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1.
Bioresour Technol ; 300: 122670, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31901512

RESUMO

Ammonia (NH3) is the predominant harmful odor emitted from sludge aerobic composting plants, however, this NH3 could be recycled and used as energy or nitrogen fertilizer. Therefore, the aim of this study was to use molecular imprinting technology to prepare an adsorbent that could separate NH3 from mixed gases. An NH3 molecular imprinted polymer (NH3-MIP) was prepared by precipitation polymerization and optimal synthesis was determined by testing several different ratios of reaction components. NH3 adsorption capacity of the optimal NH3-MIP was 1.62 times that of non-imprinted material. NH3 separation factors increased from 154 (dimethyl sulfides) and 217 (dimethyl disulfides) for non-imprinted material, to 213 (dimethyl sulfides) and 302 (dimethyl disulfides) for the NH3-MIP. The adsorption mechanism was identified as physical adsorption and hydrogen bonding between H-O on the -COOH in NH3-MIP and the nitrogen in NH3. Effective desorption at 150 °C with vacuum maintained over 95% of the NH3 adsorption capacity.


Assuntos
Compostagem , Impressão Molecular , Adsorção , Amônia , Esgotos
2.
Bioresour Technol ; 297: 122422, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31767427

RESUMO

In order to illustrate the impact that application of positive or negative potential to conductive materials can have on direct interspecies electron transfer (DIET) and reactor performance under high organic loading rates, three continuous laboratory-scale reactors with carbon-cloth electrodes poised at +0.7 V, -0.7 V (vs. Ag/AgCl) and no-potential were fed high concentrations of ethanol wastewater. While exoelectrogens and methanogens that are capable of DIET were significantly enriched in poised reactors, they performed worse than the non-current control. Volatile fatty acids (VFAs) accumulated more rapidly in the positively then negatively poised reactor, but neither could withstand high-loading rates. These results demonstrate that applying potential to conductive materials had a negative effect on anaerobic digestion under high-loading conditions.


Assuntos
Reatores Biológicos , Metano , Anaerobiose , Transporte de Elétrons , Elétrons
3.
Bioresour Technol ; 297: 122371, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31753601

RESUMO

In this study, nitrous oxide was recovered from a lab-scale moving-bed biofilm reactor (MBBR) treating partial nitrification-treated leachate supplemented with a nosZ-deficient strain of Pseudomonas aeruginosa. Batch culture tests with the nosZ-deficient strain determined that the threshold for free nitrous acid (FNA) inhibition was 0.016 mg/L and that FNA concentrations above this threshold severely inhibited denitrification and transcription of genes from the dissimilatory nitrate reduction pathway (narG, nirS, and norB). High nitrite removal and N2O conversion efficiencies (>95%) were achieved with long-term operation of this MBBR. N2O accounted for the majority of biogas (80%) produced when the MBBR was fed partial nitrification-treated leachate with high nitrite concentrations and the drainage ratio was adjusted to 30%. Bacterial community analysis revealed that the nosZ-deficient Pseudomonas strain remained metabolically active and was primarily responsible for denitrification processes in the reactor. This study presents a promising method for N2O recovery from incineration leachate.


Assuntos
Óxido Nitroso , Pseudomonas aeruginosa , Biofilmes , Reatores Biológicos , Desnitrificação , Incineração
4.
Bioresour Technol ; 298: 122547, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31837579

RESUMO

Anaerobic dynamic membrane bioreactors (AnDMBRs) can improve the efficiency of organic matter removal during wastewater treatment at a low cost. However, application of AnDMBRs for treatment of high-strength wastewater is usually unsuccessful. This study investigated whether use of conductive carbon cloth as the supporting material in an AnDMBR permits higher organic loading rates for treatment of brewery wastewater than non-conductive polyester cloth. The AnDMBR with carbon cloth operated stably with a COD removal efficiency of 98% even when high concentrations of influent COD (10,000 mg/L) were provided, while the polyester cloth reactor deteriorated when reactors were fed only 5000 mg/L influent COD. Microorganisms capable of direct interspecies electron transfer (DIET), including Geobacter and Methanothrix species, dominated the surface of the carbon cloth. These results demonstrate that carbon cloth provides an excellent supporting material for AnDMBRs by stimulating growth of microorganisms that can directly transport electrons to and from conductive materials.


Assuntos
Carbono , Águas Residuárias , Anaerobiose , Reatores Biológicos , Têxteis , Eliminação de Resíduos Líquidos
5.
Bioresour Technol ; 291: 121877, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31376672

RESUMO

Bioelectrochemical conversion of CO2 to CH4 is a promising way to increase the calorific value of biogas produced during anaerobic digestion. There are two groups of methanogens enriched in these systems, hydrogenotrophs and acetoclastic methanogens that can also directly accept electrons from an electrode or another microorganism. In this study, a microbial electrolysis cell (MEC) poised at -500 mV (vs. SHE) was operated for biogas upgrading. Methane content in the biogas increased from 71% to >90%, and 8.2% of the CO2 was converted to methane. Methanothrix, an acetoclastic methanogen that can participate in direct electron transfer (DET), and Azonexus, an acetate-oxidizing electrogen, were enriched on the cathode. Transcriptomics revealed that Methanothrix on the cathode were using the CO2 reduction pathway, while Methanothrix in the bulk sludge were using the acetate decarboxylation pathway for production of methane. These results show that stimulation of DET in MEC enhances biogas-upgrading processes.


Assuntos
Biocombustíveis , Methanosarcinaceae , Eletrodos , Eletrólise , Transporte de Elétrons , Elétrons , Metano/metabolismo , Esgotos
6.
Water Res ; 161: 570-580, 2019 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-31238222

RESUMO

The raw fresh leachate from municipal solid waste (MSW) incineration plants contains high concentrations of volatile fatty acids (VFAs), ammonia and metals, all compounds that severely limit anaerobic digestion treatment efficiencies. These inhibitory compounds make reactor systems unstable, causing reactor start-up periods to take more than 100 days, even when the leachate is diluted significantly. In this study, granular activated carbon (GAC) was incorporated into a bioreactor fed with raw incineration leachate. Addition of GAC allowed direct treatment of raw incineration leachate without any start-up acclimation period, while the non-amended control reactor soured immediately and collapsed within 17 days. When hydraulic retention time (HRT) of the GAC-amended reactor was stepwise decreased to increase organic loading rates (OLR) to 25.0 kgCOD/(m3·d), COD removal efficiencies remained stable at >90%. Metagenomic analysis of the GAC-amended reactor revealed that Geobacter and Methanosarcina, species known to participate in direct interspecies electron transfer (DIET), were more abundant in the GAC-amended reactor than the seed sludge. In addition, the abundance of genes coding for proteins thought to be involved in DIET such as electrically conductive pili and the outer membrane c-type cytochrome, OmcS, increased significantly, while genes involved in fermentation, and nitrate (narG) and sulfate (dsrA) reduction dropped significantly as the experiment progressed. These results are significant because this is the first detailed investigation into the metabolic capabilities of microbial communities involved in efficient treatment of raw incineration leachate within biomethanogenic reactors that did not require a long start-up period.


Assuntos
Carvão Vegetal , Incineração , Anaerobiose , Reatores Biológicos , Elétrons , Metano , Esgotos
7.
Ecotoxicol Environ Saf ; 181: 499-507, 2019 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-31229840

RESUMO

In recent years, increasing eutrophication in large freshwater lakes, which are an important drinking water source for cities in China, have been resulted in substantial cyanobacteria blooms that could cause serious taste and odor (T&O) problems. In this investigation, three typical lakes (Songhua Lake, Chaohu Lake and Taihu Lake) as drinking water sources located in different geographical areas in China, were selected to study the problems of cyanobacteria-derived T&O (i.e., 2-methylisobornoel, geosmin, ß-ionone, 2-isopropyl-3-methoxypyrazine, 2-isobutyl-3-methoxypyrazine, and 2-methylbenzofuran). The occurrence of T&O in target lakes was compared across various nutrition states and geographic locations, to get more information for early warning for algal bloom and T&O occurrence, being useful lake water management and purification. Results show that the occurrence of T&O in Songhua Lake was the poorest for the lowest nutrient state, as a first report in T&O research field in China. This is a lake located in Northeast China at high latitude, with lower water temperatures. The occurrence of T&O in Chaohu Lake was ranked in the middle. That in Taihu Lake was the most intensive. Finally, the relationship between water quality, T&O and its origin was analyzed by multivariate statistical methods (correlation analysis, principal component, and cluster analyses).


Assuntos
Cianobactérias/metabolismo , Lagos/microbiologia , Odorantes/análise , Paladar , China , Monitoramento Ambiental , Eutrofização , Lagos/química , Nutrientes/análise , Nutrientes/normas , Poluentes Químicos da Água/análise , Poluentes Químicos da Água/normas , Qualidade da Água
8.
PeerJ ; 7: e6778, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31086734

RESUMO

Background: Osteoporosis is a common, complex disease of bone with a strong heritable component, characterized by low bone mineral density, microarchitectural deterioration of bone tissue and an increased risk of fracture. Due to limited drug selection for osteoporosis and increasing morbidity, mortality of osteoporotic fractures, osteoporosis has become a major health burden in aging societies. Current researches for identifying specific loci or genes involved in osteoporosis contribute to a greater understanding of the pathogenesis of osteoporosis and the development of better diagnosis, prevention and treatment strategies. However, little is known about how most causal genes work and interact to influence osteoporosis. Therefore, it is greatly significant to collect and analyze the studies involved in osteoporosis-related genes. Unfortunately, the information about all these osteoporosis-related genes is scattered in a large amount of extensive literature. Currently, there is no specialized database for easily accessing relevant information about osteoporosis-related genes and miRNAs. Methods: We extracted data from literature abstracts in PubMed by text-mining and manual curation. Moreover, a local MySQL database containing all the data was developed with PHP on a Windows server. Results: OsteoporosAtlas (http://biokb.ncpsb.org/osteoporosis/), the first specialized database for easily accessing relevant information such as osteoporosis-related genes and miRNAs, was constructed and served for researchers. OsteoporosAtlas enables users to retrieve, browse and download osteoporosis-related genes and miRNAs. Gene ontology and pathway analyses were integrated into OsteoporosAtlas. It currently includes 617 human encoding genes, 131 human non-coding miRNAs, and 128 functional roles. We think that OsteoporosAtlas will be an important bioinformatics resource to facilitate a better understanding of the pathogenesis of osteoporosis and developing better diagnosis, prevention and treatment strategies.

9.
Bioresour Technol ; 285: 121311, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-30954830

RESUMO

An electric potential (EP) was applied to enhance biotreatment of anaerobically-treated leachate from municipal solid waste incineration plants using a partial nitritation-Anammox system. At an optimal EP difference of 0.06 V, total nitrogen removal efficiency reached 71.9%, 17.3% higher than the control system without an EP. Removal of organic matter was also stimulated with the EP, particularly macromolecules with molecular weight >20 kDa in the leachate. Applying EP also promoted production of extracellular polymeric substances and improved the protein/polysaccharide ratio. High-throughput DNA sequencing revealed that Anammox bacteria in the genus Candidatus Kuenenia were enriched for on electrodes with the applied EP. Heterotrophic denitrifiers, which potentially could degrade organic macromolecules, were also more abundant on the electrodes with EP compared with the control reactor. These results show that applying an EP could be a useful strategy in Anammox technologies treating real wastewater high in ammonia and refractory organic compounds.


Assuntos
Reatores Biológicos , Incineração , Amônia , Nitrogênio , Oxirredução , Águas Residuárias
10.
Bioresour Technol ; 282: 447-455, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-30889536

RESUMO

Methods for assessing odors in municipal sewage sludge aerobic composting plants (MSSACPs) have been ineffective. This study identified the emission amount of typical odor-producing compounds, including NH3 and volatile sulfide compounds from a full-scale MSSACP, and evaluated risks of odor emissions based on odor intensity and odor active value. Results revealed all sampling sites (i.e. sludge stacking yard, composting workshop, and screening workshop) produced serious odors, especially in the composting workshop. In the composting workshop, the amounts of DMDS (174.59 µg·dry kg-1) and DMS (71.64 µg·dry kg-1) emitted were far lower than that of NH3 (6062.56 µg·dry kg-1). However, DMDS and DMS showed a similar intensity as NH3 according to odor intensity assessment. Furthermore, both of their odor active values were higher than that of NH3. Using results from both odor intensity and odor active value were more reliable for the assessment of odors from MSSACPs.


Assuntos
Aminas/análise , Compostagem , Odorantes/análise , Esgotos , Sulfetos/análise
11.
Bioresour Technol ; 281: 26-30, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-30784999

RESUMO

The main aim of this work was to stimulate biofilm formation in the presence of wastewater containing aromatic compounds with different toxicities (EC50). The results indicated that wastewater with an EC50 value >85% accelerates the attachment of bacteria onto the bio-carriers because the toxic wastewater stimulates the production of extracellular polymeric substances (EPS) from the seed sludge. In order to understand the role of EPS on biofilm development, experiments were conducted using the seed sludge, from which the soluble, loosely bound, and tightly bound EPS were removed. The soluble EPS fraction was determined to be crucial for biofilm development. Firmicutes bacterium and Clostridium chromoreductans survived and were enriched in the formed biofilms in our study, which can resist toxic aromatics.


Assuntos
Biofilmes , Poluentes Químicos da Água/metabolismo , Anaerobiose , Bactérias/metabolismo , Esgotos/microbiologia , Águas Residuárias
12.
Chemosphere ; 220: 195-203, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30583212

RESUMO

Reverse osmosis is frequently used to process biologically treated leachate from municipal solid waste incineration plants. Reverse osmosis concentrate from incineration leachate (ROCIL) contains extremely high concentrations of monovalent and divalent ions (e.g. Na+, K+, Mg2+, and Ca2+) and some refractory organic pollutants (e.g. humic substances). In this study, lab-scale direct contact membrane distillation (DCMD) coupled with pre-treatment was applied to treat ROCIL. NaOH and polyacrylamide (PAM) chemical precipitation and coagulation pretreatment effectively removed Ca2+ and Mg2+ (>99%) from the ROCIL, which also significantly improved the treatment efficiency of DCMD and slowed down membrane fouling caused by Mg5(CO3)4(OH)2·4H2O and CaCO3 scaling on the membrane surface. During the long-term operation of DCMD, ROCIL was concentrated 21 times and nearly all of the inorganic ions (>99.9%) and organic matter (>99%) were removed from the pre-treated ROCIL. A strong interaction occurred due to the accumulation of humic substances and metal ions in the feed solution, which lead to inorganic and organic scaling deposited on the membrane surface and pores, but the wetting phenomenon was not serious. These results demonstrated that DCMD coupled with NaOH/PAM pre-treatment can be a potential alternative for further treatment and concentration of ROCIL to obtain high quality water.


Assuntos
Resinas Acrílicas/química , Substâncias Húmicas/análise , Membranas Artificiais , Metais/análise , Osmose , Hidróxido de Sódio/química , Purificação da Água/métodos , Precipitação Química , Destilação , Filtração/métodos , Incineração , Metais/isolamento & purificação , Poluentes Químicos da Água/análise , Poluentes Químicos da Água/isolamento & purificação
13.
Bioresour Technol ; 270: 457-466, 2018 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-30245315

RESUMO

This study analyzed emissions characteristics of NH3 and greenhouse gases (i.e. N2O, CH4, and CO2) from a municipal sewage sludge aerobic composting plant. Samples were collected during different seasons in which ambient temperatures and aeration frequencies varied. Results revealed (1) the maximum gas emissions occurred during the mesophilic phase for N2O (22%-56%) and CH4 (65%-95%), and in the thermophilic phase for NH3 (84%-86%) and CO2 (65%-74%); (2) raising ambient temperatures promoted emissions of NH3 and greenhouse gases, while improved aeration frequency increased NH3 but decreased greenhouse gas emissions; (3) CO2 and N2O were found to be the key greenhouse gases emitted during aerobic composting according to assessment of the CO2 equivalent. The results obtained from this study suggest that adjusting ambient temperature to -3 to 5 °C and aeration frequency in composting workshops can be useful approaches for the reduction of NH3 and greenhouse gas emissions from municipal sewage sludge composting plants.


Assuntos
Amônia/análise , Compostagem , Gases de Efeito Estufa/análise , Esgotos , Aerobiose , Dióxido de Carbono/análise , Óxido Nitroso/análise , Temperatura Ambiente
14.
Chemosphere ; 212: 162-169, 2018 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-30144677

RESUMO

Temperature has a known effect on ammonia oxidizing bacteria (AOB) activities, reducing its ammonia oxidizing rate (AOR) when temperature is lowered. However, little is known concerning its effect on N2O and NO emissions which are produced during ammonia oxidation having a greenhouse effect. To study this, an AOB enriched partial nitrification sequencing batch reactor (PN-SBR) was operated within a two step-wise feed under 5 different temperatures (30-25-20-15-10 °C). A decrease on the specific AOR (sAOR) was detected when decreasing the temperature. N2O emissions were also affected by the temperature but only the ones produced during the first aeration of the cycle, when AOBs shifted from a period of low activity to a period of high activity. N2O emission factors (%) detected during the second aerobic phase were similar among all temperatures tested and lower than the emissions detected during the first aerated phase. The average N2O emission factor was in the range of 0.15-0.70% N2O-N/NH4+-N oxidized in the first aeration phase and 0.14-0.15% N2O-N/NH4+-N-oxidized in the second aeration phase at 10 to 30 °C, respectively. On the other hand, NO emissions were very similar under all temperatures resulting in 0.03-0.06% of NH4+-N oxidized.


Assuntos
Reatores Biológicos/microbiologia , Nitrificação , Temperatura Ambiente , Águas Residuárias/química , Amônia/química , Óxido Nitroso/análise , Oxirredução
15.
Sci Rep ; 8(1): 11916, 2018 08 09.
Artigo em Inglês | MEDLINE | ID: mdl-30093706

RESUMO

Nitrous oxide (N2O) is formed during wastewater nitrogen removal processes. It is a strong greenhouse gas, however, if properly captured it can also be used as a renewable energy source. In this study, a nosZ-deficient strain of Pseudomonas aeruginosa was constructed. During growth under denitrifying conditions, the nosZ-deficient strain was more highly transcribing other genes from the denitrification pathway (narG, nirS, and norB) than the wild-type strain. This strain could also convert 85% of NO2--N to N2O when it was grown with acetate compared to <0.6% by the wild-type strain. When a bioreactor treating synthetic wastewater with high NO2--N concentrations (700 mg/L) was inoculated with this strain, the N2O conversion efficiencies were >73% and N2O comprised 73~81% of the biogas being generated. The energy yield from wastewater in bioaugmented reactors also reached levels as high as 1260 kJ/m3. These results are significant and show that bioaugmentation of reactors during denitrification treatment processes with nosZ-deficient strains of Pseudomonas or other core denitrifying bacteria might be an effective way to enhance N2O recovery.


Assuntos
Engenharia Genética/métodos , Óxido Nitroso/metabolismo , Pseudomonas aeruginosa/metabolismo , Energia Renovável , Águas Residuárias/química , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Sequência de Bases , Reatores Biológicos/microbiologia , Desnitrificação/genética , Mutação , Óxido Nitroso/análise , Oxirredutases/deficiência , Oxirredutases/genética , Pseudomonas aeruginosa/genética , Águas Residuárias/microbiologia
16.
Waste Manag ; 77: 593-602, 2018 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-29907364

RESUMO

The emission of volatile sulfur compounds (VSCs) causing strong odors is a major problem in municipal sewage sludge composting plants (MSSACPs). Improving the knowledge on characteristics of VSCs emission in MSAACPs is of particular significance to elimate odors, but the studies conducted on-site to identify them are scarce. To this purpose, characteristics of VSCs emission were studied on-site from a MSSACP during different ambient temperatures corresponding with seasonal variations. Results reveal that (1) the total emission of VSCs which included methyl disulfide (DMDS), methyl sulfide (DMS), carbon disulfide, methyl mercaptan, and hydrogen sulfide (H2S) was 561.89 mg/dry kg in summer, 358.45 mg/dry kg in spring, and 215.52 mg/dry kg in winter, and the greatest amounts of VSCs were emitted during the mesophilic and pre-thermophilic phases; (2) although DMDS and DMS contributed the most towards total VSCs emissions during winter (81.93%), spring (82.55%), and summer (83.90%), their odor contributions were less than that of H2S; (3) in summer, the odor nuisance of total VSCs was higher than that in winter and spring; (4) sulfur loss in the form of VSCs emissions and total sulfur loss both increased with rising ambient temperatures during the sewage sludge aerobic composting. Results obtained in this study will be beneficial towards the elimation of odors released from MSSACPs.


Assuntos
Compostagem , Esgotos , Compostos de Enxofre/análise , Poluentes Atmosféricos , Odorantes
17.
Bioresour Technol ; 262: 15-21, 2018 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-29689436

RESUMO

Wastewater containing toxic hexavalent chromium (Cr(VI)) were treated with well-organized anaerobic granular sludge in this study. Results showed that the anaerobic granular sludge rapidly removed Cr(VI), and 2000 µg·L-1 Cr(VI) was completely eliminated within 6 min, which was much faster than the reported duration of removal by reported artificial materials. Sucrose added as a carbon source acted as an initial electron donor to reduce Cr(VI) to Cr(III). This process was considered as the main mechanism of Cr(VI) removal. Methane production by anaerobic granular sludge was improved by the addition of Cr(VI) at a concentration lower than 500 µg·L-1. Anaerobic granular sludge had a well-organized structure, which presented good resistance against toxic Cr(VI). Trichoccus accelerated the degradation of organic substances to generate acetates with a low Cr(VI) concentration, thereby enhancing methane production by acetotrophic methanogens.


Assuntos
Cromo/metabolismo , Metano , Esgotos , Águas Residuárias , Purificação da Água
18.
Water Res ; 133: 142-152, 2018 04 15.
Artigo em Inglês | MEDLINE | ID: mdl-29407696

RESUMO

A broad number of natural and synthetic progestins are widely used in human and veterinary therapies. Although progestins exhibit adverse effects in aquatic organisms, information about environmental occurrence and fate have been limited to several compounds, hampering the accuracy of risk assessments of the compounds. In this study, a selective and sensitive analytical method was established to simultaneously determine 19 natural and 42 synthetic progestins in environmental waters, and the synthetic progestins included 19-nortestosterone, 17α-hydroxyprogesterone and progesterone derivatives. All of the target compounds were effectively separated using an HSS T3 column, and the recoveries for effluent and river samples were 80-115% and 75-105%, respectively. The detection limits for the 61 analytes were in the range of 0.05-0.60 ng/L and 0.03-0.40 ng/L for the effluent and river samples, respectively. The developed method is applied to analyze the target progestogens in sewage effluent and river water samples from Beijing. The detected concentrations of natural progesterone metabolites (3α-hydroxy-5ß-tetrahydroprogesterone) were up to 63 times higher than those of the parent compound. Of the three groups of synthetic progestins, the progesterone derivatives were detected for the first time and had the highest concentrations followed by the 19-nortestosterone and 17α-hydroxyprogesterone derivatives. In contrast to previous studies, the predominant derivative compounds of 19-nortestosterone were found to be 19-nortestosterone, gestodene and mifepristone, and those of 17α-hydroxyprogesterone were 6-epi-medroxy progesterone 17-acetate and melengestrol acetate. The toxicities and environmental risk of these emerging progestins deserves more attention in the future.


Assuntos
Progestinas/análise , Rios/química , Esgotos/análise , Poluentes Químicos da Água/análise , Pequim , Cromatografia Líquida de Alta Pressão/métodos , Monitoramento Ambiental , Espectrometria de Massas em Tandem/métodos
19.
Bioresour Technol ; 247: 660-668, 2018 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-28988052

RESUMO

In this study, the potential ecological risk of heavy metals (Mn, Zn, Cu, Ni, As, Cd, Pb, Cr) accumulation from anaerobic co-digestion of chicken manure (CM) and corn stover (CS) was evaluated by comparing different initial substrate concentrations, digestion temperatures, and mixture ratios. Results showed that the highest volumetric methane yield of 20.3±1.4L/L reactor was achieved with a CS:CM ratio of 3:1 (on volatile solid basis) in mesophilic solid state anaerobic digestion (SS-AD). Although co-digestion increased the concentrations of all tested heavy metals and the direct toxicity of some heavy metals, the potential ecological risk index indicated that the digestates were all classified as low ecological risk. The biogasification and risk variation of heavy metals were affected by the operating parameters. These results are significant and should be taken into consideration when optimizing co-digestion of animal manure and crop residues during full-scale projects.


Assuntos
Esterco , Metais Pesados , Anaerobiose , Animais , Galinhas , Zea mays
20.
Bioresour Technol ; 244(Pt 1): 800-809, 2017 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-28830043

RESUMO

In order to make a better understanding of the characteristics of N2O emission in A/O wastewater treatment plant, full-scale and pilot-scale experiments were carried out and a back propagation artificial neural network model based on the experimental data was constructed to make a precise prediction of N2O emission. Results showed that, N2O flux from different units followed a descending order: aerated grit tank>oxic zone≫anoxic zone>final clarifier>primary clarifier, but 99.4% of the total emission of N2O (1.60% of N-load) was monitored from the oxic zone due to its big surface area. A proper DO control could reduce N2O emission down to 0.21% of N-load in A/O process, and a two-hidden-layers back propagation model with an optimized structure of 4:3:9:1 could achieve a good simulation of N2O emission, which provided a new method for the prediction of N2O emission during wastewater treatment.


Assuntos
Águas Residuárias , Reatores Biológicos , Óxido Nitroso
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