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2.
Water Res ; 178: 115848, 2020 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-32361288

RESUMO

Micro-aerobic enhancement technology has been developed as an effective tool to enhance simultaneous removal of sulfide, nitrate and organic carbon during the integrated autotrophic-heterotrophic denitrification (IAHD) process under high loading; however, its mechanism of enhancement for functional bacteria remains ambiguous. In this study, we discovered that heterotrophic sulfide-oxidizing nitrate-reducing bacteria (h-soNRB) are responsible for enhancing IAHD performance under micro-aerobic conditions with high sulfide loading. In a continuous IAHD bioreactor, aeration rate of 2.6 mL min-1·L-1 promoted 2 to 4 times higher removal efficiencies of sulfide, nitrate and acetate with an influent sulfide concentration of 18.75 mmol/L. Metagenomic analysis revealed that trace oxygen stimulated the abundance of genes responsible for sulfide oxidation (sqr, glpE, pdo, sox and cysK), which were upregulated by 15.2%-129.9%, and the genes encoding nitrate reductase were up-regulated by 67.4%. The increased acetate removal efficiency was attributed to upregulation of ack, pta and TCA cycle related genes. The h-NRB Pseudomonas, Azoarcus, Thauera and Halomonas were detected and regarded as h-soNRB in our bioreactor. According to Illumina MiSeq sequencing, these genera were absolutely dominant in the micro-aerobic microbial community at relative abundances ranging from 82.72% to 90.84%. The sulfide, nitrate and acetate removal rates of Pseudomonas C27, a typical h-soNRB, were at least 10 times higher under micro-aerobic conditions than under anaerobic conditions. Besides, the sulfur, nitrogen and carbon metabolic network was constructed based on the Pseudomonas C27 genome. The pdo and cysK genes found in this strain may be the most advantageous for autotrophic sulfide oxidizing nitrate reducing bacteria (a-soNRB), which are closely related to the high-efficiency sulfide, nitrate and acetate removal performance under high sulfide concentrations and a limited oxygen supply. In addition, after micro-aerobic cultivation, the anaerobic sulfide loading tolerance of the IAHD bioreactor increased from 18.75 to 37.5 mmol/L with sulfide, nitrate and acetate removal efficiencies increasing 1.5 to 3 times, which suggests that intermittent micro-aeration might be a more economical and efficient regime for high-sulfide IAHD regulation.


Assuntos
Processos Autotróficos , Desnitrificação , Bactérias , Reatores Biológicos , Nitratos , Oxirredução , Sulfetos
3.
Bioresour Technol ; 310: 123465, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32388206

RESUMO

Nitrogen removal from saline wastewater is challenging due to adverse effects of salinity on biological processes. A novel sulfur-autotrophic cyclic denitrification filter (CDF) was tested for marine recirculating aquaculture systems (RAS) under varying conditions. Low ammonia, nitrite and sulfide concentrations were maintained at residence times between 4 and 12 h. After introduction of Poecilia sphenops, concentrations of NH4+-N, NO2--N, NO3--N were maintained below 1, 1, and 60 mg/L, respectively. Fish waste inputs to the CDF contributed to mixotrophic denitrification and low sulfate production. A mass balance showed that 7% of the feed nitrogen was assimilated by fish, 6% was removed by passive denitrification (e.g., in anoxic zones in filters), 60% in the CDF and 27% was discharged during sampling and solids removal. Daily fresh water addition was <2% of fish tank volumes. The results are promising as a low cost alternative for saline wastewater denitrification.


Assuntos
Reatores Biológicos , Desnitrificação , Animais , Aquicultura , Processos Autotróficos , Nitratos , Nitrogênio , Enxofre , Águas Residuárias
4.
J Environ Manage ; 265: 110576, 2020 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-32421564

RESUMO

Phosphate rock (PR) and ferric salts have been frequently used to immobilize heavy metal(loid)s in soils, but in varied efficiencies referring to different metal(loid) pollutants. This study explored the effective application of plant ash (PA) to the previous formula of phosphate rock (PR) and ferric salts (Fe(NO3)3) (PR + Fe3++PA), compared to only PR, on the bioavailability and immobility of multi-metal(loid)s of selected arsenic (As), lead (Pb) and cadmium (Cd) in soils. Results from NaHCO3- extraction and toxicity characteristic leaching procedure (TCLP) implied the increase of the As mobility in soils by 7.0% and 2.6% using PR only, but the significant reduction of the As mobility by 24.2% and 82.4% jointly using PR + Fe3++PA. Meanwhile, the application of either PR alone or PR + Fe3++PA in soil significantly decreased Pb and Cd extracting in diethylene triamine pentacetate acid (DTPA) and TCLP, particularly, the immobilization effect of PR + Fe3++PA was better than that of PR. The leaching column test further confirmed the high durability of PR + Fe3++PA on the immobilization of As and Pb under the continuous acid exposure, but likely slightly increased the mobility of Cd (the accumulated concentration of Cd, 5.88 µg/L) compared to that (3.16 µg/L) in the untreated column (UN-column), which were both much lower than the level V (100 µg/L) of the Chinese National Quality Standard for Surface Water (GB 3838-2002). Therefore, PR + Fe3++PA exhibited the significant enhancement on the immobilization of As, Pb and Cd under simulated acid rain (SAR) leaching.


Assuntos
Arsênico , Metais Pesados , Poluentes do Solo , Cádmio , Compostos Férricos , Chumbo , Nitratos , Fosfatos , Solo
6.
Chemosphere ; 251: 126364, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32443231

RESUMO

This study is among the first to systematically study the electrochemical reduction of nitrate on boron-doped diamond (BDD) films with different surface terminations and boron-doping levels. The highest nitrate reduction efficiency was 48% and the highest selectivity in the production of nitrogen gas was 44.5%, which were achieved using a BDD electrode with a hydrogen-terminated surface and a B/C ratio of 1.0%. C-H bonds served as the anchor points for attracting NO3- anions close to the electrode surface, and thus accelerating the formation of NO3-(ads). Compared to oxygen termination, hydrogen-terminated BDD exhibited higher electrochemical reactivity for reducing nitrate, resulting from the formation of shallow acceptor states and small interfacial band bending. The hydrophobicity of the hydrogen-terminated BDD inhibited water electrolysis and the subsequent adsorption of atomic hydrogen, leading to increased selectivity in the production of nitrogen gas. A BDD electrode with a boron-doping level of 1.0% increased the density of acceptor states, thereby enhancing the conductivity and promoting the formation of C-H bonds after the cathodic reduction pretreatment leading to the direct reduction of nitrate.


Assuntos
Boro/química , Técnicas Eletroquímicas , Diamante/química , Doping nos Esportes , Eletrodos , Eletrólise/métodos , Hidrogênio/química , Nitratos , Óxidos de Nitrogênio , Oxirredução , Oxigênio , Água
7.
Bioresour Technol ; 311: 123533, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32460131

RESUMO

Denitrification in mixed culture system has been extensively researched to date, but few studies have focused on accelerating the process using redox mediators to promote electron transfer. Strain L2, an iron-reducing bacteria, can remove 75.44% of nitrate under temperature of 30.60 °C, pH of 6.75 and Fe2+ concentration of 27.86 mg·L-1. Additionally, the removal rate of nitrate reached 1.516 mg·L-1·h-1 in 8 h with the addition of 0.030 mmol·L-1 2-hydroxy-1,4-naphthoquinone (HNQ), which increased by 1.38 times than control group. Furthermore, analysis by fluorescence spectroscopy, flow cytometer and gas chromatography demonstrated that HNQ positively stimulated denitrification. This study provides a reference for enhancing denitrification in mixed culture and lays the foundation for the practical application of redox mediators in groundwater treatment.


Assuntos
Naftoquinonas , Zoogloea , Desnitrificação , Nitratos , Oxirredução
8.
Chemosphere ; 248: 125754, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32422855

RESUMO

Nitrates are bioavailable compounds, which are necessary for every living organisms. However, their excess could be harmful, because it could lead to, i.e., methemoglobinemia, formation of carcinogenic nitrosamines and reservoir eutrophication. Isotopic analysis of δ15N and δ18O in nitrates allows to distinguish their different sources. To simplify the way of nitrate source monitoring, we developed a less complex and cheap "off-line" method for nitrate isotopic analysis, in which we obtain both gases required for isotopic analysis of NO3-, N2 for δ15N and CO2 for δ18O measurements, in one procedure. The developed method is based on simultaneous conversion of AgNO3 (mixed with C and placed into PtIr boat) to N2 and CO2 in a glass vacuum apparatus. A small amount of sample (8 mg of AgNO3) required for this procedure and a good reproducibility of the isotopic analysis (better than 0.3‰ for δ18O and 1‰ for δ15N) make this method a useful tool for environmental research. Using the developed method, we analyzed the isotopic composition of N and O in nitrates in the Zemborzycki Reservoir near Lublin (Poland), in 2015. The results indicate a large variation of δ15N (from -1.4 to +37.7‰) and δ18O (from +5.5 to +25.9‰) values in NO3- ions, while the concentration of NO3- varied from 0.2 to 15.3 mg/dm3. These preliminary results suggest that nitrate fertilizers probably are the main source of NO3- pollution. Our study points out the input of manure and/or sewage to the analyzed reservoir in the subsequent periods of sample collection.


Assuntos
Dióxido de Carbono/análise , Monitoramento Ambiental/métodos , Nitratos/análise , Nitrogênio/análise , Poluentes Químicos da Água/análise , Eutrofização , Fertilizantes/análise , Esterco/análise , Isótopos de Nitrogênio/análise , Isótopos de Oxigênio/análise , Polônia , Reprodutibilidade dos Testes , Esgotos/análise , Águas Residuárias/análise , Água/análise
9.
J Contemp Dent Pract ; 21(2): 119-123, 2020 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-32381813

RESUMO

AIM: The aim of this study is to compare the efficacy of dipotassium oxalate and potassium nitrate to occlude dentinal tubules. MATERIALS AND METHODS: This study utilized Parkinson model of longitudinal dentin tubule occluding properties of dentifrices under a 4-day acid challenge. Dentin disks of approximately 1.5 mm thick were sectioned from the crowns of the freshly extracted molars. The disks were randomized into three sets of 15 and treated with dipotassium oxalate, potassium nitrate, or used as a control. The disks were then subjected to a 4-day acid challenge and evaluated by scanning electron microscopy (SEM). RESULTS: On days 1, 2, and 3, dipotassium oxalate showed significant occlusion of dentinal tubules. On day 4, no significant difference was observed between dipotassium oxalate and potassium nitrate. Both test groups showed better occlusion properties in comparison to the control. CONCLUSION: Through the use of a 4-day acid challenge, this study demonstrates that both agents can indeed occlude dentinal tubules. Initially, dipotassium oxalate does occlude dentinal tubules faster than potassium nitrate. However, at the conclusion of the acid challenge, minimal differences were observed in occlusion rate among the two agents. Further studies should be conducted to determine the efficacy of these two agents. CLINICAL SIGNIFICANCE: Both dipotassium oxalate and potassium nitrate can help treat patients with dentinal hypersensitivity.


Assuntos
Permeabilidade da Dentina , Ácido Oxálico , Dentina , Humanos , Nitratos , Compostos de Potássio
10.
Bioresour Technol ; 309: 123451, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32361619

RESUMO

Micro-aeration is an effective tool that helps integrated autotrophic and heterotrophic denitrification process to withstand high sulfide concentration by making heterotrophic sulfide-oxidizing nitrate-reducing bacteria (h-soNRB) prevail. For further understanding of the dominance of h-soNRB, Pseudomonas C27 was selected as the typical bacterium and its metabolic characteristics responding to sulfide and oxygen stimulation were studied. Under high sulfide concentration condition, addition of trace oxygen led to a two-stage sulfide oxidation process, and sulfide oxidation rate in the first stage was 1.4 times more than that under anaerobic condition. According to transcriptome analysis, the pdo gene significantly up-regulated 2.36 and 2.57 times with and without oxygen under stimulation of high sulfide concentration. Additionally, two possible enhanced sulfide removal pathways coping with high sulfide concentration, namely sqr-cysI-gpx-gor-glpE and cysK-gshA-gshB-pdo-glpE, caused by oxygen were proposed in Pseudomonas C27. These findings provide a theoretical basis for locating high-efficiency sulfur oxidase in h-soNRB.


Assuntos
Oxigênio , Pseudomonas , Bactérias , Reatores Biológicos , Desnitrificação , Nitratos , Oxirredução , Sulfetos
11.
Water Res ; 180: 115916, 2020 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-32438140

RESUMO

Bio-denitrification is widely used for remediation of nitrate contaminated site or removal of nitrate from wastewater, but its efficiency is not always satisfied and high nitrite accumulation and nitrous oxide emission occur frequently. Iron plays an important role in achieving efficient biological denitrification. Nevertheless, its concentration in cells is usually inadequate, and additional supply of iron to denitrification system has been adopted in the literature. In this study, a novel approach to increase the intracellular iron concentration of denitrifying microbes by using graphene to accelerate iron transport, which significantly enhanced bio-denitrification and decreased intermediates accumulations, was reported, and the underlying mechanisms were explored. The presence of 50 mg/L of graphene was observed to not only significantly promote nitrate removal efficiency by 67.3%, but also decrease nitrite and nitrous oxide generation by 49.0% and 63.9%, respectively. It was found that graphene promoted the generation, transfer and consumption of electrons, increased the activities or gene expressions of Fe-containing enzymes (such as complex I, complex III, various cytochromes, and most denitrification reductases), and enhanced the growth of denitrifiers due to iron acquisition by denitrifying bacteria being remarkably facilitated, leading to a significant increment of intracellular iron concentration. Meanwhile, the intracellular proton-motive force and ATP levels were promoted as well. This study provided a new approach to enhancing bio-denitrification and revealed a novel insight into biological iron acquisition.


Assuntos
Desnitrificação , Grafite , Ferro , Nitratos , Nitritos
12.
Sci Total Environ ; 732: 139333, 2020 Aug 25.
Artigo em Inglês | MEDLINE | ID: mdl-32438161

RESUMO

In this work, the influence mechanism of temperature on solid phase denitrification (SPD) was investigated using a pilot-scale reactor supported with polycaprolactone (PCL). The results showed that under nitrate loads of ~31.5 mg N/(L·h), as temperature decreased from 30 °C to 13 °C, the nitrate removal efficiency declined from 94% to 57%. Furthermore, denitrification rate constants were input into Arrhenius equation and the resulting temperature coefficient was 1.04. Significantly nitrite accumulation and less effluent COD residue occurred at low-temperatures. Via stoichiometry, the sludge yield coefficient and COD demand for nitrate removal both increased as a function of increasing temperature; and were calculated at 20 °C as 0.069 g MLVSS/(g COD·d) and 3.265 g COD/g N, respectively. Carbon balance analysis indicated that the COD release rate (υ) at 30 °C was twice that at 13 °C. LEfSe analysis demonstrated that Desulfomicrobium, Desulfovibrio, and Meganema were abundant at low-temperature, while Simplicispira, Aquabacterium, and Acidovorax were enriched at high-temperature. Besides, carboxylesterase (PCL depolymerase) was more abundant at high-temperature, implying an association with a fast υ. Moreover, nar was enriched at low-temperature, while nir was depleted, which led to nitrite accumulation. These results provide reference for SPD design parameter estimation and/or optimal operation strategy.


Assuntos
Desnitrificação , Reatores Biológicos , Carbono , Nitratos , Nitritos , Nitrogênio , Esgotos , Temperatura
13.
Sci Total Environ ; 732: 139247, 2020 Aug 25.
Artigo em Inglês | MEDLINE | ID: mdl-32438183

RESUMO

This study aimed to investigate the effects of nitrate on the ultraviolet (UV) treatment of simulated washing wastes containing Trion X-100 (TX-100) surfactant and 4,4'-dibromodiphenyl ether (BDE-15) pollutant. The presence of nitrate accelerated the photodegradation of BDE-15 and TX-100, because they reacted with reactive oxygen species (ROS) produced from conversion between nitrate and nitrite. Due to nitrite having a stronger radical quenching property than nitrate, nitrite hindered TX-100 decay while the photodegradation rate of BDE-15 was similar to that in the presence of nitrate. This indicated that nitrate/nitrite affected BDE-15 photodegradation by photosensitization and TX-100 loss by ROS attack. An increased TX-100 concentration increased the loss of total inorganic nitrogen possibly owing to an increase in organic nitrogen formation through TX-100 nitration reactions. At pH < 7 HOONO rapidly isomerized to NO3-, and at pH = 7-9 it homolyzed to ONOO-, which increased OH production to decay the BDE-15 and TX-100 and also increased NO2- formation. BDE-15 mainly underwent debromination, and some rearrangement, ring formation, nitration and hydroxylation products were detected, indicating that the produced OH and NO2 attacked the BDE-15 and products. Furthermore, broken-chain, carboxylation, hydroxylation and nitro products were detected by Liquid chromatography high resolution mass spectrometry (LC-HRMS). Escherichia coli was used to assess the toxicity of washing waste containing nitrate: the presence of nitrate will increase the wastes' toxicity during UV treatment. Therefore, the presence of nitrate is deleterious to the UV treatment of washing wastes, and it is important to remove nitrates and nitrites from washing waste before UV irradiation.


Assuntos
Nitratos/análise , Éteres Difenil Halogenados , Cinética , Nitritos , Octoxinol
14.
J Environ Manage ; 268: 110674, 2020 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-32383647

RESUMO

To avoid hydrogen injection and to enhance the settleability of microbial biomass in biological treatment of nitrate-contaminated drinking water resources, a new method based on granulation of a mixture of hydrogen consumer denitrifiers (HCD) and microalgae is introduced. Decreasing hydraulic retention time (HRT) was applied as the selection pressure in an up-flow photobioreactor to increase the speed of granulation and nitrate removal under autotrophic condition during a 50-day operation. Formation of granules occurred at three phases including granule nucleation, growth of granule, and mature granule, with decreasing the values of ζ-potential from -19 mV to -4 mV. Enhancement of microbial attachment within granule formation could reduce the presence of total suspended solids in the effluent. Developed granules of HCD and microalgae could settle down with velocity of 40 ± 0.6 m/h when reaching the average size of 1.2 mm at day 40. Complete NO3--N removal from drinking water was achieved from the initial stage of granulation until the end of operation at all HRTs of 3 days-5 h. The clear treated water was obtained at the growth phase when the chemical oxygen demand and phosphate were undetectable. Therefore, the application of HCD-microalgae granule is a promising way for nitrate removal from water.


Assuntos
Água Potável , Microalgas , Purificação da Água , Processos Autotróficos , Reatores Biológicos , Desnitrificação , Hidrogênio , Nitratos
15.
Water Res ; 179: 115877, 2020 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-32402861

RESUMO

Recent reports on the occurrence and contribution of dissimilatory nitrate reduction to ammonium (DNRA) in marine, inland water, and soil systems have greatly improved our understanding of the global nitrogen (N) cycle. This also promoted the investigation of the role and ecological features of DNRA in anthropogenic ecosystems. However, so far, the use of DNRA in municipal wastewater treatment plants (WWTPs), which are one of the most common and largest biotechnologically artificial water ecosystems, has not been investigated. Accordingly, this study focused on the abundance, activity, community structure, and diversity of DNRA bacteria in full-scale WWTPs. DNRA bacteria were detected in all treatment units in six tested municipal WWTPs, even in aerobic zones (dissolved oxygen > 2 mg L-1). Although the relative abundance of DNRA bacteria (0.2-4.0%) was less than that of denitrifying bacteria (0.7-10.1%) among all investigated samples, the abundance of DNRA bacteria still reaches 109 gene copies g-1. However, 15N-isotope tracing indicated that the potential DNRA rates were significantly lower (0.4-2.1 nmol N g-1 h-1) than those of denitrification (9.5-15.7 nmol N g-1 h-1), but higher than anammox rate (0.3-1.3 nmol N g-1 h-1). The DNRA bacterial community structure was primarily affected by temperature gradient despite the treatment process. High-throughput sequencing analysis targeting the DNRA nrfA gene showed that Nitrospira accounted for the largest proportion of nrfA genes among all samples (6.2-36.3%), followed by Brocadia (5.9-22.1%). Network analysis further indicated that Nitrospira played an important role in both the DNRA bacterial community and entire bacterial community in municipal WWTPs. These results suggest that the ecological habitats of DNRA bacteria in anthropogenic ecosystems were far more abundant than previously assumed. However, the contribution to N transformation by the widespread DNRA was not significant in traditional municipal WWTPs.


Assuntos
Compostos de Amônio , China , Desnitrificação , Ecossistema , Nitratos , Nitrogênio , Oxirredução , Águas Residuárias
16.
Water Res ; 179: 115914, 2020 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-32413614

RESUMO

Iron sulphides, mainly in the form of mackinawite (FeS), pyrrhotite (Fe1-xS, x = 0-0.125) and pyrite (FeS2), are the most abundant sulphide minerals and can be oxidized under anoxic and circumneutral pH conditions by chemoautotrophic denitrifying bacteria to reduce nitrate to N2. Iron sulphides mediated autotrophic denitrification (ISAD) represents an important natural attenuation process of nitrate pollution and plays a pivotal role in linking nitrogen, sulphur and iron cycles in a variety of anoxic environments. Recently, it has emerged as a promising bioprocess for nutrient removal from various organic-deficient water and wastewater, due to its specific advantages including high denitrification capacity, simultaneous nitrogen and phosphorus removal, self-buffering properties, and fewer by-products generation (sulphate, waste sludge, N2O, NH4+, etc.). This paper provides a critical overview of fundamental and engineering aspects of ISAD, including the theoretical knowledge (biochemistry, and microbial diversity), its natural occurrence and engineering applications. Its potential and limitations are elucidated by summarizing the key influencing factors including availability of iron sulphides, low denitrification rates, sulphate emission and leaching heavy metals. This review also put forward two key questions in the mechanism of anoxic iron sulphides oxidation, i.e. dissolution of iron sulphides and direct substrates for denitrifiers. Finally, its prospects for future sustainable wastewater treatment are highlighted. An iron sulphides-based biotechnology towards next-generation wastewater treatment (NEO-GREEN) is proposed, which can potentially harness bioenergy in wastewater, incorporate resources (P and Fe) recovery, achieve simultaneous nutrient and emerging contaminants removal, and minimize waste sludge production.


Assuntos
Desnitrificação , Águas Residuárias , Processos Autotróficos , Reatores Biológicos , Compostos Ferrosos , Ferro , Nitratos , Nitrogênio , Sulfetos , Eliminação de Resíduos Líquidos
17.
Bioresour Technol ; 310: 123404, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32334362

RESUMO

Cobalt(II)-histidine [Co(II)His] is potentially a better alternative to ferrous complexes in the chemical absorption-biological reduction (CABR) flue gas denitrification process in view of its higher oxygenation reversibility. Though with excellent O2-resistant ability, Co(II)His was still gradually oxidized into Co(III)His, losing NO binding capacity. Thus, Co(III)His biological reduction is an indispensable step in CABR process. Co(III)His reduction by Paracoccus versutus LYM under aerobic condition in the presence of nitrate or nitrite was investigated. Results indicated that simultaneous Co(III)His reduction and aerobic denitrification were achieved by strain LYM. Co(III)His reduction was significantly promoted by denitrification process, but dramatically inhibited by 5-15 mM sulfite. Co(II)His absorbent regeneration could be facilitated by adjusting O2 supply properly or adding nitrogen and carbon source regularly. These findings provide a basis for the application of Co(II)His as the absorbent in the CABR process and qualify P. versutus LYM as an applicable and competitive strain for this process.


Assuntos
Desnitrificação , Paracoccus , Cobalto , Histidina , Nitratos , Nitritos , Nitrogênio
18.
Bioresour Technol ; 310: 123244, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32339888

RESUMO

High-nitrate wastewaters are known pose substantial risks to human and environmental health, while their effective treatment remains difficult. The denitrification of saline, high-NO3- wastewaters was investigated at the laboratory- and pilot-scale experiment. Complete denitrification was achieved for three different realistic wastewaters, and the maximum influent [NO3-]0 and salinity were as high as 20,500 mg/L and 7.8%, respectively. The results of microbial community structure analyses revealed that the sequences of denitrifying functional bacteria accounted for 96.2% of all sequences, and the functional genes for denitrification in bacteria were enriched with elevated salinity and [NO3-]0. A significant difference was observed in the dominant bacterial genus between synthetic and realistic wastewaters. Thauera and Halomonas species evolved to be the most common dominant genera contributing to the processes of nitrate, nitrite, and nitrous oxide reductase. This study is practically valuable for the treatment of realistic, saline, high-NO3- wastewaters via denitrification by heterotrophic bacteria.


Assuntos
Microbiota , Esgotos , Reatores Biológicos , Desnitrificação , Nitratos , Nitrogênio , Águas Residuárias
19.
J Environ Manage ; 262: 110307, 2020 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-32250790

RESUMO

Stream and riparian zone networks embedded in agricultural landscapes provide a potential intervention point to ameliorate the negative effects of agricultural runoff by reducing transport of nitrate (NO3-) and suspended sediments (SS) downstream. However, our ability to support and promote NO3- and SS attenuation is limited by our understanding of vegetative and hydrogeomorphic controls in realistic management contexts. In addition, agricultural landscapes are heterogenous on multiple management scales, from farm field to regional water management scales, and the effect of these heterogeneities and how they interact across scales to affect vegetative and hydrogeomorphic controls is poorly explored in many settings. This is especially true in irrigated agricultural settings, where stream and riparian networks are entwined with and sensitive to water management systems. To fill these gaps, we related the vegetative and hydrogeomorphic features of 67 waterway reaches across two water management districts in the California Central Valley to reach-scale NO3- and turbidity attenuation and district-scale water quality patterns. We found that in-stream NO3- attenuation was rare, but, when it did occur, it was promoted by shallow and wide riparian banks, low flows, and high channel-edge denitrification potential. Nitrate concentrations were consistently higher in upstream reaches compared to water district outlets, suggesting that while exports from the district were low, agricultural runoff may impair within-district water resources. Turbidity attenuation was highly variable and unrelated to vegetative or hydrogeomorphic features, suggesting that onfield controls are crucial to managing suspended sediments. We conclude that waterway networks have the potential to mitigate the effects of agricultural NO3- runoff in this setting, but that more effective monitoring and adoption of NO3- attenuating features is needed. Using our findings, we make specific management and monitoring recommendations at both reach and water district scales.


Assuntos
Agricultura , Nitratos , California , Monitoramento Ambiental , Óxidos de Nitrogênio , Abastecimento de Água
20.
Bioresour Technol ; 308: 123302, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32276204

RESUMO

Pyrrhotite-sulfur autotrophic denitrification (PSAD) system, using mixture of pyrrhotite and sulfur particle as electron donor, was studied through batch, column and pilot experiments. Treating synthetic secondary effluent at HRT 3 h, the PSAD system obtained the effluent with NO3--N 0.28 ± 0.14 mg·L-1 and without PO43--P to be detected. Thiobacillus was the most abundant autotrophic denitrification bacteria; autotrophic, heterotrophic and sulfate-reducing bacteria coexisted in the PSAD system; phosphate was mainly removed in forms of graftonite, dufrenite, ardealite. The H+ produced in the SAD could accelerate the PAD through promoting pyrrhotite dissolution, and iron ions produced in the PAD could accelerate the SAD through Fe3+/Fe2+ shuttle. Because of the synergistic effects between the pyrrhotite and sulfur, the PSAD system removed nitrate and phosphate deeply and efficiently. It is a promising way to meet the stringent nitrogen and phosphorus discharge standards and to recover phosphorus resources from wastewater.


Assuntos
Desnitrificação , Microbiota , Processos Autotróficos , Reatores Biológicos , Minerais , Nitratos , Nitrogênio , Fosfatos , Enxofre
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