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1.
Waste Manag ; 112: 30-39, 2020 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-32497899

RESUMO

Volatile fatty acids (VFAs) are intermediates of anaerobic digestion with high value and wide range of usage. Co-digestion of sewage sludge and external organic waste (OW) for VFA production can help achieve both resource recovery and ensure sustainable and innovative waste management. In view of this, the effect of substrate proportions on VFA production from co-digestion of primary sewage sludge and OW is studied. Long-term operation in a semi-continuous reactor was performed to assess the resilience of such a system and the VFA-rich effluent was tested for its ability to be used as carbon source for denitrification. Co-digestion was initially carried out in batch reactors with OW proportion of 0%, 25%, 50%, 75%, 100% in terms of COD and scaled up in a semi-continuous reactor operation with 50% OW. In the short-term operation in the batch mode, acetic acid dominated, however, increasing OW fraction resulted in increased valeric and caproic acid production. Moreover, in the long-term semi-continuous operation, caproic acid dominated, accounting for ≈55% of VFAs. The VFA-rich effluent from the semi-continuous reactor achieved the highest denitrification rate as a carbon source when compared with acetic acid and methanol. The results demonstrate that co-fermentation can increase VFA yield and shift products from acetic acid to caproic acid in long-term operation and the VFAs can be used within wastewater treatment plants to close the loop.


Assuntos
Reatores Biológicos , Esgotos , Ácidos Graxos Voláteis , Fermentação , Concentração de Íons de Hidrogênio , Águas Residuárias
2.
Sci Total Environ ; 729: 139035, 2020 Aug 10.
Artigo em Inglês | MEDLINE | ID: mdl-32498178

RESUMO

The presence of endocrine disruptor compounds (EDCs) in wastewater treatment plants has attracted widespread attention, but their potential impact on anaerobic fermentation of waste activated sludge (WAS) remains unclear. Therefore, this study aims to reveal the effect of typical EDC octylphenol (OP) on the recovery of volatile fatty acids (VFAs) in anaerobic fermentation. The results show that OP has a positive effect on the recovery of VFAs from WAS. The presence of 200 mg/kg dry sludge of OP increased the cumulative amount of VFAs from 3245 in the control (without OP) to 6828 mg COD/L. The increase in VFA production was mainly attributed to the accumulation of acetic acid, which rose from 1511 to 4425 mg COD/L, almost tripled. Further research found that OP promoted solubilization and hydrolysis by improving the biodegradability of WAS, and severely inhibited the methanogenesis process by inhibiting the activity of coenzyme F420, thereby significantly increasing the accumulation of acetic acid. These findings are of great significance to clarify the role of OP in anaerobic fermentation, and provide theoretical basis and guidance for the selection of target products in anaerobic fermentation of WAS containing OP.


Assuntos
Esgotos , Ácidos Graxos Voláteis , Fermentação , Concentração de Íons de Hidrogênio , Fenóis
3.
Bioresour Technol ; 309: 123400, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32371319

RESUMO

The developing approaches in the recovery of resources from biowastes for the production of renewable value-added products and fuels, using microbial cultures as bio-catalyst have now became promising aspect. In the path of anaerobic digestion, the microorganisms are assisting transformation of a complex organic feedstock/waste to biomass and biogas. This potentiality consequently leads to the production of intermediate precursors of renewable value-added products. Particularly, a set of anaerobic pathways in the fermentation process, yields small-chain fatty acids (SCFA), and medium-chain fatty acids (MCFA) via chain elongation pathways from waste valorization and CO2 fixation. This review focuses on the production of SCFA and MCFA from CO2, synthetic substrates and waste materials. Moreover, the review introduces the metabolic engineering of Escherichia coli and Saccharomyces cerevisiae for SCFAs/MCFAs production. Furtherly, it concludes that future critical research might target progress of this promising approach as a valorization of complex organic wastes.


Assuntos
Dióxido de Carbono , Ácidos Graxos , Biocombustíveis , Ácidos Graxos Voláteis , Fermentação
4.
Waste Manag ; 109: 75-84, 2020 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-32388405

RESUMO

Acidogenic fermentation of food waste for production of volatile fatty acids (VFAs) contributes to both food waste minimization and resource recovery. To gain knowledge on functional bacterial communities and facilitate continuous production of VFAs, this research firstly studied the effects of initial pH values (i.e. 5, 6 and 7) and temperatures (i.e. 35 °C and 55 °C) on VFAs production, distribution, and bacterial communities during acidogenic fermentation of food waste. The optimal conditions were determined as pH 7 and 35 °C, corresponding to the highest total VFAs yield of 11.8 g COD/L with major components of acetic, propionic and butyric acid. Bioinformatic analysis showed that the relative abundance of the dominant bacterial classes (e.g. Clostridia, Bacteroidia and Bacilli) were changed by the initial pH values in both mesophilic and thermophilic reactors. NMDS analysis confirmed a significant difference between mesophilic and thermophilic communities. Finally, the feasibility of continuous production and recovery of VFAs was validated using a two-phase leachate bed bioreactor at the optimal conditions. Average concentration and yield of the total VFAs in the continuous operation were 6.3 g COD/L and 0.29 g VFA/g VSadded, respectively. The findings in this study could provide pivotal technical supports for potential pilot- and commercial-scale biorefinery plants for VFAs production from food waste.


Assuntos
Alimentos , Eliminação de Resíduos , Reatores Biológicos , Ácidos Graxos Voláteis , Fermentação , Concentração de Íons de Hidrogênio
5.
Chemosphere ; 251: 126405, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32443235

RESUMO

In this study, different numbers of baffles were arranged in settling zone of an activated primary sedimentation tank (APST) to adjust the flow regime of sewage, and the characteristics of flow regime adjustment enhancing carbon source recovery in the APST were explored. The results showed that, compared with the APST without baffles, setting one baffle at the front end of settling zone led to the lowest sedimentation loss of soluble chemical oxygen in the settling zone, and the SCOD and volatile fatty acid concentrations in the effluent increased by 52 mg/L and 4.49 mg/L, respectively, furthermore, the SCOD/total nitrogen (TN), and SCOD/total phosphorus (TP) in the effluent also increased by 22.47%, and 11.95%, respectively. To evaluate the mechanism of setting baffles for carbon source recovery, the numerical simulation of flow regime adjustment was utilized. The results showed that, under the condition of setting one baffle, three large recirculation zones were formed which increased the probability of collision and friction between particulates to avoid the dissolved carbon that had been desorbed in the mechanical agitation zone from being re-adsorbed and settling in the settling zone. Moreover, the baffle changed the streamlines of sewage, thereby resuspending more small carbon sources that had already settled and increasing the carbon source content of effluent. Thus, this study provided a new method of adjusting sewage flow regime in APST for enhancing the efficiency of carbon source recovery which could help improving biological nitrogen and phosphorus removal in wastewater treatment plants.


Assuntos
Eliminação de Resíduos Líquidos , Reatores Biológicos , Carbono , Ácidos Graxos Voláteis , Veículos Automotores , Nitrogênio/análise , Fósforo , Esgotos/química , Águas Residuárias
6.
Bioresour Technol ; 311: 123446, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32402992

RESUMO

Wastewater treatment plants face the problem of a shortage of carbon source for denitrification. Acidogenic fermentation is an effective method for recovering short-chain fatty acids (SCFAs) as a carbon source from sewage sludge. Herein, the most recent advances in SCFAs production from primary sludge and waste activated sludge are systematically summarised and discussed. New technologies and problems pertaining to the improvement in SCFAs availability in fermentation liquids, including removal of ammoniacal nitrogen and phosphate and extraction of SCFAs from fermentation liquids, are analysed and evaluated. Furthermore, studies on the use of recovered SCFAs as a carbon source for denitrification are reviewed. Based on the above summarisation and discussion, some conclusions as well as perspectives on future studies and practical applications are presented. In particular, the recovery of carbon source/bioenergy from sewage sludge must be optimised considering nutrient removal/recovery simultaneously.


Assuntos
Desnitrificação , Esgotos , Carbono , Ácidos Graxos Voláteis , Fermentação , Eliminação de Resíduos Líquidos
7.
Bioresour Technol ; 311: 123501, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32416492

RESUMO

The accumulation of volatile fatty acids (VFAs) can decrease reactor pH and inhibit methane-producing process. For the first time, photosynthetic bacteria (PSB) were used to recover from VFAs inhibition (pH 6.0) of an anaerobic digestion system. After adding PSB for 12 days with and without light condition, the methane content recovered from 33.3% to 60.5% and from 32.1% to 59.3%, respectively; the pH increased to 7.1 and 6.8, respectively, the system alkalinity rapidly increased to 2238 and 1921 mg/L, respectively; the sCOD decreased from 5600 to 995 mg/L and from 5575 to 2025 mg/L, respectively; and the contents of formic acid, acetic acid, propionic acid and total VFA were greatly reduced. Microbial analysis found that PSB bioaugmentation could maintain microbial diversity of the system. PSB bioaugmentation could effectively relieve acids accumulation and stimulate methane production especially under light condition. It is also found that light could accelerate recovery with or without bioaugmentation.


Assuntos
Reatores Biológicos , Ácidos Graxos Voláteis , Anaerobiose , Bactérias , Bactérias Anaeróbias , Metano
8.
Bioresour Technol ; 311: 123529, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32428848

RESUMO

Volatile fatty acids (VFAs) has great potential for closed-loop production in dairy industries via resource recovery from waste-streams. In the current study, the transition of VFA production from batch reactor to anaerobic sequencing batch reactor (ASBR) by using cheese industry wastewater under alkali pH was evaluated with respect to seed sludge structure, microbial diversity and reactor type. The transition from the batch reactor to the ASBR demonstrated that the maximum VFA production yield (g COD/g SCOD) was comparable in two reactors (batch: 0.97; ASBR: 0.94), whereas, the dominant acid type was different (batch: 49% lactic acid; ASBR: 80% propionic acid). There was a significant correlation between the productions of butyric acid with Gracilibacteraceae and Desulfovibrionaceae; propionic acid with Desulfovibrionaceae and Synergistaceae; lactic acid with Pseudomonadaceae and Rhodocyclaceae. The high VFA production efficiency can be achieved by long term reactor operation, which enables the shift from industrial waste-streams to biorefineries.


Assuntos
Queijo , Águas Residuárias , Anaerobiose , Reatores Biológicos , Ácidos Graxos Voláteis , Esgotos , Eliminação de Resíduos Líquidos
9.
Bioresour Technol ; 311: 123516, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32428849

RESUMO

Crude glycerol is by-product produced from biodiesel industry and can be converted directly by mixed microbial culture (MMC) into polyhydroxyalkanoates (PHAs). This study investigated the effects of the reverse (SBR_A) and positive (SBR_B) glycerol gradient substrate strategy on PHA-accumulating culture enrichment and the maximum PHA accumulating stability under substrates with different glycerol and volatile fatty acid (VFA) proportion. The results showed that crude glycerol was mainly used for PHA production rather than biomass growth in SBR_A. The maximum qPHA was 0.65 g COD/g X-1·h-1 under sole crude glycerol condition in SBR_A, which was 2.41 times higher than that of SBR_B. Moreover, the PHA accumulating ability of the biomass from SBR_A was more stable than SBR_B. Saccharibacteria_genera_incertae_sedis was for the first time found to be the dominant genus using crude glycerol for PHA production. This research provides an insight into enrichment strategy to effectively enrich PHA-accumulating culture from crude glycerol.


Assuntos
Poli-Hidroxialcanoatos , Reatores Biológicos , Ácidos Graxos Voláteis , Glicerol , Consórcios Microbianos
10.
Bioresour Technol ; 311: 123568, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32467028

RESUMO

This review presents an emerging biorefinery platform for C2-5 bioalcohol production through chemical synthesis using the organic waste materials. Bioalcohols are the most commercialized carbon-neutral transportation fuels, compatible with existing an internal combustion (IC) engine. However, current bioalcohol fermentation processes have made from sugar-rich edible crops. Also, carbon loss from the fermentation process is substantial. To minimize carbon loss, volatile fatty acids (VFAs) can be utilized as a raw material for bioalcohol production. Thus, a two-step chemical upgrading of VFAs into C2-5 alcohols is summarized in comparison with current challenges of biological fermentation processes for bioalcohol production. This review also provides the prospect of the hybrid biological/chemical process, presenting the technical advantages of the system. Finally, economic viability of hybridized process for bioalcohol production is compared with the current biological process.


Assuntos
Fenômenos Biológicos , Ácidos Graxos Voláteis , Reatores Biológicos , Carboidratos , Fermentação , Esgotos , Resíduos
11.
Sci Total Environ ; 732: 139337, 2020 Aug 25.
Artigo em Inglês | MEDLINE | ID: mdl-32438163

RESUMO

The production of VFA using as substrate the wastewater produced in a cooked mussel processing factory, containing large COD (13.7 ±â€¯3.2 g COD/L), salt concentrations (21.8 ±â€¯2.8 g NaCl/L) and characterized by low pH (4.6 ±â€¯0.6) was evaluated. This wastewater was fed to a 5-L completely stirred tank reactor operated in continuous mode. The conversion efficiency of its COD content into volatile fatty acids (VFA) was evaluated. The maximum acidification of 43% (total VFA on soluble COD basis) was obtained when an organic loading rate of 2.5 ±â€¯0.4 g COD/(L·d) was applied to the reactor and corresponded to a VFA volumetric productivity of 0.72 ±â€¯0.07 g CODVFA/(L·d). Under steady-state conditions, the obtained mixture of VFA was composed by 80:18:2 as acetic:propionic:butyric acids (percentage of VFA on soluble COD basis). Carbohydrates were degraded up to 96% while protein fermentation did not take place, probably due to the low pH value, limiting the maximum acidification of the wastewater. Batch experiments showed that the increase of the pH from 4.2 to 4.9 by the addition of NaHCO3 resulted in the improvement of the acidification and changed the VFA mixture composition. Thus, this study demonstrates the opportunity of using complex substrates, as cooked mussel processing wastewater, to produce rich-VFA streams under unfavourable operational conditions, such as high salinity and low pH.


Assuntos
Bivalves , Anaerobiose , Animais , Reatores Biológicos , Ácidos Graxos Voláteis , Concentração de Íons de Hidrogênio , Águas Residuárias
12.
Bioresour Technol ; 310: 123444, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32361197

RESUMO

Rhizopus oligosporus is an edible filamentous fungus that can contribute to meet the growing demand for single-cell protein. Volatile fatty acids (VFAs) are favorable potential substrates for producing R. oligosporus biomass due to their capacity to be synthesized from a wide range of low-value organic solid wastes via anaerobic digestion. The goal of this work was to cultivate R. oligosporus using food waste-derived VFAs as the sole carbon source. To maintain the requisite low substrate concentrations, the fed-batch cultivation technique was applied. This resulted in a four-fold improvement in biomass production relative to standard batch cultivation. Maximum biomass yield of 0.21 ± 0.01 g dry biomass/g VFAs COD eq. consumed, containing 39.28 ± 1.54% crude protein, was obtained. In the bubble-column bioreactors, the complete uptake of acetic acid was observed, while the consumptions of caproic and butyric acids reached up to 97.64% and 26.13%, respectively.


Assuntos
Eliminação de Resíduos , Rhizopus , Anaerobiose , Biomassa , Reatores Biológicos , Ácidos Graxos Voláteis , Alimentos
13.
Bioresour Technol ; 310: 123440, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32361203

RESUMO

To investigate whether thermodynamic calculations of anaerobic digestion processes can be applied to the early warning for unstable anaerobic digestion, a group of semi-continuous digesters fed with an energy crop (Hybrid Pennisetum) were operated via a step-wise increase in the organic load rates until overload occurred. Traditional early warning indicators, such as biogas production and content, pH, alkalinity, and volatile fatty acids as well as the methane/carbon dioxide (CH4/CO2) and volatile fatty acid/alkalinity ratios, were regularly monitored during the process. The Gibbs free energy changes (ΔG) of the methanogenesis phases of valerate, butyrate, and propionate were calculated based on Nernst and Van't Hoff equations. The results demonstrate that ΔG of the three syntrophic methanogenesis phases can be used as an early warning indicator for unstable anaerobic digestion, indicating anaerobic digestion failure (ceased biogas production) up to 21 days in advance, that is, 1-8 days earlier than some other indicators.


Assuntos
Reatores Biológicos , Ácidos Graxos Voláteis , Anaerobiose , Biocombustíveis , Metano , Termodinâmica
14.
Bioresour Technol ; 309: 123366, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32305851

RESUMO

A high concentration of accumulated volatile fatty acids (VFAs) is one of the most important factors resulting in reactor failure during solid-state anaerobic digestion. In this study, the feedstock-to-inoculum (F/I) ratio (0.5, 2, 3, 4 and 6) and the recovery method after failure (biochar addition or inoculum addition) were investigated in batch solid-state anaerobic digestion fed with rice straw and pig urine. An F/I ratio of 3 was the threshold for stable operation, while the reactors failed at F/I ratios of 4 and 6 because of high accumulated VFAs concentrations (above 30 g HAc/kg). Biochar addition (10% or 20% (wet weight) of the mixture) was as effective as inoculum addition (by adjusting the F/I ratio to 2 or 3) in promoting VFAs degradation in failed reactors within a short period (<1 day). The buffering capacity of biochar was important in promoting VFAs degradation.


Assuntos
Reatores Biológicos , Metano , Anaerobiose , Animais , Carvão Vegetal , Ácidos Graxos Voláteis , Suínos
15.
Bioresour Technol ; 309: 123379, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32315918

RESUMO

In order to prolong the effect of CaO2 on improvement of short-chain fatty acids (SCFAs) production in sludge anaerobic fermentation, CaO2 particles were successfully loaded onto the porous surface of steel slag pre-modified with salicylic acid-methanol (SAM-SS). The prepared CaO2/SAM-SS was then characterized and investigated for its effects on anaerobic fermentation. Experimental results revealed that, due to the slow release and reaction of CaO2/SAM-SS, SCFAs concentrations in CaO2/SAM-SS tests were significantly higher than in the control and SAM-SS tests, and high SCFAs concentration was sustained for a longer period than in the CaO2 tests. Since most bacterial indexes were reduced by CaO2/SAM-SS, more supply of "raw materials" from a better disintegration and hydrolysis, which was associated with the alkalinity and •OH radicals released from the reaction of CaO2 with H2O, contribute to the higher SCFAs yields. This study provides a new approach towards a higher and longer SCFAs harvesting.


Assuntos
Esgotos , Aço , Anaerobiose , Ácidos Graxos Voláteis , Fermentação , Concentração de Íons de Hidrogênio , Peróxidos
16.
Water Res ; 177: 115783, 2020 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-32283434

RESUMO

The effects of micro-aeration on the performance of anaerobic sequencing batch reactors (ASBR) for blackwater treatment were investigated in this study. Different micro-aeration rates, 0, 5, 10, 50, and 150 mg O2/L-reactor/cycle, and their effect on the hydrolysis, acidogenesis, and methanogenesis of blackwater were evaluated and compared at ambient temperature. Source-diverted blackwater (toilet water) contains high organic contents which can be recovered as biogas. Previous studies have found that anaerobic digestion of blackwater without micro-aeration can only recover upwards of less than 40% of chemical oxygen demand (COD) to methane at room temperature due to the low hydrolysis rate of biomass content in blackwater. This study achieved increases in blackwater hydrolysis (from 34.7% to 48.7%) and methane production (from 39.6% to 50.7%) with controlled micro-aeration (5 mg O2/L-reactor/cycle). The microbial analysis results showed that hydrolytic/fermentative bacteria and acetoclastic methanogens (e.g. Methanosaeta) were in higher abundances in low-dose micro-aeration reactors (5 and 10 mg O2/L-reactor/cycle), which facilitated syntrophic interactions between microorganisms. The relative abundance of oxygen-tolerant methanogen such as Methanosarcina greatly increased (from 1.5% to 11.4%) after oxygen injection. High oxygen dosages (50 and 150 mg O2/L-reactor/cycle) led to reduced methane production and higher accumulation of volatile fatty acids, largely due to the oxygen inhibition on methanogens and degradation of organic matters by aerobic growth and respiration, as indicated by the predicted metagenome functions. By combining reactor performance results and microbial community analyses, this study demonstrated that low-dose micro-aeration improves blackwater biomethane recovery by enhancing hydrolysis efficiency and promoting the development of a functional microbial population, while medium to high-dose micro-aeration reduced the activities of certain anaerobes. It was also observed that medium-dose micro-aeration maximizes VFA accumulation, which may be used in two-stage anaerobic digesters.


Assuntos
Reatores Biológicos , Esgotos , Anaerobiose , Ácidos Graxos Voláteis , Metano
17.
Bioresour Technol ; 307: 123227, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32229411

RESUMO

The effects of different hypochlorite types (namely Ca(OCl)2 and NaOCl) on the waste activated sludge (WAS) anaerobic fermentation, and microbial community and activity were investigated. The results indicated that both Ca(OCl)2 and NaOCl contributed to volatile fatty acids (VFAs) production by simultaneously enhancing the solubilization, hydrolysis and acidification processes. The maximal VFAs was respectively 1379.5 (at 10 d) and 1621.5 (at 8 d) mg COD/L at the optimal dose of NaOCl and Ca(OCl)2 while it was merely 157.4 (at 6 d) mg COD/L in the control. However, the Ca(OCl)2 might affect the anaerobic process in a continuous mode while the NaOCl was relatively transient, which caused distinctive influences on the microbial structure and activity, and subsequently VFAs production in WAS fermentation systems. Moreover, Ca(OCl)2 treatments showed advantages over NaOCl on WAS dewatering and VSS reduction, implying the superiority of utilizing Ca(OCl)2 as additives for WAS disposal.


Assuntos
Microbiota , Esgotos , Ácidos Graxos Voláteis , Fermentação , Concentração de Íons de Hidrogênio , Hidrólise , Ácido Hipocloroso
18.
Bioresour Technol ; 308: 123250, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32244132

RESUMO

This work investigated the effect of biochar addition to mitigate VFA accumulation and enhance methane production in mesophilic food waste/sludge co-digestion. Different types of biochar derived from agricultural and forestry residues at two pyrolysis temperatures were tested. Results showed that wheat straw biochar 550 °C supported the highest specific methane yield of 381.9 LCH4/kg VSadded and VS removal efficiency of 41.62% among all treatments. Degradation of propionic acid and long-chain fatty acids such as valeric, caproic and isovaleric acids was observed. This also corresponded to an increase in methanogenic favorable substrates including acetic acid (>40%) and butyric acid (~20%) over the control. Consequently, a 24% increase in overall methane production was obtained as compared to control. This demonstrated that biochar addition had positive effects on VFA degradation and methane production which could be a useful strategy to increase the organic loading in co-digestions without the fear of process failure.


Assuntos
Eliminação de Resíduos , Esgotos , Anaerobiose , Reatores Biológicos , Carvão Vegetal , Ácidos Graxos Voláteis , Alimentos , Metano
19.
Bioresour Technol ; 308: 123226, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32251864

RESUMO

The present research explored the optimization of volatile fatty acids (VFA) production from cheese whey in an anaerobic sequencing batch reactor (AnSBR). For that purpose, changes of solid and hydraulic retention times (SRT and HRT) were applied. Moreover, the experiments were coupled to metagenomic analyses by 16S rRNA sequencing. The results showed an enhancement of the process effectiveness at longer SRT and shorter HRT. The degree of acidification (DA) improved from 0.73 to 0.83 when increasing the SRT from 5 to 15 days. It also increased from 0.79 to 0.83 when lowering the HRT from 3 to 1 day. The acidification yield (YVFA/S) improved from 0.78 to 0.87 and from 0.86 to 0.90 g COD-VFA g COD-Lactose-1 when increasing the SRT from 5 to 15 days and decreasing the HRT from 3 to 1 day, respectively. Hydrolytic bacteria dominated the microbial community at the shortest SRT, although they were replaced by acidogenic bacteria at longer SRT.


Assuntos
Queijo , Soro do Leite , Anaerobiose , Reatores Biológicos , Ácidos Graxos Voláteis , Fermentação , RNA Ribossômico 16S
20.
Bioresour Technol ; 308: 123291, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32276203

RESUMO

This study investigated the combination of low-thermal and sodium dodecylbenzene sulfonate (SDBS) as a pretreatment method to improve the volatile fatty acids (VFA) production from waste activated sludge (WAS). The results showed that the maximum VFA yield of 320 ± 7.7 mg COD/g VS was obtained in the combined pretreatment (0.01 g SDBS/g TS + 70 °C for 60 min), which was 1.8, 1.7 and 4.0 times of that from sole low-thermal, sole SDBS and the control test. The mechanism study revealed the combined pretreatment had synergetic effect on enhancement of disintegration of WAS. Moreover, low-thermal exhibited greater performance on releasing organic matters, and SDBS accelerated hydrolysis and acidogenesis, thus contributing to the enhancement of VFA production in the combined pretreatment. The microbial community analysis demonstrated that the combined pretreatment increased the abundance of phyla Firmicutes which might be responsible for the improvement of VFA production.


Assuntos
Ácidos Graxos Voláteis , Esgotos , Derivados de Benzeno , Fermentação , Hidrólise , Sódio
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