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Occurrence of hexabromocyclododecane (HBCD) in sewage sludge from Shanghai: Implications for source and environmental burden.
Chemosphere
PUBLISHED: 06-19-2014
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Sewage sludge is regarded as one important sink for hydrophobic pollutants, including hexabromocyclododecane (HBCD), but the current pollution situation of HBCD in sludge from China is unknown, despite that many studies have reported its occurrence in other environmental compartments across China. In this study, we collected 27 sludge samples from Shanghai to investigate the occurrence and distribution, to examine the diastereoisomer profile and sources, and to provide advice for future pollution control. HBCD is ubiquitous in sludge with a mean concentration of 4.7ngg(-1) dry weight (dw) (range: 0.10-37.2ngg(-1) dw), lower than data from European countries and the United States. Sludge from wastewater treatment plants (WWTPs) treating industrial wastewater contained high levels of HBCD. However, no significant relationships were found between HBCD and four parameters (total organic carbon, the percentage of industrial wastewater, capacity and sludge production of WWTPs). ?- and ?-HBCD were two main components with the corresponding contributions of 47.9% and 48.0%. Comparing with the annual production of HBCD in China, its storage in sewage sludge is extremely low (less than 0.002%), indicating future release of HBCD from waste polystyrene foam will be significant, and careful considerations should be taken during waste disposal. To our knowledge, this is the first report on HBCD in sewage sludge from China.
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New insight into chemical changes of dissolved organic matter during anaerobic digestion of dewatered sewage sludge using EEM-PARAFAC and two-dimensional FTIR correlation spectroscopy.
Bioresour. Technol.
PUBLISHED: 02-17-2014
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Dissolved organic matter (DOM) is a key component in reaction network of anaerobic digestion. In this study, fluorescent excitation-emission matrix-parallel factor (EEM-PARAFAC) analysis and two-dimensional (2D) FTIR correlation spectroscopy were firstly used to explore chemical changes of soluble intermediates in high-solid biogas reactor. EEM-PARAFAC showed that fluorescent components (tyrosine-like, tryptophan-like and humic-like groups) in DOM over time increased gradually, implying that these groups were reluctant to biodegrade (acidogenesis). The resistance to biodegradation presented the following order: humic-like group>tyrosine-like group>tryptophan-like group. 2D FTIR correlation spectroscopy indicated that the DOM change sequence with time followed the order: protein-like groups>structural carbohydrates and carboxylic acids>polysaccharides-like groups. Fluorescence intensities from EEM-PARAFAC and main bands of FTIR spectra correlated significantly with other chemical parameters, e.g. biogas production and dissolved organic carbon content. These findings supply novel realization for degradation degree and order of individual DOMs during anaerobic digestion for dewatered sewage sludge.
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Earthworm eco-physiological characteristics and quantification of earthworm feeding in vermifiltration system for sewage sludge stabilization using stable isotopic natural abundance.
J. Hazard. Mater.
PUBLISHED: 02-10-2014
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Previous studies showed that the presence of earthworm improves treatment performance of vermifilter (VF) for sewage sludge stabilization, but earthworm eco-physiological characteristics and effects in VF were not fully investigated. In this study, earthworm population, enzymatic activity, gut microbial community and stable isotopic abundance were investigated in the VF. Results showed that biomass, average weight, number and alkaline phosphatase activity of the earthworms tended to decrease, while protein content and activities of peroxidase and catalase had an increasing tendency as the VF depth. Earthworm gut microbial communities were dominated by Gammaproteobacteria, and the percentages arrived to 76-92% of the microbial species detected. (15)N and (13)C natural abundance of the earthworms decreased with operation time, and increased as the VF depth. Quantitative analysis using ?(15)N showed that earthworm feeding and earthworm-microorganism interaction were responsible for approximately 21% and 79%, respectively, of the enhanced volatile suspended solid reduction due to the presence of earthworm. The finding provides a quantitative insight into how earthworms influence on sewage sludge stabilization in vermifiltration system.
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Polybrominated diphenyl ethers (PBDEs) and dechlorane plus (DP) in a conventional wastewater treatment plant (WWTP) in Shanghai: seasonal variations and potential sources.
Sci. Total Environ.
PUBLISHED: 02-07-2014
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Wastewater treatment plants (WWTPs) are considered an important medium for the transport and transformation of organic pollutants, such as polybrominated diphenyl ethers (PBDEs) and dechlorane plus (DP). However, limited data on PBDEs and no data on DP were available regarding wastewater and sludge from China, especially in Shanghai, one of the most developed cities in China. This study examined the occurrence of PBDEs and DP in a conventional WWTP in Shanghai for one year. The levels of the total PBDEs in the influent and dewatered sludge ranged from 5.31 to 27.9 ng/L and 31.0 to 99.5 ng/g, respectively, which were at the low end of the global range. DP was reported in wastewater with a mean concentration of 0.46 ng/L (range: 0.05 to 1.40 ng/L) and sludge contained DP in the range of 1.1 to 2.0 ng/g. For both PBDEs and DP, there were no significant seasonal variations observed in the four seasons. Indoor dust and outdoor air could be two main sources of PBDEs and DP in the WWTP. In both the influent and sewage sludge, BDE-209 was the most abundant congener, with contributions to the total PBDE levels ranging from 52.9 to 82.6% and 82.7 to 84.0%, respectively. The fraction of anti-DP was consistently higher than that of syn-DP, and the average of fsyn ranged from 0.16 to 0.33, which fell in the range of two commercial DP mixtures. The annual releases of PBDEs and DP via sewage sludge from WWTPs in Shanghai were estimated to be 6,370 g and 164.8 g, respectively. The fate and risk of these compounds after being released into the environment require further research. To the best of our knowledge, this study is the first to report on the occurrence of DP in wastewater.
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Flow of sewage sludge-borne phthalate esters (PAEs) from human release to human intake: implication for risk assessment of sludge applied to soil.
Sci. Total Environ.
PUBLISHED: 01-03-2014
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The wide production and use of phthalate esters (PAEs) in both industry and commercial products lead to their ubiquitous existence in the environment. However, understanding flow and pathway of human exposure to PAEs from sources to receptors is necessary and challenging. In this study, we selected final sewage sludge, an inevitable byproduct of wastewater treatment plants (WWTP), as one type of important carrier/sources of PAEs to clarify the flow of PAEs between human and the environment, e.g. the release by human to sludge and in turn ingestion by human after these sludges were disposed as soil amendment. Twenty-five sludge samples were collected from 25 wastewater treatment plants (WWTPs) in Shanghai, East China. Of all 16 PAE congeners, di(2-ethylhexyl) phthalate (DEHP) and dibutyl phthalate (DnBP) were predominant with mean concentrations of 97.4 and 22.4 ?g/g dw, respectively, both locating at the high end of the global range. WWTP treating industrial waster generally contained higher PAEs compared to those treating domestic wastewater, but no positive relationship was found between PAE levels with the percentage of industrial wastewater. Principal component analysis (PCA) showed that similar PAE sources for all WWTPs in Shanghai with three exceptions, in which specific PAE products were made. The annual mass loadings via sludge of DEHP, DnBP, and ?16PAEs were 31.4, 7.44, and 39.6 tons in Shanghai and 1042, 247, and 1314 tons in China, respectively, only accounting for 0.09% of the total consumption of PAEs in China. If this sludge is applied in soil, human will take 16.4 and 3.8 ?g/kg bw for DEHP and DnBP every day, respectively, via dietary and soil ingestion, which were lower than the toxicological safety parameters. To the best of our knowledge, this is the first report to analyze the flow of sludge-borne PAEs from human release to human intake.
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Effect of increasing total solids contents on anaerobic digestion of food waste under mesophilic conditions: performance and microbial characteristics analysis.
PLoS ONE
PUBLISHED: 01-01-2014
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The total solids content of feedstocks affects the performances of anaerobic digestion and the change of total solids content will lead the change of microbial morphology in systems. In order to increase the efficiency of anaerobic digestion, it is necessary to understand the role of the total solids content on the behavior of the microbial communities involved in anaerobic digestion of organic matter from wet to dry technology. The performances of mesophilic anaerobic digestion of food waste with different total solids contents from 5% to 20% were compared and the microbial communities in reactors were investigated using 454 pyrosequencing technology. Three stable anaerobic digestion processes were achieved for food waste biodegradation and methane generation. Better performances mainly including volatile solids reduction and methane yield were obtained in the reactors with higher total solids content. Pyrosequencing results revealed significant shifts in bacterial community with increasing total solids contents. The proportion of phylum Chloroflexi decreased obviously with increasing total solids contents while other functional bacteria showed increasing trend. Methanosarcina absolutely dominated in archaeal communities in three reactors and the relative abundance of this group showed increasing trend with increasing total solids contents. These results revealed the effects of the total solids content on the performance parameters and the behavior of the microbial communities involved in the anaerobic digestion of food waste from wet to dry technologies.
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Biodegradation of polyacrylamide by anaerobic digestion under mesophilic condition and its performance in actual dewatered sludge system.
Bioresour. Technol.
PUBLISHED: 09-16-2013
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Polyacrylamide (PAM) used in sludge dewatering widely exists in high-solid anaerobic digestion. Degradation of polyacrylamide accompanied with accumulation of its toxic monomer is important to disposition of biogas residues. The potential of anaerobic digestion activity in microbial utilization of PAM was investigated in this study. The results indicated that the utilization rate of PAM (as nitrogen source) was influenced by accumulation of ammonia, while cumulative removal of amide group was accorded with zeroth order reaction in actual dewatered system. The adjoining amide group can combined into ether group after biodegradation. PAM can be broken down in different position of its carbon chain backbone. In actual sludge system, the hydrolytic PAM was liable to combined tyrosine-rich protein to form colloid complex, and then consumed as carbon source to form monomer when easily degradable organics were exhausted. The accumulation of acrylamide was leveled off ultimately, accompanied with the yield of methane.
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Hydrolysis and acidification of dewatered sludge under mesophilic, thermophilic and extreme thermophilic conditions: effect of pH.
Bioresour. Technol.
PUBLISHED: 07-25-2013
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This study investigated the effect of pH (uncontrolled, 8.0, 10.0 and 12.0) and temperature (mesophilic, thermophilic and extreme thermophilic) on hydrolysis and acidification of dewatered sludge in 7-day batch fermentation experiment. Solublization of COD, protein and carbohydrates as well as concentration and composition of VFAs were investigated. Sludge hydrolysis was enhanced with higher pH and temperature. The maximum SCOD, soluble protein and carbohydrates was observed at pH 12.0 at extreme thermophilic condition. The maximum VFAs yield was obtained at thermophilic and was 2.15 times that at mesophilic condition, but it took more time to reach the maximum. The VFAs consisted of acetic, propionic, iso-butyric, n-butyric, iso-valeric, and n-valeric acids, and acetic acid was the prevalent product in most cases except for uncontrolled pH and pH 8.0 at mesophilic condition. The methane production was as follows: pH 8.0>pH 10.0>uncontrolled (0.015)>pH 12.0; mesophilic>thermophilic>extreme thermophilic.
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Organic matter humification in vermifiltration process for domestic sewage sludge treatment by excitation-emission matrix fluorescence and Fourier transform infrared spectroscopy.
J. Hazard. Mater.
PUBLISHED: 05-01-2013
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Performance of a conventional biofilter (BF) and two vermifilters (VFs, different heights) containing earthworms was investigated for domestic sewage sludge (DWS) treatment. Humic-acid like (HAL) fraction isolated from the influent sludge (IS) and effluent sludge of BF (ESBF) and VFs (ESVFs) were determined the elemental and functional composition, and structural characteristics using various analytical approaches. Results showed that performance of DWS treatment in the VFs was preferable to that in the BF. With respect to IS-HAL and ESBF-HAL, ESVFs-HAL had low C, H and N contents and C/O ratio, and high O, carboxyl and phenolic OH group contents, and C/N, C/H and E4/E6 ratios, and large molecular weight. The excitation-emission (Ex/Em) matrix spectra revealed that an additional peak was found at Ex/Em wavelength pairs of 345/435 nm in ESVFs-HAL. Further, Fourier transform infrared spectra showed that vermifiltration led to the loss of aliphatic materials and carbohydrates, and the enrichment of carbonyl and phenolic OH groups in HAL fractions. Additionally, the increase in VF height seemed to accelerate humification degree of organic matter in the effluent sludge. In summary, vermifiltration is alternate technology for transformation of organic matter into humic substances, and thus improves quality of DWS as soil organic fertilizer.
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Improved bioproduction of short-chain fatty acids from waste activated sludge by perennial ryegrass addition.
Water Res.
PUBLISHED: 03-19-2013
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To improve short-chain fatty acids (SCFAs) production from waste activated sludge (WAS), studies that focus on pre-treatment methods, pH control or adding extra carbon like rice were reported. In this study, a kind of green waste (perennial ryegrass) was used as carbon source to adjust carbon to nitrogen ratio (C/N) in WAS to enhance SCFAs production. The effects of different C/N ratio ranging from 26/1 to 7/1 on SCFAs production and cellulose, hemicellulose, and lignin consumption were investigated in detail. It was observed that the maximal SCFAs yield was 368.71 g COD per kilogram of total solids (TS) at C/N 20/1 with fermentation time of 12 d, which was, respectively, over 4 and 12 times than that at C/N 26/1 (sole perennial ryegrass) and C/N 7/1 (sole WAS). Meanwhile, cellulose, hemicellulose and lignin consumptions were 109.12, 148.74, 20.90 g COD/kg TS, respectively, at C/N 20/1 with fermentation time of 12 d. The analysis of the composition of SCFAs showed that acetic acid ranked the first among other acids from C/N ratio of 26/1 to 18/1, whereas propionic acid was the dominant product from C/N ratio of 16/1 to 7/1. Because the results of this study were different from previous studies of SCFAs generation, the mechanism of improved SCFAs at C/N ratio of 20/1 by perennial ryegrass addition was investigated. Results showed that as soluble COD, soluble protein and soluble carbohydrate increased, more substrates were available for SCFAs production at C/N ratio of 20/1. In addition, with the drop of pH to 4.82, methane generating was inhabitant and the SCFAs production was therefore significantly enhanced. Additionally, the mechanism of improved SCFAs generation was analyzed from the view of enzyme activities and microbial community. The experiments revealed that at C/N ratio of 20/1 the activities of enzymes were the highest comparing with other C/N ratios and lignin was the rate-limiting steps in WAS anaerobic digestion by perennial ryegrass addition. The 16S rRNA gene clone library demonstrated that Clostridia, Spirochaetes, and Bacteroidetes were the dominant microbial community at C/N ratio of 20/1.
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High-solid anaerobic digestion of sewage sludge under mesophilic conditions: feasibility study.
Bioresour. Technol.
PUBLISHED: 09-10-2011
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Feasibility of high-solid anaerobic digestion of sewage sludge was investigated in single-stage completely stirred tank reactors at 35±1 °C. System stability and the effect of organic loading rate (OLR), sludge retention time (SRT) and total solid (TS) content on the performance of high-solid system was examined. Experimental results showed that, with the concentration of free ammonia nitrogen (FAN) lower than 600 mg l(-1), high-solid anaerobic digestion of sewage sludge could maintain satisfactory stability. Slight, moderate and significant inhibition was found with FAN concentration ranging from 250 to 400, 400 to 600 and 600 to 800 mg l(-1), respectively. The VFA/TA criteria could not foresee system instability in significant ammonia inhibition system by its traditional ratio grades. High-solid system could support higher OLR (4-6 times as high) and obtain similar methane yield and VS reduction as conventional low-solid system at the same SRT, thus reach much higher volumetric methane production rate.
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Electrochemical impedance spectroscopy to characterize inflammatory atherosclerotic plaques.
Biosens Bioelectron
PUBLISHED: 07-13-2011
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Despite advances in diagnosis and therapy, atherosclerotic cardiovascular disease remains the leading cause of morbidity and mortality in the Western world. Predicting metabolically active atherosclerotic lesions has remained an unmet clinical need. We hereby developed an electrochemical strategy to characterize the inflammatory states of high-risk atherosclerotic plaques. Using the concentric bipolar microelectrodes, we sought to demonstrate distinct Electrochemical Impedance Spectroscopic (EIS) measurements for unstable atherosclerotic plaques that harbored active lipids and inflammatory cells. Using equivalent circuits to simulate vessel impedance at the electrode-endoluminal tissue interface, we demonstrated specific electric elements to model working and counter electrode interfaces as well as the tissue impedance. Using explants of human coronary, carotid, and femoral arteries at various Stary stages of atherosclerotic lesions (n=15), we performed endoluminal EIS measurements (n=147) and validated with histology and immunohistochemistry. We computed the vascular tissue resistance using the equivalent circuit model and normalized the resistance to the lesion-free regions. Tissue resistance was significantly elevated in the oxLDL-rich thin-cap atheromas (1.57±0.40, n=14, p<0.001) and fatty streaks (1.36±0.28, n=33, p<0.001) as compared with lesion-free region (1.00±0.18, n=82) or oxLDL-absent fibrous atheromas (0.86±0.30, n=12). Tissue resistance was also elevated in the calcified core of fibrous atheroma (2.37±0.60, n=6, p<0.001). Despite presence of fibrous structures, tissue resistance between ox-LDL-absent fibroatheroma and the lesion-free regions was statistically insignificant (0.86±0.30, n=12, p>0.05). Hence, we demonstrate that the application of EIS strategy was sensitive to detect fibrous cap oxLDL-rich lesions and specific to distinguish oxLDL-absent fibroatheroma.
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Changes of heavy metal speciation during high-solid anaerobic digestion of sewage sludge.
Bioresour. Technol.
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The sequential extraction procedure developed by Tessier et al. was used in sludge anaerobic digestion to determine the heavy metal speciation. Sludge samples were taken every three days to investigate humic substances, VS/TS, pH, VFA, alkalinity, ammonia, the total content of Zn, Pb, Cu, Ni, and Cr, and also their distribution into EXCH, CARB, FeMnOx, OMB and RESI fractions. Results showed that, (1) Heavy metals were concentrated during the anaerobic digestion process. The concentration of all five kinds of heavy metals increased by about 50%. (2) The distribution of these heavy metals differed. (3) High-solid anaerobic digestion much or less increased the bioavailability of Cu, Zn, Ni and Cr while decreased the bioavailability of Pb. (4) There were significant degrees of correlation between heavy metal fractions and changes of some selected parameters (for example, pH, VS/TS, and VFA content). Except for Pb, the contents of total mobile fractions for Cu, Zn, Ni, Cr could be predictable from its total content.
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High-solids anaerobic co-digestion of sewage sludge and food waste in comparison with mono digestions: stability and performance.
Waste Manag
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System stability and performance of high-solids anaerobic co-digestion of dewatered sludge (DS) and food waste (FW) in comparison with mono digestions were investigated. System stability was improved in co-digestion systems with co-substrate acting as a diluting agent to toxic chemicals like ammonia or Na(+). For high-solids digestion of DS, the addition of FW not only improved system stability but also greatly enhanced volumetric biogas production. For high-solids digestion of FW, the addition of DS could reduce Na(+) concentration and help maintain satisfactory stability during the conversion of FW into biogas. System performances of co-digestion systems were mainly determined by the mixing ratios of DS and FW. Biogas production and volatile solids (VSs) reduction in digestion of the co-mixture of DS and FW increased linearly with higher ratios of FW. A kinetic model, which aimed to forecast the performance of co-digestion and to assist reactor design, was developed from long-term semi-continuous experiments. Maximum VS reduction for DS and FW was estimated to be 44.3% and 90.3%, respectively, and first order constant k was found to be 0.17d(-1) and 0.50 d(-1), respectively. Experimental data of co-digestion were in good conformity to the predictions of the model.
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Atrial fibrillation pacing decreases intravascular shear stress in a New Zealand white rabbit model: implications in endothelial function.
Biomech Model Mechanobiol
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Atrial fibrillation (AF) is characterized by multiple rapid and irregular atrial depolarization, leading to rapid ventricular responses exceeding 100 beats per minute (bpm). We hypothesized that rapid and irregular pacing reduced intravascular shear stress (ISS) with implication to modulating endothelial responses. To simulate AF, we paced the left atrial appendage of New Zealand White rabbits (n = 4) at rapid and irregular intervals. Surface electrical cardiograms were recorded for atrial and ventricular rhythm, and intravascular convective heat transfer was measured by microthermal sensors, from which ISS was inferred. Rapid and irregular pacing decreased arterial systolic and diastolic pressures (baseline, 99/75 mmHg; rapid regular pacing, 92/73; rapid irregular pacing, 90/68; p < 0.001, n = 4), temporal gradients ([Formula: see text] from 1,275 ± 80 to 1,056 ± 180 dyne/cm(2) s), and reduced ISS (from baseline at 32.0 ± 2.4 to 22.7 ± 3.5 dyne/cm(2)). Computational fluid dynamics code demonstrated that experimentally inferred ISS provided a close approximation to the computed wall shear stress at a given catheter to vessel diameter ratio, shear stress range, and catheter position. In an in vitro flow system in which time-averaged shear stress was maintained at [Formula: see text] , we further demonstrated that rapid pulse rates at 150 bpm down-regulated endothelial nitric oxide, promoted superoxide (O 2 (.-) ) production, and increased monocyte binding to endothelial cells. These findings suggest that rapid pacing reduces ISS and [Formula: see text] , and rapid pulse rates modulate endothelial responses.
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Ultrasonic-pretreated waste activated sludge hydrolysis and volatile fatty acid accumulation under alkaline conditions: Effect of temperature.
J. Biotechnol.
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The effect of temperature on the hydrolysis and acidification of ultrasonic-pretreated waste activated sludge (WAS) under alkaline conditions was investigated in this study. The experiment temperatures were set at 10, 20, 37, and 55°C. Experimental results showed that the hydrolysis of ultrasonic-pretreated WAS under alkaline conditions increased significantly with temperature from 10 to 55°C, while the volatile fatty acid (VFA) accumulation was not augmented as temperature increased. Among the four temperatures tested, 37°C was the point with the highest VFA accumulation after 72h fermentation. VFA accumulation decreased markedly at 55°C compared to 37°C. Mechanism investigation revealed that among all the temperatures tested, 37°C was the temperature at which consumptions of WAS protein and carbohydrate, activities of key enzymes related to VFA formation and ratio of Bacteria to Archaea all reached the maximum. Due to activities of related microorganisms inhibited by higher temperature (55°C), VFA accumulation decreased at 55°C.
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Microbial community dynamics in batch high-solid anaerobic digestion of food waste under mesophilic conditions.
J. Microbiol. Biotechnol.
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Microbial community shifts, associated with performance data, were investigated in an anaerobic batch digester treating high-solid food waste under mesophilic conditions using a combination of molecular techniques and chemical analysis methods. The batch process was successfully operated with an organic removal efficiency of 44.5% associated with biogas yield of 0.82 L/g VSremoval. Microbial community structures were examined by denaturing gel gradient electrophoresis (DGGE). Clostridium and Symbiobacterium organisms were suggested to be mainly responsible for the organic matter catabolism in hydrolysis and acidogenesis reactions. The dynamics of archaeal and methanogenic population were monitored using real-time PCR targeting 16S rRNA genes. Methanosarcina was the predominant methanogen suggesting that the methanogenesis took place mainly via aceticlastic pathway. Hydrogenotrophic methanogens were also supported in high-solid anaerobic digestion of food waste through syntrophism with syntrophic bacterium. Microbial community shifts showed good agreement with the performance parameters in anaerobic digestion implying the possibility of diagnosing a high-solid anaerobic digestion process by monitoring microbial community shifts. On the other hand, the batch results could be relevant to the start-up period of a continuous system and could also provide useful information to set up a continuous operation.
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