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1.
The pretreatment of waste-activated sludge (WAS) by electron beam irradiation was studied in order to improve anaerobic sludge
digestion. The irradiation dose of the electron beam was varied from 0.5 to 10 kGy. Batch and continuous-flow stirred tank
reactors (CFSTRs) were operated to evaluate the effect of the electron beam pretreatment on anaerobic sludge digestion. Approximately
30–52% of the total chemical oxygen demand (COD) content of the WAS was solubilized within 24 h after electron beam irradiation.
A large quantity of soluble COD, protein, and carbohydrates leached out from cell ruptures caused by the electron beam irradiation.
Volatile fatty acids production from the irradiated sludge was approx 90% higher than that of the unirradiated sludge. The
degradation of irradiated sewage sludge was described by two distinct first-order decay rates (k
1 and k
2). Most initial decay reaction accelerated within 10 d, with an average k
1 of 0.06/d for sewage sludge irradiated at all dosages. The mean values for the long-term batch first-order decay coefficient
(k
2) were 0.025/d for irradiated sewage sludge and 0.007/d for unirradiated sludge. Volatile solids removal efficiency of the
control reactor fed with unirradiated sewage sludge at a hydraulic retention time (HRT) of 20 d was almost the same as that
of the CFSTRs fed with irradiated sludge at an HRT of 10 d. Therefore, disintegration of sewage sludge cells using electron
beam pretreatment could reduce the reactor solid retention time by half. 相似文献
2.
《中国化学快报》2023,34(6):107890
The massive use of polyhexamethylene guanidine (PHMG), as a typical bactericidal agent, raised environmental concerns to the public. This work comprehensively revealed the hormesis effects of PHMG occurred in waste activated sludge (WAS) on the generation of volatile fatty acids (VFAs) during anaerobic fermentation. The low level of PHMG (100 mg/g TSS) significantly promoted the VFAs generation (1283 mg COD/L, compared with 337 mg COD/L in the control) via synchronously facilitating the solubilization, hydrolysis, and acidification steps but inhibiting methanogenesis. Metagenomic analysis showed that the functional anaerobe (i.e., Bacteroides, Macellibacteroide and Parabacteroide) and corresponding genetic expressions responsible for extracellular hydrolysis (i.e., clpP), membrane transport (i.e., ffh and gspF), intracellular substrates metabolism (i.e., ald and paaF) and VFAs biosynthesis (i.e., ACACA and FASN) were enhanced in the optimal presence of PHMG. Moreover, the anaerobic species could respond and adapt to low PHMG stimuli via quorum sensing (i.e., cqsA, rpfC and rpfG), and thus maintain the high microbial metabolic activities. However, they were unable to tolerate the toxicity of excessive PHMG, resulting in the extremely low VFAs production. This work enlightened the effects of emerging pollutants on WAS fermentation at the genetic levels, and provided guidance on the WAS treatment and resource recovery. 相似文献
3.
Jiehong Cheng Yuehong Ji Feng Kong Xian Chen 《Applied biochemistry and biotechnology》2013,171(7):1701-1714
One-stage autothermal thermophilic aerobic digestion (ATAD) is effective for the reduction of volatile solids (VSs) and pathogen in sewage sludges. A novel process of combining mesophilic (<35 °C) anaerobic digestion with a thermophilic (55 °C) aerobic digestion process (AN/TAD) occurred in a one-stage digester, which was designed for aeration energy savings. The efficiency of sludge degradation and variation of sludge properties by batch experiments were evaluated for the AN/TAD digester with an effective volume of 23 L for 30 days compared with conventional thermophilic aerobic digestion (TAD). The AN/TAD system can efficiently achieve sludge stabilization on the 16th day with a VS removal rate of 38.1 %. The AN/TAD system was operated at lower ORP values in a digestion period with higher contents of total organic compounds, volatile fatty acids, protein, and polysaccharide in the soluble phase than those of the TAD system, which can rapidly decreased and had low values in the late period of digestion for the AN/TAD system. In the AN/TAD system, intracellular substances had lysis because of initial hydrolytic acidification. 相似文献
4.
《中国化学快报》2023,34(4):107661
The distinct influences of cephalosporins (CEPs, i.e., cefamandole nafate and cefpirome sulfate) affiliated to different generations on the volatile fatty acids (VFAs) production and antibiotic resistance genes (ARGs) fates during waste activated sludge (WAS) fermentation were unveiled. The presence of CEPs mainly exhibited negative effects on the total VFAs production (5%–15% reduction), especially the cefamandole nafate, which is quite different to previous understanding. Further investigation revealed that the CEPs contributed to the solubilization and hydrolysis but inhibited the acidification process by affecting the functional microbial populations (i.e., Tissierella) and general microbial metabolic activities (i.e., pyruvate metabolism and VFAs biosynthesis). In addition, CEPs (especially the cefpirome sulfate) caused the propagation of ARGs (i.e., blaTEM, tetX and mexF) during WAS fermentation. CEPs enhanced the cell membrane permeability to promote the antibiotics mechanism of efflux pump and the horizontal transfer of ARGs. Also, the CEPs altered the regulatory systems (i.e., two component system) and microbial populations associated with ARGs, resulting in the proliferation of specific ARGs. Overall, the dissimilarity of different CEPs impacts on the WAS fermentation for VFAs production and ARGs variations enlightened the diverse environmental behaviors of anthropogenic pollutants and evoked the caution of ecological risks. 相似文献
5.
Kim Jung K. Cho Jae H. Lee Jung S. Hahm Kyung S. Park Don H. Kim Si W. 《Applied biochemistry and biotechnology》2002,98(1-9):753-764
We developed a process for production of methane at a pilot scale. This process consists of three stages. The first stage
is a semianaerobic hydrolysis/acidogenic step in which organic wastes are converted to various sugars, amino acids, and volatile
fatty acids (VFAs). Operation temperature and pH were 45°C, and 5.0–5.5, respectively. Hydraulic retention time (HRT) was
2 d. To remove the putrid odor and to enhance the hydrolysis of organic wastes, a mixture of bacteria isolated from landfill
soil was inoculated into the reactor. Total chemical oxygen demand (tCOD) and biological oxygen demand (BOD) were 36,000 mg/L
and 40,000 mg/L, respectively. The second stage was an anaerobic acidogenic process, which can produce large amount of VFAs
including acetate, propionate, butyrate, valerate, and caproate. Operation temperature and pH were 35°C, and 5.0–5.5, respectively.
HRT was 2 d. The third stage was a strictly anaerobic methane fermentation step producing methane and carbon dioxide from
VFAs. The working volume of upflow anaerobic sludge blanket (UASB) type reactor was 1200 L, and operation temperature and
pH were 41°C, and 7.7–7.9, respectively. HRT was 12 d. Seventy two percent of methane at maximum was generated and the yield
was 0.45–0.50 m3/kg VS of food wastes. Through the process, 88% of tCOD and 95% of BOD were removed. The wastewater was treated with the biological
aerobic and anaerobic filters immobilized with heterotrophic and autotrophic nitrifying and denitrifying bacteria. Ninety
percent of total nitrogen (T-N) was removed by this treatment. The residual T-N and total phosphorous (T-P) were removed by
the algal periphyton treatment system. The final concentrations of nitrogen and phosphorous in the drain water were 53 and
7 mg/L, respectively. 相似文献
6.
The effect of pH on the separation of manure nutrients with reverse osmosis membranes 总被引:2,自引:0,他引:2
This paper reports on the effect of pH on the retention of dry matter (DM), total ammonia-nitrogen (TAN), potassium, phosphorus and volatile fatty acids (VFAs) during the filtration of pretreated swine manure by three highly selective reverse osmosis (RO) membranes. The manure was pretreated using various combinations of biological and physical technologies, namely anaerobic digestion (AD), vacuum filtration through diatomaceous earth (DE), nanofiltration (NF), and a first stage RO filtration. The objective was to establish the level of acidification required to optimize permeate quality while minimizing chemical addition. 相似文献
7.
In the present work, the Anaerobic Digestion Model No. 1 (ADM1) for computer simulation of anaerobic processes was extended to the processes of sulfate reduction. The upgrade maintained the structure of ADM1 and included additional blocks describing sulfate-reducing processes (multiple reaction stoichiometry, microbial growth kinetics, conventional material balances for ideally mixed reactor, liquid-gas interactions, and liquid-phase equilibrium chemistry). The extended model was applied to describe a longterm experiment on sulfate reduction in a volatile fatty acid-fed upflow anaerobic sludge bed reactor and was generally able to predict the outcome of competition among acetogenic bacteria, methanogenic archaea, and sulfate- reducing bacteria for these substrates. The computer simulations also showed that when the upward liquid velocity in the reactor exceeds 1 m/d, the structure of the sludge becomes essential owing to bacterial detachment. 相似文献
8.
9.
Wangliang Li Guangyi Zhang Zhikai Zhang Guangwen Xu 《Applied biochemistry and biotechnology》2014,172(5):2670-2681
The digestibility of lignocellulosic biomass is limited by its high content of refractory components. The objective of this study is to investigate hydrothermal pretreatment and its effects on anaerobic digestion of sorted organic waste with submerged fermentation. Hydrothermal pretreatment (HT) was performed prior to anaerobic digestion, and three agents were examined for the HT: hot compressed water, alkaline solution, and acidic solution. The concentrations of glucose and xylose were the highest in the sample pretreated in acidic solution. Compared with that of the untreated sample, the biogas yields from digesting the samples pretreated in alkaline solution, acidic solution, and hot water increased by 364, 107, and 79 %, respectively. The decrease of chemical oxygen demand (COD) in liquid phase followed the same order as for the biogas yield. The initial ammonia content of the treated samples followed the order sample treated in acidic solution > sample treated in alkaline solution > sample treated in hot water. The concentrations of volatile fatty acids (VFAs) were low, indicating that the anaerobic digestion process was running at continuously stable conditions. 相似文献
10.
The performances of rice straw (RS) degradation and biogas production were examined at different pretreatment temperatures from 90℃ to 130℃ to improve biogas fermentation efficiency and net energy production in whole slurry. Test at 100℃ pretreatment, which achieved 12.8% higher net energy production from RS than that observed in the control, could be considered as the optimal choice. 相似文献
11.
Two types of sewage sludge anaerobic digestion were carried out: mesophilic and thermophilic. Metal speciation analysis was
performed revealing some changes in the chemical form of the metals during the stabilization process of sludge. After both
methane fermentation processes, a comparable level of organic matter distribution was obtained (≈ 40 %). The amount of produced
methane during thermophilic and mesophilic digestion was 560 mL of CH4 and 580 mL of CH4 from 1 g of removed organic matter, respectively. Low concentration of heavy metal ions in the liquid phase of sludge was
observed. Metal ions precipitated and remained bound throughout the stabilization process. No accumulation of heavy metals
in the mobile fractions of sludge (exchangeable and carbonate) was observed for either digestion process. The highest increase
of zinc, copper, nickel, cadmium, and chromium concentration was observed in the organic-sulfide fraction, whereas the highest
increase of lead was found in the residual fraction. 相似文献
12.
Kinetics of biomethanation of solid tannery waste and the concept of interactive metabolic control 总被引:1,自引:0,他引:1
Anaerobic digestion of calf skin collagenous waste was optimized for a batch process based on accelerated maximal methane
yield per gram of input volatile solid. A kinetic analysis with respect to changes in the levels of volatile solid, collagen,
amino sugars, amino acids, hydroxyproline, ammonium ions, and volatile fatty acid were followed for a period of 80 d. Distinct
metabolic phases included an initial high rate collagenolysis for 4 d, with 50% degradation and was followed by an acidogenic
phase between 4–12 d with voltatile fatty acids levels increasing to 215 mmol/L. Subsequently methanogenesis ensued and was
maximal between 12–24 d when volatile fatty acids attained steady state levels. During the period of 80 d, the overall decrease
in volatile solid level was 65%, whereas the collagen level declined by 85% with 0.45 L of methane yield/g of volatile solid
degraded. Based on the levels of various metabolites detected, the concept of interactive metabolic control earlier proposed
has been validated. 相似文献
13.
The analysis of volatile siloxanes in waste activated sludge 总被引:1,自引:0,他引:1
The increasing presence of siloxanes in waste activated sludge (WAS) considerably hampers the energy use of the biogas obtained during the anaerobic digestion of the sludge when concentrations exceed critical limits. To prevent the occurrence of unacceptable operating conditions, it is hence necessary to have a reliable analysis method for determining the siloxane content of the sludge. This paper describes and validates such a method, consisting of the extraction of the siloxanes using n-hexane and a subsequent analysis of the extract using GC-FID. The validation procedure confirms the excellent recovery and repeatability of the proposed method. 相似文献
14.
Fan Luo Bin Dong Lingling Dai Qunbiao He Xiaohu Dai 《Journal of Thermal Analysis and Calorimetry》2013,114(1):307-312
The moisture distribution and thermal drying characteristics of dewatered sludge in anaerobic digestion were investigated by a thermo-gravimetric analyzer (TG) and the isothermal kinetic characteristics during the drying were developed by an unreacted core model. The TG results showed that the bound water was partly converted to the free water with the invariant interstitial water and surface water after anaerobic digestion, which enhanced the drying performance of sludge. The time required for the complete drying of digestate was less than that of the raw sludge in the same temperature. The moisture evaporative efficiency of digestate was related to the vapor diffusion rate of the outer surface, and the drying efficiency of digested sludge cannot be enhanced by increased temperatures. 相似文献
15.
Chua Hong Li Xiang Z. Yu Peter H. F. Tam Chung Y. Huang Yu L. Yang Shang T. 《Applied biochemistry and biotechnology》2000,84(1-9):469-478
Biological processes have become popular for odor treatment. In this study, a novel fibrous bed bioreactor was applied for
treatment of odorous gas. The column reactor was packed with spirally wound fibrous sheet material on which a consortium of
microorganisms selected from activated sludge was immobilized. The first stage of this work comprised a preliminary study
that aimed at investigating the feasibility of the fibrous bed bioreactor for treatment of odorous volatile fatty acids (VFAs).
In this stage, the performance of a fibrous bed bioreactor at increasing mass loadings ranging from 9.7 to 104.2 g/(m3·h) was studied. VFA removal efficiencies above 90% were achieved at mass loadings up to 50.3 g/(m3·h). At a mass loading of 104.2 g/(m3·h), removal efficiency was found to be 87.7%. In the second stage of the work, the process was scaled up with design and
operational considerations, namely, packing medium, process condition, and configuration selections. A trickling biofilter
with synthetic fibrous packing medium was selected. It was operated under countercurrent flow of gas and liquid streams. The
effects of inlet concentration and empty bed retention time on bioreactor performance were studied. The bioreactor was effective
in treating odorous VFAs at mass loadings up to 32g/(m3·h), at which VFAs started to accumulate in the recirculation liquid, indicating that the biofilm was unable to degradeall
the VFAs introduced. Although VFAs accumulated in the liquid phase, the removal efficency remained above 99%, implying that
the biochemical reaction rate, rather than gas-to-liquid mass transfer rate, was the limiting factor of this process. The
bioreactor was stable for longterm operation; no clogging and degeneration of the packing medium was observed during the 4-mo
operation. 相似文献
16.
Pessiot J Nouaille R Jobard M Singhania RR Bournilhas A Christophe G Fontanille P Peyret P Fonty G Larroche C 《Applied biochemistry and biotechnology》2012,167(6):1728-1743
This work aimed at setting up a fully instrumented, laboratory-scale bioreactor enabling anaerobic valorization of solid substrates through hydrogen and/or volatile fatty acid (VFA) production using mixed microbial populations (consortia). The substrate used was made of meat-based wastes, especially from slaughterhouses, which are becoming available in large amounts as a consequence of the growing constraints for waste disposal from meat industry. A reconstituted microbial mesophilic consortium without Archaebacteria (methanogens), named PBr, was cultivated in a 5-L anaerobic bioreactor on slaughterhouse wastes. The experiments were carried out with sequential fed-batch operations, including liquid medium removal from the bioreactor and addition of fresh substrate. VFAs and nitrogen were the main metabolites observed, while hydrogen accumulation was very low and no methane production was evidenced. After 1,300 h of culture, yields obtained for VFAs reached 0.38 g/g dry matter. Strain composition of the microbial consortium was also characterized using molecular tools (temporal temperature gradient gel electrophoresis and gene sequencing). 相似文献
17.
18.
Regina J. Patinvoh Elisabeth Feuk-Lagerstedt Magnus Lundin Ilona Sárvári Horváth Mohammad J. Taherzadeh 《Applied biochemistry and biotechnology》2016,180(7):1401-1415
Chicken feathers are available in large quantities around the world causing environmental challenges. The feathers are composed of keratin that is a recalcitrant protein and is hard to degrade. In this work, chicken feathers were aerobically pretreated for 2–8 days at total solid concentrations of 5, 10, and 20 % by Bacillus sp. C4, a bacterium that produces both α- and β-keratinases. Then, the liquid fraction (feather hydrolysate) as well as the total broth (liquid and solid fraction of pretreated feathers) was used as substrates for biogas production using anaerobic sludge or bacteria granules as inoculum. The biological pretreatment of feather waste was productive; about 75 % of feather was converted to soluble crude protein after 8 days of degradation at initial feather concentration of 5 %. Bacteria granules performed better during anaerobic digestion of untreated feathers, resulting in approximately two times more methane yield (i.e., 199 mlCH4/gVS compared to 105 mlCH4/gVS when sludge was used). Pretreatment improved methane yield by 292 and 105 % when sludge and granules were used on the hydrolysate. Bacteria granules worked effectively on the total broth, yielded 445 mlCH4/gVS methane, which is 124 % more than that obtained with the same type of inoculum from untreated feather. 相似文献
19.
20.
The production of short-chained volatile fatty acids (VFAs) by the anaerobic bacterial digestion of sewage (wastewater) affords an excellent opportunity to alternative greener viable bio-energy fuels (i.e., microbial fuel cell). VFAs in wastewater (sewage) samples are commonly quantified through direct injection (DI) into a gas chromatograph with a flame ionization detector (GC-FID). In this study, the reliability of VFA analysis by the DI-GC method has been examined against a thermal desorption (TD-GC) method. The results indicate that the VFA concentrations determined from an aliquot from each wastewater sample by the DI-GC method were generally underestimated, e.g., reductions of 7% (acetic acid) to 93.4% (hexanoic acid) relative to the TD-GC method. The observed differences between the two methods suggest the possibly important role of the matrix effect to give rise to the negative biases in DI-GC analysis. To further explore this possibility, an ancillary experiment was performed to examine bias patterns of three DI-GC approaches. For instance, the results of the standard addition (SA) method confirm the definite role of matrix effect when analyzing wastewater samples by DI-GC. More importantly, their biases tend to increase systematically with increasing molecular weight and decreasing VFA concentrations. As such, the use of DI-GC method, if applied for the analysis of samples with a complicated matrix, needs a thorough validation to improve the reliability in data acquisition. 相似文献