过酸化失稳是困扰有机废物厌氧消化(AD)过程高效稳定运行的一大难题.为探析不同诱导方式造成过酸化的AD系统微生态特征差异,在餐厨垃圾中温AD反应器中分别引人负荷扰动(R2)、温度及搅拌扰动(R3)以诱发系统过酸化,利用宏基因组学测序技术,对比考察稳定与酸化系统微生物群落结构及主要产甲烷功能路径差异.结果表明,两种方式均成功诱发系统过酸化失稳,过酸化系统中挥发性脂肪酸(VFA)过量富集(R2、R3系统中分别高达(12.53±1.96)g·L-1和(8.00±0.81)g·L-1)的同时,丙酸等多碳VFA组分比例大幅升高.R2、R3系统酸化后其产甲烷菌及相关酶受到高浓度VFA的显著抑制,酸积累程度更高的R2受抑制更为明显.且经相关性分析发现,多碳酸尤其是丙酸是抑制产甲烷作用的关键因素.与R2相比,R3具有更高的耗氢能力,耗氢微生物如可耗H2产酸的Treponema属和氢营养型产甲烷菌Methanoculleus属、Methanospirillum属等相对丰度显著高于R2.酸化系统均以乙酸营养型产甲烷为主要的产甲烷途径,并以Methanosaeta属为主要的乙酸型产甲烷菌.酸化系统中更高含量的乙酸产甲烷途径的AK-PTA酶有利于促进对乙酸的利用,增强厌氧消化微生物菌群对高浓度乙酸的耐受能力.本研究中的相关结果可为提高有机废物AD微生态抗酸化能力提供理论依据和数据支撑.

Carbamazepine (CBZ) is a typical pharmaceutical residue commonly found in aqueous environments, but its removal through activated carbon or advanced oxidation processes is often disrupted by co-existing organic matter. An imprinting system which consisted of the target pollutant CBZ (template molecule) and 10 different kinds of functional monomers was constructed via molecular simulation to screen for appropriate monomers, thereby addressing CBZ removal disruptions. An annealing method simulation was used to search for stable, low-energy conformations of the template-monomer interaction system to calculate the binding energy of these different monomers with CBZ. The order of binding affinity calculated was: 4-vinylbenzoic acid > itaconic acid > methacrylic acid, which was consistent with the experimental observations. The adsorption capacity of the molecular imprinted polymer (MIP) prepared using 4-vinylbenzoic acid reached 28.40 mg/g, and the imprinting factor reached 2.72. The simulation and measurement of the ultraviolet spectrum of the imprinting system showed that a new interaction system was formed between the template and monomers, and that multiple binding conformations between them took place when specific recognition occurred. Energy calculation and hydrogen bond analysis revealed that the van der Waals force, including the π-π conjugate and electrostatic forces including hydrogen bonding, played an important role during selective adsorption, which was confirmed by infrared spectroscopy analysis.

Molecular simulation can provide valuable theoretical guidance for rapid selection of functional monomers in imprinted adsorbents. The recognition systems were constructed , which consisted of targeted pollutant carbamazepine (CBZ) as template molecule and 14 functional monomers respectively. The low-energy conformations of template-monomer interaction system were searched by simulated quenching method. This method overcame the shortcoming of the existing searching method by which the conformations were prone to fall into local potential wells. Molecular simulation indicated that the binding capacity of itaconic acid (IA) as monomer to CBZ was the strongest. Adsorption experiments showed that IA-prepared imprinted adsorbent (IA-MIP) performed better than the adsorbent prepared by traditional monomer methylacrylic acid. The adsorption capacity of IA-MIP could reach 9. 28 mg/g in aqueous solution. IA-MIP also showed high selectivity to carbamazepine in filtration effluent. After 10 reuses , the adsorption capacity decreased by only 1. 3% . The ultraviolet spectra of the imprinted system were calculated theoretically and measured. The experimental results confirmed that a new interaction system was formed between IA and CBZ. Molecular simulation could predict the ultraviolet spectra of IA and CBZ in aqueous solution very well. However, the prediction of the ultraviolet spectra of the interaction system was not ideal, which suggested that there existed a variety of interaction conformations during the specific adsorption process. Energy calculation and hydrogen bond analysis demonstrated that van der Waals and electrostatic force played a major role in the recognition process. Infrared analysis confirmed the existence of hydrogen bond in the system, and the recognition site was located between the carboxylic group of IA and carbamazepine amide , which was consistent with the results of molecular simulation.

A plug-flow reactor (PFR) (R1) and a completely-stirred tank reactor (CSTR) (R2) were operated under mesophilic temperature (37±1℃) for high-solids digestion of kitchen waste to investigate the microbial community characteristics before and after sludge-bulking using MiSeq high-throughput sequencing technology. The results showed that the archaeal community structure changed little after sludge-bulking, and acetoclastic methanogen Methanosaeta and mixotrophic methanogen Methanosarcina dominated in both reactors. There was a marked increase in the relative abundance of bacteria genera that might be related to sludge bulking. Those proliferated bacteria genera are those capable of producing biosurfactants (Corynebacterium, Lactobacillus, etc.) and those containing mycolic acids in cell walls (Actinomyces, Corynebacterium, etc.). In addition, volatile fatty acids (VFAs) and total ammonia nitrogen (TAN) were accumulated in these reactors before sludge-bulking. Accordingly, bacteria that can contribute to the accumulation of VFAs (Petrimonas, Anaerosalibacter and Fastidiosipila, etc.) and TAN (Proteiniphilum, Tepidimicrobium and Aminobacterium, etc.) were observed to proliferate.

To identify the most efficient system for conversion of food waste (FW) into biogas,FW fermentation was investigated in two types of reactors:a completely-stirred tank reactor (CSTR) and a plug-flow reactor with a reflux ratio (R-PFR).The efficiency,stability,and microbial community structure in the reactors were compared.Stable fermentation was achieved under an organic loading rate (OLR) of 3.0 kgVS· m-3· d-1 in both reactors.Compared with the CSTR,total alkalinity (TA) and ratio of volatile fatty acids (VFA) to TA (VFA/TA) were more stable,and inhibitors such as total ammonia-nitrogen (TAN) and free ammonia-nitrogen (FAN) concentrations were lower in R-PFR.However,specific methane production (SMP) was higher in the CSTR.The phyla Chloroflexi (37.35％) and Firmicutes (31.22％) were predominant in the R-PFR,whereas Firmicutes (44.41％) and Bacteroidetes (31.14％) were more abundant in the CSTR.The genus Methanosaeta accounted for 98.72％ and 84.90％ of the total population in the CSTR and R-PFR,respectively,indicating that the main methanogenic pathway in both reactors was acetoclastic methanogenesis.In addition to Methanosaeta,mixotrophic methanogens such as Methanosarcina (9.72％) and hydrogenotrophic methanogens such as Methanospirillum and Methanolinea were detected in the CSTR.The methanogenic community obtained in the CSTR had a greater tolerance to high ammonia and VFA levels,which is conducive to stable and efficient methanogenesis.R-PFR may be more appropriate for highly variable substrate,as shock loads can vary spatially in the reactor.However,R-PFR systems are not suitable for long-term treatment of highly degradable substrate such as FW,as local acidification may occur.Our results provide a basis for the optimization of anaerobic FW digestion.

To investigate the influence of biomass concentration (BC) and organic loading rate (OLR) on the performance and kinetics of anaerobic digestion (AD) of food waste (FW),BC and OLR grading experiments were carried out in batch mesophilic digesters.Physical-chemical analysis was performed to monitor state parameters and the digestion kinetics were evaluated by the application of first-order and modified Gompertz models.Results revealed that the overloading can reduce the process efficiency and stability while increased BC can otherwise minimize the organic loading of unit cell so as to optimize the AD process.Methanogenesis is the rate-limiting step in the digestion of FW.Under all experimental conditions,the hydrolysis rate constant (k) is always greater than the methanogenesis rate constant (Rm').The influence of OLR and BC,on k and Rm'respectively,is fluctuant,so the value of these two parameters are unable to determine the stability of the digesters.In contrast,the ratio of k/Rm'in highly efficient digesters maintained at a level of (2.54-± 0.62) and increased monotonously with the increase of OLR as well as the decrease of BC.Moreover,along with the increase of k/Rm',the efficiency of the AD process dropped as well.From the perspective of reaction kinetics,this study confirms that the increase in OLR exacerbates the mismatch between acid production and consumption,eventually resulting in process acidification and instability.However,the increased BC concentration tends to alleviate this imbalance,which is of significance for the efficiency and stability of the AD process.

The correlations between kinetic parameters and both operational conditions and process performance during the anaerobic digestion of food waste were investigated. Substrate concentration (SC), biomass concentration (BC), and substrate-inoculum ratio (S/I) were selected as the operational conditions, while first-order and modified Gompertz models were introduced to evaluate digestion kinetics. The results indicated that no significant correlations between both hydrolysis and methanogenesis kinetic parameters (k and R-m) relative to the operational conditions and process parameters could be determined; however, k/R'(m) was observed to significantly correlate with these parameters. Specifically, substrate load (both SC and S/I) positively influenced k/R'(m) via its impact on volatile fatty acid (VFA) and pH, while BC reduced k/R'(m) by increasing the alkalinity of the system. Moreover, k/R'(m) was negatively correlated with process efficiency. The methane recovery rate exceeded 90% when 1.55 4.64 (p = 0.05). These findings provide a scientific foundation for predicting the behavior of anaerobic systems and optimizing the digestion process. (C) 2017 Elsevier B.V. All rights reserved.

An anaerobic digestion system for treating food waste contains a large amount of compounds with surface activity.The presence of those substances can decrease the surface tension and increase the foaming potential,even resulting in serious foaming.Therefore,understanding the effects of those substances on surface properties and foaming potential of the system is of great significance in foaming prevention and process recovery.This paper studied the sludge of a mesophilic anaerobic digestion system.The effects of different concentrations of substrate and intermediate compounds of one-component and their mixtures on sludge properties,such as surface tension and viscosity,were investigated and compared with the effects on foaming tendency and foam stability.The results showed that there was no consistent correlation between foaming potential and surface tension or the viscosity of the tested sludge.A preferred way to determine the foaming property was to directly measure foaming tendency and foam stability.During the digestion process,oleic acid and gelatin showed the highest foaming tendency and stability,which could be considered as the main potential foaming problem.The corn oil can not only decrease the surface tension,but also reduce the foaming tendency of the sludge.Thus,it might have an inhibited effect on the foam generation.Acetic acid,starch and peptone can also intensify foaming tendency.However,they could not induce stable foams.Those results can be applied to practical application and provide a theoretical support for handling the foaming problems of anaerobic digestion system when treating food waste.

Foaming negatively affects anaerobic digestion of food waste (FW). To identify the causes of foaming, reactor performance and microbial community dynamics were investigated in three mesophilic digesters treating FW. The digesters were operated under different modes, and foaming was induced with several methods. Proliferation of specific bacteria and accumulation of surface active materials may be the main causes of foaming. Volatile fatty acids (VFAs) and total ammonia nitrogen (TAN) accumulated in these reactors before foaming, which may have contributed to foam formation by decreasing the surface tension of sludge and increasing foam stability. The relative abundance of acid-producing bacteria (Petrimonas, Fastidiosipila, etc.) and ammonia producers (Proteiniphilum, Gelria, Aminobacterium, etc.) significantly increased after foaming, which explained the rapid accumulation of VFAs and NH4 + after foaming. In addition, the proportions of microbial genera known to contribute to foam formation and stabilization significantly increased in foaming samples, including bacteria containing mycolic acid in cell walls (Actinomyces, Corynebacterium, etc.) and those capable of producing biosurfactants (Corynebacterium, Lactobacillus, 060F05-B-SD-P93, etc.). These findings improve the understanding of foaming mechanisms in FW digesters and provide a theoretical basis for further research on effective suppression and early warning of foaming.

A serious foaming incident occurred in a mesophilic food waste digester. The effects of foaming on reactor efficiency parameters were investigated, including specific biogas production (SBP), specific methane production (SMP) and volatile solids (VS) removal rate. The possible causes of foaming were evaluated according to a series of stability parameters including volatile fatty acids (VFAs), the ratio of VFA to total alkalinity (VFA/TA) combined with the ammonia nitrogen concentration (TAN), as well as the bacterial community structure in pre- and post-foaming system. The SBP, SMP and VS removal rate during the stable stage were (0.950 ± 0.104) m3/kg VS, (0.574 ± 0.072) m3CH4/kg VS and (87.14 ± 2.76)%, respectively. However, those parameters decreased to (0.717 ± 0.100) m3/kg VS, (0.432 ± 0.070) m3CH4/kg VS and (84.24 ± 4.44)% with the appearance of the foaming incident, which indicated that the efficiency of the digester had been significantly influenced by the foaming incident. Prior to the foaming, there appeared to be a rapid accumulation of VFAs along with a reduction in the proportion of acetic acid in VFAs. The propionic acid, which is believed to play a major role in enhancing the foaming tendency, increased in its proportion in VFAs as well. The filamentous bacteriaLongilinea arvoryzae,Levilineaand the myxobacteriumCytophaga fermentans had stronger band intensities after foaming. Their filamentous structure or mucilage can be a significant contributor to the initiation of foaming to some extent. In conclusion, foaming may be caused by the combination of VFAs accumulation and the proliferation of specific bacteria.

为研究总氨氮(TAN)在餐厨垃圾中温干式厌氧消化系统内的积累及抑制作用,在单相完全搅拌式(CSTR)反应器内进行餐厨垃圾中温厌氧消化,反应器在3 g·L-1·d-1(以VS计)的负荷下连续运行230余天,期间不断监测TAN及其余物化指标的变化.试验结果表明,TAN在系统内的积累呈现先快后慢的趋势,且不会持续积累,而是积累到一定程度后会保持稳定.游离氨(FAN)是氨抑制中起主导作用的因素,FAN大于150 mg·L-1时就会影响到系统效率;大干200 mg·L-1时会影响系统稳定性;大于300 mg·L-1后会产生强烈抑制,引发稳态型抑制,甚至导致系统出现泡沫.此外,氨抑制会影响系统产气动力学,导致产气速率降低,产气量减少.寻找合理的措施消除氨抑制对保障系统稳定运行具有重要意义.

为了研究进料油脂含量(5％～25％)和有机负荷(40 ～ 60 kg VS/m3)对餐厨垃圾中温干式厌氧消化的共同影响,采用软件Design-Expert 8.0.6设计进料参数,以容积产甲烷率作为响应值,对14组序批式实验的结果进行回归分析,并建立容积产甲烷率与油脂含量和有机负荷间的回归方程.结果表明,当有机负荷为40 kg VS/m3时,甲烷产率随油脂含量的增加而增大;当有机负荷为50 kg VS/m3时,甲烷产率随油脂含量的增加先增大后减小;当有机负荷为60 kg VS/m3时甲烷产率随油脂含量的增加丽减小.序批式实验中进料的最佳油脂含量和有机负荷分别为18.7％和42.9 kg VS/m3,对应响应面的理论容积产甲烷率最大值为32.74 L CH4/L.研究结论可以应用到实际工程中,为餐厨垃圾干式厌氧消化技术的推广提供一定的理论基础.

To explore the relationship between process stability and microbial community in anaerobic digestion, organic loading rate (OLR) disturbances were introduced into an anaerobic digester treating food waste (FW) to induce different process stages. Physico-chemical analysis along with the 454-pyrosequencing microbial technique were performed to monitor the responses of state parameters as well as the dynamics of microbial community. Results showed that balanced community structure ensured the stable operation of the digester. Under steady-state conditions, the methane yield reached (0.50±0.01) LCH4/gVS and volatile solids (VS) removal rate reached (89.58±0.08) %. Under high OLR conditions, the relative abundance of acid-producing bacteria (phyla Tenericutes and Actinobacteria) increased dramatically, which induced the proliferation of syntrophic fatty acid degrading bacteria (class Clostridia), while the abundance and activity of syntrophic hydrogenotrophic methanogens decreased. The imbalance relationship between methanogens and syntrophic fatty acid degrading bacteria caused their inefficient syntrophy, eventually resulting in volatile fatty acid (VFA) accumulation and process deterioration. Moreover, the accumulated VFA and ammonia reduced the specific acetoclastic methanogenic activity (SAMA) and specific methanogenic activity (SMA) by 60.12% and 72.51%, respectively, which further deteriorated the digestion process. Although the digester afterwards recovered to its original operational conditions and process performance, the microbial community profile changed and achieved new steady-state conditions.

BACKGROUND:Anaerobic digesters become unstable when operated at a high organi c loading rate (OLR). Investigating the microbial community response to OLR disturbance is helpful for achieving efficient and stable process operation. However, previous studies have only focused on community succession during different process stages. How does community succession influence process stability? Is this kind of succession resilient? Are any key microbial indicator closely related to process stability? Such relationships between microbial communities and process stability are poorly understood.RESULTS:In this study, a mesophilic anaerobic digester for treating food waste (FW) was operated to study the microbial diversity and dynamicity due to OLR disturbance. Overloading resulted in proliferation of acidogenic bacteria, and the resulting high volatile fatty acid (VFA) yield triggered an abundance of acetogenic bacteria. However, the abundance and metabolic efficiency of hydrogenotrophic methanogens decreased after disturbance, and as a consequence, methanogens and acetogenic bacteria could not efficiently complete the syntrophy. This stress induced the proliferation of homoacetogens as alternative hydrogenotrophs for converting excessive H2 to acetate. However, the susceptible Methanothrix species also failed to degrade the excessive acetate. This metabolic imbalance finally led to process deterioration. After process recovery, the digester gradually returned to its original operational conditions, reached close to its original performance, and the microbial community profile achieved a new steady-state. Interestingly, the abundance of Syntrophomonas and Treponema increased during the deteriorative stage and rebounded after disturbance, suggesting they were resilient groups.CONCLUSIONS:Acidogenic bacteria showed high functional redundancy, rapidly adapted to the increased OLR, and shaped new microbial community profiles. The genera Syntrophomonas and Treponema were resilient groups. This observation provides insight into the key microbial indicator that are closely related to process stability. Moreover, the succession of methanogens during the disturbance phase was unsuitable for the metabolic function needed at high OLR. This contradiction resulted in process deterioration. Thus, methanogenesis is the main step that interferes with the stable operation of digesters at high OLR. Further studies on identifying and breeding high-efficiency methanogens may be helpful for breaking the technical bottleneck of process instability and achieving stable operation under high OLR.

In recent years , the quantity of harmless treatment of domestic garbage in Chongqing city has been increasing at 9%annually , but the processing capacity is relatively lagging behind .Based on the analysis of the current situation of domestic garbage disposal in Chongqing , this paper discussed the main problems existed in the process , and proposed further improving and perfecting disposal measures.Firstly, further promote the amount of incineration disposal in order to increase the rate of resource treatment and utilization . Secondly, accelerate the reconstruction and extension of landfill to improve the treatment capacity of emergency .Thirdly, rebuild the leachate treatment facilities of landfill aiming at reducing secondary pollution .Fourthly, improve the collection and transportation systems , and expand the coverage of municipal domestic garbage disposal facilities .Lastly, promote the classification of domestic garbage to improve the level of reduction .

为研究驯化对餐厨垃圾厌氧消化系统微生物群落结构的影响,在单相完全搅拌式(CSTR)反应器内,以农村户用沼气池污泥为接种污泥,进行了餐厨垃圾中温厌氧消化.反应器在3 g·L-1·d-1(以VS计)的负荷下成功启动,并连续45 d维持性能稳定,表明驯化成功.期间采用454焦磷酸测序技术分析了驯化前后系统内的微生物群落结构.结果表明,微生物群落结构与底物密切相关,驯化后细菌及古菌群落都发生明显变化.从细菌群落看,与复杂有机物降解相关的菌类显著下降(如梭菌纲(Clostridia)和(vadinHA17),而易降解碳水化合物发酵菌(如Petrimonas)和脂肪降解菌(如Erysipelotrichia)显著增加.这与餐厨垃圾易降解有机物含量高,且富含淀粉和脂肪相关.丰富的易降解有机物还使得反应器内总挥发性脂肪酸(VFA)浓度((2203±174) mg· L-1)远高于种泥水平((222.0±0.3) mg· L-1),这导致了产甲烷菌由乙酸型的甲烷鬃菌属(Methanosaeta,占85.01％)绝对主导转向氢营养型的甲烷螺菌属(Methanospirillum,占35.35％)、甲烷囊菌属(Methanoculleus,占9.89％)与之(46.97％)共同主导的局面.然而,驯化后Methanosaeta在非最优条件下依然保持主导地位,可见接种污泥的群落组成对厌氧消化系统群落结构的塑造也具有重大影响.

采用化学破乳-Fenton试剂处理乳化液废水,考察了相关因素对处理效果的影响特点和规律.实验结果表明,酸化作用中,静电作用对破乳有着关键性影响,降低乳化液废水pH值,有利于乳化液废水的油水分离;混凝剂投加量和废水pH值直接决定着破乳效果,油滴分散体系脱稳的适宜pH值既能使油滴间静电斥力较小,又能使大分子量的、大比表面积的多核络合离子通过电中和、吸附架桥、卷扫的作用来强化油水分散体系脱稳.Fenton氧化中,对于特定的Fe2+浓度,随着n(H2O2)/n(Fe2+)增加,COD去除程度增加,但增加的幅度越来越小,同时COD去除率达到稳定所需要的时间相应增加,适宜的摩尔比为20;废水Fenton体系H2O2开始阶段急速降低然后趋于平缓,体系Fe2+反应开始很短时间内急剧降低并趋于某一稳定值,H2O2浓度、Fe2+浓度随时间变化遵循一级反应动力学模型.

针对现今餐厨垃圾单相厌氧酸化系统缺乏有效的恢复性监控指标,提出可有效表征酸化系统恢复的监控指标.在中温条件下,连续对餐厨垃圾单相厌氧消化系统进行负荷冲击及恢复,分别对pH、沼气产率及成分、挥发性脂肪酸组成成分、总碱度(TA)和碳酸氢盐碱度(BA)及其组合指标进行监测分析.结果表明,传统单因子参数不能有效地指示系统恢复,选取VFA/BA和丙酸/乙酸的比值作为餐厨垃圾单相厌氧酸化系统恢复指示性参数.在酸化系统恢复过程中,当丙酸/乙酸≤1.4、VFA/BA≤0.4时,表明系统中各种挥发酸浓度值已恢复正常,且具有足够的缓冲能力,可提高反应器负荷,保证反应器恢复启动运行.

通过投加不同混凝剂、助凝剂和氧化剂,对含溴氰菊酯农药的某水库原水进行强化混凝-氧化处理,探讨了不同条件下对原水的处理效果.结果表明,当对水样仅作常规混凝处理时,聚合氯化铝(PAC)的处理效果优于其他混凝剂,最佳投加量为18mg/L,最佳pH为9,最高去除率可达64.5％.投加助凝剂可提高混凝效果,聚丙烯酰胺(PAM)助凝效果优于水玻璃.混凝后水样再用高锰酸钾(KMnO4)氧化处理,结果表明,在水样pH为5,KMnO4投加量为0.6mg/L,氧化时间为25 min的条件下,溴氰菊酯去除率最高可达82.4％.

Organic loading rate (OLR) disturbances were introduced into a mesophilic anaerobic digester treating food waste (FW) to induce stable and deteriorative phases. The microbial community of each phase was investigated using 454-pyrosequencing. Results show that the relative abundance of acid-producing bacteria and syntrophic volatile fatty acid (VFA) oxidizers increased dramatically at deteriorative phase, while the dominant methanogens did not shift from acetoclastic to hydrogenotrophic groups. The mismatching between bacteria and methanogens may partially be responsible for the process deterioration. Moreover, the succession of predominant hydrogenotrophic methanogens reduced the consumption efficiency of hydrogen; meanwhile, the dominant Methanosaeta with low acetate degradation rate, and the increase of inhibitors concentrations further decreased its activity, which may be the other causes for the process failure. These results improve the understanding of the microbial mechanisms of process instability, and provide theoretical basis for the efficient and stable operation of anaerobic digester treating FW.