Degradation Of Acetic Acid Research Articles

Enhancement for Anaerobic Digestion of Waste Activated Sludge Based on Microwave Pretreatment Combined with Zero Valent Iron

In this study, we investigated the enhanced performance after addition of zero valent iron (ZVI) under different dosages (low range of 5.19-41.51 g·kg-1 TS and high range of 83.35-853.46 g·kg-1 TS), combined with microwave (MW) pretreatment for anaerobic digestion (AD) of waste activated sludge (WAS). The results demonstrated that the methane production potential of WAS could be increased by 17%-24% with the addition of ZVI combined with MW pretreatment, and especially the methane production rate was enhanced in the initial days (1-4d). ZVI addition could further improve the enhanced performance of AD under MW pretreatment. Compared with the performance of AD with only MW pretreatment, the methane production potential was increased by 7.42%, and methane production flow rate at 2 d was increased by 11.02% with 31.13 g·kg-1 TS of ZVI addition. However, the higher dosage of added ZVI did not show further enhanced performance. It was concluded that ZVI addition promoted the release of dissolved organics at the initial stage of AD. For instance, soluble proteins were increased by 21.16% with the ZVI addition of 31.13 g·kg-1 TS compared with pretreated WAS without ZVI addition. Furthermore, ZVI addition accelerated the degradation of acetic acid, iso-butyric acid, and iso-valeric acid, and led to a significant reduction of orthophosphate and sulfate in the supernatant of the digested sludge. The concentration of iron in the supernatant decreased even with a high dosage of ZVI. Thus, the formation of precipitate that occurred due to reactions between iron and orthophosphate or sulfate, may be the main reason for the lack of enhanced performance even with high dosage of ZVI addition.

The contribution of selected organic substrates to the anaerobic cometabolism of sulfamethazine

Biodegradation of organic micropollutants is likely to occur due to cometabolism by particular microbial groups. In an effort to identify the stages of anaerobic digestion potentially involved in the biodegradation of the veterinary antimicrobial sulfamethazine (SMZ), the influence of selected carbon sources (sucrose, glucose, fructose, ethanol, meat extract, cellulose, soluble starch, soy oil, acetic acid, propionic acid and butyric acid) on SMZ removal by anaerobic sludge was evaluated in short-term batch experiments. Adsorption to the granular sludge constituted a significant removal mechanism, accounting for 39% of SMZ removal in control experiments. The presence of glucose, fructose, sucrose and meat extract exerted an inducing effect on SMZ degradation, resulting in removal efficiencies of 54, 53, 58 and 61%, respectively, indicating the occurrence of cometabolism. Time courses of sucrose and meat extract degradation revealed markedly distinct organic acid profiles but resulted in similar SMZ removals. Temporal profiles of acetic and propionic acid degradation were not associated with SMZ removal, as changes in SMZ concentration were observed even after the organic acids had been completely removed. The experimental results suggest that SMZ cometabolism is not associated to sucrose hydrolysis, acetoclastic methanogenesis and acetogenesis from propionic acid.

Photocatalytic Selectivities of Ethane, Methane and Dimethylether Controlled by Reaction Conditions and TiO2 Structure in the Degradation of Acetic Acid

AbstractThe impact of photon flux, humidity and residence time using TiO2 P25 and of the surface area of a series of CristalActiv PC TiO2 anatase, on the selectivities of products formed in the continuous photocatalytic degradation of gaseous acetic acid (AA) on the scale of a few hundred ppm, in the presence or absence of O2, was investigated. Under a continuous flow of air HCHO and C2H6 were the most important products detected. CH3OH was also formed but to a lesser extent. Under a continuous flow of N2, the formation of these three products decreases whereas CH3OCH3, an interesting product which can be used as alternative fuel and CH4, is yielded. The impact of the experimental conditions on product formation, taking into account the intermediate formation of H2O2 and the favorable impact of the surface area on the formation of CH4 in the absence of oxygen and its opposite effect on the formation of C2H6 in the presence of air, was discussed.The presence of rutile phase in TiO2 P25 was also highlighted.

Ammonia Inhibition of Anaerobic Volatile Fatty Acid Degrading Microbial Communities.

Ammonia inhibition is an important reason for reactor failures and economic losses in anaerobic digestion. Its impact on acetic acid degradation is well-studied, while its effect on propionic and butyric acid degradation has received little attention and is consequently not considered in the Anaerobic Digestion Model No. 1 (ADM1). To compare ammonia inhibition of the degradation of these three volatile fatty acids (VFAs), we fed a mixture of them as sole carbon source to three continuous stirred tank reactors (CSTRs) and increased ammonium bicarbonate concentrations in the influent from 52 to 277 mM. The use of this synthetic substrate allowed for the determination of degradation efficiencies for the individual acids. While butyric acid degradation was hardly affected by the increase of ammonia concentration, propionic acid degradation turned out to be even more inhibited than acetic acid degradation with degradation efficiencies dropping to 31 and 65% for propionic and acetic acid, respectively. The inhibited reactors acclimatized and approximated pre-disturbance degradation efficiencies toward the end of the experiment, which was accompanied by strong microbial community shifts, as observed by amplicon sequencing of 16S rRNA genes and terminal restriction fragment length polymorphism (T-RFLP) of mcrA genes. The acetoclastic methanogen Methanosaeta was completely replaced by Methanosarcina. The propionic acid degrading genus Syntrophobacter was replaced by yet unknown propionic acid degraders. The butyric acid degrading genus Syntrophomonas and hydrogenotrophic Methanomicrobiaceae were hardly affected. We hypothesized that the ammonia sensitivity of the initially dominating taxa Methanosaeta and Syntrophobacter led to a stronger inhibition of the acetic and propionic acid degradation compared to butyric acid degradation and hydrogenotrophic methanogenesis, which were facilitated by the ammonia tolerant taxa Syntrophomonas and Methanomicrobiaceae. We implemented this hypothesis into a multi-taxa extension of ADM1, which was able to simulate the dynamics of both microbial community composition and VFA concentration in the experiment. It is thus plausible that the effect of ammonia on VFA degradation strongly depends on the ammonia sensitivity of the dominating taxa, for syntrophic propionate degraders as much as for acetoclastic methanogens.

Process performance and microbial community functional structure in a thermophilic anaerobic baffled reactor coupled with biocatalysed electrolysis

ABSTRACTIn this study, the performances of a conventional anaerobic baffled reactor (ABR) and an ABR combined with microbial electrolysis cells (MECs) for enhancing degradation of volatile fatty acids (VFAs) were evaluated in 55°C. The ABR-MECs system achieved a total chemical oxygen demand (COD) removal rate of 97.2% and a methane yield of 236 ± 5 mL g−1 CODremoved at organic loading rate (OLR) of 6.9 kg COD m−3 d−1, which were higher than those of the ABR with 77.6% and 207 ± 5 mL g−1 CODremoved, respectively, at OLR of 5.1 kg COD m−3 d−1. The pyrosequencing analysis confirmed that the introduction of MECs into ABR was conducive to establishing stable functional communities of syntrophic fatty acids oxidizing bacteria (SFOB), exoelectrogens and hydrogenotrophic methanogens, such as Syntrophobacter (5.4%), Thermodesulfovibrio (2.0%), Methanobacterium (43.8%), Methanolinea (20.4%). The content of unclassified bacteria increased from 12.4% in the ABR system to 52.3% in the ABR-MECs system. In contrast, the proportion of aceticlastic methanogens decreased from 50.1% in the ABR to 24.5% in the ABR-MECs system. The improved performance of the thermophilic ABR-MECs system resulted from phase separation, wide ecological niche and intensification of methanogenesis process via functional microbes, which significantly enhanced the degradation of propionic acid and acetic acid.

Oxygen vacancy of CeO2 improved efficiency of H2O2/O3 for the degradation of acetic acid in acidic solutions

Abstract In order to completely mineralization of contaminants, it is necessary to develop new methods which can effectively degrade final products of chemical oxidation. Acetic acid (HAc) has been considered one of the typical end products of chemical oxidation of pollutants and thus chosen as a representative target pollutant in the study. Nano-cerium oxide (CeO2), an environment-friendly rare-earth material, was prepared to catalytic ozonation of HAc in acidic solutions. Experimental results show that the prepared CeO2 could greatly enhance efficiency of H2O2/O3, and also have good stability and recyclability. The Raman spectra indicate that H2O2 interacts with oxygen vacancies of CeO2 to form peroxide-like species, which could effectively initiate the decomposition of ozone to produce hydroxyl radicals. A mechanism is proposed to explain the activity of peroxide-like species for the decomposition of ozone. The effects of different parameters such as initial pH value, catalyst dosage, and the concentration of H2O2 are also investigated. The results indicate that the CeO2/H2O2/O3 may provide a convenient and effective method for degrading refractory organic pollutants in acidic wastewaters.

Effect of hydrodynamic mixing conditions on wet oxidation reactions in a stirred vessel reactor

The aim of this study was to investigate the impact of mixing intensity and mixing flow patterns on solid waste degradation, and production of valuable intermediate by-products such as acetic acid. Total suspended solids generally decreased, soluble chemical oxygen demand, dissolved organic carbon, and acetic acid concentration generally increased with the progress of the reaction and increase in the mixing intensity. The results showed that axial-radial flow pattern (using pitch blade impeller) and medium impeller speed (500 rpm) resulted in a higher degree of solid degradation and production of acetic acid.

Correlation between Photocatalytic Activity and Carrier Lifetime: Acetic Acid on Single-Crystal Surfaces of Anatase and Rutile TiO2

Photocatalytic activity and lifetime of photoexcited carriers on well-defined single-crystalline anatase and rutile TiO2 surfaces with different surface orientation have been systematically studied by photoelectron spectroscopy. Photocatalytic activity, evaluated with reference to the photocatalytic degradation of acetic acid, has a positive and linear correlation with carrier lifetime at the crystal surface, which was determined by following the time evolution of the ultraviolet-induced surface photovoltage. This indicates that the carrier lifetime is a prime factor for the photocatalytic activity so that it can be viewed as the origin of the crystal-surface-orientation dependence of the photocatalytic activity.

Mechanism of MgO/GAC Catalyzed Ozonation of Organic Compounds

MgO/granular activated carbon (MgO/GAC-1) was prepared via an impregnation method, and its activity in ozonation of diuron and acetic acid was investigated. MgO/GAC-1 was also compared in stability to the same catalyst prepared via precipitation according to the literature (MgO/GAC-2). The results showed that MgO/GAC-1 could increase efficiency of ozonation by 15%-35% in the process of degradation of diuron and acetic acid. When the pH of the solution was neutral or alkaline, MgO/GAC-1 could effectively retard the decrease in pH owing to formation of small molecular organic acids, thus ensuring the efficiency of ozone. When the pH of the solution was acidic, MgO/GAC-1 could increase the pH of the solution to a certain extent, thereby enhancing the efficiency of ozonation. The adjusting effect of pH value is the reason why MgO can significantly improve the efficiency of ozonation, a fact that was ignored in the relevant literature. Although MgO/GAC-1 had a larger specific surface area, MgO/GAC-1 had better activity in ozonation. A recycling test also indicated that MgO/GAC-1 had better stability, showing a good prospect for application.

Consolidated bioprocessing of lignocellulosic biomass to lactic acid by a synthetic fungal-bacterial consortium.

Consolidated bioprocessing (CBP) of lignocellulosic feedstocks to platform chemicals requires complex metabolic processes, which are commonly executed by single genetically engineered microorganisms. Alternatively, synthetic consortia can be employed to compartmentalize the required metabolic functions among different specialized microorganisms as demonstrated in this work for the direct production of lactic acid from lignocellulosic biomass. We composed an artificial cross-kingdom consortium and co-cultivated the aerobic fungus Trichoderma reesei for the secretion of cellulolytic enzymes with facultative anaerobic lactic acid bacteria. We engineered ecological niches to enable the formation of a spatially structured biofilm. Up to 34.7 gL-1 lactic acid could be produced from 5% (w/w) microcrystalline cellulose. Challenges in converting pretreated lignocellulosic biomass include the presence of inhibitors, the formation of acetic acid and carbon catabolite repression. In the CBP consortium hexoses and pentoses were simultaneously consumed and metabolic cross-feeding enabled the in situ degradation of acetic acid. As a result, superior product purities were achieved and 19.8 gL-1 (85.2% of the theoretical maximum) of lactic acid could be produced from non-detoxified steam-pretreated beech wood. These results demonstrate the potential of consortium-based CBP technologies for the production of high value chemicals from pretreated lignocellulosic biomass in a single step.

Influence of ultrasound on the heterogeneous Fenton-like oxidation of acetic acid.

The main objective of this study is to investigate the effect of ultrasound on the heterogeneous Fenton-like oxidation of acetic acid, which is one of the most resistant carboxylic acids to oxidation. For this purpose, firstly, the degradation of acetic acid was examined by using ultrasound alone and the effects of different parameters such as: type of sonication system, ultrasonic power, and addition of H2O2 were investigated on the degradation of acetic acid. There was no chemical oxygen demand (COD) reduction in the presence of sonication alone. In the presence of the heterogeneous Fenton-like oxidation process alone, at 303 K, COD reduction reached only 7.1% after 2 h of reaction. However, the combination of the heterogeneous Fenton-like oxidation process with ultrasound increased the COD reduction from 7.1% to 25.5% after 2 h of reaction in an ultrasonic bath operated at 40 kHz, while the COD reduction only increased from 7.1% to 8.9% in the ultrasonic reactor operated at 850 kHz. This result indicates that the hybrid process of ultrasound and heterogeneous Fenton-like oxidation is a promising process to degrade acetic acid.

A comparison of anaerobic 2, 4-dichlorophenoxy acetic acid degradation in single-fed and sequencing batch reactor systems

This paper compares the practical limits of 2, 4-dichlorophenoxy acetic acid (2,4-D) degradation that can be obtained in two laboratory-scale anaerobic digestion systems; namely, a sequencing batch reactor (SBR) and a single-fed batch reactor (SFBR) system. The comparison involved synthesizing a decade of research conducted by the lead author and drawing summative conclusions about the ability of each system to accommodate industrial-strength concentrations of 2,4-D. In the main, 2 L liquid volume anaerobic SBRs were used with glucose as a supplemental carbon source for both acid-phase and two-phase conditions. Volatile fatty acids however were used as a supplemental carbon source for the methanogenic SBRs. The anaerobic SBRs were operated at an hydraulic retention time of 48 hours, while being subjected to increasing concentrations of 2,4-D. The SBRs were able to degrade between 130 and 180 mg/L of 2,4-D depending upon whether they were operated in the acid-phase or two-phase regime. The methanogenic-only phase did not achieve 2,4-D degradation however this was primarily attributed to difficulties with obtaining a sufficiently long SRT. For the two-phase SFBR system, 3.5 L liquid-volume digesters were used and no difficulty was experienced with degrading 100 % of the 2,4-D concentration applied (300 mg/L).

Evaluation of the effects of low energetic microwave irradiation on anaerobic digestion

The present study investigates the effects of microwave irradiation on the performance of anaerobic digestion processes. A first set of experiments is performed to distinguish the upper limit of the applied energy levels. Secondly, the effects of these treatments on the performance of the digestion process are evaluated in 3 experimental setups: (i) monitoring the acetic acid degradation, (ii) performing a biological methane potential (BMP) assay and (iii) conducting a specific methanogenic activity (SMA) test. The solubilisation experiment reveals a limited degree of disintegration of anaerobic biomass up to a microwave treatment of 10000 kJ/kg TS. Above this threshold value the soluble COD level started to rise, with up to 350% at 30000 kJ/kg TS regardless of the microwave output power. Because solubilisation of the biomass increases the easily degradable content, this would lead to false observations regarding increased activity. Therefore, solubilisation is minimized by limiting the microwave treatment to a maximum of 6000 kJ/kg TS during the second part of the experiments. Monitoring the degradation of acetic acid after a low intensity microwave treatment, reveals that microwave irradiation shortens the lag phase, e.g., from 21 to 3 h after a microwave treatment of 1000 kJ/kg TS at 100 W. However most treatments also result in a decrease of the maximum degradation and of the degradation rate of acetic acid. BMP assays are performed to evaluate the activity and performance of the entire anaerobic community. Every treatment results in a decreased biogas production potential and decreased biogas production rate. Moreover, each treatment induced an increase of the lag phase. The SMA experiments show no influence of the microwave irradiation in terms of biogas or methane production.

Irradiation of liquid phase plasma on photocatalytic decomposition of acetic acid-containing wastewater over metal oxide photocatalysts

The photocatalytic decomposition of acetic acid-containing wastewater was assessed for the removal of pollutants and the production of hydrogen. The effects of irradiation of the liquid phase plasma were evaluated in the photocatalytic decomposition reaction. The evolution of hydrogen was also characterized by the photocatalytic decomposition of wastewater. Ni-loaded TiO2 photocatalysts were introduced to the photocatalytic reaction. With the Ni loading to the TiO2, the adsorption wavelength was enlarged to the visible range. The photochemical decomposition by irradiation of the liquid phase plasma without photocatalysts produced some hydrogen evolution with the degradation of acetic acid, which was attributed to the decomposition of the reactant by active species generated by the irradiation of liquid phase plasma. The rate of hydrogen evolution from water on the photocatalyst was ca. 1.6mmol/min at 1h of process time. The photocatalytic decomposition of acetic acid was improved by the addition of Ni-loaded TiO2 photocatalysts by the irradiation of liquid phase plasma. The Ni loading on TiO2 brought out an enhancement of acetic acid degradation and hydrogen evolution. Hydrogen evolution was accelerated significantly due to the additional hydrogen production by the photocatalytic decomposition of acetic acid.

Kinetics and mechanism of the photocatalytic degradation of acetic acid in absence or presence of O 2

Abstract Transforming pollution into valuable compounds and more especially into energy is an important challenge for a sustainable future. The objective of our work was to better understand the mechanism of the photocatalytic degradation of acetic acid (AA) in the gas phase under an air or oxygen-free atmosphere, by comparing the disappearance, mineralization and selectivity of the intermediate products formed in the presence of non-doped TiO 2 . It was found that in both environments decarboxylation is the first step of AA degradation. However, the fate of the methyl group depends on the carrier gas and gas phase concentration. In air, at low AA molar flow the methyl group is oxidized into methanol, formaldehyde, and CO 2 with no formic acid detected. At molar flows larger than 0.55 μmol/min, corresponding to the saturation of the TiO 2 surface, ethane is formed due to the combination of two methyl groups. In an O 2 -free atmosphere, three new products were detected: methane (CH 4 ), acetone (CH 3 COCH 3 ) and acetaldehyde (CH 3 COH). However, the use of CH 3 13 COOH shows that acetone and acetaldehyde do not arise from the reduction of the carboxylic group. Under air, a mechanism explaining the formation of methanol, formaldehyde and ethane occurring on the surface of TiO 2 , involving either a direct oxidation of AA with the holes or an oxidation with the hydroxyl radicals was proposed, together with the regeneration of the TiO 2 surface and the formation of H 2 O 2 .

Effect of Iron Oxide Promoted Sulfated Zirconia on the Oxidative Efficiency of H2O2/O3 for Acetic Acid Degradation in Strong Acidic Water

Acetic acid (HAc), a hydroxyl radical probe in ozonation, was chosen as a target contaminant to be degraded in strong acidic solution by different ozone-based processes. The highest removal rate of HAc was obtained by SZF/H2O2/O3. The indirect method of dimethyl sulfoxide (DMSO) capture showed that hydroxyl radical was effectively produced in this process. A mechanism study indicated that the S–Fe(III) peroxo complex intermediate played an important role in the process. The effects of different parameters such as pH value, amount of catalyst, concentration of H2O2, and rate of ozone input were investigated. The experimental results showed that the presence of SO2–4/ZrO2–Fe2O3, abbreviated as SZF, could greatly improve the oxidative efficiency of H2O2/O3 in the pH range from 0 to 5.0. The result is very significant to the application of H2O2/O3 in strong acid wastewater pretreatment.

Single cell-strain부터 유래된 무세포 효소 시스템을 이용한 톨루엔 및 아세트산 분해

This study deals with the possible degradation of toluene and acetic acid when subjected to cell-free enzyme system from the toluene degrading bacteria Pseudomonas putida and acetic acid degrading bacteria Cupriavidus necator. P. putida produces toluene dioxygenase only under the existence of toluene in culture medium and toluene is degraded to cis-toluene dihydrodiol by this enzyme. C. necator produces acetyl coenzyme A synthetase-1 and converts acetic acid to acetyl CoA in order to synthesize ATP to need for growth or PHA which is biodegradable polymer. In case of toluene degradation, the experiment was conducted before and after production of toluene dioxygenase as this enzyme, produced by P. putida, is an inducible enzyme. Toluene was detected using gas chromatography (GC). Similar amount of toluene was found in control group and before production of toluene dioxygenase (experimental group 1). However, reduction in toluene was detected after the production of toluene dioxygenase (experimental group 2). Acetic acid was detected through application of gas chromatography-mass spectrometer (GC-MS). The results showed the acetic acid peak was not detected in the experimental group to apply cell-free enzyme system. These results show that the cell-free enzyme system obtained from P. putida and C. necator retained the ability to degrade toluene and acetic acid. However, P. putida needs to produce the inducible enzyme before preparation of the cell-free enzyme system.

Process simulation and modeling: Anaerobic digestion of complex organic matter

This work is focused on evaluating kinetic models of complex organic matters hydrolysis and volatile fatty acids degradation in anaerobic digestion process, simulated using SuperPro design software. Kinetic model evaluation was also carried for simulated integrated system of liquid anaerobic digestion (LAD) of dairy manure and solid state anaerobic digestion (SS-AD) of corn stover. Already developed hydrolysis and volatile fatty acid (VFA) degradation kinetic constants were used to simulate anaerobic digestion processes of dairy manure and corn stover separately and in the integrated process as well. Hydrolysis of complex soluble organic matters such as protein, carbohydrate and fat was modelled using first-order kinetics. Monod model was tested for the VFAs such as acetic, propionic and butyric acid degradation and biogas production. Comparative study has been done between the experimental data published already and results obtained from SuperPro simulated processes. The simulated results were well comparable with the experimental results.

Inhibitor degradation and lipid accumulation potentials of oleaginous yeast Trichosporon cutaneum using lignocellulose feedstock

Oleaginous yeast Trichosporon cutaneum is robust to high levels of lignocellulose derived inhibitor compounds with considerable lipid accumulation capacity. The potential of lipid accumulation of T. cutaneum ACCC 20271 was investigated using corn stover hydrolysates with varying sugar and inhibitor concentrations. Biodiesel was synthesized using the extracted lipid and the product satisfied the ASTM standards. Among the typical inhibitors, T. cutaneum ACCC 20271 is relatively sensitive to furfural and 4-hydroxybenzaldehyde, but strongly tolerant to high titers of formic acid, acetic acid, levulinic acid, HMF, vanillin, and syringaldehyde. It is capable of complete degradation of formic acid, acetic acid, vanillin and 4-hydroxybenzaldehyde. Finally, the inhibitor degradation pathways of T. cutaneum ACCC 20271 were constructed based on the newly sequenced whole genome information and the experimental results. The study provided the first insight to the inhibitor degradation of T. cutaneum and demonstrated the potentials of lipid production from lignocellulose.

Photocatalytic degradation of acetic acid in the presence of visible light-active TiO2-reduced graphene oxide photocatalysts

Visible light-active TiO2–reduced graphene oxide photocatalysts were prepared using simple mechanical mixing of titanium dioxide with different amounts of rGO (0.1, 0.5, 1.0 and 2.0wt.%) in the presence of 1-butyl alcohol. Structures and morphologies of the samples were examined by means of FTIR/DRS, UV–vis/DR, XRD, SEM, TEM and Raman spectroscopy. The photocatalytic properties were checked on the basis of acetic acid photooxidation (the steady rate of linear increase of the CO2 yield was used for the estimation of photocatalytic activity). The maximum photodegradation rate was observed for TiO2 decorated with 0.5 wt.% of rGO. The enhancement of photodegradation efficiency should be related to π-conjugation system, two-dimensional planar structure and efficient charge separation of reduced graphene oxide nanosheets.