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1.
Chemosphere ; 247: 125874, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-31945722

RESUMO

Over 90% of microplastics that enter wastewater treatment plants end in the wasted activated sludge. The effect of microplastic abundance on the activated sludge anaerobic digestion has been rarely reported. This study investigated the methane production performance during anaerobic digestion with different abundance of microplastic doses (0, 1,000, 3,000, 6,000, 10,000, 30,000, 60,000, 100,000 and 200,000 polyester particle/kg activated sludge). The methane production was reduced to 88.53 ± 0.5%, 90.09 ± 1.2%, 89.95 ± 4.7%, 95.08 ± 0.5%, 90.29 ± 0.5%, 93.16 ± 0.8%, 92.92 ± 1.3%, and 92.72 ± 0.6% as compared with control after digestion for 59 days. The methane production of all conditions was fitted with the logarithm model (R2 > 0.95) and one-substrate model (R2 > 0.99). The predicted and actual methane production values of digestion for 59 days had high correlation in all conditions with R2 > 0.95. The analysis based on the biochemical methane potential test model indicated that the methane production potential (B0) and hydrolysis coefficient (k) decreased at nearly all tested conditions. The reactor digestate with microplastics retained higher organic matter and nutrient concentration and had slightly lower dewaterability than the control. The inhibition of methane production potential could be attributed to the incomplete digestion with the existence of microplastics. The microbial community showed no significant difference with and without microplastics.


Assuntos
Anaerobiose/efeitos dos fármacos , Microplásticos/toxicidade , Eliminação de Resíduos Líquidos , Poluentes Químicos da Água/toxicidade , Reatores Biológicos , Hidrólise , Metano/biossíntese , Plásticos , Esgotos , Águas Residuárias
2.
Chemosphere ; 238: 124654, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31524611

RESUMO

Nitrate is a byproduct of the anaerobic ammonium oxidation (anammox) process and is related to its electron transfer. However, little is known about the influence of nitrate on the anammox process. In this work, the biphasic effect of exogenous nitrate on the anammox process was investigated in an upflow biofilter (UBF) reactor with ammonium as the sole electron donor. The responses of anammox to increased nitrate were analyzed by one-way ANOVA test and found to be significantly different under a constant and decreased nitrite condition (p < 0.01). With a single increase in nitrate and constant ammonium and nitrite in the influent, the total nitrogen removal rate (TNRR) of anammox was uninhibited, but stoichiometry deviated and nitrate production always showed a linear decrease. In contrast, anammox exhibited a range of activity with constant ammonium and simultaneously increased nitrate and decreased nitrite in the influent, including a continuous reduction of TNRR, a nonpersistent ammonium overconsumption and a pronounced nonlinear response of nitrate production. Correlation analysis shows that the lack of ammonium overconsumption was accompanied by the disappearance of nitrate underproduction. Kinetic models of product formation were effectively used to explore the nitrate production behavior of anammox subjected to increased nitrate, and the metabolite of nitrate was divided into a growth negative coupling type and growth (partial) coupling type under a constant and decreased nitrite condition, respectively. These findings collectively suggest that nitrate has a biphasic effect on the anammox process and is correlated with the availability of nitrite.


Assuntos
Compostos de Amônio/química , Anaerobiose/efeitos dos fármacos , Nitratos/farmacologia , Reatores Biológicos , Desnitrificação , Cinética , Nitratos/química , Nitritos/química , Nitrogênio/química , Oxirredução
3.
Food Chem ; 303: 125346, 2020 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-31446364

RESUMO

The effect of a respiratory quotient dynamic controlled atmosphere (DCA - RQ), which induces ethanol production through low oxygen storage, and ethanol application on softening of Braeburn apples stored at different temperatures was investigated. DCA - RQ storage was associated with the activation of the alcohol dehydrogenase (ADH) and greater anaerobic metabolism in comparison with DCA - CF (chlorophyll fluorescence) and controlled atmosphere (CA) storage. Greater anaerobic metabolism resulted in lower ethylene production, ACC oxidase activity, membrane permeability, -galactosidase activity and, therefore, less softening after long-term storage. Ethanol application after CA storage decreased ethylene biosynthesis, respiration rate and membrane permeability. Storage at 3 °C resulted in the lowest soluble solids and acidity, but not softening. In conclusion, Braeburn apples could be stored at 3 °C under DCA - RQ1.5. Additionally, ethanol produced by the fruit, or applied externally, had a significant effect on inhibiting softening during and after storage.


Assuntos
Atmosfera , Etanol/farmacologia , Malus/efeitos dos fármacos , Malus/metabolismo , Oxigênio/metabolismo , Anaerobiose/efeitos dos fármacos , Frutas/efeitos dos fármacos , Frutas/metabolismo
4.
Ecotoxicol Environ Saf ; 186: 109753, 2019 Dec 30.
Artigo em Inglês | MEDLINE | ID: mdl-31604159

RESUMO

Nitrite is a common toxic substance in culture systems of Litopenaeus vannamei, and the stress may disturb hemocyanin synthesis and energy metabolism and result in shrimp death. In the present study, nitrite at concentrations of 0 (control), 3.3 (46.2 NO2-N mg/L), 6.6 (92.4) and 9.9 mM (138.6) was used to evaluate the responses of hemocyanin level and energy metabolism in L. vannamei (5.80 ±â€¯0.44 cm, 1.88 ±â€¯0.38 g) for 96 h. The mortality rate at 96 h increased with nitrite concentration (50% at 9.9 mM, 40% at 6.6 mM, 30% at 3.3 mM, and 10% at 0 mM). In general, HIF-1α and hemocyanin mRNA expression in the nitrite stress groups was upregulated from 6 to 12 h and downregulated from 24 to 96 h. In the hemolymph, nitrite levels were significantly elevated in a dose-dependent manner, and exposure to nitrite stress significantly decreased the oxyhemocyanin content from 24 to 96 h. The glucose and lactate levels in the hemolymph in the nitrite stress groups were higher than those in the control group from 12 to 96 h. Compared with the control group, the shrimp in the nitrite stress groups exhibited decreased glycogen concentrations in the hepatopancreas. The triglyceride (TG) levels in the nitrite stress groups were all higher than those in the control group from 48 to 96 h. The hexokinase (HK) activity in the hepatopancreas and muscle increased in the nitrite stress groups from 48 to 96 h. In general, nitrite stress enhanced the activities of pyruvate kinase (PK), phosphofructokinase (PFK) and lactate dehydrogenase (LDH) in muscle from 24 to 96 h. In addition, nitrite stress decreased the activities of succinate dehydrogenase (SDH) and fatty acid synthase (FAS) from 24 to 96 h in the hepatopancreas and muscle. This study indicates that exposure to nitrite stress can enhance the accumulation of nitrite in the hemolymph and then reduce oxygenation and hemocyanin synthesis, leading to tissue hypoxia and thereby resulting in accelerated anaerobic metabolism and the inhibition of aerobic metabolism. The effects of nitrite stress on hemocyanin synthesis and energy metabolism may be one of the reasons for the mortality of L. vannamei in culture systems.


Assuntos
Anaerobiose/efeitos dos fármacos , Metabolismo Energético/efeitos dos fármacos , Hemocianinas/metabolismo , Nitritos/toxicidade , Oxigênio/metabolismo , Penaeidae/efeitos dos fármacos , Estresse Fisiológico , Animais , Aquicultura , Glicogênio/metabolismo , Hemolinfa/efeitos dos fármacos , Hemolinfa/metabolismo , Hepatopâncreas/efeitos dos fármacos , Hepatopâncreas/metabolismo , Subunidade alfa do Fator 1 Induzível por Hipóxia/metabolismo , Metabolismo dos Lipídeos/efeitos dos fármacos , Músculos/efeitos dos fármacos , Músculos/metabolismo , Penaeidae/crescimento & desenvolvimento , Penaeidae/metabolismo , Alimentos Marinhos , Triglicerídeos/metabolismo
5.
Mater Sci Eng C Mater Biol Appl ; 104: 109943, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31500025

RESUMO

The main objective of this work was to reduce the inhibitory effects of high contents of organics, ammonia, and heavy metals in an anaerobic buffled reactor (ABR), and to prevent the sludge wash-out using zeolites as media. In this work, a pilot scale of ABR with 8 compartments and a working volume of 14.4 L was used, and the last four ABR compartments were filled with a zeolite. The bioreactor was operated at HRTs of 3, 4, and 5 days, zeolite filling ratios of 10, 20, and 30%, and influent chemical oxygen demand (COD) concentrations of 10,000, 20,000, and 30,000 mg/L. The results obtained showed that the maximum removal efficiencies of COD and BOD5 reached 78 and 68%, respectively. The maximum removal was observed at a HRT of 5 days, a 30% medium filling ratio, and a COD of 10,000 mg/L. Increasing the filling ratio in the reactor increased the removal efficiencies of COD and BOD5 but increasing the concentration of the influent COD and decreasing HRT reduced the removal efficiency of the reactor. The initial BOD5/COD ratio was equal to 0.36, which increased by 46% when the medium filling ratio was elevated to 30%. The maximum biogas yield was 0.23 L/g of CODRemoved, and the specific methanogenic activity test verified the toxicity effect of the leachate on the gas-producer organisms. The results of scanning electronic microscopy and EDS showed that the zeolite medium immobilized the microorganisms and a biofilm was formed. Also the zeolite, as a well-known ion exchanger, decreased the concentrations of the major inhibitors (ammonia and heavy metals) and improved the reactor efficiency.


Assuntos
Anaerobiose/efeitos dos fármacos , Biodegradação Ambiental/efeitos dos fármacos , Zeolitas/química , Amônia/química , Biofilmes/efeitos dos fármacos , Biocombustíveis , Análise da Demanda Biológica de Oxigênio/métodos , Reatores Biológicos , Metais Pesados/química , Oxigênio/química , Esgotos/química , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/química
6.
PLoS One ; 14(8): e0219713, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31454355

RESUMO

Reduction of tetrazolium salts to colored formazan products by metabolically active cells is widely used for assessment of cell viability. Among the tetrazolium compounds most commonly used is MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide]. Numerous studies about sites and mechanisms of cellular reduction of MTT, performed in mammalian cell cultures, have identified various parameters that affect formazan production and can lead to overestimation/underestimation of viable cells or effects of treatment. Irrespective of lack of such data for prokaryotic cells, the MTT assay is commonly used for microbiological studies, which often leads to contradictory results or misinterpretation of data. The aim of this study was to investigate how components of growth media and conditions of growth, affect formazan formation by microbial cells. Results showed that MTT reduction depended on the amino acid composition of the medium. Several amino acids potentiated formazan production by Gram-positive and Gram-negative bacteria, with histidine having the strongest effect. Results of this study demonstrate that data obtained with the MTT test should be interpreted with caution, particularly when different growth media are used or treatments affect metabolic pathways, and that evaluation of the reliability of the MTT assay under specific conditions should be performed, to avoid erroneous results. Performing the assay with cells suspend in glucose-supplemented buffer would eliminate the effects of metabolites and will limit cell division during incubation with MTT. Another critical element to be considered is the choice of a proper solvent for dissolution of formazan crystals.


Assuntos
Colorimetria/métodos , Meios de Cultura/química , Escherichia coli/citologia , Staphylococcus aureus/citologia , Anaerobiose/efeitos dos fármacos , Escherichia coli/efeitos dos fármacos , Escherichia coli/crescimento & desenvolvimento , Formazans/metabolismo , Staphylococcus aureus/efeitos dos fármacos , Staphylococcus aureus/crescimento & desenvolvimento , Sais de Tetrazólio/metabolismo , Sais de Tetrazólio/farmacologia , Tiazóis/metabolismo , Tiazóis/farmacologia
7.
Bioresour Technol ; 291: 121803, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31326686

RESUMO

This study investigated the effects of tylosin (0, 10, and 100 mg/kg dry weight) on the denitrification genes and microbial community during the anaerobic digestion of cattle manure. N2 emissions were reduced and N2O emissions were increased by 10 mg/kg tylosin. Adding 100 mg/kg tylosin increased the emission of both N2O and N2. The different responses of denitrifying bacteria and genes to tylosin may have been due to the presence of antibiotic resistance genes (ARGs). Network analysis indicated that denitrification genes and ARGs had the same potential host bacteria. intI1 was more important for the horizontal transfer of denitrification genes and ARGs during anaerobic digestion than intI2. The anaerobic digestion of manure containing tylosin may increase nitrogen losses and the associated ecological risk.


Assuntos
Antibacterianos/farmacologia , Resistência Microbiana a Medicamentos/efeitos dos fármacos , Esterco/microbiologia , Tilosina/farmacologia , Anaerobiose/efeitos dos fármacos , Animais , Bovinos , Desnitrificação/efeitos dos fármacos , Resistência Microbiana a Medicamentos/genética , Microbiota/efeitos dos fármacos , Nitrogênio/metabolismo
8.
Bioresour Technol ; 291: 121847, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31357044

RESUMO

Effects of magnetite on methane production and fate of antibiotic resistance genes (ARGs) during anaerobic digestion (AD) of swine manure were investigated. Results showed that methane production was increased by maximum 16.1%, and magnetite could enhance the acetoclastic methanogenesis not hydrogenotrophic methanogenesis reflected by the functional gene quantification and microbial community analysis. The propionate degradation rate was improved, and it was syntrophic oxidized into H+/e-/CO2 for direct interspecies electron transfer (DIET) and acetate, where DIET was further enhanced by magnetite and the acetate was transformed into methane through syntrophic acetate oxidation (SAO) pathway. Magnetite mainly influenced the ARGs at the interim period of AD, where ARGs especially ermF were significantly enriched. Magnetite did not influence the total ARGs abundance at the end, although the tetM was enriched and mefA was reduced finally. Statistical analysis indicated that magnetite influenced the ARGs fate mainly through the changes of microbial community.


Assuntos
Óxido Ferroso-Férrico/farmacologia , Esterco , Metano/biossíntese , Anaerobiose/efeitos dos fármacos , Animais , Antibacterianos/farmacologia , Resistência Microbiana a Medicamentos/genética , Transporte de Elétrons , Microbiota/efeitos dos fármacos , Oxirredução , Suínos
9.
Artigo em Inglês | MEDLINE | ID: mdl-31188049

RESUMO

This work explores the effect of two metallic wastes (mining wastes, MW; fly ashes, FA) and micro-aeration (MA) on the anaerobic digestion of wastewater which is rich in sulfate and sulfide. Two initial COD concentrations (5,000 and 10,000 mg/L) were studied under both conditions in batch systems at 35 °C, with a fixed COD/SO42- ratio = 10, with 100 mg/L of S2-. It was observed that the use of MW and FA in the assays with an initial COD concentration of 10,000 mg/L resulted in a simultaneous increase in COD removal, sulfate removal, sulfide removal and methane generation, while MA only improved the COD and sulfide removals in comparison with the control system. On the contrary, the use of MW, FA or MA in systems with initial COD concentrations equal to or lower than 5,000 mg/L did not show any improvement with respect to the control system in terms of COD removal, sulfate removal or methane generation, with only sulfide removal being positively affected by MW and FA.


Assuntos
Metais/farmacologia , Metano/biossíntese , Sulfatos/isolamento & purificação , Sulfetos/isolamento & purificação , Águas Residuárias/química , Anaerobiose/efeitos dos fármacos , Reatores Biológicos , Catálise/efeitos dos fármacos , Resíduos Industriais , Mineração , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/isolamento & purificação , Poluentes Químicos da Água/farmacologia , Purificação da Água/métodos
10.
Chemosphere ; 229: 461-470, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31091487

RESUMO

Anaerobic digestion (AD) is regarded as a promising technology in energy recovery and the spread mitigation of antibiotic resistance. However, the performance of AD is dependent on various factors, and substrate type is one of the most important. In this study, the fate of antibiotic resistance genes (ARGs) response to the substrate types was investigated, and three typical environmental reservoirs of ARGs (pig manure, chicken manure and sewage sludge) were selected. The role of substrate microbial community on the fate of ARGs was clarified through the comparison between the AD of the substrates with and without a prior autoclave-disinfected step. Results showed that substrate types significantly influenced the fate of ARGs, while the influence from the substrate microbial community was limited. The concentration of antibiotics, the horizontal gene transfer reflected by intI1 and co-selection from heavy metals reflected by metal resistance genes (MRGs) were all reduced effectively. Microbial community varied from substrate types and dominated the ARGs fate concerning the standardized total effects through the mantel test and SEM analysis. The fate of tetX, ermF, tetM and ermB was mainly determined by the physicochemical parameters and the phyla of Firmicutes and Bacteroides. The phyla of Actinobacteria, pcoA and czcA contributed most to the reduction of blaTEM and mcr-1, and the phyla of Proteobacteria, Chloroflexi, Synergistetes, Euryarchaeote, intI1 and merA correlated significantly with the fate of blaCTX-M, ereA, tetG and sulI. This study highlighted the importance of substrate types when considering the fate of ARGs during AD.


Assuntos
Resistência Microbiana a Medicamentos/genética , Esterco/microbiologia , Microbiota/genética , Eliminação de Resíduos Líquidos/métodos , Anaerobiose/efeitos dos fármacos , Anaerobiose/genética , Animais , Antibacterianos/análise , Bactérias/efeitos dos fármacos , Bactérias/genética , Galinhas , Transferência Genética Horizontal , Genes Bacterianos/efeitos dos fármacos , Esterco/análise , Metais Pesados/farmacologia , Microbiota/efeitos dos fármacos , Esgotos/microbiologia , Suínos , Eliminação de Resíduos Líquidos/instrumentação , beta-Lactamases/genética
11.
Sci Total Environ ; 678: 85-93, 2019 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-31075606

RESUMO

The effect of membrane cleaning chemical, NaOCl on specific acetoclastic methanogenic activity (SAMA) of biomass in the anaerobic fluidized membrane bioreactors (AFMBRs) was assessed. Granular activated carbon (GAC) was used as a fluidizing media in the AFMBR to provide membrane scouring effect and surface for biofilm attachment. Effect of NaOCl on methane production was negligible for GAC with biofilm (bGAC) samples up to 150 mg NaOCl/g VSS, but was significant for the bulk liquid samples with noticeable lag period over 300 h even at the dosage of 50 mg NaOCl/g VSS. The toxicity of NaOCl on methane production was reduced in samples with virgin GAC (vGAC) by allowing 14 days of biomass buildup period prior to NaOCl addition, although the vGAC alone did not alleviate the toxicity. The results revealed that NaOCl concentrations beyond 100 mg/L within the reactor inhibited methanogenic activity and the effects were more pronounced on suspended biomass than the immobilized biomass on GAC.


Assuntos
Anaerobiose/efeitos dos fármacos , Reatores Biológicos , Metano/metabolismo , Hipoclorito de Sódio/toxicidade , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/toxicidade
12.
Bioprocess Biosyst Eng ; 42(7): 1175-1184, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30955092

RESUMO

Microbial community dynamics during the anaerobic co-digestion of pig manure, pasteurized slaughterhouse waste and glycerin were studied in a lab-scale CSTR. The feed composition was optimized through progressive co-substrate additions for enhanced methane production and organic matter removal without accumulation of intermediate compounds. Microbial community structure of biomass samples was studied by means of qPCR and DGGE profiling of 16S rRNA genes (Bacteria and Archaea), and genus-specific qPCR of the methyl coenzyme M reductase gene (mcrA), which encodes for an enzyme universally involved in methanogenesis. The composition of the dominant bacterial populations remained relatively stable, when compared to those in the influent, but the highest changes were observed upon the introduction of glycerin. Biodiversity of archaea was restricted to a few representatives of the genera Methanosaeta and Methanosarcina, but Methanospirillum sp. was detected only when glycerin was introduced in the feeding. Glycerin supplementation coincided with the strongest increase in methane yield (from 0.22 to 0.64 m3CH4 m-3 d-1).


Assuntos
Matadouros , Archaea/crescimento & desenvolvimento , Bactérias/crescimento & desenvolvimento , Glicerol/farmacologia , Consórcios Microbianos/efeitos dos fármacos , Eliminação de Resíduos Líquidos , Anaerobiose/efeitos dos fármacos , Animais , Esterco/microbiologia , Suínos
13.
Crit Rev Biotechnol ; 39(5): 746-757, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-30955366

RESUMO

The objective of this study is to summarize the effects of surfactants on anaerobic digestion (AD) of waste activated sludge (WAS). The increasing amount of WAS has caused serious environmental problems. Anaerobic digestion, as the main treatment for WAS containing three stages (i.e. hydrolysis, acidogenesis, and methanogenesis), has been widely investigated. Surfactant addition has been demonstrated to improve the efficiency of AD. Surfactant, as an amphipathic substance, can enhance the efficiency of hydrolysis by separating large sludge and releasing the encapsulated hydrolase, providing more substance for subsequent acidogenesis. Afterwards, the short chain fatty acids (SCFAs), as the major product, have been produced. Previous investigations revealed that surfactant could affect the transformation of SCFA. They changed the types of acidification products by promoting changes in microbial activity and in the ratio of carbon to nitrogen (C/N), especially the ratio of acetic and propionic acid, which were applied for either the removal of nutrient or the production of polyhydroxyalkanoate (PHA). In addition, the activity of microorganisms can be affected by surfactant, which mainly leads to the activity changes of methanogens. Besides, the solubilization of surfactant will promote the solubility of contaminants in sludge, such as organic contaminants and heavy metals, by increasing the bioavailability or desorbing of the sludge.


Assuntos
Ácidos Graxos/metabolismo , Metano/metabolismo , Esgotos , Tensoativos/farmacologia , Eliminação de Resíduos Líquidos/métodos , Anaerobiose/efeitos dos fármacos , Poluição da Água
14.
J Environ Sci Health B ; 54(6): 449-458, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30939985

RESUMO

Fipronil is a broad-spectrum insecticide that has a good control effect on pests of commercial poultry. Although many studies have reported the environmental fate of fipronil, the influence of residual fipronil in poultry waste on biogas production has not been further explored yet. In this article, an experimental comparative study on anaerobic digestion (AD) of chicken manure (CM) and corn straw (CS) with different fipronil concentrations (FCs) was carried at 8% of total solid (TS) and mid-temperature (35 ± 1)°C. The results showed that fipronil had a significant effect on biogas production during AD of CM and CS. When the FC is at a low level (≤10 mg·kg-1), the biogas production rate is increased and the digestion period was shortened, while higher FC (≥ 20 mg·kg-1) showed an inhibitory effect. During the monitoring of enzyme activity, low FC showed no significant effect on cellulase and saccharase, but the urease activity increased in the early stage. High FC showed inhibition of activity of cellulase and urease, but the saccharase activity was significantly inhibited until FC reached 40 mg·kg-1. This study also confirms that the environment in anaerobic digester is favorable for the degradation of fipronil, and its half-life is about 15.83 days.


Assuntos
Biocombustíveis , Esterco , Pirazóis , Eliminação de Resíduos Líquidos/métodos , Zea mays , Anaerobiose/efeitos dos fármacos , Animais , Celulase/antagonistas & inibidores , Celulase/metabolismo , Galinhas , Meia-Vida , Inseticidas/metabolismo , Inseticidas/farmacologia , Metano , Caules de Planta/metabolismo , Pirazóis/metabolismo , Pirazóis/farmacologia , Temperatura , Eliminação de Resíduos Líquidos/instrumentação , beta-Frutofuranosidase/antagonistas & inibidores , beta-Frutofuranosidase/metabolismo
15.
Sci Total Environ ; 654: 1064-1071, 2019 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-30841381

RESUMO

Nitrite, a product of the nitritation of sewage or digestion liquid, has been used to pretreat waste activated sludge (WAS) before anaerobic digestion. In this study, the effects of free nitrous acid (FNA) and nitrite on two-phase anaerobic sludge bioconversion were investigated. The experimental results indicated that both nitrite and FNA promoted sludge organic solubilization. Notably, nitrite promoted volatile fatty acids (VFAs) accumulation while FNA inhibited VFA accumulation in the first phase (acidogenic phase). In the second phase (methanogenic phase), neither nitrite nor FNA improved the net cumulative methane production from WAS. Although net cumulative methane production was not enhanced by the addition of nitrite or FNA, the volatile solids (VS) degradation rate was improved with nitrite addition in the two-phase anaerobic digestion process, indicating that nitrite is more favorable than FNA for the two-phase anaerobic digestion of WAS. It is expected that these findings can offer useful insights into future design of anaerobic digestion system with the treatment by the nitrite from digestion liquid.


Assuntos
Anaerobiose/efeitos dos fármacos , Nitritos/análise , Ácido Nitroso/análise , Eliminação de Resíduos Líquidos/métodos , Reatores Biológicos , Ácidos Graxos Voláteis , Esgotos/microbiologia
16.
Bioresour Technol ; 283: 138-147, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30903820

RESUMO

The toxicity of hexavalent chromium (Cr(VI)) is one of the challenges in implementing Anammox process to ammonium-rich wastewater treatment. However, the response of Anammox process to Cr(VI) stress and the inhibition mechanism remain unclear. Here, two Anammox UASB reactors were operated for 285 days under different Cr(VI) stresses. The results showed Anammox performance was not affected at low Cr(VI) concentration (i.e., 0-0.5 mg L-1), but was severely inhibited at 0.8 mg L-1. Attempts to domesticate Anammox process to higher Cr(VI) by lowering nitrogen loading rate were failed. Examination of Cr(VI) fate showed the occurrence of extracellular and intracellular Cr(VI) reduction to Cr(III). The inhibition was ascribed to the significant intracellular Cr(VI) reduction, accounting for 99.78% of the total Cr(VI) reduction. Moreover, under long-term Cr(VI) exposure, most nitrite was oxidized to nitrate. But microbial community showed no enrichment of Cr(VI) reducing bacteria and other nitrogen transformation-related bacteria.


Assuntos
Compostos de Amônio/metabolismo , Cromo/farmacologia , Nitritos/metabolismo , Anaerobiose/efeitos dos fármacos , Nitratos/metabolismo , Nitrogênio/metabolismo , Oxirredução
17.
J Biosci Bioeng ; 128(1): 72-79, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30765135

RESUMO

The anaerobic degradation of petroleum is an important process in natural environments. So far, few studies have considered the response of the microbial community to nanomaterials during this process. This study explored the potential effects of graphene oxide and biochar on the anaerobic degradation of petroleum hydrocarbons in long-term experiments. Cyclic voltammetry and electrochemical impedance spectroscopy indicated that the addition of carbon-based materials promoted the electrochemical activity of anaerobic cultures that degrade petroleum hydrocarbons. The maximum degradation rates for benzene, toluene, ethylbenzene, and xylene (BTEXs) in the cultures incubated for 10 weeks with graphene oxide (0.02 mg/L) and biochar (20 mg/L) were 76.5% and 77.6%, respectively. The maximum degradation rates of n-alkanes in the cultures incubated for 10 weeks with graphene oxide (2 mg/L) and biochar (100 mg/L) were 70.0% and 77.8%, respectively. The 16S rDNA copy numbers in the treatments with 0.02 mg/L graphene oxide and 20 mg/L biochar were significantly higher than others during the process (P < 0.05). In the 2nd week, the maximum copy numbers of the masD and bamA genes in the treatments with biochar were 349 copies/mL (20 mg/L) and 422 copies/mL (20 mg/L), respectively, and in the treatments with graphene oxide were 289 copies/mL (0 mg/L) and 366 copies/mL (0.02 mg/L). The contents of carbon-based materials had slight effects on the microbial community structure, whereas the culture time had obvious effects. Paracoccus denitrificans, Pseudomonas aeruginosa, and Hydrogenophaga caeni were the dominant microorganisms in the culture systems under all treatments.


Assuntos
Carvão Vegetal/farmacologia , Recuperação e Remediação Ambiental/métodos , Grafite/farmacologia , Hidrocarbonetos/metabolismo , Petróleo/metabolismo , Anaerobiose/efeitos dos fármacos , Biodegradação Ambiental/efeitos dos fármacos , Carvão Vegetal/química , Grafite/química , Humanos , Microbiota , Indústria de Petróleo e Gás/métodos , Petróleo/microbiologia , Poluição por Petróleo , Esgotos/química , Esgotos/microbiologia
18.
Biodegradation ; 30(1): 87-100, 2019 02.
Artigo em Inglês | MEDLINE | ID: mdl-30710246

RESUMO

Vegetable waste (VW) is highly perishable and susceptible to acidification during anaerobic digestion, which inhibits biogas production. Effective process monitoring, diagnosis and control are necessary to maintain stable anaerobic digestion at a high organic loading rate (OLR). Continuous mesophilic digestion was conducted at OLRs of 0.5, 1.0, 1.5, 2.0, 3.0, 3.5 and 4.0 g volatile solids (VS)/(L d) with effluent recirculation (ER) in a reactor with total volume of 70 L. The effectiveness of three early warning indicators was validated. The ability of trace elements (TEs) (Fe, Co and Ni) to recover unstable VW digestion systems was evaluated. The results showed that the ratio of bicarbonate alkalinity (BA) to total alkalinity (TA) was a more effective warning indicator than the ratios of methane (CH4) to carbon dioxide and volatile fatty acids (VFAs) to TA. When the ratio of BA/TA was lower than 0.9, the digestion system tended to be unstable. ER maintained a stable OLR of 1.5 g VS/(L d). The addition of TEs achieved a maximum stable OLR of 3.5 g VS/(L d) with an average volumetric biogas production rate of 1.91 L/(L d). Severe VFAs accumulation and unrecoverable instability occurred at an OLR of 4.0 g VS/(L d). The supplementation of ammonium bicarbonate was not useful for the recovery of the unstable system when the OLR was greater than 3.5 g VS/(L d) for the digestion of VW. The specific methane production was approximately 340 L/kg VS during the stable period with a digestion efficiency of 85%.


Assuntos
Álcalis/química , Bicarbonatos/química , Oligoelementos/farmacologia , Verduras/química , Resíduos/análise , Anaerobiose/efeitos dos fármacos , Bicarbonatos/farmacologia , Biodegradação Ambiental , Biocombustíveis/análise , Reatores Biológicos , Concentração de Íons de Hidrogênio , Oxigênio/análise
19.
Bioresour Technol ; 276: 204-210, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-30634163

RESUMO

Sewage can become a valuable source if its treatment is re-oriented. Forward osmosis (FO) is an effective pre-treatment for concentrating solutions. A laboratory-scale anaerobic digestion (AD) bioreactor was setup for the treatment of concentrated real sewage by FO membrane to investigate the removal of chemical oxygen demand (COD) and biogas production. Inhibitory batch tests were carried out for the impact of NaCl and NH4+-N. Results showed that the concentrated sewage could be purified with 80% COD removal, and energy recovery could be achieved. But the process was inhibited. The results of inhibitory batch test showed that (i) when the NH4+-N concentration was lower (<200 mg/L), the biogas production was promoted, when it went high, the inhibition appeared; (ii) single existence of NaCl had negative influence on methane production; (iii) the inhibition was more severe with co-existence of NaCl and NH4+-N. The AD performance could be recovered via sludge acclimation.


Assuntos
Amônia/farmacologia , Esgotos , Cloreto de Sódio/farmacologia , Anaerobiose/efeitos dos fármacos , Biocombustíveis , Análise da Demanda Biológica de Oxigênio , Reatores Biológicos , Osmose , Esgotos/análise
20.
Bioresour Technol ; 276: 91-96, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-30611091

RESUMO

Based on the phenomenon of the sharp decrease of H2S concentration in biogas during high solid anaerobic digestion (HSAD), the potential inhibitors of H2S production and their impact upon the stability of digesters during waste activated sludge (WAS) anaerobic digestion (AD) were evaluated. The results showed that H2S concentration in biogas decreased over 80% during HSAD compared to conventional AD. The results of biochemical methane potential tests indicated NH4Cl at a dosage ratio of 2.50 g·L-1 was determined as the optimum inhibitor of H2S in-situ prevention (ISP). H2S concentration in conventional AD decreased by over 45% at the same NH4Cl dosage ratio. Subsequent stable biogas yield under a small fluctuation of pH and biogas components in digesters revealed that the stability of digester was not affected. NH4Cl dosage showed an H2S ISP effect during WAS conventional AD under the condition that AD reactors were stable.


Assuntos
Cloreto de Amônio/farmacologia , Sulfeto de Hidrogênio/metabolismo , Esgotos , Anaerobiose/efeitos dos fármacos , Biocombustíveis , Concentração de Íons de Hidrogênio , Metano/biossíntese
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