Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 25.470
Filtrar
1.
J Environ Qual ; 49(3): 545-556, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-33016384

RESUMO

Water reuse is believed to be a sustainable solution to overcome the scarcity of freshwater. Aerobic and anaerobic membrane bioreactors are becoming an effective technology for wastewater treatment and reuse. Aerobic membrane bioreactors show good nutrient removal, whereas those that are anaerobic have nutrient-rich effluent, enabling the direct agricultural use of the effluent. As a result, the end use will dictate the potential environmental impacts of the bioreactor's application. Therefore, with the consideration of the end use (i.e., discharge or reuse) of the effluent, this study aimed to compare the environmental and economic impacts associated with full-scale aerobic and anaerobic membrane bioreactors for municipal wastewater treatment under different end use scenarios using life cycle assessment and cost analysis. The results of these analyses show that anaerobic bioreactors have greater environmental impacts and life cycle cost than aerobic bioreactors in the discharge scenario due to the incorporation of a biological nutrient removal system. In the reuse scenario, anaerobic membrane bioreactors have lower impacts that are attributable to the offset of the nutrients required for crops, and the potential benefits vary depending on the types of crops receiving the reclaimed water. Integrating anaerobic membrane bioreactors with agricultural fertigation resulted in effluent water nitrate concentrations (after crop uptake and soil treatment) of <2 mg L-1 in most U.S. states. This indicated that the use of the anaerobic membrane bioreactors effluent for fertigation could be a win-win solution to both irrigation water shortage and high environmental impact associated with nutrient removal.


Assuntos
Purificação da Água , Anaerobiose , Reatores Biológicos , Água Doce , Águas Residuárias
2.
J Environ Qual ; 49(3): 700-711, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-33016390

RESUMO

Increased phosphorus (P) availability under flooded, anaerobic conditions may accelerate P loss from soils to water bodies. Existing knowledge on P release to floodwater from flooded soils is limited to summer conditions and/or room temperatures. Spring snowmelt runoff, which occurs under cold temperatures with frequent freeze-thaw events, is the dominant mode of P loss from agricultural lands to water bodies in the Canadian Prairies. This research examined the effects of temperature on P dynamics under flooded conditions in a laboratory study using five agricultural soils from Manitoba, Canada. The treatments were (a) freezing for 1 wk at -20 °C, thawing and flooding at 4 ± 1 °C (frozen, cold); (b) flooding unfrozen soil at 4 ± 1 °C (unfrozen, cold); and (c) flooding unfrozen soil at 20 ± 2 °C (warm). Pore water and surface water were collected weekly over 8 wk and analyzed for dissolved reactive phosphorus (DRP), pH, calcium, magnesium, iron (Fe), and manganese (Mn). Soils under warm flooding showed enhanced P release with significantly higher DRP concentrations in pore and surface floodwater compared with cold flooding of frozen and unfrozen soils. The development of anaerobic conditions was slow under cold flooding with only a slight decrease in Eh, whereas under warm flooding Eh declined sharply, favoring reductive dissolution reactions releasing P, Fe, and Mn. Pore water and floodwater DRP concentrations were similar between frozen and unfrozen soil under cold flooding, suggesting that one freeze-thaw event prior to flooding had minimal effect on P release under simulated snowmelt conditions.


Assuntos
Fósforo/análise , Solo , Anaerobiose , Canadá , Congelamento , Temperatura
3.
J Environ Qual ; 49(2): 509-515, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-33016413

RESUMO

Organic waste materials are sources of anthropogenic methane (CH4 ) emissions. Anaerobic digestion (AD) is a technology that produces biogas from organic waste materials, and CH4 is the primary component of biogas. Unintended emission of CH4 from biogas facilities could undercut the environmental benefits of this technology. The objective of this study was to determine if the implementation of an AD system affected ambient CH4 concentrations ([CH4 ]) on a commercial dairy farm over 5 yr, from before installation into full operation. Concentrations at 4.5-m height on a tower receiving wind that originated from various directions, comprising components of the dairy farm such as the AD facility, crop fields, or main barn, were measured using a closed-path tunable diode laser trace-gas analyzer. In 2012 and 2013, the first 2 yr of AD operation, [CH4 ] was not significantly different than pre-AD levels in 2011 (2.04 ± 0.01 µl L-1 ). However, mean [CH4 ] increased to 2.47 ± 0.03 and 2.48 ± 0.04 µl L-1 in 2014 and 2015, respectively, and the occurrence of high [CH4 ] (>10 µl L-1 ) increased from <0.05% in Year 1 (pre-AD) to 12% in Years 4 and 5. These elevated concentrations were related to an increased use of food waste feedstocks over time and suggest that the biogas system was a source of fugitive CH4 emissions. Food waste materials have a high biogas potential and are a valuable resource that require appropriate facility design and management to fully harness their benefits.


Assuntos
Metano , Eliminação de Resíduos , Anaerobiose , Fazendas , Alimentos
4.
Waste Manag ; 118: 655-666, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-33011543

RESUMO

Anaerobic sludge originating from the co-digestion of used disposable nappies and expired food products treated in a pilot two-stage system was examined as feed material for a continuous pilot-scale composter (capacity: 300 L feed per week). The feed materials and final compost products were analyzed and evaluated for their suitability as compost materials. Ιn terms of stability, the compost products were identified as stable through static respiratory index measurement (0.11-0.24 g O2/(kg Volatile Solids h)), heavy metals concentrations were within acceptable limits (i.e. concentration of Cu, Cd, Zn, Pb, Cr, As lower than 1 mg/kg dry mass) as well as polycyclic aromatic hydrocarbons (0.06-0.34 mg/kg dry mass lower than 6 mg/kg dry mass). During composting, significant losses of nitrogen from the digestate and the urea added for C/N correction were observed (51-75%), indicating that the adjustment of C/N ratio through the addition of chemicals is not efficient in composting processes with forced aeration and the pre-existing nitrogen in digestate was susceptible to air-stripping. The continuous composting process implemented proved capable of producing mature compost with a retention time of 14 d. The final products were within acceptable limits for all the parameters examined, except for the presence of pathogens (Salmonella and Enterococcus) which were not eliminated, even though the composter reached 56 °C for 3-4 days at the thermophilic stage. The characteristics of the anaerobic sludge samples examined indicate that direct land application of the anaerobic effluent should be considered as an option.


Assuntos
Compostagem , Metais Pesados , Anaerobiose , Metais Pesados/análise , Esgotos , Solo
5.
Water Sci Technol ; 82(7): 1380-1392, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-33079717

RESUMO

A scientific basis is given to the traditional method of inferring effluent quality based on visualization of samples in transparent flasks. A scale of 1-6, with different printed grey intensities, is placed behind transparent PET bottles containing the sample, and gives an indication of the range of turbidity in the sample (1 is the most transparent and can only be visualized if the effluent is well clarified; in the other spectrum, 6 is the darkest and indicates highly turbid effluents). Turbidity has been correlated with total suspended solids (TSS), particulate biochemical oxygen demand (BOD) and particulate chemical oxygen demand (COD) based on thousands of monitored data collected in the effluent from seven different treatment processes in Brazil: upflow anaerobic sludge blanket (UASB) reactor, trickling filters, activated sludge, horizontal wetland, vertical wetland, polishing ponds and coarse filter after pond. The method is simple and instantaneous, can be used in virtually all places and in every visit of the operator to the remote treatment plant, allows recording of the image in smartphones, does not use any equipment, chemicals or energy, and has been showed to represent well the effluent quality of existing treatment plants. This essay is complementary and does not substitute specific traditional sampling and analysis, but allows easy inference of deterioration of effluent quality.


Assuntos
Eliminação de Resíduos Líquidos , Águas Residuárias , Anaerobiose , Reatores Biológicos , Brasil
6.
Water Sci Technol ; 82(6): 1070-1080, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-33055397

RESUMO

A novel coupling process using an aerobic bacterial reactor with nitrification and sulfur-oxidization functions followed by a microalgal reactor was proposed for simultaneous biogas desulfurization and anaerobic digestion effluent (ADE) treatment. ADE nitrified by bacteria has a potential to be directly used as a culture medium for microalgae because ammonium nitrogen, including inhibitory free ammonia (NH3), has been converted to harmless NO3-. To demonstrate this hypothesis, Chlorella sorokiniana NIES-2173, which has ordinary NH3 tolerance; that is, 1.6 mM of EC50 compared with other species, was cultivated using untreated/treated ADE. Compared with the use of a synthetic medium, when using ADE with 1-10-fold dilutions, the specific growth rate and growth yield maximally decreased by 44% and 88%, respectively. In contrast, the algal growth using undiluted ADE treated by nitrification-desulfurization was almost the same as with using synthetic medium. It was also revealed that 50% of PO43- and most metal concentrations of ADE decreased following nitrification-desulfurization treatment. Moreover, upon NaOH addition for pH adjustment, the salinity increased to 0.66%. The decrease in metals mitigates the bioconcentration of toxic heavy metals from wastewater in microalgal biomass. Meanwhile, salt stress in microalgae and limiting nutrient supplementation, particularly for continuous cultivation, should be of concern.


Assuntos
Chlorella , Microalgas , Anaerobiose , Nitrificação , Águas Residuárias
7.
Water Sci Technol ; 82(6): 1081-1091, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-33055398

RESUMO

Combining microalgae and nitrifiers in a single photobioreactor has attracted attention as an alternative approach for conventional nitrogen removal from wastewater. However, nitrifiers are known to be sensitive to light exposure. This study demonstrated the effectiveness of using fluidized carriers to mitigate light stress in nitrifiers. An outdoor raceway pond containing microalgae and nitrifiers with fluidized carriers was used to treat two-fold diluted anaerobic digestion effluent (785 mg-N L-1 as a form of dissolved total Kjeldahl nitrogen: TKN) over 50 days. The average daily sunlight intensity reached the inhibition level of nitrifiers (423 µmol photons m-2 s-1); however, stable nitrification with a specific ammonium oxidation rate of 55 mg-N g-total suspended solid-1 day-1 was observed. TKN was mostly removed via nitrifier metabolism (ammonium oxidation and uptake: 40.1%) and partially via microalgae uptake (5.7%). Different microalgae-based processes including that of this study were compared in terms of tolerances to a high dissolved TKN concentration and strong light. Our system showed a relatively higher resistance to not only light exposure but also TKN because the nitrification process decreased the free ammonia level to less than 0.25 mg L-1, which allowed microalgae to grow despite the high ammonium concentration.


Assuntos
Microalgas , Tanques , Anaerobiose , Fotobiorreatores , Eliminação de Resíduos Líquidos
8.
Water Sci Technol ; 82(1): 144-156, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32910799

RESUMO

To accelerate the degradation of substrate, 50% liquid digestate recirculation (LDR) was used in the anaerobic digestion (AD) of corn straw. The effects of recirculation on the enzyme activities and biogas production were investigated by comparing with control reactor (ReactorCK). During the AD process, the fermentation system with 50% LDR was more stable. The average biogas and methane production in ReactorLDR were 7,891 mL·d-1 and 347 mL CH4·g-1 VSadded·d-1 respectively. The total volatile fatty acids (TVFAs) concentration in the two reactors both increased at first and then decreased with time. The LDR made the VFAs accumulation significant, especially propionic acid accumulation in 4 ∼ 16 days. The maximum peak value of cellulase, xylanase, dehydrogenase and coenzyme F420 activities in ReactorLDR were 0.51 mg·g-1·h-1, 0.29 mg·g-1·h-1, 4.88 mL·g-1·h-1 and 6.69 µmol·L-1, respectively, which were higher than that in ReactorCK. With or without recirculation, the concentration of TVFAs was positively correlated with cellulase, xylanase and dehydrogenase activities, while was negatively correlated with coenzyme F420 activity. Besides, a very significant correlation existed between hydrolase and dehydrogenase activities and daily biogas production in ReactorCK. And the peaks of cellulase, xylanase and dehydrogenase activities appeared ahead of the peak of daily biogas production with the LDR.


Assuntos
Biocombustíveis , Zea mays , Anaerobiose , Ácidos Graxos Voláteis , Fermentação
9.
Proc Biol Sci ; 287(1934): 20201538, 2020 09 09.
Artigo em Inglês | MEDLINE | ID: mdl-32873198

RESUMO

We here report the phylogenetic position of barthelonids, small anaerobic flagellates previously examined using light microscopy alone. Barthelona spp. were isolated from geographically distinct regions and we established five laboratory strains. Transcriptomic data generated from one Barthelona strain (PAP020) were used for large-scale, multi-gene phylogenetic (phylogenomic) analyses. Our analyses robustly placed strain PAP020 at the base of the Fornicata clade, indicating that barthelonids represent a deep-branching metamonad clade. Considering the anaerobic/microaerophilic nature of barthelonids and preliminary electron microscopy observations on strain PAP020, we suspected that barthelonids possess functionally and structurally reduced mitochondria (i.e. mitochondrion-related organelles or MROs). The metabolic pathways localized in the MRO of strain PAP020 were predicted based on its transcriptomic data and compared with those in the MROs of fornicates. We here propose that strain PAP020 is incapable of generating ATP in the MRO, as no mitochondrial/MRO enzymes involved in substrate-level phosphorylation were detected. Instead, we detected a putative cytosolic ATP-generating enzyme (acetyl-CoA synthetase), suggesting that strain PAP020 depends on ATP generated in the cytosol. We propose two separate losses of substrate-level phosphorylation from the MRO in the clade containing barthelonids and (other) fornicates.


Assuntos
Evolução Biológica , Eucariotos/fisiologia , Filogenia , Anaerobiose , Eucariotos/metabolismo , Mitocôndrias/metabolismo , Organelas/metabolismo
10.
Waste Manag Res ; 38(10): 1161-1175, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32907525

RESUMO

Quantification, measurement of quality, post-treatment, and leachate control has been a significant problem due to the dumping of waste in an unscientific manner across the globe, and especially in developing countries like India. In this context, the objective of this study was to investigate the degradation of fresh mixed municipal solid waste (MSW) in an anaerobic landfill reactor operated with rainfall addition in laboratory conditions. Experiments were carried out in a landfill reactor of 1 m length × 1 m width × 1.1 m height. The reactor was simulated with 50 years weighted average actual rainfall rate of India. It contained the waste composition of 73% wet waste (food and kitchen) and 27% dry waste (paper, plastic, wood, textiles, and others). The leachate parameters were continually monitored for 39 weeks. In the fresh MSW landfill reactor it was evident that concentrations of leachate parameters were high initially, and there was a significant decrease in BOD5 (7041-39310 mg L-1), COD (15692-71630 mg L-1) and TS (9077-33200 mg L-1) in leachate. Therefore, rainfall had a direct influence on leachate quality. The developed first-order decay models were used for BOD5, COD, and total solids with adjusted R2 of 0.83, 0.92, and 0.96, respectively. Therefore, this model can be applied for leachate strength estimation at any given time from the period of deposition of waste under similar rainfall and waste compositions, and is largely applicable in India and tropical areas. This study is expected to be a good simulation for cities with the waste composition of high wet waste (>70%) as the estimations of important design parameters such as BOD5, COD, VFA, and NH4+-N were studied in this research. As the importance of moisture (precipitation) has been established in this study, some moisture additions can be designed in areas with low rainfall, such as arid zones.


Assuntos
Eliminação de Resíduos , Poluentes Químicos da Água , Anaerobiose , Reatores Biológicos , Índia , Resíduos Sólidos/análise , Instalações de Eliminação de Resíduos , Poluentes Químicos da Água/análise
11.
J Environ Manage ; 263: 110395, 2020 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-32883477

RESUMO

One of the main drawbacks of upflow anaerobic sludge blanket (UASB) reactors that treat low-strength sewage at room temperature is related to the low quality of their effluents in terms of dissolved methane, organic matter, and nitrogen content. The present study aims to evaluate the feasibility of using an integrated fixed-film activated sludge (IFAS) system as an alternative post-treatment technology to mitigate the environmental impact of such effluents. For this purpose, a pilot plant composed of a UASB (120 L) followed by an IFAS (66 L) system was operated for 407 days. Special attention was paid to the suspended biomass retention capacity and the dissolved methane and nitrogen removal potential of the IFAS post-treatment system. Furthermore, the role of carriers on denitrification and nitrification processes and the microbial communities present in the biofilm were also analyzed. Average total chemical oxygen demand (CODT) and ammonium removal efficiencies of 92 ± 3% and around 57 ± 16% were attained throughout the entire operation, respectively. During a first period in which biomass was maintained in both biofilms and suspension, and nitrite was the main electron acceptor, maximum nitrogen removal and methane removal efficiencies of 32.5 mg TN L-1 and 93% were observed in the IFAS system, respectively. However, throughout the second period, in which suspended biomass was completely washed out from the IFAS system, and nitrate became the main electron acceptor, these values decreased to 18 ± 4 mg TN Lfeed-1 and 77 ± 12%, respectively. Surprisingly, throughout the entire operation, it was observed that around 50 and 41% of the total nitrogen and methane removals observed in the IFAS system, respectively, were carried out in the aerobic compartment. Aerobic methane oxidizers and anammox were detected with significant relative abundances in the biofilm carriers used in the anoxic and aerobic compartments using 16S rRNA gene amplicon sequencing analysis. Therefore, the use of an IFAS system could be suited to diminish greenhouse gas emissions and nutrients concentration for those sewage treatment plants that used UASB systems, especially in countries with temperate and warm climates.


Assuntos
Nitrogênio , Esgotos , Anaerobiose , Reatores Biológicos , Metano , RNA Ribossômico 16S , Eliminação de Resíduos Líquidos
12.
Water Sci Technol ; 82(3): 549-564, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32960799

RESUMO

Sludge from textile effluent treatment plants (ETP) remains a challenge for many industries due to inefficient and limited waste management strategies. This study explores the potential of using anaerobic digestion (AD) to improve the environmental quality of textile ETP sludge. The AD of ETP sludge is affected by the low C/N ratio (3.7), heavy metal content, and toxicity. To improve the process, co-digestion of ETP sludge with different substrates (sewage sludge, cow dung, and sawdust) under mesophilic conditions (37 °C), followed by a thermochemical pretreatment was assessed. The results showed that anaerobic co-digestion of the textile sludge with the co-substrates is effective in reducing pollution load. It was found that organic matters degraded during the 30-day AD process. The chemical oxygen demand and biological oxygen demand reduction was in the range of 33.1-88.5% and 48.1-67.1%, respectively. Also, heavy metal (cadmium, lead, iron, and, mercury) concentration was slightly reduced after digestion. Maximal biogas yield was achieved from co-digestion of textile sludge and sewage sludge at a mixing ratio of 3:1, 1:1, and 1:3, and methane content was respectively 87.9%, 68.9%, and 69.5% of the gas composition. The results from this study show that co-digestion will not only reduce the environmental pollution and health risks from the textile industry but also recover useful energy.


Assuntos
Esgotos , Águas Residuárias , Anaerobiose , Animais , Biocombustíveis , Reatores Biológicos , Bovinos , Feminino , Metano , Têxteis
13.
J Environ Sci (China) ; 97: 11-18, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32933725

RESUMO

It is known that many kinds of fermentative antibiotics can be removed by temperature-enhanced hydrolysis from production wastewater based on their easy-to-hydrolyze characteristics. However, a few aminoglycosides are hard to hydrolyze below 100°C because of their stability expressed by high molecular energy gap (ΔE). Herein, removal of hard-to-hydrolyze kanamycin residue from production wastewater by hydrothermal treatment at subcritical temperatures was investigated. The results showed the reaction temperature had a significant impact on kanamycin degradation. The degradation half-life (t1/2) was shortened by 87.17-fold when the hydrothermal treatment temperature was increased from 100°C to 180°C. The t1/2 of kanamycin in the N2 process was extended by 1.08-1.34-fold compared to that of the corresponding air process at reaction temperatures of 140-180°C, indicating that the reactions during hydrothermal treatment process mainly include oxidation and hydrolysis. However, the contribution of hydrolysis was calculated as 75%-98%, which showed hydrolysis played a major role during the process, providing possibilities for the removal of kanamycin from production wastewaters with high-concentration organic matrices. Five transformation products with lower antibacterial activity than kanamycin were identified using UPLC-QTOF-MS analysis. More importantly, hydrothermal treatment could remove 97.9% of antibacterial activity (kanamycin EQ, 1,109 mg/L) from actual production wastewater with CODCr around 100,000 mg/L. Furthermore, the methane production yield in anaerobic inhibition tests could be increased about 2.3 times by adopting the hydrothermal pretreatment. Therefore, it is concluded that hydrothermal treatment as a pretreatment technology is an efficient method for removing high-concentration hard-to-hydrolyze antibiotic residues from wastewater with high-concentration organic matrices.


Assuntos
Canamicina , Águas Residuárias , Anaerobiose , Hidrólise , Metano , Oxirredução , Temperatura
14.
Water Sci Technol ; 82(2): 227-241, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32941165

RESUMO

The wastewater industry is undergoing a paradigm shift from focusing solely on treatment to incorporating concepts aimed at mitigating environmental impacts such as energy and nutrient recovery and water reuse. This study uses life cycle assessment and life cycle cost analysis to investigate the effect of expanding anaerobic digestion (AD) capacity and adding combined heat and power on environmental and cost indicators at a mid-sized wastewater treatment facility (WWTF) in Massachusetts, USA. Since 2014, Massachusetts has banned the disposal of organic waste from commercial organizations producing more than one ton of material per week. The WWTF's additional digester capacity allows the co-digestion of municipal solids with a food-based engineered bioslurry due to this ban. Study data were compiled for several AD feedstock quantity and performance scenarios, and compared to a baseline scenario representative of historic plant operations prior to co-digestion. Reductions in environmental impact are demonstrated for six of eight environmental impacts, including global climate change potential and cumulative energy demand. Eutrophication potential increases by 10 percent and 24 percent across assessed scenarios. Water use remains relatively constant across scenarios. Facility energy production increases dramatically with co-digestion, satisfying 100 percent of the WWTF's thermal energy requirement and producing surplus electricity assuming full AD capacity utilization.


Assuntos
Eliminação de Resíduos , Águas Residuárias , Anaerobiose , Análise Custo-Benefício , Alimentos
15.
Water Sci Technol ; 82(2): 373-385, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32941178

RESUMO

To evaluate the enhancing of the biological nitrogen removal effectiveness by electromagnetic wave loading on returned sludge in the A/A/O reactor, some experiments were completed with the returned sludge loaded by 2,450 MHz electromagnetic wave. The excess sludge yield and pollutant removal effect of the system were evaluated. Results showed that stronger denitrification effect and less sludge yield were achieved. When 30% of the returned sludge was loaded by electromagnetic wave, the actual denitrification efficiency increased by 7% without dosage. The dissolution of carbon, nitrogen and phosphorus from loaded returned sludge was detected, thus providing the system with a supplemental carbon source of 4.6 g/d SCOD. The specific oxygen uptake rate of the oxic activated sludge increased by 14%, and the denitrification rate of the anoxic activated sludge increased by 29%. Illumina MiSeq analysis showed that the microbial richness increased obviously, and denitrifying bacteria (i.e. Dechloromonas, Zoogloea and Azospira, etc.) were accumulated.


Assuntos
Nitrogênio , Esgotos , Anaerobiose , Reatores Biológicos , Desnitrificação , Radiação Eletromagnética , Fósforo , Eliminação de Resíduos Líquidos
16.
Waste Manag ; 118: 452-462, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32977305

RESUMO

Relieving from ammonia inhibition and enhancing the utilization of thermodynamically unfavorable propionate are crucial for methane harvest in the high solid anaerobic digestion (HSAD) of ammonia-rich swine manure. In this study, the potential of dosing zero-valent iron (ZVI, 150 um) for enhancing the methanogenesis to resist total ammonia (TAN) over 5.0 g-N·L-1 was investigated via batch experiments under mesophilic condition. The cumulative methane production was enhanced by 22.2% at ≥160 mM ZVI dosage and the HSAD duration was further shortened by 50.6% at ≥320 mM ZVI dosage. The enhanced methanogenesis was mainly resulted from the full utilization of propionate and the accelerated collapse of posterior-biodegradable organics which might be driven by ZVI. Results of microbial community and qPCR (mcrA) showed that ZVI might trigger the blooming of Methanosarcina (from 27.9% to 78.3%) and Syntrophomonas (0.5% to 3.7%) and attribute to their possible direct interspecies electron transfer (DIET) to enhance propionate utilization. Besides, the main methanogenesis might remain in the effective aceticlastic pathway even under free ammonia (FAN) almost 1.0 g-N·L-1 because syntrophic acetate oxidizing bacteria (SAOB) decreased to almost none at 320 mM ZVI dosage. Dosing ZVI could relieve HSAD from TAN inhibition and more dosage was required to resist FAN inhibition.


Assuntos
Amônia , Esterco , Anaerobiose , Animais , Reatores Biológicos , Ferro , Metano , Suínos
17.
Waste Manag ; 118: 481-490, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32979779

RESUMO

Although commonly viewed as a promising method, dry anaerobic digestion is not been widely applied to dispose of food wastes, especially in developing countries because of its insufficiency in handling with lower mass transfer and high acidic accumulation of the system. Zero valent iron (ZVI) has been found to demonstrate superior performance such as enhancing methane production. However, up to date, the mechanism of ZVI remains unclear. In this study, adding 5 g/L ZVI could improve interspecies hydrogen transfer (IHT) to enhance the dry anaerobic digestion of food wastes, but was unable to resist the shocks of high organic loading. With increasing ZVI dosage to 10 g/L, the performances of digestion systems were improved to maintain the systems stable. With 10 g/L of ZVI addition, electron transfer capacity of the sludge increased by 5.4 folds, and electroactive proteins of sludge increased by 2.3 folds. Microbial community analysis also indicated that the relative abundances of Methanothrix and Methanosarcina performing direct interspecies electron transfer were enriched to 67.5% and 27.2% with 10 g/L ZVI addition, respectively. These results suggested that direct interspecies electron transfer could be established with a proper dosage of ZVI that served as a conductive material to connect electron exchange among microorganisms. Thus, ZVI played a dual role including improving interspecies hydrogen transfer and promoting direct interspecies electron transfer to keep the systems efficient to treat high-solid food wastes.


Assuntos
Hidrogênio , Ferro , Anaerobiose , Reatores Biológicos , Elétrons , Metano , Esgotos
18.
Waste Manag ; 118: 541-551, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32980733

RESUMO

The present work explored the production of volatile fatty acids through the anaerobic co-digestion of sewage sludge (SS) and cheese whey (CW). Two batch experiments were conducted to evaluate the effect of the substrate mixing ratio (SS%:CW% of total COD of feedstock) and the initial pH on the acidogenic fermentation of SS with CW at different temperatures. The first batch experiment showed that a decrease of the SS proportion in the co-digestion with CW led to a higher degree of acidification observing a synergistic effect at a SS:CW mixing ratio of 25:75 (SS25:CW75). In the second batch experiment, three temperatures (30 °C, 38 °C and 50 °C) and two initial pH (5.5 and 9) were studied at SS60:CW40 and SS25:CW75 substrate mixing ratios. Maximum degrees of acidification of 56% and 73% were achieved, at 50 °C and initial pH of 5.5, for the SS60:CW40 and SS25:CW75 substrate mixing ratios, respectively. Finally, the performance of a semi-continuous reactor was demonstrated at laboratory scale reactor. Different hydraulic retention times (HRT) (10 and 20 days), pH (uncontrolled, 5.5 and 9) and the effect of a thermal pre-treatment of the SS was studied. The maximum degree of acidification in the lab-scale reactor was 45% at 37 °C, HRT of 20 days and pH of 5.5. Under these conditions, the volatile fatty acids (VFA) profile was dominated by butyric and acetic acids.


Assuntos
Queijo , Esgotos , Anaerobiose , Reatores Biológicos , Ácidos Graxos Voláteis , Concentração de Íons de Hidrogênio , Soro do Leite
19.
Ecotoxicol Environ Saf ; 205: 111318, 2020 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-32979806

RESUMO

The retention of polyether sulfone (PES) and bisphenol A (BPA) in wastewater has received extensive attention. The effects of PES and BPA on the removal of organic matter by anaerobic granular sludge were investigated. We also analyzed the changes in the electron transport system and the effects on the composition of extracellular polymeric substances (EPS), as well as alternations of the microbial community in the anaerobic granular sludge. In the experimental groups which received BPA, the removal of the chemical oxygen demand (COD) were significantly suppressed, which an average removal efficiency of less than 65%, 30% lower than that of the control group. In the loosely-bound EPS (LB-EPS) excitation-emission matrix (EEM) spectra, the absorption peak of tryptophan disappeared when the BPA pollutants was added, which it was present in the control group without added pollutants. The addition of PES and BPA also affected protease, acetate kinase, and coenzyme F420 activities in the anaerobic granular sludge. Especially, the coenzyme F420 reduced from 0.0045 to 0.0017 µmol/L in the presence of PES and BPA. The relative abundance of Spirochaetes decreased in the presence of PES and BPA, while the relative abundance of Bacteroidetes increased from 12.98% to 22.87%. At the genus level, in the presence of PES and BPA, the relative abundance of Acinetobacter increased from 2.20% to 9.64% and Hydrogenophaga decreased sharply from 15.58% to 0.12%.


Assuntos
Compostos Benzidrílicos/análise , Microplásticos/análise , Fenóis/análise , Polímeros/química , Sulfonas/química , Eliminação de Resíduos Líquidos , Anaerobiose , Compostos Benzidrílicos/toxicidade , Análise da Demanda Biológica de Oxigênio , Matriz Extracelular de Substâncias Poliméricas , Microbiota/efeitos dos fármacos , Microplásticos/toxicidade , Fenóis/toxicidade , Plásticos , Esgotos/química , Águas Residuárias
20.
Bioresour Technol ; 317: 124052, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32877845

RESUMO

In this study, ten spent edible fungus (SEF) with different compositional features were used for the maximum methanogenic potential (P0) evaluation, and the prediction models including regression and kinetics based on this were developed separately. The results showed that the regression model with more chemical components had a good correlation with the P0, and at least three chemical compositions could reach the threshold of sensitivity. The Cone model showed the best fitting effect on P0 in all kinetic models, which had higher R-square (>0.994) and lower error (1.004-5.672%). Meanwhile, the minimum digestive testing time (14 days) was determined by the evaluation of sensitivity via statistical indicators. It is concluded that the determination of the prediction model of P0 should be evaluated with the combination of statistical indicators and specific requirements.


Assuntos
Fungos , Metano , Anaerobiose , Reatores Biológicos , Cinética
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA