The anaerobic acid production experiments were conducted with the pretreated kitchen waste under pH adjustment.The results showed that pH 8 was considered to be the most suitable condition for acid production,especial...The anaerobic acid production experiments were conducted with the pretreated kitchen waste under pH adjustment.The results showed that pH 8 was considered to be the most suitable condition for acid production,especially for the formation of acetic acid and propionic acid.The average value of total volatile fatty acid at pH 8 was 8814 mg COD/L,1.5 times of that under blank condition.The average yield of acetic acid and propionic acid was 3302 mg COD/L and 2891 mg COD/L,respectively.The activities of key functional enzymes such as phosphotransacetylase,acetokinase,oxaloacetate transcarboxylase and succinylcoA transferase were all enhanced.To further explore the regulatory mechanisms within the system,the distribution of microorganisms at different levels in the fermentation system was obtained by microbial sequencing,results indicating that the relative abundances of Clostridiales,Bacteroidales,Chloroflexi,Clostridium,Bacteroidetes and Propionibacteriales,which were great contributors for the hydrolysis and acidification,increased rapidly at pH 8 compared with the blank group.Besides,the proportion of genes encoding key enzymes was generally increased,which further verified the mechanism of hydrolytic acidification and acetic acid production of organic matter under pH regulation.展开更多
Recently,using anaerobic hydrolysis of waste activated sludge (WAS) to recover volatile fatty acids (VFAs) as carbon sources for denitrification has been widely studied,and the key is to solve the problem of improving...Recently,using anaerobic hydrolysis of waste activated sludge (WAS) to recover volatile fatty acids (VFAs) as carbon sources for denitrification has been widely studied,and the key is to solve the problem of improving the solubility and bioavailability of WAS organic matter.Considering the energy consumption and chemical cost,this paper used low-dose nanozero-valent iron (NZVI) coupled with low-intensity ultrasonication (US) to pretreat WAS,and explored the effects of different treatment sequences on the fragmentation of WAS flocs particles,the dissolution of organic matter,and the subsequent biofermentation conversion process.The results showed low-dose NZVI synchronized with low-intensity US (NZVIUS)worked best for WAS anaerobic fermentation.Compared with 2062 mg/L in control group,soluble chemical oxygen demand (SCOD) after NZVIUS treatment reached up to 2786 mg/L during the fermentation cycle,and the initial release rate of SCOD increased by 69%.The VFAs production was elevated from 1522 to 1940 mg COD/L.NZVIUS pretreatment promoted the solubilization of attached organic matter,manifested by the fragmentation of WAS flocs and cell lysis.At the same time,proteins and carbohydrates in the extracellular polymeric substances (EPS) had different types of migration and transformation,and transfer of EPS can contribute 35.6% to SCOD.Moreover,adding NZVI promoted PO_(4)^(3-)-P recovery in the fermentation supernatant by 22.3% more than in day 4 control.This study demonstrated that the NZVIUS pretreatment method can effectively improve the production of VFAs by WAS anaerobic fermentation,meeting the practical needs of wastewater plants.展开更多
Anaerobic fermentation is an efficient method to extract phosphorus from excess sludge,thereby facilitating its recovery and mitigating the phosphorus resource shortage.However,the prevalent metal-bound phosphorus spe...Anaerobic fermentation is an efficient method to extract phosphorus from excess sludge,thereby facilitating its recovery and mitigating the phosphorus resource shortage.However,the prevalent metal-bound phosphorus species within sludge was difficult to release into the fermentation liquor.To address this,this study evaluated the enhanced phosphorus release performance from sludge containing iron-phosphorus compounds(Fe-P)via co-fermenting it with agriculture wastes.Specifically,protein-rich feather(Feather Group)and polysaccharide-rich tea residue(Tea Group)was respectively dosed into batch-scale fermentation jar.Results showed that the Feather Group exhibited significantly higher levels of released soluble phosphorus(2.1 folds)and volatile fatty acids(41.4 folds)compared to the Control Group,with concentrations reaching up to 280 mg/L and 9366 mg chemical oxygen demand/L,respectively.The activities ofα-glucosidase,neutral protease and acetate kinase in the Feather group were increased by 11.1%,92.3%and 37.6%,respectively,compared with the Control group.Methanogen abundance decreased while hydrolytic acid-producing bacteria and iron-reducing bacteria increased significantly after supplying agricultural wastes.Metagenomic analysis demonstrated a significant increase in genes related to acetic acid synthesis.Mechanism elucidation suggested that increased iron-reducing bacteria abundance promoted Fe3+reduction into Fe2+,thus enhancing phosphorus release from Fe-P compounds.This work may provide valuable information for developing effective strategy to extract phosphorus resource from complex environmental wastes.展开更多
In the suspended sludge system, when pH and temperature were suitable and carbon source was not limited, the denitrification and C-uptake rate followed a zero-order reaction. Mixed VFA C-source had higher denitrificat...In the suspended sludge system, when pH and temperature were suitable and carbon source was not limited, the denitrification and C-uptake rate followed a zero-order reaction. Mixed VFA C-source had higher denitrification rate than single VFA C-source consisting of them. When VFA were used as carbon source, consumed carbon quantity for denitrification was closed to 1. 07 mg VFA-C/mg NO-N. About 20% of the applied C/N was used for assimilative purposes. As rising up influent C/N by increasing the C load ,the sludge yield YN increased. The part of carbon consumption increased and the effluent oxidized nitrogen decreased. At pH 7. 5, 25℃ and sludge yield 0.72 mg VSS/mg NO-N, the calculated influent VFA-C /NO critical value was 1. 43 for complete denitrification.展开更多
This study investigated the impacts of the degree of unsaturation （unsaturity） of long-chain fatty acids on volatile fatty acid （VFA） profiles of rumen fermentation in vitro. Six types of long-chain fatty acids, i...This study investigated the impacts of the degree of unsaturation （unsaturity） of long-chain fatty acids on volatile fatty acid （VFA） profiles of rumen fermentation in vitro. Six types of long-chain fatty acids, including stearic acid （C18：0, control group）, oleic acid （C18：1, n-9）, linoleic acid （C18：2, n-6）, a-linolenic acid （C18：3, n-3）, arachidonic acid （C20：4, n-6） and eicosapentaenoic acid （C20：5, n-3）, were tested. Rumen fluid from three goats fitted with ruminal fistulae was used as inoculum and the inclusion rate of long-chain fatty acid was at 3% （w/w） of substrate. Samples were taken for VFA analysis at 0, 3, 6, 9, 12, 18 and 24 h of incubation, respectively. The analysis showed that there were significant differences in the total VFA among treatments, sampling time points, and treatment×time point interactions （P〈0.01）. a-Linolenic acid had the highest total VFA （P〈0.01） among different long-chain fatty acids tested. The molar proportion of acetate in total VFA significantly differed among treatments （P〈0.01） and sampling time points （P〈0.01）, but not treatment×time point interactions （P〉0.05）. In contrast, the molar proportion of propionate did not differ among treatments during the whole incubation （P〉0.05）. However, for butyrate molar proportions, significant differences were found not only among sampling time points but also among treatments and treatment×time point interactions （P〈0.01）, with eicosapentaenoic acid having the highest value （P〈0.01）. Additionally, no statistically significant differences were found in the acetate to propionate ratios among treatments groups （P〉0.05）, even the treatments stearic acid and a-linolenic acid were numerically higher than the others. The inclusion of 3% long-chain unsaturated fatty acids differing in the degree of unsaturation brought out a significant quadratic regression relation between the total VFA concentration and the double bond number of fatty acid. In conclusion, the a-linolenic acid with 3 double bonds appeared better for improving rumen microbial fermentation and the total VFA concentration.展开更多
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 activa...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.,clp P),membrane transport(i.e.,ffh and gsp F),intracellular substrates metabolism(i.e.,ald and paa F)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.,cqs A,rpf C and rpf G),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.展开更多
Effects of sludge age on volatile fatty acids (VFAs) production and Phosphorus (P) release during anaerobic acidification of waste activated sludge (WAS) were investigated.Sequencing batch reactors (SBR) fed with simu...Effects of sludge age on volatile fatty acids (VFAs) production and Phosphorus (P) release during anaerobic acidification of waste activated sludge (WAS) were investigated.Sequencing batch reactors (SBR) fed with simulating domestic sewage were applied to produce WAS of different sludge ages,and batch tests were used for anaerobic acidification.The maximum dissolved total organic carbon,release of PO_(4)^(3+)-P,and accumulation of acetate (C2),propionate (C3),butyrate (C4),and valerate (C5) decreased by 56.2%,55.8%,52.6%,43.7%,82.4%and 84.8%,respectively,as the sludge age of WAS increased from 5 to 40 days.Limited degradation of protein played a dominating role in decreasing DTOC and VFAs production.Moreover,the increase in molecular weight of organics and organic nitrogen content in the supernatant after acidification suggested that the refractory protein in WAS increased as sludge age extended.Although the production of C2,C3,C4,and C5 from WAS decreased as the sludge age increased,the proportions of C2 and C3 in VFAs increased,which might be due to the declined production of C5 from protein and the faded genus Dechlorobacter.Keeping sludge age of WAS at a relatively low level (<10 days) is more appropriate for anaerobic acidification of WAS as internal carbon sources and P resource.展开更多
Volatile fatty acids(VFAs), which are largely generated during the anaerobic acidification process, are considered to be reliable indicators of the stable process operation. However,the common methods for monitoring V...Volatile fatty acids(VFAs), which are largely generated during the anaerobic acidification process, are considered to be reliable indicators of the stable process operation. However,the common methods for monitoring VFAs are offline, and they are typically manual requiring time-consuming, costly and complex instruments. This study aims to develop a novel online analyzer for automatic measuring VFAs, which was based on the 5-p H point titration, embedded with a proportional-integral-derivative(PID) feedback control system. The results show that it can achieve accurate and rapid monitoring of VFAs ranging between 0-400 mg/L(<9 min/sample) but simultaneously faces the problems of overtitration and interference of complex characteristics of wastewater. In order to improve its accuracy and stability, the effects of three general coefficients(K_(I),K_(P), and K_(D)) of PID on the titration were investigated, and the optimal values of K_(I), K_(P), and K_(D)were found to be 1.5, 1.0, and-1.0~0.5,respectively. Besides, the initial titration speed was set at 0.06 m L/min, equal to the minimum speed of the peristaltic pump, and the dichotomy approach was integrated into the PID feedback controller. Owing to the above improvements, the relative mean deviation and standard deviation of measuring VFAs in both synthetic and real wastewaters were mostly lower than 5.0% and 5.0 mg/L, proving the online analyzer is rapid, accurate and reliable.展开更多
This study investigated a combined low-thermal and CaO_(2)pretreatment to enhance the volatile fatty acid(VFA)production from waste activated sludge(WAS).The fermentative product was added to a sequencing batch reacto...This study investigated a combined low-thermal and CaO_(2)pretreatment to enhance the volatile fatty acid(VFA)production from waste activated sludge(WAS).The fermentative product was added to a sequencing batch reactor(SBR)as an external carbon source to enhance nitrogen removal.The results showed that the combined pretreatment improved WAS solubilization,releasing more biodegradable substrates,such as proteins and polysaccharides,from TB-EPS to LB-EPS and S-EPS.The maximum VFA production of 3529±188 mg COD/L was obtained in the combined pretreatment(0.2 g CaO_(2)/g VS+70℃for 60 min),which was 2.1 and 1.4-fold of that obtained from the sole low-thermal pretreatment and the control test,respectively.Consequently,when the fermentative liquid was added as an external denitrification carbon source,the effluent total nitrogen decreased to Class A of the discharge standard for pollutants in rural wastewater treatment plants in most areas of China.展开更多
Mesophilic and thermophilic anaerobic fermentation performance of waste activated sludge(WAS)pretreated by enzymes catalysis associated with microbial community shifts were investigated.WAS disintegration was boosted ...Mesophilic and thermophilic anaerobic fermentation performance of waste activated sludge(WAS)pretreated by enzymes catalysis associated with microbial community shifts were investigated.WAS disintegration was boosted considerably by enzymolysis with 8750 mg/L of soluble COD release within 180 min.Mesophilic anaerobic fermentation(MAF)produced nearly equal VFA accumulation with over 3200 mg COD/L compared with that of thermophilic fermentation(TAF).Bacterial community consortia showed great shifting differences in dynamics of main T⁃RFs between MAF and TAF.Moreover,MAF was conducive to form intermediate bacterial community evenness compared to TAF,which preserved a robust function of VFA production.The enzymes catalysis prompted bio⁃energy(electricity)recovery potential of WAS organics via anaerobic fermentation(MAF/TAF)with evaluating electricity conversion efficiency of 0.75-0.82 kW·h/kg VSS(3.9 times higher than control test).Finally,this study proposed some novel thinking on future WAS treatment/management towards energy recovery coupled with energy⁃sufficient wastewater treatment by co⁃locating WAS anaerobic fermentation,MFC plant with wastewater treatment plant(s).展开更多
This study investigated the degradation and production of volatile fatty acids（VFAs）in the acidogenic phase reactor of a two-phase anaerobic system.20 mmol/L bromoethanesulfonic acid（BESA）was used to inhibit acido...This study investigated the degradation and production of volatile fatty acids（VFAs）in the acidogenic phase reactor of a two-phase anaerobic system.20 mmol/L bromoethanesulfonic acid（BESA）was used to inhibit acidogenic methanogens（which were present in the acidogenic phase reactor）from degrading VFAs.The impact of undissociated volatile fatty acids（un VFAs）on＂net＂VFAs production in the acidogenic phase reactor was then evaluated,with the exclusion of concurrent VFAs degradation.＂Net＂VFAs production from glucose degradation was partially inhibited at high un VFAs concentrations,with 59%,37% and 60% reduction in production rates at 2190 mg chemical oxygen demand（COD）/L undissociated acetic acid（un HAc）,2130 mg COD/L undissociated propionic acid（un HPr）and 2280 mg COD/L undissociated n-butyric acid（un HBu）,respectively.The profile of VFAs produced further indicated that while an un VFA can primarily affect its own formation,there were also un VFAs that affected the formation of other VFAs.展开更多
Background:This study aimed to develop a combined model to quantify the net absorption of volatile fatty acids(VFA)in the large intestine(LI)of pigs.Methods:Fifteen female growing pigs(Duroc×Large White×Land...Background:This study aimed to develop a combined model to quantify the net absorption of volatile fatty acids(VFA)in the large intestine(LI)of pigs.Methods:Fifteen female growing pigs(Duroc×Large White×Landrace)were ranked by body weight(30±2.1 kg)on day 0 and assigned to one of three treatments,namely the basal diet containing different crude fiber(CF)levels(LCF:3.0%CF,MCF:4.5%CF,and HCF:6.0%CF).The pigs were implanted with the terminal ileum fistula and the cannulation of the ileal mesenteric vein(IMV),portal vein(PV),and left femoral artery(LFA)from days 6 to 7.[13 C]-Labeled VFA and P-aminohippuric acid were constantly perfused into the terminal ileum fistula and the cannulation of the IMV(day 15),respectively.Blood samples were collected from the PV and the LFA during perfusion(5 h),and LI samples were collected.Results:The net flux of[12 C]-acetic acid in the PV was greater for LCF versus MCF(p=0.045),but no difference was observed in the net flux of[12 C]-propionic acid(p=0.505)and[12 C]-butyric acid(p=0.35)in the PV among treatments.The deposition of[12 C]-acetic acid in the LI was greater for LCF versus MCF(p=0.014),whereas the deposition of[12 C]-propionic acid(p=0.007)and[12 C]-butyric acid(p=0.037)in the LI was greater for LCF versus HCF.Conclusions:In conclusion,this pig model was found conducive to study the net absorption of VFAs in the LI,and LCF had more net absorption of VFAs in the LI than MCF and HCF.展开更多
Background Isoacids are the product of branched-chain amino acid fermentation and are naturally producedin the hindgut by microbial fermentation. In ruminants, supplementation of isoacids as a feed additive improvesfi...Background Isoacids are the product of branched-chain amino acid fermentation and are naturally producedin the hindgut by microbial fermentation. In ruminants, supplementation of isoacids as a feed additive improvesfiber utilization, with a positive impact on animal productivity. However, information on how isoacids impact nutrientdigestibility in swine is limited. The objective of this experiment was to determine the optimal inclusion levelof an isoacid blend product based on apparent ileal digestibility (AID) and apparent total tract digestibility (ATTD)of nutrients and fermentation products in the ileal digesta and feces of growing pigs fed a corn-soybean meal diet.Methods Twelve ileal cannulated pigs (20.9 ± 0.6 kg) were used in a 5-period crossover design with 6 diets and 2replicate pigs in each period. Dietary treatments consisted of increasing levels (0%, 0.5%, 0.75%, 1%, 1.25%, and 1.5%)of an isoacid blend (isobutyrate, isovalerate, and 2-methyl butyrate, 1:1:1) added to a corn-soybean meal basal diet.Each experimental period consisted of 14 d: 10 d for acclimatization to the diets, 2 d for fecal collection, and 2 dfor digesta collection.Results Isoacids supplementation quadratically improved the AID of hemicellulose (P < 0.05) and tended to improvethe AID of crude fiber (P < 0.1). The AID of most indispensable amino acids (except Met + Cys, Trp, and Val) as wellas the ATTD of crude protein, gross energy, neutral detergent fiber, and hemicellulose improved or tended to improvelinear or quadratically (P < 0.05 or P < 0.1). In addition, the ATTD values of Arg, His, Ile, Leu, Met + Cys, Phe, Thr, and Valincreased quadratically (P < 0.05). Collectively, 1% of isoacids inclusion resulted in the greatest response. Furthermore,isoacids supplementation tended to increase (P = 0.071, quadratically) the concentration of ammonia and decreased(P < 0.05) the concentrations of acetic acid and total volatile fatty acids with a tendency to decrease (P = 0.064) isovalericacid in the ileal digesta. In fecal samples, the proportion of acetic acid decreased (P < 0.05) quadratically, whereas the proportionsof propionic, valeric, and caproic acids tended to increase linearly and/or quadratically (P < 0.1).Conclusions Isoacids supplementation at 1% in swine diets can improve nutrient digestibility, particularly aminoacids and fiber at the ileal level and ATTD of crude protein, gross energy, and hemicellulose.展开更多
The valorization of sewage sludge and food waste to produce energy and fertilizers is a well-stablished strategy within the circular economy.Despite the success of numerous laboratory-scale experiments in converting w...The valorization of sewage sludge and food waste to produce energy and fertilizers is a well-stablished strategy within the circular economy.Despite the success of numerous laboratory-scale experiments in converting waste into high-value products such as volatile fatty acids(VFAs),large-scale implementation remains limited due to various technical and environmental challenges.Here,we evaluate the environmental performance of a hypothetical large-scale VFAs biorefinery located in Galicia,Spain,which integrates fermentation and purification processes to obtain commercial-grade VFAs based on primary data from pilot plant operations.We identify potential environmental hotspots,assess the influence of different feedstocks,and perform sensitivity analyses on critical factors like transportation distances and pH control methods,using life cycle assessment.Our findings reveal that,on a per-product basis,food waste provides superior environmental performance compared to sewage sludge,which,conversely,performs better when assessed per mass of waste valorized.This suggests that higher process productivity from more suitable wastes leads to lower environmental impacts but must be balanced against increased energy and chemical consumption,as food waste processing requires more electricity for pretreatment and solid-liquid separation.Further analysis reveals that the main operational impacts are chemical-related,primarily due to the use of NaOH for pH adjustment.Additionally,facility location is critical,potentially accounting for up to 99%of operational impacts due to transportation.Overall,our analysis demonstrates that the proposed VFAs biorefinery has a carbon footprint comparable to other bio-based technologies.However,enhancements in VFAs purification processes are necessary to fully replace petrochemical production.These findings highlight the potential of waste valorization into VFAs as a sustainable alternative,emphasizing the importance of process optimization and strategic facility placement.展开更多
During the acidogenic fermentation converting waste activated sludge (WAS) into shortchain fatty acids (SCFA), hydrolysis of complex organic polymers is a limiting step and the transformation of harmful substances (su...During the acidogenic fermentation converting waste activated sludge (WAS) into shortchain fatty acids (SCFA), hydrolysis of complex organic polymers is a limiting step and the transformation of harmful substances (such as antibiotics) during acidogenic fermentation is unknown. In this study, potassium ferrate (KFeO) oxidation was used as a pretreatment strategy for WAS acidogenic fermentation to increase the hydrolysis of sludge and destruct the harmful antibiotics. Pretreatment with KFeOcan effectively increase the SCFA production during acidogenic fermentation and change the distribution of SCFA components.With the dosage of 0.2 g/g TS, the maximum SCFA yield was 4823 mg COD/L, which is 28.3times that of the control group;acetic acid accounts for more than 90% of the total SCFA. The higher dosage (0.5 g/g TS) can further increase the proportion of acetic acid, but inhibit the overall performance of SCFA production. Apart from the promotion of hydrolysis and acidogenesis, KFeOpretreatment can also simultaneously oxidizes and degrades part of the antibiotics in the sludge. When the dosage is 0.5 g/g TS, the degradation efficacy of antibiotics is the most significant, and the contents of ofloxacin, azithromycin, and tetracycline in the sludge are reduced by 69%, 42%, and 50%, respectively. In addition, KFeOpretreatment can also promote the release of antibiotics from sludge flocs, which is conducive to the simultaneous degradation of antibiotics in the subsequent biological treatment process.展开更多
The occurrence of the Maillard reaction and melanoidins formation during the hydrothermal treatment of food waste can reduce the yield of volatile fatty acids(VFA);however, few studies have investigated the adverse ef...The occurrence of the Maillard reaction and melanoidins formation during the hydrothermal treatment of food waste can reduce the yield of volatile fatty acids(VFA);however, few studies have investigated the adverse effects of the Maillard reaction. This study identified the impact of hydrothermal treatment parameters on hydrolysis and melanoidins formation and optimized the hydrothermal treatment conditions to enhance VFA production by minimizing the impact of the Maillard reaction. A response surface methodology was employed to optimize the hydrothermal treatment parameters and VFA production was evaluated. Results showed that temperature, reaction time, and pH were significant interacting factors with respect to hydrolysis and melanoidins formation while the C/N ratio and moisture content of food waste had little impact. The optimal conditions for hydrothermal treatment(temperature of 132 °C, reaction time of 27 min, and a pH of 5.6) enhanced VFA production by 22.1%. Under optimal hydrothermal treatment conditions, a higher initial C/N ratio further increased VFA production.展开更多
It is well known that acid-volatile sulfide (AVS) plays an important role in influencing the toxicity of divalent cationic metals within anoxic sediments. In studying sediment core samples collected from tidal flats w...It is well known that acid-volatile sulfide (AVS) plays an important role in influencing the toxicity of divalent cationic metals within anoxic sediments. In studying sediment core samples collected from tidal flats within the Jiaozhou Bay, China, we found that the AVS concentration gradually increases with depth and decreases from high tidal flat to low tidal flat areas. We evaluated the chemical activity and bioavailability of heavy metals in the tidal flat based on the molar ratio of simultaneously ex- tracted metals (SEM) and AVS. The value of SEM/AVS is generally less than 1 in this area except for the surface layer, which suggests that the heavy metals only have chemical activity in the surface layer. SEM is most highly concentrated at the boundary of the redox layer. SEM have similar depth distributions throughout the tidal flat. The aeration of low tidal flat sediment indicates that SEM gradually move to deeper sites via interstitial water.展开更多
A new sesquiterpenoid,named baimuxifuranic acid,has been isolated from the volatile oil of Aquilaria sinensis(Lour.)Gilg.belonging to the family Thymelaceae by silica gel column chromatography.Based on spectral analys...A new sesquiterpenoid,named baimuxifuranic acid,has been isolated from the volatile oil of Aquilaria sinensis(Lour.)Gilg.belonging to the family Thymelaceae by silica gel column chromatography.Based on spectral analysis its structure was deduced as(1).Reduction of baimuxifuranic acid by LiAlH_4 gave a展开更多
The bioavailability of five divalent cationic heavy metals （Pb, Cd, Cu, Zn and Ni） in 10 superficial sediment samples from Baihua Lake was assessed based on the molar ratio of simultaneously extracted metals （SEMs...The bioavailability of five divalent cationic heavy metals （Pb, Cd, Cu, Zn and Ni） in 10 superficial sediment samples from Baihua Lake was assessed based on the molar ratio of simultaneously extracted metals （SEMs） to acid volatile sulfide （AVS）. Atomic absorption spectrometry （AAS） and X-ray powder diffraction （XRD） were used to determine the heavy metal concentrations and examine the mineralogy of the crystalline phases, respectively. The AVS loadings in sediments from Baihua Lake ranged from 64.30 to 350.08 ~rnol/g （dry weight）. The corresponding SEM levels for the sampling sites varied from 1.770 to 14.660 vrnol/g. The molar ratio of SEMs to AVS ranged from 0.014 to 0.084 with a mean value of 0.034. The XRD analysis also confirmed the presence of some metal sulfides in sediments from Baihua Lake. The SEMs/AVS ratios for all sampling sites were significantly lower than 1.0, indicating that AVS in the sediments was sufficient to bind the five heavy metals; thus, these heavy metals are currently not significantly bioavailable to benthic organisms. Comparing the SEMs results to published guideline values for metal toxicity to benthic organisms in sediments, however, suggests that Zn and Ni pose a risk at some sampling locations in Baihua Lake.展开更多
This study aims at investigating the effects of ultrasonic and acid pretreatment on food waste( FW)disintegration and volatile fatty acid( VFA) production. Single-factor experiments are carried out to obtain optimal c...This study aims at investigating the effects of ultrasonic and acid pretreatment on food waste( FW)disintegration and volatile fatty acid( VFA) production. Single-factor experiments are carried out to obtain optimal conditions of individual ultrasonic and acid pretreatment,and response surface method( RSM) is applied to optimize the conditions of the combination of ultrasonic and acid( UA) pretreatment. Results show that the optimal acid,ultrasonic and UA pretreatments conditions are individual pH 2,individual ultrasonic energy density of 1. 0 W / mL and the combination of ultrasonic energy density1. 11 W / mL and pH 1. 43,respectively. Correspondingly,the maximum disintegration degrees( DD) of 46. 90%,57. 38% and68. 83%are obtained by acid,ultrasonic and UA pretreatments,respectively. After optimizing pretreatment conditions,batch experiments are operated to produce VFA from raw and pretreated FW under anaerobic fermentation process. Both the maximum VFA production( 976. 17 mg COD / gV S) and VFA / SCOD( 72. 89%) are obtained with ultrasonic pretreatment, followed by UA pretreatment, non-pretreatment and acid pretreatment,respectively. This observation demonstrates that a higher acidity on acid and UA pretreatments inhibits the generation of VFA. Results suggest that ultrasonic pretreatment is preferable to promote the disintegration degree of FW and VFA production.展开更多
基金supported by the National Key Research and Development Program of China(No.2019YFC1906304).
文摘The anaerobic acid production experiments were conducted with the pretreated kitchen waste under pH adjustment.The results showed that pH 8 was considered to be the most suitable condition for acid production,especially for the formation of acetic acid and propionic acid.The average value of total volatile fatty acid at pH 8 was 8814 mg COD/L,1.5 times of that under blank condition.The average yield of acetic acid and propionic acid was 3302 mg COD/L and 2891 mg COD/L,respectively.The activities of key functional enzymes such as phosphotransacetylase,acetokinase,oxaloacetate transcarboxylase and succinylcoA transferase were all enhanced.To further explore the regulatory mechanisms within the system,the distribution of microorganisms at different levels in the fermentation system was obtained by microbial sequencing,results indicating that the relative abundances of Clostridiales,Bacteroidales,Chloroflexi,Clostridium,Bacteroidetes and Propionibacteriales,which were great contributors for the hydrolysis and acidification,increased rapidly at pH 8 compared with the blank group.Besides,the proportion of genes encoding key enzymes was generally increased,which further verified the mechanism of hydrolytic acidification and acetic acid production of organic matter under pH regulation.
基金supported by Sichuan Environmental Protection Industry Group Co.,Ltd.,China(No.2021-CNSW-A01).
文摘Recently,using anaerobic hydrolysis of waste activated sludge (WAS) to recover volatile fatty acids (VFAs) as carbon sources for denitrification has been widely studied,and the key is to solve the problem of improving the solubility and bioavailability of WAS organic matter.Considering the energy consumption and chemical cost,this paper used low-dose nanozero-valent iron (NZVI) coupled with low-intensity ultrasonication (US) to pretreat WAS,and explored the effects of different treatment sequences on the fragmentation of WAS flocs particles,the dissolution of organic matter,and the subsequent biofermentation conversion process.The results showed low-dose NZVI synchronized with low-intensity US (NZVIUS)worked best for WAS anaerobic fermentation.Compared with 2062 mg/L in control group,soluble chemical oxygen demand (SCOD) after NZVIUS treatment reached up to 2786 mg/L during the fermentation cycle,and the initial release rate of SCOD increased by 69%.The VFAs production was elevated from 1522 to 1940 mg COD/L.NZVIUS pretreatment promoted the solubilization of attached organic matter,manifested by the fragmentation of WAS flocs and cell lysis.At the same time,proteins and carbohydrates in the extracellular polymeric substances (EPS) had different types of migration and transformation,and transfer of EPS can contribute 35.6% to SCOD.Moreover,adding NZVI promoted PO_(4)^(3-)-P recovery in the fermentation supernatant by 22.3% more than in day 4 control.This study demonstrated that the NZVIUS pretreatment method can effectively improve the production of VFAs by WAS anaerobic fermentation,meeting the practical needs of wastewater plants.
基金supported by the“Pioneer”and“Leading Goose”R&D Program of Zhejiang(No.2023C03149).
文摘Anaerobic fermentation is an efficient method to extract phosphorus from excess sludge,thereby facilitating its recovery and mitigating the phosphorus resource shortage.However,the prevalent metal-bound phosphorus species within sludge was difficult to release into the fermentation liquor.To address this,this study evaluated the enhanced phosphorus release performance from sludge containing iron-phosphorus compounds(Fe-P)via co-fermenting it with agriculture wastes.Specifically,protein-rich feather(Feather Group)and polysaccharide-rich tea residue(Tea Group)was respectively dosed into batch-scale fermentation jar.Results showed that the Feather Group exhibited significantly higher levels of released soluble phosphorus(2.1 folds)and volatile fatty acids(41.4 folds)compared to the Control Group,with concentrations reaching up to 280 mg/L and 9366 mg chemical oxygen demand/L,respectively.The activities ofα-glucosidase,neutral protease and acetate kinase in the Feather group were increased by 11.1%,92.3%and 37.6%,respectively,compared with the Control group.Methanogen abundance decreased while hydrolytic acid-producing bacteria and iron-reducing bacteria increased significantly after supplying agricultural wastes.Metagenomic analysis demonstrated a significant increase in genes related to acetic acid synthesis.Mechanism elucidation suggested that increased iron-reducing bacteria abundance promoted Fe3+reduction into Fe2+,thus enhancing phosphorus release from Fe-P compounds.This work may provide valuable information for developing effective strategy to extract phosphorus resource from complex environmental wastes.
文摘In the suspended sludge system, when pH and temperature were suitable and carbon source was not limited, the denitrification and C-uptake rate followed a zero-order reaction. Mixed VFA C-source had higher denitrification rate than single VFA C-source consisting of them. When VFA were used as carbon source, consumed carbon quantity for denitrification was closed to 1. 07 mg VFA-C/mg NO-N. About 20% of the applied C/N was used for assimilative purposes. As rising up influent C/N by increasing the C load ,the sludge yield YN increased. The part of carbon consumption increased and the effluent oxidized nitrogen decreased. At pH 7. 5, 25℃ and sludge yield 0.72 mg VSS/mg NO-N, the calculated influent VFA-C /NO critical value was 1. 43 for complete denitrification.
基金financially supported by the Graduate Student Innovation Project of Jiangsu Province,China (KYLX15_1377)the Natural Science Foundation of Jiangsu Province,China (BK20151312)the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD),China
文摘This study investigated the impacts of the degree of unsaturation （unsaturity） of long-chain fatty acids on volatile fatty acid （VFA） profiles of rumen fermentation in vitro. Six types of long-chain fatty acids, including stearic acid （C18：0, control group）, oleic acid （C18：1, n-9）, linoleic acid （C18：2, n-6）, a-linolenic acid （C18：3, n-3）, arachidonic acid （C20：4, n-6） and eicosapentaenoic acid （C20：5, n-3）, were tested. Rumen fluid from three goats fitted with ruminal fistulae was used as inoculum and the inclusion rate of long-chain fatty acid was at 3% （w/w） of substrate. Samples were taken for VFA analysis at 0, 3, 6, 9, 12, 18 and 24 h of incubation, respectively. The analysis showed that there were significant differences in the total VFA among treatments, sampling time points, and treatment×time point interactions （P〈0.01）. a-Linolenic acid had the highest total VFA （P〈0.01） among different long-chain fatty acids tested. The molar proportion of acetate in total VFA significantly differed among treatments （P〈0.01） and sampling time points （P〈0.01）, but not treatment×time point interactions （P〉0.05）. In contrast, the molar proportion of propionate did not differ among treatments during the whole incubation （P〉0.05）. However, for butyrate molar proportions, significant differences were found not only among sampling time points but also among treatments and treatment×time point interactions （P〈0.01）, with eicosapentaenoic acid having the highest value （P〈0.01）. Additionally, no statistically significant differences were found in the acetate to propionate ratios among treatments groups （P〉0.05）, even the treatments stearic acid and a-linolenic acid were numerically higher than the others. The inclusion of 3% long-chain unsaturated fatty acids differing in the degree of unsaturation brought out a significant quadratic regression relation between the total VFA concentration and the double bond number of fatty acid. In conclusion, the a-linolenic acid with 3 double bonds appeared better for improving rumen microbial fermentation and the total VFA concentration.
基金financially supported by the National Natural Science Foundation of China(No.52070069)Jiangsu Province Natural Science Foundation(No.BK20211207)+3 种基金China Postdoctoral Science Foundation(No.2021M692423)Shanghai Post-doctoral Excellence Program(No.2020419)State Key Laboratory of Pollution Control and Resource Reuse Foundation(No.PCRRF20005)the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD),China。
文摘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.,clp P),membrane transport(i.e.,ffh and gsp F),intracellular substrates metabolism(i.e.,ald and paa F)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.,cqs A,rpf C and rpf G),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.
基金supported by the National Natural Science Foundation of China(Grant No.52000139)the China Post-doctoral Science Foundation(Grant number 2020M680058).
文摘Effects of sludge age on volatile fatty acids (VFAs) production and Phosphorus (P) release during anaerobic acidification of waste activated sludge (WAS) were investigated.Sequencing batch reactors (SBR) fed with simulating domestic sewage were applied to produce WAS of different sludge ages,and batch tests were used for anaerobic acidification.The maximum dissolved total organic carbon,release of PO_(4)^(3+)-P,and accumulation of acetate (C2),propionate (C3),butyrate (C4),and valerate (C5) decreased by 56.2%,55.8%,52.6%,43.7%,82.4%and 84.8%,respectively,as the sludge age of WAS increased from 5 to 40 days.Limited degradation of protein played a dominating role in decreasing DTOC and VFAs production.Moreover,the increase in molecular weight of organics and organic nitrogen content in the supernatant after acidification suggested that the refractory protein in WAS increased as sludge age extended.Although the production of C2,C3,C4,and C5 from WAS decreased as the sludge age increased,the proportions of C2 and C3 in VFAs increased,which might be due to the declined production of C5 from protein and the faded genus Dechlorobacter.Keeping sludge age of WAS at a relatively low level (<10 days) is more appropriate for anaerobic acidification of WAS as internal carbon sources and P resource.
基金supported by the National Natural Science Foundation of China (No. 52100040)the National Key Research & Development Program of China (No. 2019YFC1904005)the Natural Science Foundation of Hubei Province (No. 2020CFB403)。
文摘Volatile fatty acids(VFAs), which are largely generated during the anaerobic acidification process, are considered to be reliable indicators of the stable process operation. However,the common methods for monitoring VFAs are offline, and they are typically manual requiring time-consuming, costly and complex instruments. This study aims to develop a novel online analyzer for automatic measuring VFAs, which was based on the 5-p H point titration, embedded with a proportional-integral-derivative(PID) feedback control system. The results show that it can achieve accurate and rapid monitoring of VFAs ranging between 0-400 mg/L(<9 min/sample) but simultaneously faces the problems of overtitration and interference of complex characteristics of wastewater. In order to improve its accuracy and stability, the effects of three general coefficients(K_(I),K_(P), and K_(D)) of PID on the titration were investigated, and the optimal values of K_(I), K_(P), and K_(D)were found to be 1.5, 1.0, and-1.0~0.5,respectively. Besides, the initial titration speed was set at 0.06 m L/min, equal to the minimum speed of the peristaltic pump, and the dichotomy approach was integrated into the PID feedback controller. Owing to the above improvements, the relative mean deviation and standard deviation of measuring VFAs in both synthetic and real wastewaters were mostly lower than 5.0% and 5.0 mg/L, proving the online analyzer is rapid, accurate and reliable.
基金supported by the Major Science and Technology Program for Water Pollution Control and Treatment(No.2018ZX07110-002)。
文摘This study investigated a combined low-thermal and CaO_(2)pretreatment to enhance the volatile fatty acid(VFA)production from waste activated sludge(WAS).The fermentative product was added to a sequencing batch reactor(SBR)as an external carbon source to enhance nitrogen removal.The results showed that the combined pretreatment improved WAS solubilization,releasing more biodegradable substrates,such as proteins and polysaccharides,from TB-EPS to LB-EPS and S-EPS.The maximum VFA production of 3529±188 mg COD/L was obtained in the combined pretreatment(0.2 g CaO_(2)/g VS+70℃for 60 min),which was 2.1 and 1.4-fold of that obtained from the sole low-thermal pretreatment and the control test,respectively.Consequently,when the fermentative liquid was added as an external denitrification carbon source,the effluent total nitrogen decreased to Class A of the discharge standard for pollutants in rural wastewater treatment plants in most areas of China.
基金Sponsored by the Scientific Research Funds of Huaqiao University(Grant No.605-50Y18055).
文摘Mesophilic and thermophilic anaerobic fermentation performance of waste activated sludge(WAS)pretreated by enzymes catalysis associated with microbial community shifts were investigated.WAS disintegration was boosted considerably by enzymolysis with 8750 mg/L of soluble COD release within 180 min.Mesophilic anaerobic fermentation(MAF)produced nearly equal VFA accumulation with over 3200 mg COD/L compared with that of thermophilic fermentation(TAF).Bacterial community consortia showed great shifting differences in dynamics of main T⁃RFs between MAF and TAF.Moreover,MAF was conducive to form intermediate bacterial community evenness compared to TAF,which preserved a robust function of VFA production.The enzymes catalysis prompted bio⁃energy(electricity)recovery potential of WAS organics via anaerobic fermentation(MAF/TAF)with evaluating electricity conversion efficiency of 0.75-0.82 kW·h/kg VSS(3.9 times higher than control test).Finally,this study proposed some novel thinking on future WAS treatment/management towards energy recovery coupled with energy⁃sufficient wastewater treatment by co⁃locating WAS anaerobic fermentation,MFC plant with wastewater treatment plant(s).
基金supported and administered by the Singapore National Research Foundation(NRF-CRP5-2009-2)
文摘This study investigated the degradation and production of volatile fatty acids（VFAs）in the acidogenic phase reactor of a two-phase anaerobic system.20 mmol/L bromoethanesulfonic acid（BESA）was used to inhibit acidogenic methanogens（which were present in the acidogenic phase reactor）from degrading VFAs.The impact of undissociated volatile fatty acids（un VFAs）on＂net＂VFAs production in the acidogenic phase reactor was then evaluated,with the exclusion of concurrent VFAs degradation.＂Net＂VFAs production from glucose degradation was partially inhibited at high un VFAs concentrations,with 59%,37% and 60% reduction in production rates at 2190 mg chemical oxygen demand（COD）/L undissociated acetic acid（un HAc）,2130 mg COD/L undissociated propionic acid（un HPr）and 2280 mg COD/L undissociated n-butyric acid（un HBu）,respectively.The profile of VFAs produced further indicated that while an un VFA can primarily affect its own formation,there were also un VFAs that affected the formation of other VFAs.
基金National Natural Science Foundation of China,Grant/Award Number:31201833 and 31872373Open Project of Hubei Key Laboratory of Animal Nutrition and Feed Science,Grant/Award Number:202306Scientific Research Plan Guiding Project of Hubei Provincial Education Department,Grant/Award Number:B2018082。
文摘Background:This study aimed to develop a combined model to quantify the net absorption of volatile fatty acids(VFA)in the large intestine(LI)of pigs.Methods:Fifteen female growing pigs(Duroc×Large White×Landrace)were ranked by body weight(30±2.1 kg)on day 0 and assigned to one of three treatments,namely the basal diet containing different crude fiber(CF)levels(LCF:3.0%CF,MCF:4.5%CF,and HCF:6.0%CF).The pigs were implanted with the terminal ileum fistula and the cannulation of the ileal mesenteric vein(IMV),portal vein(PV),and left femoral artery(LFA)from days 6 to 7.[13 C]-Labeled VFA and P-aminohippuric acid were constantly perfused into the terminal ileum fistula and the cannulation of the IMV(day 15),respectively.Blood samples were collected from the PV and the LFA during perfusion(5 h),and LI samples were collected.Results:The net flux of[12 C]-acetic acid in the PV was greater for LCF versus MCF(p=0.045),but no difference was observed in the net flux of[12 C]-propionic acid(p=0.505)and[12 C]-butyric acid(p=0.35)in the PV among treatments.The deposition of[12 C]-acetic acid in the LI was greater for LCF versus MCF(p=0.014),whereas the deposition of[12 C]-propionic acid(p=0.007)and[12 C]-butyric acid(p=0.037)in the LI was greater for LCF versus HCF.Conclusions:In conclusion,this pig model was found conducive to study the net absorption of VFAs in the LI,and LCF had more net absorption of VFAs in the LI than MCF and HCF.
基金financially supported by Zinpro Corporation(grant number:SA2300029,2022–2025).
文摘Background Isoacids are the product of branched-chain amino acid fermentation and are naturally producedin the hindgut by microbial fermentation. In ruminants, supplementation of isoacids as a feed additive improvesfiber utilization, with a positive impact on animal productivity. However, information on how isoacids impact nutrientdigestibility in swine is limited. The objective of this experiment was to determine the optimal inclusion levelof an isoacid blend product based on apparent ileal digestibility (AID) and apparent total tract digestibility (ATTD)of nutrients and fermentation products in the ileal digesta and feces of growing pigs fed a corn-soybean meal diet.Methods Twelve ileal cannulated pigs (20.9 ± 0.6 kg) were used in a 5-period crossover design with 6 diets and 2replicate pigs in each period. Dietary treatments consisted of increasing levels (0%, 0.5%, 0.75%, 1%, 1.25%, and 1.5%)of an isoacid blend (isobutyrate, isovalerate, and 2-methyl butyrate, 1:1:1) added to a corn-soybean meal basal diet.Each experimental period consisted of 14 d: 10 d for acclimatization to the diets, 2 d for fecal collection, and 2 dfor digesta collection.Results Isoacids supplementation quadratically improved the AID of hemicellulose (P < 0.05) and tended to improvethe AID of crude fiber (P < 0.1). The AID of most indispensable amino acids (except Met + Cys, Trp, and Val) as wellas the ATTD of crude protein, gross energy, neutral detergent fiber, and hemicellulose improved or tended to improvelinear or quadratically (P < 0.05 or P < 0.1). In addition, the ATTD values of Arg, His, Ile, Leu, Met + Cys, Phe, Thr, and Valincreased quadratically (P < 0.05). Collectively, 1% of isoacids inclusion resulted in the greatest response. Furthermore,isoacids supplementation tended to increase (P = 0.071, quadratically) the concentration of ammonia and decreased(P < 0.05) the concentrations of acetic acid and total volatile fatty acids with a tendency to decrease (P = 0.064) isovalericacid in the ileal digesta. In fecal samples, the proportion of acetic acid decreased (P < 0.05) quadratically, whereas the proportionsof propionic, valeric, and caproic acids tended to increase linearly and/or quadratically (P < 0.1).Conclusions Isoacids supplementation at 1% in swine diets can improve nutrient digestibility, particularly aminoacids and fiber at the ileal level and ATTD of crude protein, gross energy, and hemicellulose.
基金supported by the European Union NextGenerationEU/PRTR,and the project Biological Resources Certifications Schemes(BIORECER)funded by the European Executive Agency under call HORIZON CL6-2021-ZEROPOLLUTION-01(101060684)It was also carried out thanks to the INTERREG ECOVAL and CIGAT CIRCULAR projects,funded by Interreg Sudoe and the Xunta de Galicia and Viaqua,respectively.
文摘The valorization of sewage sludge and food waste to produce energy and fertilizers is a well-stablished strategy within the circular economy.Despite the success of numerous laboratory-scale experiments in converting waste into high-value products such as volatile fatty acids(VFAs),large-scale implementation remains limited due to various technical and environmental challenges.Here,we evaluate the environmental performance of a hypothetical large-scale VFAs biorefinery located in Galicia,Spain,which integrates fermentation and purification processes to obtain commercial-grade VFAs based on primary data from pilot plant operations.We identify potential environmental hotspots,assess the influence of different feedstocks,and perform sensitivity analyses on critical factors like transportation distances and pH control methods,using life cycle assessment.Our findings reveal that,on a per-product basis,food waste provides superior environmental performance compared to sewage sludge,which,conversely,performs better when assessed per mass of waste valorized.This suggests that higher process productivity from more suitable wastes leads to lower environmental impacts but must be balanced against increased energy and chemical consumption,as food waste processing requires more electricity for pretreatment and solid-liquid separation.Further analysis reveals that the main operational impacts are chemical-related,primarily due to the use of NaOH for pH adjustment.Additionally,facility location is critical,potentially accounting for up to 99%of operational impacts due to transportation.Overall,our analysis demonstrates that the proposed VFAs biorefinery has a carbon footprint comparable to other bio-based technologies.However,enhancements in VFAs purification processes are necessary to fully replace petrochemical production.These findings highlight the potential of waste valorization into VFAs as a sustainable alternative,emphasizing the importance of process optimization and strategic facility placement.
基金supported by the National Natural Science Foundation of China (No. 51978595)。
文摘During the acidogenic fermentation converting waste activated sludge (WAS) into shortchain fatty acids (SCFA), hydrolysis of complex organic polymers is a limiting step and the transformation of harmful substances (such as antibiotics) during acidogenic fermentation is unknown. In this study, potassium ferrate (KFeO) oxidation was used as a pretreatment strategy for WAS acidogenic fermentation to increase the hydrolysis of sludge and destruct the harmful antibiotics. Pretreatment with KFeOcan effectively increase the SCFA production during acidogenic fermentation and change the distribution of SCFA components.With the dosage of 0.2 g/g TS, the maximum SCFA yield was 4823 mg COD/L, which is 28.3times that of the control group;acetic acid accounts for more than 90% of the total SCFA. The higher dosage (0.5 g/g TS) can further increase the proportion of acetic acid, but inhibit the overall performance of SCFA production. Apart from the promotion of hydrolysis and acidogenesis, KFeOpretreatment can also simultaneously oxidizes and degrades part of the antibiotics in the sludge. When the dosage is 0.5 g/g TS, the degradation efficacy of antibiotics is the most significant, and the contents of ofloxacin, azithromycin, and tetracycline in the sludge are reduced by 69%, 42%, and 50%, respectively. In addition, KFeOpretreatment can also promote the release of antibiotics from sludge flocs, which is conducive to the simultaneous degradation of antibiotics in the subsequent biological treatment process.
基金supported by the National Natural Science Foundation of China(Nos.51778580,51878611)the China Scholarship Council(No.iCET 2017)。
文摘The occurrence of the Maillard reaction and melanoidins formation during the hydrothermal treatment of food waste can reduce the yield of volatile fatty acids(VFA);however, few studies have investigated the adverse effects of the Maillard reaction. This study identified the impact of hydrothermal treatment parameters on hydrolysis and melanoidins formation and optimized the hydrothermal treatment conditions to enhance VFA production by minimizing the impact of the Maillard reaction. A response surface methodology was employed to optimize the hydrothermal treatment parameters and VFA production was evaluated. Results showed that temperature, reaction time, and pH were significant interacting factors with respect to hydrolysis and melanoidins formation while the C/N ratio and moisture content of food waste had little impact. The optimal conditions for hydrothermal treatment(temperature of 132 °C, reaction time of 27 min, and a pH of 5.6) enhanced VFA production by 22.1%. Under optimal hydrothermal treatment conditions, a higher initial C/N ratio further increased VFA production.
基金This work is supported by the National Natural Science Foundation of China(40476063).
文摘It is well known that acid-volatile sulfide (AVS) plays an important role in influencing the toxicity of divalent cationic metals within anoxic sediments. In studying sediment core samples collected from tidal flats within the Jiaozhou Bay, China, we found that the AVS concentration gradually increases with depth and decreases from high tidal flat to low tidal flat areas. We evaluated the chemical activity and bioavailability of heavy metals in the tidal flat based on the molar ratio of simultaneously ex- tracted metals (SEM) and AVS. The value of SEM/AVS is generally less than 1 in this area except for the surface layer, which suggests that the heavy metals only have chemical activity in the surface layer. SEM is most highly concentrated at the boundary of the redox layer. SEM have similar depth distributions throughout the tidal flat. The aeration of low tidal flat sediment indicates that SEM gradually move to deeper sites via interstitial water.
文摘A new sesquiterpenoid,named baimuxifuranic acid,has been isolated from the volatile oil of Aquilaria sinensis(Lour.)Gilg.belonging to the family Thymelaceae by silica gel column chromatography.Based on spectral analysis its structure was deduced as(1).Reduction of baimuxifuranic acid by LiAlH_4 gave a
基金Supported by the National Natural Science Foundation of China(No.20967003)the Project of the Government of Guiyang City(No.[2010]5-2)
文摘The bioavailability of five divalent cationic heavy metals （Pb, Cd, Cu, Zn and Ni） in 10 superficial sediment samples from Baihua Lake was assessed based on the molar ratio of simultaneously extracted metals （SEMs） to acid volatile sulfide （AVS）. Atomic absorption spectrometry （AAS） and X-ray powder diffraction （XRD） were used to determine the heavy metal concentrations and examine the mineralogy of the crystalline phases, respectively. The AVS loadings in sediments from Baihua Lake ranged from 64.30 to 350.08 ~rnol/g （dry weight）. The corresponding SEM levels for the sampling sites varied from 1.770 to 14.660 vrnol/g. The molar ratio of SEMs to AVS ranged from 0.014 to 0.084 with a mean value of 0.034. The XRD analysis also confirmed the presence of some metal sulfides in sediments from Baihua Lake. The SEMs/AVS ratios for all sampling sites were significantly lower than 1.0, indicating that AVS in the sediments was sufficient to bind the five heavy metals; thus, these heavy metals are currently not significantly bioavailable to benthic organisms. Comparing the SEMs results to published guideline values for metal toxicity to benthic organisms in sediments, however, suggests that Zn and Ni pose a risk at some sampling locations in Baihua Lake.
基金Sponsored by the National Natural Science Foundation of China(Grant Nos.51008105 and 51121062)the State Key Laboratory of Urban Water Resource and Environment(Grant No.2014TS06)+1 种基金the Department of Education Fund for Doctoral Tutor(Grant No.20122302110054)the Special S&T Project on Treatment and Control of Water Pollution(Grant No.2013ZX07201007-001)
文摘This study aims at investigating the effects of ultrasonic and acid pretreatment on food waste( FW)disintegration and volatile fatty acid( VFA) production. Single-factor experiments are carried out to obtain optimal conditions of individual ultrasonic and acid pretreatment,and response surface method( RSM) is applied to optimize the conditions of the combination of ultrasonic and acid( UA) pretreatment. Results show that the optimal acid,ultrasonic and UA pretreatments conditions are individual pH 2,individual ultrasonic energy density of 1. 0 W / mL and the combination of ultrasonic energy density1. 11 W / mL and pH 1. 43,respectively. Correspondingly,the maximum disintegration degrees( DD) of 46. 90%,57. 38% and68. 83%are obtained by acid,ultrasonic and UA pretreatments,respectively. After optimizing pretreatment conditions,batch experiments are operated to produce VFA from raw and pretreated FW under anaerobic fermentation process. Both the maximum VFA production( 976. 17 mg COD / gV S) and VFA / SCOD( 72. 89%) are obtained with ultrasonic pretreatment, followed by UA pretreatment, non-pretreatment and acid pretreatment,respectively. This observation demonstrates that a higher acidity on acid and UA pretreatments inhibits the generation of VFA. Results suggest that ultrasonic pretreatment is preferable to promote the disintegration degree of FW and VFA production.
