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1.
J Environ Manage ; 266: 110586, 2020 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-32392139

RESUMO

Expanded granular sludge bed (EGSB) reactors were rarely applied for complete ammonium removal over nitrite. In this study, a high ammonium loading rate of 3677 mg N/L/d was achieved in an EGSB reactor. Approximately 5.5-8.5% of influent ammonium was converted to nitrous oxide (N2O) that is a potent greenhouse gas. Moreover, the percentage increased linearly with the increase in ammonium load. A model well matched the reactor dynamics. The model indicated that hydroxylamine (NH2OH) oxidation contributed to over 40% of produced N2O, and denitrification by ammonium oxidizing bacteria contributed to N2O emission significantly. Furthermore, the model suggests that a low oxygen concentration can result in a low N2O emission at the cost of a slightly low ammonium removal rate while influent organic matter play a minor role in reducing N2O emission. This study shows that EGSB reactors are effective in ammonium removal. In addition, the emission of N2O is significant.


Assuntos
Desnitrificação , Nitritos , Processos Autotróficos , Reatores Biológicos , Nitrogênio , Óxido Nitroso , Esgotos
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.
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
5.
Bioresour Technol ; 307: 123229, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32247270

RESUMO

The inclusion of S0 hydrolysis in a kinetic model of autotrophic denitrification has been recently proposed; however the model has not been calibrated or validated yet. Thus, a new methodology was developed and applied to calibrate and validate this kinetic model for the first time. An inoculum adapted from a poultry wastewater treatment plant at stoichiometric S0/NO3- ratio was used. The model was calibrated with batch data (initial nitrate concentrations of 50 and 6.25 mg NO3--N/L) at an S0/N ratio = 2.29 mg S/mg N and validated with seven different batch data. The sensitivity analysis showed that the most sensitive parameters are related to S0 hydrolysis. The kinetic model was successfully calibrated with the new methodology and validated, with Theil inequality coefficient values lower than 0.21. Thus, the proposed model and methodology were proved to be well suited for the simulation of elemental sulfur-based autotrophic denitrification in batch systems.


Assuntos
Reatores Biológicos , Desnitrificação , Processos Autotróficos , Calibragem , Nitratos , Enxofre
6.
Environ Sci Technol ; 54(6): 3609-3617, 2020 03 17.
Artigo em Inglês | MEDLINE | ID: mdl-32125831

RESUMO

For the production of edible microbial protein (MP), ammonia generated by the Haber-Bosch process or reclaimed ammonia from waste streams is typically considered as the nitrogen source. These processes for ammonia production are highly energy intensive. In this study, the potential for using nitrogen gas (N2) as a direct nitrogen source for MP production by hydrogen-oxidizing bacteria (HOB) was evaluated. The use of N2 versus ammonium as nitrogen source during the enrichment process resulted in differentiation of the bacterial community composition of the enrichments. A few previously unknown potential N2-fixing HOB taxa (i.e., representatives of the genus Azonexus and the family Comamonadaceae) dominated the enrichments. The biomass yield of a N2-fixing HOB enrichment was 30-50% lower than that of the ammonium-based HOB enrichment from the same inoculum source. The dried biomass of N2-fixing HOB had a high protein content (62.0 ± 6.3%) and an essential amino acid profile comparable to MP from ammonium-based HOB. MP from N2-fixing HOB could potentially be produced in situ without entailing the emissions caused by ammonia production and transportation by conventional means. It could be a promising substitute for N2-fixing protein-rich soybean because it has 70% higher protein content and double energy conversion efficiency from solar energy to biomass.


Assuntos
Processos Autotróficos , Hidrogênio , Bactérias , Nitrogênio , Fixação de Nitrogênio , Oxirredução
7.
Syst Appl Microbiol ; 43(2): 126064, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-32044151

RESUMO

The ability to grow by anaerobic CO oxidation with production of H2 from water is known for some thermophilic bacteria, most of which belong to Firmicutes, as well as for a few hyperthermophilic Euryarchaeota isolated from deep-sea hydrothermal habitats. A hyperthermophilic, neutrophilic, anaerobic filamentous archaeon strain 1505=VKM B-3180=KCTC 15798 was isolated from a terrestrial hot spring in Kamchatka (Russia) in the presence of 30% CO in the gas phase. Strain 1505 could grow lithotrophically using carbon monoxide as the energy source with the production of hydrogen according to the equation CO+H2O→CO2+H2; mixotrophically on CO plus glucose; and organotrophically on peptone, yeast extract, glucose, sucrose, or Avicel. The genome of strain 1505 was sequenced and assembled into a single chromosome. Based on 16S rRNA gene sequence analysis and in silico genome-genome hybridization, this organism was shown to be closely related to the Thermofilum adornatum species. In the genome of Thermofilum sp. strain 1505, a gene cluster (TCARB_0867-TCARB_0879) was found that included genes of anaerobic (Ni,Fe-containing) carbon monoxide dehydrogenase and genes of energy-converting hydrogenase ([Ni,Fe]-CODH-ECH gene cluster). Compared to the [Ni,Fe]-CODH-ECH gene clusters occurring in the sequenced genomes of other H2-producing carboxydotrophs, the [Ni,Fe]-CODH-ECH gene cluster of Thermofilum sp. strain 1505 presented a novel type of gene organization. The results of the study provided the first evidence of anaerobic CO oxidation coupled with H2 production performed by a crenarchaeon, as well as the first documented case of lithotrophic growth of a Thermofilaceae representative.


Assuntos
Monóxido de Carbono/metabolismo , Hidrogênio/metabolismo , Thermofilaceae/crescimento & desenvolvimento , Thermofilaceae/metabolismo , Aldeído Oxirredutases/genética , Anaerobiose , Processos Autotróficos , Proteínas de Bactérias/genética , DNA Bacteriano/genética , Genoma Bacteriano/genética , Fontes Termais/química , Fontes Termais/microbiologia , Hidrogenase/genética , Complexos Multienzimáticos/genética , Família Multigênica , Oxirredução , Filogenia , RNA Ribossômico 16S/genética , Federação Russa , Análise de Sequência de DNA , Thermofilaceae/classificação , Thermofilaceae/genética
8.
Sci Total Environ ; 717: 136981, 2020 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-32092802

RESUMO

Total nitrogen (TN) removal is the major technical challenge for wastewater treatment plants to meet the more stringent discharge standard. In this study, lab- (0.05 m3/d), pilot- (1000 m3/d) and full-scale (10,000 m3/d) combined heterotrophic and autotrophic denitrification reactors (HARs) were designed and operated to treat municipal secondary effluent. During the 110-day stable operation, the effluent TN was reduced below 2.5 mg/L without secondary pollution causing by the excessive addition of organics, close to Class IV of Environmental Quality Standards for Surface Water. The bacterial richness and diversity increased with the expansion of reactor scale. Denitrifying bacteria (DB) dominated in all reactors, however, Thiomonas (12.42%), Methylotenera (6.35%), Thiobacillus (20.62%), Methyloverstatilis (5.44%) and Thauera (8.21%) were the main genera in lab-, pilot- and full-scale reactors respectively. The denitrification efficiency temporarily deteriorated at the later stage, and redundancy analysis (RDA) indicated the obviously increased sulfate reducing bacteria (SRB) and sulfide were main contributors. Sludge supplement rapidly recovered the reactors performance in five days. This study suggests that HARs could be a promising technique for advanced denitrification of the municipal secondary effluent.


Assuntos
Processos Autotróficos , Desnitrificação , Processos Heterotróficos , Bactérias , Reatores Biológicos , Nitratos , Nitrogênio , Águas Residuárias
9.
PLoS One ; 15(2): e0225677, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32084664

RESUMO

Heterotrophic growth mode is among the most promising strategies put forth to overcome the low biomass and secondary metabolites productivity challenge. To shedding light on the underlying molecular mechanisms, transcriptome meta-analysis was integrated with weighted gene co-expression network analysis (WGCNA), connectivity analysis, functional enrichment, and hubs identification. Meta-analysis and Functional enrichment analysis demonstrated that most of the biological processes are up-regulated at heterotrophic growth condition, which leads to change of genetic architectures and phenotypic outcomes. WGNCA analysis of meta-genes also resulted four significant functional modules across logarithmic (LG), transition (TR), and production peak (PR) phases. The expression pattern and connectivity characteristics of the brown module as a non-preserved module vary across LG, TR, and PR phases. Functional analysis identified Carotenoid biosynthesis, Fatty acid metabolism and Methane metabolism as enriched pathways in the non-preserved module. Our integrated approach was applied here, identified some hubs, such as a serine hydroxymethyltransferase (SHMT1), which is the best candidate for development of metabolites accumulating strains in microalgae. Current study provided a new insight into underlying metabolite accumulation mechanisms and opens new avenue for the future applied studies in the microalgae field.


Assuntos
Processos Autotróficos/genética , Processos Heterotróficos/genética , Microalgas/metabolismo , Metabolismo Secundário/fisiologia , Biologia de Sistemas/métodos , Ciclo do Carbono/fisiologia , Carotenoides/metabolismo , Ácidos Graxos/metabolismo , Perfilação da Expressão Gênica , Redes Reguladoras de Genes , Glicina Hidroximetiltransferase/metabolismo , Metano/metabolismo , Microalgas/crescimento & desenvolvimento , Transcriptoma
10.
PLoS One ; 15(2): e0228448, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32017799

RESUMO

Upwelling is an important source of inorganic nutrients in marine systems, yet little is known about how gradients in upwelling affect primary producers on coral reefs. The Southern Line Islands span a natural gradient of inorganic nutrient concentrations across the equatorial upwelling region in the central Pacific. We used this gradient to test the hypothesis that benthic autotroph ecophysiology is enhanced on nutrient-enriched reefs. We measured metabolism and photophysiology of common benthic taxa, including the algae Porolithon, Avrainvillea, and Halimeda, and the corals Pocillopora and Montipora. We found that temperature (27.2-28.7°C) was inversely related to dissolved inorganic nitrogen (0.46-4.63 µM) and surface chlorophyll a concentrations (0.108-0.147 mg m-3), which increased near the equator. Contrary to our prediction, ecophysiology did not consistently track these patterns in all taxa. Though metabolic rates were generally variable, Porolithon and Avrainvillea photosynthesis was highest at the most productive and equatorial island (northernmost). Porolithon photosynthetic rates also generally increased with proximity to the equator. Photophysiology (maximum quantum yield) increased near the equator and was highest at northern islands in all taxa. Photosynthetic pigments also were variable, but chlorophyll a and carotenoids in Avrainvillea and Montipora were highest at the northern islands. Phycobilin pigments of Porolithon responded most consistently across the upwelling gradient, with higher phycoerythrin concentrations closer to the equator. Our findings demonstrate that the effects of in situ nutrient enrichment on benthic autotrophs may be more complex than laboratory experiments indicate. While upwelling is an important feature in some reef ecosystems, ancillary factors may regulate the associated consequences of nutrient enrichment on benthic reef organisms.


Assuntos
Antozoários/crescimento & desenvolvimento , Clorófitas/crescimento & desenvolvimento , Nitrogênio/metabolismo , Rodófitas/crescimento & desenvolvimento , Animais , Antozoários/metabolismo , Processos Autotróficos , Clorófitas/metabolismo , Recifes de Corais , Ecossistema , Ilhas do Pacífico , Fotossíntese , Rodófitas/metabolismo , Temperatura
11.
Chemosphere ; 247: 125831, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-31935576

RESUMO

Moving-bed biofilm reactor (MBBR) is a well-established technology for simultaneous nitrification and denitrification (SND). In MBBR, biofilm development and pollutant removal performance are strictly governed by the physico-chemical properties of the carriers. In this study, novel surface-modified carriers with enhanced hydrophilicity (surface contact angle of 60.2 ± 2.3°) and positively-charged surfaces (+11.7 ± 1.1 mV, pH 7.0) had been prepared successfully via polymer blending, and they had also been implemented in SND system for the treatment of real domestic wastewater. Results showed that accelerated startup of SND with more biomass on the carriers was observed in MBBR system filled with surface-modified carriers. At low DO level (0.6-0.8 mg L-1) and low C/N ratio (≤5), highly efficient organics removal and SND performance could be achieved with COD removal, TN removal and SND efficiencies of 79.3-85.7%, 62.0-75.9% and 58.5-71.8%, respectively. The efficient performance of SND in MBBR system filled with surface-modified carriers was mainly attributed to the coexistence of enriched mixtrophic nitrifiers and denitrifiers like autotrophic nitrifers (Nitrosomonas, Nitrospira, Nitrobacter), heterotrophic nitrifers (Rudaea), aerobicdenitrifiers (Dokdonella, Terrimonas), anoxic denitrifiers (Gemmobacter, Ottowia, Methyloversatilis, Thermomonas) and N2O producer (Mesorhizobium).


Assuntos
Desnitrificação , Nitrificação , Eliminação de Resíduos Líquidos/métodos , Águas Residuárias/química , Purificação da Água/métodos , Processos Autotróficos , Bactérias/metabolismo , Biofilmes , Biomassa , Reatores Biológicos/microbiologia , Processos Heterotróficos , Nitrogênio/análise , Nitrogênio/metabolismo
12.
Int J Syst Evol Microbiol ; 70(3): 1837-1842, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31958046

RESUMO

Two novel, strictly aerobic, sulfur-dependent, thermoacidophilic strains, IC-006T and IC-007, were isolated from a solfataric field at Hakone Ohwaku-dani, Kanagawa, Japan. Cells of the two strains were irregular cocci with a diameter of 1.0-1.8 µm. They were strict aerobes and grew in a temperature range between 45 and 69 °C (optimally at 65 °C) and a pH range between 0.4 and 5.5 (optimally at pH 3.5). They required sulfur or a reduced sulfur compound, and sulfur was oxidized to sulfate. They grew autotrophically or mixotrophically utilizing several sugars and complex organic substances as carbon sources. The DNA G+C content was 42.4 mol%. A comparison of the 16S rRNA gene sequences among members of the order Sulfolobales indicated that they were closely related to Sulfolobus metallicus, forming an independent lineage within this order. The two isolates and Sulfolobus metallicus were also diffentiated based on their phenotypic properties from the other members of the order Sulfolobales. Detailed comparisons of the phenotypic properties and DNA-DNA hybridization study illustrated that the two isolates belong to a species different from Sulfolobus metallicus. On the basis of the phylogenetic and phenotypic comparisons, we propose a new genus and species, Sulfuracidifex tepidarius gen. nov., sp. nov. to accommodate strains IC-006T and IC-007. The type strain of Sulfuracidifex tepidarius is IC-006T (=JCM 16833T=DSM 104736T). In addition, Sulfolobus metallicus should be transferred to the new genus as Sulfuracidifex metallicus comb. nov.: the type strain is Kra23T (=DSM 6482T=JCM 9184T=NBRC 15436T).


Assuntos
Filogenia , Microbiologia do Solo , Sulfolobaceae/classificação , Sulfolobus/classificação , Processos Autotróficos , Técnicas de Tipagem Bacteriana , Composição de Bases , DNA Bacteriano/genética , Japão , Hibridização de Ácido Nucleico , RNA Ribossômico 16S/genética , Análise de Sequência de DNA , Sulfolobaceae/isolamento & purificação
13.
Bioresour Technol ; 299: 122686, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31902635

RESUMO

Denitrification with non-organic electron donors for treating low C/N ratio wastewater has attracted growing interests. Hydrogen, reduced sulfur compounds and ferrous ions are mainly used in autotrophic denitrification, holding promise for achieving practical applications. Recently, the development of autotrophic denitrification-based processes, such as bioelectrochemically-supported hydrogenotrophic denitrification and sulfur-/iron-based denitrification assisted multi-contaminant removal, provide opportunities for applying these processes in wastewater treatment. Exploration of the autotrophic denitrification process in terms of contaminant removal mechanism, interaction among functional microorganisms, and potential full-scale applications is thus of great importance. Here, an overview of the commonly used non-organic electron donors, e.g., hydrogen, reduced sulfur compounds and ferrous ions, in denitrification for treating low C/N ratio wastewater is provided. Also, the feasibility of applying the combined processes based on autotrophic denitrification with the compounds is discussed. Furthermore, challenges and future possibilities as well as concerns about the practical applications are envisaged in this review.


Assuntos
Desnitrificação , Águas Residuárias , Processos Autotróficos , Reatores Biológicos , Elétrons , Nitratos , Nitrogênio
14.
Bioresour Technol ; 300: 122682, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31901555

RESUMO

This work aimed to study a pilot-scale sulfur-limestone autotrophic denitrification biofilter (SLADB) to remove nitrogen from municipal tailwater. The capacity of nitrogen removal and spatial distribution of microbial community at low temperature condition were analyzed. Low temperature inhibits nitrogen removal; while prolonging hydraulic retention time (HRT) increased nitrogen removal efficiency. TN and NO3--N removal efficiency reached 81.1% and 85.3%, respectively, with HRT of 18 h at the temperature ranging from 6.4 to 9.8 °C. Proteobacteria and Chloroflexi were two dominant phyla. Along the reactor, class ß-proteobacteria and ε-proteobacteria decreased, while γ-proteobacteria and Acidobacteria increased. For genus classification, Thiobacillus, Sulfurimonas, and Ferritrophicum which promote sulfur autotrophic denitrification, decreased significantly. While Anaerolineae promoting heterotrophic denitrification increased obviously. Sphingobacteriia coexisted in SLADB and were beneficial to nitrogen removal. Microbial community spatial distribution patterns were related to nitrogen removal. This study achieved reliable pilot-scale application of SLADB under low temperature for municipal tailwater.


Assuntos
Desnitrificação , Microbiota , Processos Autotróficos , Reatores Biológicos , Carbonato de Cálcio , Nitratos , Nitrogênio , Enxofre
15.
Bioresour Technol ; 301: 122731, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31927457

RESUMO

Nitrate removal from low carbon-to-nitrogen ratio (C/N) wastewater has always been a knotty problem due to the deficiency of organics. Here, a novel iron-based chemical reduction and autotrophic denitrification (ICAD) system was developed. ICAD system could maintain average nitrate removal efficiency of 97.2% for 131 days with feeding 20.3 mg NO3--N/L at hydraulic retention time (HRT) of 24 h. The optimal operational conditions was further explored, and results demonstrated that average nitrate removal efficiency of 85.5% and 98.4% could be achieved at HRT of 12 h and 24 h (influent 20.3 mg NO3--N/L), while average nitrate removal efficiency could reach 96.3% at optimal HRT of 12 h (influent 10.3 mg NO3--N/L). Hydrogenophaga, which can carry out hydrogenotrophic denitrification, showed a positive correlation with nitrate removal efficiency of the ICAD system. Low cost and simple operation make the ICAD system suitable for large-scale application.


Assuntos
Desnitrificação , Águas Residuárias , Processos Autotróficos , Reatores Biológicos , Carbono , Ferro , Nitratos , Nitrogênio , Eliminação de Resíduos Líquidos
16.
J Environ Manage ; 261: 110157, 2020 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-31999611

RESUMO

H2S-based denitrification could achieve synchronous removal of nitrate and H2S and had been regarded as an efficient way for biogas desulfurization and wastewater denitrification. Using CO2 in biogas as carbon source had a potential of saving cost further, but the performance deteriorated due to the drop in pH. Two kinds of nature ore, medical stone and phosphate ore, were added as new pH adjustment materials in this study, and feasibility of using CO2 as sole carbon source for H2S-based denitrification was investigated. As a result, both materials could increase the pH from 4.5 to above 6.0. Compared with medical stone, higher level of pH (up to 6.39) and nitrate removal efficiency (99.1%) were obtained with phosphate ore. In addition, ATP increased more rapidly than the control, reflecting improvement on microbial activities. Therefore, phosphate ore as the pH adjustment material could improve H2S-based denitrification performance obviously.


Assuntos
Dióxido de Carbono , Desnitrificação , Processos Autotróficos , Reatores Biológicos , Carbono , Concentração de Íons de Hidrogênio , Nitratos
17.
Mycorrhiza ; 30(1): 51-61, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31965295

RESUMO

Some mixotrophic plants from temperate forests use the mycorrhizal fungi colonizing their roots as a carbon source to supplement their photosynthesis. These fungi are also mycorrhizal on surrounding trees, from which they transfer carbon to mixotrophic plants. These plants are thus reputed difficult to transplant, even when their protection requires it. Here, we take profit of a successful ex situ pot cultivation over 1 to 3 years of the mixotrophic orchid Epipacis helleborine to investigate its mycorrhizal and nutrition status. Firstly, compared with surrounding autotrophic plants, it did not display the higher N content and higher isotopic (13C and 15N) abundance that normally feature mixotrophic orchids because they incorporate N-, 13C-, and 15N-rich fungal biomass. Second, fungal barcoding by next-generation sequencing revealed that the proportion of ectomycorrhizal fungi (expressed as percentage of the total number of either reads or operational taxonomic units) was unusually low compared with E. helleborine growing in situ: instead, we found a high percentage of rhizoctonias, the usual mycorrhizal partners of autotrophic orchids. Altogether, this supports autotrophic survival. Added to the recently published evidence that plastid genomes of mixotrophic orchids have intact photosynthetic genes, this suggests that at least some of them have abilities for autotrophy. This adds to the ecological plasticity of mixotrophic plants, and may allow some reversion to autotrophy in their evolution.


Assuntos
Micorrizas , Orchidaceae , Processos Autotróficos , Fotossíntese , Raízes de Plantas , Simbiose
18.
Water Res ; 170: 115300, 2020 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-31756614

RESUMO

Autotrophic iron-dependent denitrification (AIDD) is arising as a promising process for nitrogen removal from wastewater with a low carbon to nitrogen ratio. However, there is still a debate about the existence of such a process in activated sludge systems. This work provides evidence and elucidated the feasibility of autotrophic Fe(II)-oxidizing nitrate-reducing culture for nitrogen removal by long-term reactor operation, batch experimental verification, unstructured kinetic modeling and microbial community analyses. A relatively stable nitrate removal rate was achieved coupled with the oxidation of ferrous ions in 3-month operation of reactor. The kinetic modeling suggests that the iron oxidation was a growth-associated process in AIDD. Utilization of extracellular polymeric substances (and/or soluble microbial products) as electron donor for denitrification by heterotrophic denitrifiers was not mainly responsible for nitrogen removal in the reactor. After long-term operation of the reactor with activated sludge as inoculum, the enrichment culture KS-like consortium, dominated by Fe(II) oxidizer, Gallionellaceae, was successfully acclimated for autotrophic Fe(II)-oxidizing nitrate reduction. This work extents our understanding about the existence of such an autotrophic Fe(II)-oxidizing nitrate-reducing culture in both natural and engineered systems, and opens a door for its potential application in wastewater treatment.


Assuntos
Desnitrificação , Esgotos , Processos Autotróficos , Reatores Biológicos , Ferro , Nitratos , Nitrogênio
19.
Aquat Toxicol ; 218: 105360, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31765943

RESUMO

Labile dissolved organic carbon (DOC) is a major pollutant in coastal marine environments affected by anthropogenic impacts, and may significantly contribute to coral bleaching and subsequent mortality on coastal reefs. DOC can cause bleaching indirectly through the rapid proliferation of copiotrophic and pathogenic bacteria. Here we demonstrate that labile DOC compounds can also impair the coral-dinoflagellate symbiosis by directly affecting coral physiology on both the host and algal symbiont level. In a controlled aquarium experiment, we monitored over several weeks key physiological parameters of the tropical coral Stylophora pistillata exposed to ambient and elevated labile DOC levels (0.1 and 1.0 mM) in combination with low and high nitrogen (i.e. ammonium) conditions (0.2 and 4.0 µM). At the symbiont level, DOC exposure under low ammonium availability decreased the photosynthetic efficiency accompanied by ∼75 % Chl a and ∼50 % symbiont cell reduction. The photosynthetic functioning of the symbionts recovered once the DOC enrichment ceased indicating a reversible shift between autotrophic and heterotrophic metabolism. At the host level, the assimilation of exogenous DOC sustained the tissue carbon reserves, but induced a depletion of the nitrogen reserves, indicated by ∼35 % decreased protein levels. This suggests an imbalanced exogenous carbon to nitrogen supply with nitrogen potentially limiting host metabolism on the long-term. We also demonstrate that increased ammonium availability delayed DOC-induced bleaching likely by keeping symbionts in a photosynthetically competent state, which is crucial for symbiosis maintenance and coral survival. Overall, the present study provides further insights into how coastal pollution can de-stabilize the coral-algal symbiosis and cause coral bleaching. Therefore, reducing coastal pollution and sustaining ecological integrity are critical to strengthen the resilience of coral reefs facing climate change.


Assuntos
Compostos de Amônio/farmacologia , Antozoários/efeitos dos fármacos , Dinoflagelados/efeitos dos fármacos , Compostos Orgânicos/toxicidade , Simbiose/efeitos dos fármacos , Poluentes Químicos da Água/toxicidade , Animais , Antozoários/metabolismo , Processos Autotróficos , Mudança Climática , Recifes de Corais , Dinoflagelados/metabolismo , Processos Heterotróficos , Oceano Índico , Fotossíntese/efeitos dos fármacos
20.
Water Res ; 169: 115084, 2020 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-31669906

RESUMO

Elemental sulfur-driven autotrophic denitrification (SADN) is a cost-effective approach for treating secondary effluent from wastewater treatment plants (WWTPs). Additional organics are generally supplemented to promote total nitrogen (TN) removal, reduce nitrite accumulation and sulfate production, and balance the pH decrease induced by SADN. However, understanding of the impacts of organic supplementation on microbial communities, nitrogen metabolism, denitrifier activity, and SADN rates in sulfur-based denitrification reactors is still limited. Here, a sulfur-based denitrification reactor was continuously operated for 272 days during which six different C/N ratios were tested successively (2.7, 1.5, 0.7, 0.5, 0.25, and 0). Organic supplementation improved TN removal and decreased NO2- accumulation, but reduced the relative abundance of denitrifiers and the contribution of autotrophic nitrate-reducing bacteria (aNRB) to TN removal during the long-term operation of reactor. Predictive functional profiling showed that nitrogen metabolism potential increased with decreasing C/N ratios. SADN was the predominant removal process when the C/N ratio was ≤0.7 (achieving 60% contribution when C/N = 0.7). Although organic supplementation weakened the dominant role of aNRB in denitrification, batch tests for the first time demonstrated that it could accelerate the SADN rate, attributed to the improvement of sulfur bioavailability, likely via the formation of polysulfide. A possible nitrogen removal pathway with multiple electron donors (i.e., sulfur, organics, sulfide, and polysulfide) in a sulfur-based denitrification reactor with organic supplementation was therefore proposed. However, supplementation with a high level of organics could increase the operational cost and effluent concentrations of sulfide and organics as well as enrich heterotrophic denitrifiers. Moreover, microbial community had substantial changes at C/N ratios of >0.5. Accordingly, an optimal C/N ratio of 0.25-0.5 was suggested, which could simultaneously minimize the additional operating cost associated with organic supplementation and maximize TN removal and SADN rates.


Assuntos
Reatores Biológicos , Desnitrificação , Processos Autotróficos , Suplementos Nutricionais , Nitratos , Nitrogênio , Enxofre
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