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1.
Huan Jing Ke Xue ; 40(7): 3195-3200, 2019 Jul 08.
Artigo em Chinês | MEDLINE | ID: mdl-31854718

RESUMO

This study investigated the inhibitory effect of free nitrous acid (FNA) on the activity of ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) under anoxic conditions with different mixed liquid suspended solids (MLSS). Sequencing batch reactors were used to study the changes in the activity of AOB and NOB in nitrifying activated sludge based on four different MLSS (8398, 11254, 15998, and 19637 mg·L-1), after treatment, under anoxic conditions with FNA (at an initial concentration of 1.3 mg·L-1) for 48 h. The results showed that the pH increased by approximately 0.9, but the concentration of NO2--N did not decrease significantly. With over-aeration, the concentration of NH4+-N gradually degraded to 0 mg·L-1, and the removal rate of NH4+-N gradually increased to a maximum of 4.4-6.8 mg·(L·h)-1 which time used was shorter with the increase of the inhibition MLSS. The nitrite accumulation rate was more than 92% when the sludge concentration was 8398, 11254, 15998, and 19637 mg·L-1 and with over-aeration for 0-396 h, 0-396 h, 0-372 h, and 0-168 h, respectively. When aerated for 468 h, 468 h, 444 h, and 264 h, the NO2--N concentration and NAR decreased to 0, and NO3--N concentrations increased to their highest with the values of 42.6, 49.9, 42.9, and 47.9 mg·L-1 respectively.


Assuntos
Bactérias/metabolismo , Nitritos/análise , Ácido Nitroso/química , Esgotos/microbiologia , Amônia/análise , Reatores Biológicos/microbiologia , Nitrificação
2.
Environ Sci Pollut Res Int ; 26(32): 33181-33191, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31520377

RESUMO

Fine particulate matter (i.e., PM2.5) has gained extensive attention owing to its adverse effects. The impacts of PM2.5 may vary in time and space due to the spatiotemporal variations of PM2.5 number size distribution and chemical compositions. This research analyzed the latest PM2.5 chemical compositions measurements with an aim to better understand the dynamic changes of PM2.5 in response to emission reductions due to the new regulations. The particulate measurements from the Southeastern Aerosol Research and Characterization (SEARCH) network between 2001 and 2016 were analyzed for the spatiotemporal variations of PM2.5 and inorganic PM2.5 (iPM2.5 = SO42- + NH4+ + NO3-) chemical compositions in the Southeastern United States (U.S.). It was discovered that PM2.5 and iPM2.5 mass concentrations exhibited significant downward trends in 2001-2016. Both PM2.5 and iPM2.5 mass concentrations were higher at urban and inland sites than rural/suburban and coastal sites. The higher iPM2.5 concentrations at agricultural sites were attributed to the influences of ammonia (NH3) emissions from animal feeding operations (AFOs). The iPM2.5 was the dominant contributor to PM2.5 in 2001-2016 at the coastal sites, whereas organic carbon matter (OCM) was the major contributor to PM2.5 after 2011 at the inland sites. Our data analysis suggests that significant decrease of PM2.5 concentrations is attributed to the reductions in nitrogen oxides (NOx) and sulfur dioxide (SO2) emissions in 2001-2016. Findings from this research provide insights into the development of effective PM2.5 control strategies and assessment of air pollutants exposure.


Assuntos
Poluentes Atmosféricos/análise , Poluição do Ar/estatística & dados numéricos , Monitoramento Ambiental , Material Particulado/análise , Aerossóis/análise , Poluição do Ar/análise , Amônia/análise , Animais , Óxidos de Nitrogênio/análise , Sudeste dos Estados Unidos , Dióxido de Enxofre/análise
3.
Artigo em Inglês | MEDLINE | ID: mdl-31505898

RESUMO

Currently, composting is one of the most effective methods for treating fecal waste on large-scale livestock and poultry farms, but the quality effects of different composting methods are different. In this study, we implemented four composting methods, including farmer compost (FC), anaerobic compost (AnC), mixed compost (MC), and aerobic compost (AC), to study the effects of different composting methods on nitrogen (N) losses while composting dairy manure. Our results showed that the germination indexes (GIs) of three of the composting treatments (AnC, MC, and AC) exceeded 80%, which met the maturity requirements for composted products. Ammonia (NH3) emissions were the main contributor to nitrogen losses, while accumulated nitrous oxide (N2O) emissions accounted for the lowest proportion of nitrogen losses. The cumulative N losses via the leachate of the AC treatment were the lowest and accounted for 0.38% of the initial total nitrogen (TN). The accumulated N losses of the AC, FC, AnC, and MC treatments accounted for 13.13% 15.98%, 15.08%, and 19.75%, respectively, of the initial TN. Overall, the AC method significantly reduced N losses via leachates, further reducing TN losses. This observation suggests that AC might be an appropriate method for highly efficient nitrogen management during dairy manure composting.


Assuntos
Compostagem/métodos , Indústria de Laticínios , Esterco/análise , Nitrogênio/análise , Amônia/análise , China , Óxido Nitroso/análise
4.
Environ Pollut ; 255(Pt 1): 113160, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31521996

RESUMO

The intensive use of antibiotics results in the continuous release of antibiotics into wastewater treatment systems, leading to the spread of antibiotic resistance. Nitrifying system is reported to be capable of degrading antibiotics, yet few studies have systematically investigated the inherent correlation among ammonium oxidation rate, antibiotic degradation and genetic expression of nitrifying bacteria along the process. This study selected a widely used sulfonamide antibiotic, sulfadiazine (SDZ), to investigate its biodegradation potential by an enriched nitrifying culture and the response of nitrifying bacteria against antibiotic exposure. Our results demonstrated that SDZ degradation was mainly contributed by cometabolism of ammonia-oxidizing bacteria (AOB), rather than biomass adsorption. The quantitative reverse transcription PCR (RT-qPCR) analysis revealed that the expression level of amoA gene was down-regulated due to the SDZ exposure. In addition, the degradation products of SDZ did not exhibit inhibitory effect on Escherichia coli K12, indicating the biotoxicity of SDZ could be mitigated after biodegradation. The findings offer insights regarding the biodegradation process of sulfonamide antibiotics via cometabolism by AOB.


Assuntos
Antibacterianos/metabolismo , Biodegradação Ambiental , Escherichia coli K12/metabolismo , Nitrificação/fisiologia , Sulfadiazina/metabolismo , Purificação da Água/métodos , Amônia/análise , Compostos de Amônio/análise , Oxirredução , Esgotos/microbiologia , Águas Residuárias/química
5.
Nat Commun ; 10(1): 3944, 2019 09 02.
Artigo em Inglês | MEDLINE | ID: mdl-31477724

RESUMO

Microscale interactions in soil may give rise to highly localised conditions that disproportionally affect soil nitrogen transformations. We report mechanistic modelling of coupled biotic and abiotic processes during drying of soil surfaces and biocrusts. The model links localised microbial activity with pH variations within thin aqueous films that jointly enhance emissions of nitrous acid (HONO) and ammonia (NH3) during soil drying well above what would be predicted from mean hydration conditions and bulk soil pH. We compared model predictions with case studies in which reactive nitrogen gaseous fluxes from drying biocrusts were measured. Soil and biocrust drying rates affect HONO and NH3 emission dynamics. Additionally, we predict strong effects of atmospheric NH3 levels on reactive nitrogen gas losses. Laboratory measurements confirm the onset of microscale pH localisation and highlight the critical role of micro-environments in the resulting biogeochemical fluxes from terrestrial ecosystems.


Assuntos
Amônia/análise , Dessecação/métodos , Gases/análise , Ácido Nitroso/análise , Solo/química , Algoritmos , Amônia/química , Atmosfera/química , Clima Desértico , Ecossistema , Microbiologia Ambiental , Concentração de Íons de Hidrogênio , Modelos Teóricos , Nitrogênio/análise , Nitrogênio/química , Ácido Nitroso/química , Água/metabolismo
6.
Artigo em Inglês | MEDLINE | ID: mdl-31426348

RESUMO

A coupled model is an effective tool to understand the nutrient fate associated with hydrodynamic and ecosystem processes and thereby developing a water resource management strategy. This paper presents a coupled modeling approach that consists of a watershed model and a hydrodynamic model to evaluate the nutrient fate in a river-reservoir system. The results obtained from the model showed a good agreement with field observations. The results revealed that the Shuikou reservoir (Fuzhou, China)exhibited complicated hydrodynamic characteristics, which may induce the pattern of nutrient export. Reservoirs can greatly lower water quality as a result of decreasing water movement. Three scenarios were analyzed for water management. The NH3-N (Ammonia Nitrogen) decreased sharply in the outlet of Shuikou reservoir after NH3-N level in its tributary was reduced. After removing the farming cages, the water quality of the outlet of Shuikou reservoir was improved significantly. The DO (Dissolved Oxygen) had increased by 3%-10%, NH3-N had reduced by 5%-17%, and TP (Total Phosphorus) had reduced by 6%-21%. This study demonstrates that the proposed coupled modeling approach can effectively characterize waterway risks for water management in such a river-reservoir system.


Assuntos
Hidrodinâmica , Modelos Teóricos , Rios , Abastecimento de Água , Amônia/análise , China , Monitoramento Ambiental , Fósforo/análise , Movimentos da Água , Poluentes Químicos da Água/análise , Qualidade da Água
7.
J Dairy Sci ; 102(10): 8850-8861, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31378500

RESUMO

The objectives of this study were (1) to predict ruminal pH and ruminal ammonia and volatile fatty acid (VFA) concentrations by developing artificial neural networks (ANN) using dietary nutrient compositions, dry matter intake, and body weight as input variables; and (2) to compare accuracy and precision of ANN model predictions with that of a multiple linear regression model (MLR). Data were collected from 229 published papers with 938 treatment means. The data set was randomly split into a training data set containing 70% of the observations and a test data set with the remaining observations. A series of ANN with a range of 1 to 9 artificial neurons in 1 hidden layer were examined, and the best one was selected to compare with the best-fitted MLR model. The performance of model predictions was evaluated by root mean square errors (RMSE) and concordance correlation coefficients (CCC) using cross-evaluations with 100 iterations. When using the ANN to predict ruminal pH and concentrations of ammonia, total VFA, acetate, propionate, and butyrate, the RMSE were 4.2, 41.4, 20.9, 22.3, 32.9, and 29.7% of observed means, respectively. The RMSE for the MLR were 4.2, 37.8, 18.3, 19.9, 29.8, and 26.6% of the observed means. The CCC for ruminal pH, ruminal concentrations of ammonia, total VFA, acetate, propionate, and butyrate were 0.57, 0.49, 0.45, 0.40, 0.52, and 0.40, using the ANN, and 0.37, 0.48, 0.40, 0.29, 0.43, and 0.35, using the MLR. Evaluations of the MLR and the ANN indicated that these 2 model forms exhibited similar prediction errors, with 4.2, 39.6, 19.6, 21.1, 31.3, and 28.1% of observed means for pH, ammonia, total VFA, acetate, propionate, and butyrate. Although the ANN increased the precision of predictions related to ruminal metabolism, it failed to improve the accuracy compared with the linear regression model.


Assuntos
Amônia/análise , Ácidos Graxos Voláteis/análise , Rúmen/química , Acetatos/análise , Animais , Butiratos/análise , Bovinos , Dieta/veterinária , Feminino , Concentração de Íons de Hidrogênio , Modelos Lineares , Masculino , Propionatos/análise
8.
Molecules ; 24(13)2019 Jul 09.
Artigo em Inglês | MEDLINE | ID: mdl-31324049

RESUMO

Odor emissions represent one of the important issues of aerobic composting. The addition of microbial agents to compost is an important method for solving this problem, but this process is often unstable when a single microbial agent is added to the compost. Therefore, in this study, five treatments comprising different proportions of Bacillus stearothermophilus, Candida utilis, and Bacillus subtilis were tested to determine the best combination of the three microbial agents for ammonia reduction, as follows: control group (CK), 2:1:1 (A), 1:1:2 (B), 1:2:1 (C), and 1:1:1 (D). Compared with the CK group, the A, B, C, and D groups reduced ammonia emissions by 17.02, 9.68, 53.11, and 46.23%, respectively. The total ammonia emissions were significantly lower in C and D than in CK (p < 0.05). These two treatment groups had significantly increased nitrate nitrogen concentrations and decreased pH values and ammonium nitrogen concentrations (p < 0.05). Throughout the composting process, the total bacterial number was significantly higher in C and D than in CK (p < 0.05). Therefore, it is likely that B. stearothermophilus, C. utilis, and B. subtilis compounded from 1:2:1 (C) to 1:1:1 (D) reduced the ammonia emissions due to (1) a reduction in the pH and (2) the promotion of the growth of ammonia-oxidizing bacteria and the conversion of ammonium nitrogen to nitrate nitrogen. This study provides a theoretical basis and technical support for the odor problem of layer manure compost and promotes the development of composting technology.


Assuntos
Amônia/química , Biodegradação Ambiental , Compostagem , Microbiologia Ambiental , Esterco , Amônia/análise , Candida/metabolismo , Geobacillus stearothermophilus/metabolismo , Concentração de Íons de Hidrogênio , Nitrogênio/metabolismo , Oxirredução , Temperatura Ambiente
9.
Artigo em Inglês | MEDLINE | ID: mdl-31319582

RESUMO

Excess consumption of water resources and environmental pollution have become major challenges restricting sustainable development in China. In order to prevent the pollution of water resources, policymakers should have reliable emission reduction strategies. This paper aims to contribute new knowledge by analyzing the spatial-temporal characteristics and driving forces of point source emission. The chemical oxygen demand (COD) and ammonia nitrogen (NH4-N) emission variations in 31 provinces and municipalities of mainland China during the years 2004-2017 are analyzed. The results obtained using the logarithmic mean Divisia index (LMDI) method indicate that: (1) the COD and NH4-N emission effects have similar temporal characteristics. Technology improvement and pollutant emission intensity are the main factors inhibiting the incremental COD and NH4-N emission effects, while economic development is the main driving factor of COD and NH4-N emission effects. Population increases play a relatively less important role in COD and NH4-N emission effects. (2) The spatial features of COD and NH4-N emission effects show differences among provinces and municipalities. The reduction of COD emission effects in each province and municipality is obviously better than that of NH4-N emissions. (3) In the eastern, central, and the western regions of China, the total COD emission effect shows a downward trend, while apart from the central region, the NH4-N emission effect appears to be rising in the east and west of China. Therefore, increasing investment into pollution treatment, promoting awareness of water conservation, strengthening technological and financial support from the more developed eastern to the less developed central and western regions, can help to reduce the COD and NH4-N emissions in China.


Assuntos
Análise da Demanda Biológica de Oxigênio , Nitrogênio/análise , Análise Espacial , Águas Residuárias/análise , Poluição da Água , Algoritmos , Amônia/análise , China , Desenvolvimento Econômico
10.
Sci Total Environ ; 690: 620-628, 2019 Nov 10.
Artigo em Inglês | MEDLINE | ID: mdl-31301502

RESUMO

For determining setback distances considering multiple air pollutants, a comprehensive study was conducted to simulate the atmospheric dispersion of odour, ammonia (NH3), hydrogen sulfide (H2S), and respirable dust using an US EPA air dispersion model AERMOD for a commercial dairy, broiler, and cage-layer barn in the Canadian Prairies. The simulation was conducted using five years of meteorological data. Setback distances were determined with the input of varying monthly emission rates of all four air pollutants and odour impact criteria specifically developed for all three odour sources. Results showed the layer barn had the greatest odour impact area (maximum 3023 m for an annual average odour concentration of 0.01 OU m-3) followed by the broiler and dairy barns. Due to the prevailing south wind for all three barns, odour traveled farthest in the north. Using the suggested odour impact criteria by the Government of Saskatchewan defined for all odour sources, maximum setback distances were decreasing from 1941 to 641 m for the layer barn and from 980 to 320 m for the broiler barn along with the increasing of odour concentration (OC) thresholds (1-6 OU m-3), all in the north direction. While for the dairy barn, setback distances were determined only under an OC limit of 1 OU m-3; maximum 205 m in the north and minimum 171 m in the south. Using the newly developed odour impact criteria specifically for the three odour sources, maximum setback distance of 558 m in the north was determined for the layer barn under an odour threshold of 9 OU m-3. Additionally, the results suggest the use of odour impact criteria for determining setback distance rather than using gas/respirable threshold limits set in ambient air quality standards as the former always requires much greater setback distances than the latter.


Assuntos
Poluentes Atmosféricos/análise , Monitoramento Ambiental , Pradaria , Modelos Químicos , Odorantes/análise , Poluição do Ar/estatística & dados numéricos , Amônia/análise , Criação de Animais Domésticos , Animais , Poeira/análise , Sulfeto de Hidrogênio/análise , Aves Domésticas , Saskatchewan
11.
Environ Sci Pollut Res Int ; 26(25): 25596-25608, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31267394

RESUMO

Since NH3 is a significant precursor to ammonium in PM2.5 and contributes significantly to atmospheric nitrogen deposition but largely remains unregulated in China, the insight into the source of NH3 emissions by the isotopic investigation is important in controlling NH3 emissions. In this study, atmospheric concentrations of NH3 and water-soluble ion composition in PM2.5 as well as nitrogen isotope ratios in NH4+ (δ15N-NH4+) in Xiamen, China, were measured. Results showed that average NH3 concentration for the five sites in Xiamen was 7.9 µg m-3 with distinct higher values in the warm season and lower values in the cold season, and PM2.5 concentration for the two sites (urban and suburban) was 59.2 µg m-3 with lowest values in summer. In the PM2.5, NH4+ concentrations were much lower than NH3 and showed a stronger positive correlation with NO3- than that with SO42- suggesting the formation of NH4NO3 and equilibrium between NH3 and NH4+. Although the concentrations of NH3 at the urban site were significantly higher than those at the suburban site, no significant spatial difference in NH4+ and δ15N-NH4+ was obtained. The distinct heavier δ15N-NH4+ values in summer than in other seasons correlated well with the equilibrium isotopic effects between NH3 and NH4+ which depend on temperature. The initial δ15N-NH3 values were in the range of waste treatment (- 25.42‰) and fossil fuel combustion (- 2.5‰) after accounting for the isotope fractionation. The stable isotope mixing model showed that fossil fuel-related NH3 emissions (fossil fuel combustion and NH3 slip) contributed more than 70% to aerosol NH4+. This finding suggested that the reduction of NH3 emissions from urban transportation and coal combustion should be a priority in the abatement of PM2.5 pollution in Xiamen.


Assuntos
Aerossóis/análise , Amônia/análise , Compostos de Amônio/análise , Carvão Mineral/análise , Monitoramento Ambiental/métodos , Isótopos de Nitrogênio/análise , Nitrogênio/análise , Poluentes Atmosféricos/análise , China , Combustíveis Fósseis , Estações do Ano
12.
Environ Pollut ; 252(Pt B): 1500-1508, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31272009

RESUMO

The application of low ozone dosage to minimize the problems caused by filamentous foaming was evaluated in two bioreactors of an urban wastewater treatment plant. Filamentous and nitrifying bacteria, as well as protist and metazoa, were monitored throughout a one-year period by FISH and conventional microscopy to examine the effects of ozone application on these specific groups of microorganisms. Multivariate data analysis was used to determine if the ozone dosage was a key factor determining the low carbon and nitrogen removal efficiencies observed throughout the study period, as well as to evaluate its impact on the biological communities monitored. The results of this study suggested that ozonation did not significantly affect the COD removal efficiency, although it had a moderate effect on ammonia removal efficiency. Filamentous bacteria were the community most influenced by ozone (24.9% of the variance explained by ozone loading rate), whilst protist and metazoa were less affected (11.9% of the variance explained). Conversely, ozone loading rate was not a factor in determining the nitrifying bacterial community abundance and composition, although this environmental variable was correlated with ammonia removal efficiency. The results of this study suggest that different filamentous morphotypes were selectively affected by ozone.


Assuntos
Microbiota/efeitos dos fármacos , Nitrogênio/análise , Ozônio/química , Esgotos/microbiologia , Águas Residuárias/microbiologia , Purificação da Água/métodos , Amônia/análise , Desnitrificação , Nitrificação , Esgotos/química , Águas Residuárias/química
13.
Artigo em Inglês | MEDLINE | ID: mdl-31261730

RESUMO

Identifying nitrogen-transforming genes and the microbial community in the lacustrine sedimentary environment is critical for revealing nitrogen cycle processes in eutrophic lakes. In this study, we examined the diversity and abundance of ammonia-oxidizing bacteria (AOB), ammonia-oxidizing archaea (AOA), denitrifying bacteria (DNB), and anammox bacteria (AAOB) in different trophic status regions of Lake Taihu using the amoA, Arch-amoA, nirS, and hzo genes as functional markers. Quantitative Polymerase Chain Reaction (qPCR) results indicated that the abundance of the nirS gene was the highest, while the amoA gene had the lowest abundance in all regions. Except for the primary inflow area of Lake Taihu, Arch-amoA gene abundance was higher than the hzo gene in three lake bays, and the abundance of the nirS gene increased with decreasing trophic status. The opposite pattern was observed for the amoA, Arch-amoA, and hzo genes. Phylogenetic analyses showed that the predominant AOB and AOA were Nitrosomonas and Nitrosopumilus maritimus, respectively, and the proportion of Nitrosomonas in the eutrophic region (87.9%) was higher than that in the mesotrophic region (71.1%). Brocadia and Anammoxoglobus were the two predominant AAOB in Lake Taihu. Five novel unknown phylotypes of AAOB were observed, and Cluster AAOB-B was only observed in the inflow area with a proportion of 32%. In the DNB community, Flavobacterium occurred at a higher proportion (22.6-38.2%) in all regions, the proportion of Arthrobacter in the mesotrophic region (3.6%) was significantly lower than that in the eutrophic region (15.6%), and the proportions of Cluster DNB-E in the inflow area (24.5%) was significantly higher than that in the lake bay (7.3%). The canonical correspondence analysis demonstrated that the substrate concentration in sedimentary environments, such as NOx--N in the sediment, NH4+-N in the pore water, and the total organic matter, were the key factors that determined the nitrogen-transforming microbial community. However, the temperature was also a predominant factor affecting the AOA and AAOB communities.


Assuntos
Lagos/microbiologia , Microbiota , Nitrogênio/metabolismo , Estações do Ano , Amônia/análise , Sedimentos Geológicos/química , Ciclo do Nitrogênio , Oxirredução , Filogenia
14.
Sci Total Environ ; 693: 133425, 2019 Nov 25.
Artigo em Inglês | MEDLINE | ID: mdl-31362224

RESUMO

This study investigates the impact of bio-carriers' surface area and shape, wastewater chemistry and operating temperature on ammonia removal from real wastewater effluents using Moving bed biofilm reactors (MBBRs) operated with three different AnoxKaldness bio-carriers (K3, K5, and M). The study concludes the surface area loading rate, specific surface area, and shape of bio-carrier affect ammonia removal under real conditions. MBBR kinetics and sensitivity for temperature changes were affected by bio-carrier type. High surface area bio-carriers resulted in low ammonia removal and bio-carrier clogging. Significant ammonia removals of 1.420 ±â€¯0.06 and 1.103 ±â€¯0.06 g - N/m2. d were achieved by K3(As = 500 m2/m3) at 35 and 20 °C, respectively. Lower removals were obtained by high surface area bio-carrier K5 (1.123 ±â€¯0.06 and 0.920 ±â€¯0.06 g - N/m2. d) and M (0.456 ±â€¯0.05 and 0.295 ±â€¯0.05 g - N/m2. d) at 35 and 20 °C, respectively. Theta model successfully represents ammonia removal kinetics with θ values of 1.12, 1.06 and 1.13 for bio-carrier K3, K5 and M respectively. MBBR technology is a feasible choice for treatment of real wastewater effluents containing high ammonia concentrations.


Assuntos
Amônia/análise , Reatores Biológicos , Eliminação de Resíduos Líquidos/métodos , Águas Residuárias/análise , Biofilmes , Cinética , Temperatura Ambiente
15.
Environ Pollut ; 254(Pt A): 112903, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31362259

RESUMO

Dissimilatory nitrate reduction to ammonia (DNRA) is an important nitrate reduction pathway in lake sediments; however, little is known about the biotic factors driving the DNRA potential rates and contributions to the fate of nitrate. This study reports the first investigation of DNRA potential rates and contributions in lake sediments linked to DNRA community structures. The results of 15N isotope-tracing incubation experiments showed that 12 lakes had distinct DNRA potentials, which could be clustered into 2 groups, one with higher DNRA potentials (rates varied from 2.7 to 5.0 nmol N g-1 h-1 and contributions varied from 27.5% to 35.4%) and another with lower potentials (rates varied from 0.6 to 2.3 nmol N g-1 h-1 and contributions varied from 8.1% to 22.8%). Sediment C/N and the abundance of the nrfA gene were the key abiotic and biotic factors accounting for the distinct DNRA potential rates, respectively. A high-throughput sequencing analysis of the nrfA gene revealed that the sediment C/N could also affect the DNRA potential rates by altering the ecological patterns of the DNRA community composition. In addition, the interactions between the DNRA community and the denitrifying community were found to be obviously different in the two groups. In the higher DNRA potential group, the DNRA community mainly interacted with heterotrophic denitrifiers, while in the lower DNRA potential group, both heterotrophic and sulfur-driven autotrophic denitrifiers might cooperate with the DNRA community. The present study highlighted the role of the sulfur-driven nitrate reduction pathway in C-limited sediments, which has always been overlooked in freshwater environments, and gave new insights into the molecular mechanism influencing the fate of nitrate.


Assuntos
Amônia/metabolismo , Sedimentos Geológicos/química , Nitratos/metabolismo , Poluentes da Água/metabolismo , Amônia/análise , China , Desnitrificação , Monitoramento Ambiental , Lagos/química , Nitratos/análise , Óxidos de Nitrogênio , Poluentes da Água/análise
16.
Chemosphere ; 233: 660-666, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31195270

RESUMO

Ammonia in gas phase has an unpleasant smell and is hazardous to human health. Though activated carbon has been widely used as a representative adsorbent, it is significantly vulnerable to humidity. In the study, a nonwoven fibrous polypropylene polymer was synthesized using a photo-graft reaction with imidazole followed by quaternization with CH3I. The time of each reaction was optimized for the maximum adsorption. The FT-IR confirmed that 1-vinyl imidazole (Vim) and methyl group (-CH3) were successfully introduced into PP fibers. The Langmuir isotherm characterized that the adsorption capacity was 44.84 mg NO3-N g-1. The adsorption intensity, 1/n, by Freundlich adsorption isotherm was 0.41 indicating that the adsorption of NO3-N onto PP-g-Vim-CH3I was favorable at the studied conditions. In the gas phase, maximum adsorption of was calculated to be 40 ±â€¯0.69 mg NH3 g-1 by BET model. Though the adsorption amount decreased by 2.5 times as the temperature increased from 15 °C to 45 °C, the amounts and rates of adsorption were not influenced by humidity. In conclusion, the synthesized PP-g-Vim-CH3I was able to ammonia in the gas phase at a range of humidity.


Assuntos
Amônia/análise , Imidazóis/química , Modelos Químicos , Polipropilenos/química , Adsorção , Amônia/química , Cinética , Espectroscopia de Infravermelho com Transformada de Fourier , Temperatura Ambiente
17.
Environ Pollut ; 252(Pt A): 305-316, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31158659

RESUMO

Intensive farming practices are typically used for aquaculture. To prevent disease outbreaks, antibiotics are often used to reduce pathogenic bacteria in aquaculture animals. However, the effects of antibiotics on water quality and microbial communities in euryhaline fish culture ponds are largely unknown. The aim of this study was to investigate the interactions between sulfamethoxazole (SMX), water quality and microbial communities in milkfish (Chanos chanos) culture ponds. The results of small-scale milkfish pond experiments indicated that the addition of SMX decreased the abundance of ammonia-oxidizing bacteria (AOB), nitrite-oxidizing bacteria (NOB) and photosynthetic bacteria. Consequently, the levels of ammonia and total phosphorus in the fish pond water increased, causing algal and cyanobacterial blooms to occur. In contrast, the addition of the SMX-degrading bacterial strains A12 and L effectively degraded SMX and reduced the levels of ammonia and total phosphorus in fish pond water. Furthermore, the abundances of AOB, NOB and photosynthetic bacteria were restored, and algal and cyanobacterial blooms were inhibited. This study demonstrate the influences of SMX on water quality and microbial community composition in milkfish culture ponds. Moreover, the use of the bacterial strains A12 and L as dual function (bioaugmentation and water quality maintenance) beneficial bacteria was shown to provide an effective approach for the bioremediation of SMX-contaminated euryhaline milkfish culture ponds.


Assuntos
Bactérias/metabolismo , Biodegradação Ambiental , Tanques/química , Tanques/microbiologia , Sulfametoxazol/metabolismo , Qualidade da Água , Amônia/análise , Animais , Aquicultura , Bactérias/classificação , Bactérias/isolamento & purificação , Peixes , Microbiota , Ciclo do Nitrogênio , Fósforo/análise
18.
Environ Sci Pollut Res Int ; 26(33): 34332-34344, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31175569

RESUMO

Struvite precipitation is an effective method to remove and recover ammonia and phosphate from livestock wastewater. Struvite has properties similar to those of the traditional ammonium-phosphate fertilizer, which does not burn the roots owing to its slow-release characteristics. Struvite is an effective fertilizer as its nutrient-releasing rate is very slow. But the release rate of ammonia and phosphate in soil depends on the size of crystals. In this study, the nutrient-releasing pattern of three types of struvite crystals and liquid fertilizer was compared using soil column. X-Ray fluorescence spectrometry was conducted to investigate the potential use of struvite as a fertilizer. Various struvite crystalline fertilizers were evaluated for their fertilizer performance by cultivating potted vegetable crops. The nitrogen removal efficiency of zeolite-seeded struvite was higher than that of no seed struvite. The ammonia nitrogen removal efficiency was more than 99% irrespective of the kind of zeolite. The soil column test revealed that nutrient releasing from liquid fertilizer and zeolite-seeded struvite recovered from livestock wastewater was 11 and 63 days, respectively. Struvite recovered from livestock wastewater contained more than 20% (w/w) potassium oxide; however, the concentration of heavy metals, such as copper and zinc, was very low. Therefore, we considered that the synthesized struvite using livestock wastewater has high value as fertilizer. The recovered struvite was effective under appropriate concentrations to cultivate all the applied vegetable crops in this study.


Assuntos
Fertilizantes/análise , Estruvita/química , Verduras/crescimento & desenvolvimento , Amônia/análise , Metais Pesados/análise , Nitrogênio/análise , Nutrientes , Fosfatos/química , Fósforo , Solo , Águas Residuárias/química
19.
Artigo em Inglês | MEDLINE | ID: mdl-31242650

RESUMO

Poultry manure is the main source of agricultural and rural non-point source pollution, and its effective disposal through anaerobic digestion (AD) is of great significance; meanwhile, the high nitrogen content of chicken manure makes it a typical feedstock for anaerobic digestion. The performance of chicken-manure-based AD at gradient organic loading rates (OLRs) in a continuous stirred tank reactor (CSTR) was investigated herein. The whole AD process was divided into five stages according to different OLRs, and it lasted for 150 days. The results showed that the biogas yield increased with increasing OLR, which was based on the volatile solids (VS), before reaching up to 11.5 g VS/(L·d), while the methane content was kept relatively stable and maintained at approximately 60%. However, when the VS was further increased to 11.5 g VS/(L·d), the total ammonia nitrogen (TAN), pH, and alkalinity (CaCO3) rose to 2560 mg·L-1, 8.2, and 15,000 mg·L-1, respectively, while the volumetric biogas production rate (VBPR), methane content, and VS removal efficiency decreased to 0.30 L·(L·d)-1, 45%, and 40%, respectively. Therefore, the AD performance immediately deteriorated and ammonia inhibition occurred. Further analysis demonstrated that the microbial biomass yield and concentrations dropped dramatically in this period. These results indicated that the AD stayed steady when the OLR was lower than 11.5 g VS/(L·d); this also provides valuable information for improving the efficiency and stability of AD of a nitrogen-rich substrate.


Assuntos
Reatores Biológicos , Esterco , Agricultura , Amônia/análise , Anaerobiose , Animais , Biocombustíveis/análise , Galinhas , Metano/análise , Nitrogênio/análise
20.
Chemosphere ; 233: 472-481, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31181494

RESUMO

Ammonia-rich lagoon supernatant was treated using anammox process in an integrated fixed-film activated sludge (IFAS) laboratory reactor. Effective anammox activities were demonstrated over 259 days of operation. The ammonium removal efficiency reached 94% in Phase I with influent concentrations of NH4+, NO2- and chemical oxygen demand (COD) at 250 mg-N/L, 325 mg-N/L, and 145 mg-COD/L, and reached 88% in Phase II at 420 mg-N/L, 525 mg-N/L, and 305 mg-COD/L. When supplemented with nitritation effluent for nitrite sources in Phase III, the influent COD concentration increased to 583 mg-COD/L without loss of ammonia removal efficiency (87%). The specific anammox activity was higher in biofilm than in the suspended flocs (P < 0.05), increased from Phase I to II (P < 0.05), and decreased in Phase III. Ammonia removal related genes were quantified using qPCR. Results showed higher anammox gene (AMX nirS) prevalence in biofilm, while denitrification genes (nosZ and narG) were higher in flocs (P < 0.05). Microbial community analysis showed that the seeded anammox bacteria Candidatus Brocadia was maintained at 19% in the biofilm and only 0.3% in the flocs. The major taxa in the flocs were related to denitrifiers. The floc community was affected largely under high COD conditions, but the biofilm community was not. These results suggest that the anammox activity in biofilm is resilient to high COD loadings, due to the existence of flocs with denitrification activity. The segregation of bacterial communities between biofilm and flocs in the anammox IFAS system resulted in high ammonia removal efficiency and resistance to high organic loadings.


Assuntos
Amônia/análise , Biofilmes/crescimento & desenvolvimento , Reatores Biológicos/microbiologia , Esgotos/microbiologia , Purificação da Água/métodos , Análise da Demanda Biológica de Oxigênio , Desnitrificação/genética , Genes Bacterianos , Modelos Teóricos , Planctomycetales/genética
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