostos Ferrosos , Nitrogênio , Oxirredução
11.
Water Res ; 189: 116662, 2021 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-33271414

RESUMO

In this study, pyrrhotite is applied to remove arsenite (As(III)) and NO3- from groundwater simultaneously. Batch experiments find that sulfur autotrophic denitrifiers are not inhibited by As(III) with concentration up to 70 mg·L-1, and pyrrhotite autotrophic denitrification (PAD) can effectively remove As(III), NO3- and PO43- simultaneously. Treating water with As(III) 874.50±32.76 µg·L-1, NO3--N 30 mg·L-1, and PO43--P 0.5 mg·L-1, the pyrrhotite-sulfur-limestone autotrophic denitrification (PSLAD) biofilter can achieve effluent with total Arsenic (As) 7.84±7.29 µg·L-1, NO3--N 3.78±1.14 mg·L-1, and PO43--P below detection limit at hydraulic retention time 6 h. In the PSLAD biofilter, Thiobacillus is the most abundant bacterium, and it uses pyrrhotite and sulfur as electron donor to reduce NO3-, and basically Fe2+ and As(III) are oxidized to Fe3+ and arsenate, respectively. As and PO43- were mainly removed through precipitates FeAsO4 and FePO4, respectively. Technology based on the PAD is a simple, cost-effective and efficient way for remediation of As(III) and NO3- co-contaminated groundwater, and avoiding contaminants transference between groundwater and surface water.


Assuntos
Arsenitos , Água Subterrânea , Processos Autotróficos , Reatores Biológicos , Desnitrificação , Nitratos/análise
12.
Bioresour Technol ; 322: 124430, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-33383476

RESUMO

Biochar was utilized to intensify constructed wetland (CW) for further organic and nitrogen removal from secondary wastewater. Four sets of non-aerated biochar amended vertical flow CW (VFCW) were developed to investigate the synergistic effects of biochar and microbes on pollutant removal. Results showed that the average COD and nitrogen removal efficiencies of VFCW1 (with 1% w/w biochar with microbe and plants) achieved 89.1 ± 5.6% and 90.2 ± 3.1% respectively, and their corresponding removal rates of 10.2 ± 0.8 mg-COD/(m3.d) and 3.57 ± 0.3 mg-TN/(m3.d) which were 35 and 52.3% higher than control. The biochar's dissolved organic carbon release in VFCWs indicated that water and acidic media portray the optimum conditions for nitrogen removal. The 16S RNA gene sequencing analysis indicated that in the biochar-amended VFCWs, bacterial phylum Proteobacteria (24.13-51.95%) followed by Chloroflexi (5.64-25.01%), Planctomycetes (8.48-14.43%), Acidobacteria (2.29-11.65%) were abundantly enhanced. Conclusively, incorporating biochar in non-aerated VFCWs is an efficient technique for enhancing nitrogen removal from secondary effluent.


Assuntos
Microbiota , Áreas Alagadas , Carbono , Carvão Vegetal , Desnitrificação , Nitrogênio/análise , Eliminação de Resíduos Líquidos , Águas Residuárias
13.
Sci Total Environ ; 757: 143764, 2021 Feb 25.
Artigo em Inglês | MEDLINE | ID: mdl-33248788

RESUMO

Nitrate pollution in water is a worldwide health and environmental concern. Biological nitrate removal of wastewater is widely used countering eutrophication of water bodies; however it could be troublesome and expensive when influent carbon source is insufficient. Here we present a novel process, the microbial fuel cell (MFC)-resistance-type electrical stimulation denitrification process (RtESD) using microbial weak electricity originated from the wastewater, to enhance nitrate removal. Results show that the optimal nitrate dependent denitrification rate (0.027 mg N/L·h) and nitrate removal efficiency (98.1%) can be achieved; partial autotrophic denitrification was enhanced in RtESD under stimulation of 0.2 V of microbial weak electricity (MWE). Aromatic proteins also increased in the presence of 0.2 V MWE stimulation according to three-dimensional excitation-emission matrix (3D-EEM) fluorescence spectroscopy profiles, indicating that electron transfer could be improved in the case of MWE stimulation. Furthermore, the microbial community structure and diversity analysis results demonstrated that MWE stimulation inhibited the heterotrophic denitrifying bacteria and activated the autotrophic denitrifying bacteria in RtESD. Two hypotheses, enhancement of electron transfer and improvement of microorganism activity, were proposed regarding to the MWE stimulated pathways. This study provided a promising method utilizing MWE derived from wastewater to improve the denitrification rate and removal efficiency of nitrate-containing wastewater treatment processes.


Assuntos
Nitratos , Águas Residuárias , Reatores Biológicos , Desnitrificação , Eletricidade , Nitrogênio
14.
Sci Total Environ ; 757: 143928, 2021 Feb 25.
Artigo em Inglês | MEDLINE | ID: mdl-33316511

RESUMO

Many properties of denitrifying anaerobic methane oxidation (DAMO) bacteria have been explored since their first discovery, while DAMO archaea have attracted less attention. Since nitrate is more abundant than nitrite not only in wastewater but also in the natural environment, in depth investigations of the nitrate-DAMO process should be conducted to determine its environmental significance in the global carbon and nitrogen cycles. This review summarizes the status of research on DAMO archaea and the catalyzed nitrate-dependent anaerobic methane oxidation, including such aspects as laboratory enrichment, environmental distribution, and metabolic mechanism. It is shown that appropriate inocula and enrichment parameters are important for the culture enrichment and thus the subsequent DAMO activity, but there are still relatively few studies on the environmental distribution and physiological metabolism of DAMO archaea. Finally, some hypotheses and directions for future research on DAMO archaea, anaerobic methanotrophic archaea, and even anaerobically metabolizing archaea are also discussed.


Assuntos
Archaea , Metano , Anaerobiose , Reatores Biológicos , Desnitrificação , Nitritos , Oxirredução
15.
Sci Total Environ ; 757: 143908, 2021 Feb 25.
Artigo em Inglês | MEDLINE | ID: mdl-33316516

RESUMO

The highly complex microbial communities in biofilm play crucial roles in the pollutant removal performance of wastewater treatment plants (WWTPs). In the present study, using multi-omics analysis, we studied microbial structure, key enzymes, functional traits, and key metabolic pathways of pre-denitrification biofilter in an urban WWTP in China. The analysis results of metagenomic and metaproteomic showed that Betaproteobacteria and Flavobacteriia were dominant in biofilms. The integrated metagenomic and metaproteomic data showed that the expression of nitrogen metabolism genes was high, and the high proportion of denitrification module indicating that denitrification was the main nitrogen removal pathway. The most abundant denitrifying bacterial genera were: Dechloromonas, Acidovorax, Bosea, Polaromonas, and Chryseobacterium. And microorganisms with denitrification potential may not be able to denitrify in the actual operation of the filter. The integrated analysis of metaproteomic and metabolomic showed that there was a correlation between biofilm microorganisms and metabolites. Metabolomic analysis indicated that metabolic profiles of biofilms varied with layer height. This study provides the first detailed microbial communities and metabolic profiles in a full-scale pre-denitrification biofilter and clarifies the mechanism of denitrification.


Assuntos
Desnitrificação , Microbiota , Biofilmes , Reatores Biológicos , China , Nitrogênio , Águas Residuárias
16.
Environ Sci Pollut Res Int ; 28(3): 3008-3018, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-32897473

RESUMO

Organic matter and NH4+-N are two major pollutants in domestic sewage. This study evaluated the influence of plant and circuit operation mode on the performance of constructed wetlands integrated with microbial fuel cells (CW-MFCs) and investigated the removal mechanisms of organic matter and nitrogen. Better chemical oxygen demand (COD) removal was achieved in closed-circuit CW-MFCs regardless of planting or not, with average removal efficiencies of 83.19-86.28% (closed-circuit CW-MFCs) and 76.54-83.19% (open-circuit CW-MFCs), respectively. More than 70% organic matter was removed in the anaerobic region of all CW-MFCs. In addition, the planted CW-MFCs outperformed the unplanted CW-MFCs in ammonium, nitrate, and total nitrogen removal irrespective of circuit connection or not, for example, the NH4+-N removal efficiencies of 95.91-96.82% were achieved in planted CW-MFCs compared with 56.54-59.95% achieved by unplanted CW-MFCs. Besides, 33.14-55.69% of NH4+-N was removed in the anaerobic region. Throughout the experiment, the average voltages of planted and unplanted CW-MFCs were 264 mV and 108 mV, with the corresponding maximum voltage output of 544 mV and 321 mV, respectively. Furthermore, planted CW-MFCs, simultaneously producing a peak power density of 92.05 mW m-3 with a coulombic efficiency of 0.50%, exhibited better than unplanted CW-MFCs (3.29 mW m-3 and 0.21%, respectively) in bioelectricity generation characteristics. Graphical abstract.


Assuntos
Fontes de Energia Bioelétrica , Análise da Demanda Biológica de Oxigênio , Desnitrificação , Nitrogênio , Águas Residuárias , Áreas Alagadas
17.
Bioresour Technol ; 321: 124445, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-33276210

RESUMO

A novel denitrifying phosphorus-accumulating bacterium was isolated from contaminated sediment and identified as Pseudomonas stutzeri ADP-19. Bio-safety assays demonstrated that the strain was γ-hemolytic, antibiotic-sensitive, and had no decarboxylase activity. It removed 96.5% of NH4+-N and 73.3% of PO43--P (at initial concentrations of 100 mg/L and 20 mg/L) under aerobic conditions, and the corresponding maximum removal rates were 3.44 and 0.41 mg/L/h, respectively. Nitrogen removal was achieved through a fully nitrification-denitrification pathway [NH4+-N â†’ NH2OH â†’ NO2--N â†’ NO3--N â†’ NO2--N → (NxO) â†’ N2], while phosphorus removal mainly depended on the phosphate assimilation and the excessive poly-P accumulation. Strain ADP-19 also showed a strong salt tolerance within a wide salinity range of 0-5%. The enhanced biological treatment of anaerobic-digested wastewater in a sequencing batch reactor (SBR) indicated that the strain improved the microbial diversity of the activated sludge and significantly enhanced the nitrogen and phosphorus removal efficiency.


Assuntos
Fósforo , Pseudomonas stutzeri , Difosfato de Adenosina , Reatores Biológicos , Desnitrificação , Nitrificação , Nitrogênio , Esgotos , Eliminação de Resíduos Líquidos , Águas Residuárias
18.
Waste Manag ; 120: 76-84, 2021 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-33285376

RESUMO

A two-stage bioreactor operated under anoxic denitrifying conditions was evaluated for desulfurization of synthetic biogas laden with H2S concentrations between 2500 and 10,000 ppmv. H2S removal efficiencies higher than 95% were achieved for H2S loads ranging from 16.2 to 51.9 gS mliquid-3h-1. Average H2S oxidation performance (fraction of S-SO42- produced per gram of S-H2S absorbed) ranged between 8.2 ± 1.2 and 18.7 ± 5.3% under continuous liquid operation. Nitrogen mass balance showed that only 2-6% of the N-NO3- consumed was directed to biomass growth and the rest was directed to denitrification. Significant changes in the bacterial community composition did not hinder the H2S removal efficiency. The bioreactor configuration proposed avoided clogging issues due to elemental sulfur accumulation as commonly occurs in packed bed bioreactors devoted to H2S-rich biogas desulfurization.


Assuntos
Biocombustíveis , Sulfeto de Hidrogênio , Reatores Biológicos , Desnitrificação , Nitratos , Enxofre
19.
Bioresour Technol ; 321: 124468, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-33296774

RESUMO

The efficient removal of ammonium nitrogen (NH4+-N) is vital to eliminating black and odorous water bodies. In this work, tidal flow constructed wetlands with gravel (TFCW-G) and with a mixture of zeolite and gravel (TFCW-Z) were set up to treat black and odorous water bodies at different hydraulic loading rates (HLRs). Results showed that zeolite significantly enhanced nitrogen removal, and the maximum NH4+-N removal efficiency of 96.69% was achieved in TFCW-Z at HLR of 3 m·d-1 with a flooding and drying cycle of 2 h. Zeolite addition changed the microbial community structure and the abundance of nitrification genes. Comammox Nitrospira was the only enriched strain accounting for NH4+-N removal in TFCW-G, while the co-occurrence of comammox Nitrospira and the canonical and potential ammonia-oxidizing bacteria were identified in TFCW-Z. Summarily, high performance, together with low footprint and low maintenance cost, are characteristics that make the TFCW-Z a promising and competitive alternative.


Assuntos
Compostos de Amônio , Áreas Alagadas , Afro-Americanos , Desnitrificação , Humanos , Nitrogênio , Eliminação de Resíduos Líquidos , Água
20.
Bioresour Technol ; 321: 124447, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-33302007

RESUMO

In the current research, a novel bioreactor composed of porous polymer carriers and iron-carbon (PPC@FeC) was established through bacterial immobilized technology. The influence of key factors was studied on the nitrate removal performance of the PPC@FeC bioreactor. The experimental results showed that the highest removal rate of nitrate (7.33 mg L-1 h-1) can be obtained with short hydraulic retention times (HRT = 2.0 h) and low carbon-to-nitrogen ratio (C/N = 2.0). The results of high-throughput sequencing revealed that Zoogloea sp. L2 was the dominant strain in bioreactor responsible for nitrate removal. Moreover, the SEM and XRD analyses elucidated that Fe2O3 was the final product produced by the interaction of FeC and strain L2. These findings showed that the PPC@FeC bioreactor successfully combined micro-electrolysis and biological denitrification, which exhibited great potential in removing nitrate effectively from wastewater under low C/N ratio and short HRT conditions.


Assuntos
Nitratos , Águas Residuárias , Reatores Biológicos , Carbono , Desnitrificação , Eletrólise , Ferro , Nitrogênio , Polímeros , Porosidade
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