活性污泥产酸发酵研究进展

有机物的厌氧生物处理一般经过三个阶段:水解阶段、产酸发酵阶段和产甲烷阶段;研究证明,产酸相不同发酵类型的形成对产甲烷相乃至整个工艺的稳定运行具有至关重要的作用,此外,污泥厌氧消化过程所产生的大量的挥发性脂肪酸(VFAs),如乙酸、丙酸、丁酸及戊酸等,还可作为化工原料用于发酵工业生产各种高附加值产品.近年来,产酸发酵受到越来越多的关注,该文主要对污泥产酸阶段的产酸发酵类型、产酸发酵细菌的生态学、产酸过程的影响因素和生态因子以及产酸发酵的液相末端产物VFAs的测定方法进行了论述.     

化工上的应用

372354利用温州蜜柑皮发醉甲烷的研究.1.在产酸发酵中由温州蜜柑皮生产挥发性脂肪酸〔日〕/Kashiwagi,S,…了公害一一985,20(6)一257~267〔译自CBA-1986,(8),3217〕 产酸的细菌在其适应的厌氧条件下可将温州蜜柑皮转化为挥发性脂肪酸。为了从原始消化污泥巾消除产申烷细菌,要使     

嗜酸产甲烷菌及其在厌氧处理中的应用

产甲烷菌在自然界碳素循环过程中发挥着重要作用.酸性泥炭沼泽环境中存在着多种未知的产甲烷古菌,其中嗜酸产甲烷菌因其特殊的生长代谢特征近年来引起学者的广泛关注.若将嗜酸产甲烷菌应用于高浓度有机废物或废水的厌氧消化过程中,可从本质上克服因酸积累造成的产甲烷抑制,减少运行成本,扩展厌氧消化处理技术的应用范围.本文综述了嗜酸产甲烷菌的富集分离培养方法、生理生化特性、代谢特征及相关分子生物学研究等内容,并对其在厌氧处理中的应用前景进行了分析和展望,提出了未来研究的方向.     

生物强化污泥厌氧发酵产酸研究进展*

污泥厌氧发酵生产挥发性脂肪酸相较产甲烷,是更具应用价值的污泥稳定途径及资源化利用方式,得到国内外学者的普遍重视。考虑到产酸量低和产酸过程的不稳定性是限制污泥发酵产酸的主要问题,采用生物强化方法实现挥发性脂肪酸的大量积累,与物理和化学方法相比,具有成本低、无二次污染等优点。根据生物强化制剂的类型,归纳了微生物纯培养物、微生物混合培养物及生物酶强化对污泥厌氧发酵产酸的影响,并在此基础上对生物强化技术控制污泥定向产酸、调控奇偶数碳比率等方面的应用进行讨论。此外,分析了影响挥发性脂肪酸产量和组分的因素,如pH、温度、底物、水力停留时间和污泥龄等。最后对生物强化技术的发展方向进行了展望,以期为深入探究污泥资源化利用提供借鉴。     

污泥厌氧消化产酸发酵过程中乙酸累积机制

[目的]研究污泥厌氧消化产挥发性脂肪酸(VFA)过程中的有机物碳流的转化机制,阐明乙酸累积机理。[方法]研究溴乙烷磺酸盐(BES)和氯仿(CHCl3)抑制模型下中间代谢产物和气体的累积,检测各产乙酸功能菌群数量,推断污泥产酸发酵过程中的有机物碳流方向和乙酸累积机理。[结果]BES模型乙酸浓度达27 mmol/L,fhs基因拷贝数比对照组高2-3倍,产氢产乙酸菌略有下降。CHCl3模型乙酸浓度达22 mmol/L,fhs基因拷贝数比BES组低一个数量级,产氢产乙酸菌下降明显。[结论]BES特异性较高,除产甲烷菌外对其他厌氧产酸细菌没有影响,乙酸浓度增加并且其主要来源于水解发酵产酸以及同型产乙酸过程。氯仿除抑制产甲烷菌外,对同型乙酸菌和产氢产乙酸菌也有强烈的抑制作用。     

餐厨垃圾和市政污泥配料比对厌氧产甲烷特性及微生物多样性的影响

在(38±0.5)℃的温度下,研究不同配料比对餐厨垃圾和市政污泥混合厌氧消化过程中系统参数及微生物群落多样性的影响,设定餐厨垃圾和市政污泥的挥发性固体的质量比为1∶0、0∶1、1∶1、1∶2和2∶1,并采用高通量测序技术分析厌氧消化过程中微生物组成的多样性。结果表明:质量比为1∶1的体系混合厌氧消化时,产甲烷效果最佳,单位质量的挥发性固体含量的产甲烷量可达到232.86 L/kg,挥发性固体含量的去除率达46.09%。各个混合比例体系中的优势物种为拟杆菌门(Bacteroidetes)和甲烷八叠球菌属(Methanosarcina)。在餐厨垃圾中添加市政污泥混合厌氧消化能够提高微生物群落的多样性,促进菌种间的协同作用,进而提升产气效率。     

厌氧消化工艺抑制因素研究进展

随着对厌氧消化技术不断深入的研究,厌氧消化技术的应用取得了快速的发展,但仍然存在如处理效率低、运行稳定性差等问题。本文综述了厌氧消化工艺中主要的抑制因素及其抑制机理,为厌氧消化工艺的应用提供理论依据。     

畜禽粪便和粪水厌氧消化技术分析与展望

随着我国畜禽养殖集约化程度的不断提高,畜禽粪污导致的环境污染已成为畜禽养殖业发展面临的重要制约因素。粪污通过厌氧消化可回收能源、生产沼肥和消灭病原菌,避免对环境产生危害,是畜禽粪污处理和资源利用技术链条的核心环节。根据原料性质的差异,将粪污区分为畜禽粪便与养殖废水,分别探讨了这两种处理对象厌氧消化处理的不同技术难点和发展方向。针对畜禽粪便,重点探讨了高含氮粪便厌氧消化过程中存在的氨抑制问题及解除氨抑制的方法;针对养殖废水,介绍了废水处理与回用标准,比较分析了升流式厌氧污泥床、厌氧膜生物反应器、厌氧折流板反应器和自搅拌厌氧折流板反应器等几种代表性的和新型的废水厌氧处理工艺,并展望了技术的创新发展,旨在为畜禽粪便和养殖废水的厌氧消化及废水回用技术的发展提供参考。     

城市污泥添加厨余垃圾厌氧发酵产挥发性脂肪酸的研究

为了考察污泥产酸工业化的可行性和添加食品废弃物对污泥产酸的影响,本实验在实验室的基础上进行扩大研究,考察了不同的底物总固体浓度对产挥发性脂肪酸的影响.结果显示添加厨余垃圾之后挥发性脂肪酸的累积量可达到17.62g/L.综合产挥发性脂肪酸效果、底物降解效果和产率等情况建议在较大规模的生产过程中选择130g/L的底物浓度为...     

多级逆流工艺促进城市污泥厌氧发酵生产挥发性脂肪酸

采用一种新型的厌氧发酵工艺——多级逆流发酵工艺对城市污泥进行厌氧发酵, 实现高效产挥发性脂肪酸的目的。结果表明, 实验条件下应用多级逆流发酵工艺, 挥发性脂肪酸浓度与产率分别达到(10.5±0.5) g/L和0.20 gVFAs/ gVS, 与普通厌氧发酵工艺相比, 分别提高了31%和54%。此外, 在多级逆流工艺中, 底物有机质去除率可达50%, 较普通厌氧发酵提高了37%。进一步分析多级逆流工艺产酸的机制, 发现产酸效率的提高在于降低了发酵产物对厌氧产酸细菌的抑制效应, 并且工艺的VFAs产率以及有机质去除率分别取决于第一级和第三级厌氧发酵过程。因此, 城市污泥采用多级逆流工艺厌氧发酵不仅能够有效促进挥发性脂肪酸的生成, 而且能够较大程度上提高污泥中有机质的去除率。     

Comparison of treatment efficacy and stability of microbial populations between raw and anaerobically treated liquid pig manure, using PCR-DGGE and 16S sequencing

The effects of adding an adapted inoculum to liquid pig manure (LPM) prior to anaerobic digestion were evaluated by standard analytical methods. In parallel, the phylogenetic diversity of the microbial community of raw and anaerobically digested pig manure was studied by both denaturing gradient gel electrophoresis (DGGE) and sequence analysis of 16S rRNA fragments amplified by polymerase chain reaction. Gas production, volative fatty acid production, removal of soluble chemical oxygen demand, and removal of volatile soluble solids were measured on raw and on inoculated liquid pig manure subjected to anaerobic digestion. DGGE profiles of 16S rRNA genes were used to compare the major elements of the bacterial community composition in raw LPM with those present under various incubation conditions. Major bands were excised and sequenced to gain insight into the identities of the bacterial populations from LPM treated under different conditions. The results show that the addition of an adapted inoculum did not have a major impact on the conversion of pig manure into soluble organic matter and did not significantly change the microbial populations present during anaerobic digestion of LPM. Bacterial composition also indicated that Clostridium species are important constituents of the LPM community.     

Assessment and parameter identification of simplified models to describe the kinetics of semi-continuous biomethane production from anaerobic digestion of green and food waste

Biochemical reactions occurring during anaerobic digestion have been modelled using reaction kinetic equations such as first-order, Contois and Monod which are then combined to form mechanistic models. This work considers models which include between one and three biochemical reactions to investigate if the choice of the reaction rate equation, complexity of the model structure as well as the inclusion of inhibition plays a key role in the ability of the model to describe the methane production from the semi-continuous anaerobic digestion of green waste (GW) and food waste (FW). A parameter estimation method was used to investigate the most important phenomena influencing the biogas production process. Experimental data were used to numerically estimate the model parameters and the quality of fit was quantified. Results obtained reveal that the model structure (i.e. number of reactions, inhibition) has a much stronger influence on the quality of fit compared with the choice of kinetic rate equations. In the case of GW there was only a marginal improvement when moving from a one to two reaction model, and none with inclusion of inhibition or three reactions. However, the behaviour of FW digestion was more complex and required either a two or three reaction model with inhibition functions for both ammonia and volatile fatty acids. Parameter values for the best fitting models are given for use by other authors.     

城市污泥中邻苯二甲酸酯(PAEs)的厌氧微生物降解

邻苯二甲酸酯(PAEs)是城市污泥中普遍存在的一类具有内分泌干扰性作用的有机污染物.研究污泥厌氧生物处理过程中PAEs的微生物降解对保障污泥农用的安全性十分必要.本文以污泥中两种主要的PAEs——邻苯二甲酸二丁酯(DBP)和邻苯二甲酸(2-乙基己)酯(DEHP)为研究对象,通过比较PAEs在污泥厌氧消化系统与发酵产氢系统中降解过程的差异及系统污泥特性的变化,分析不同污泥厌氧生物处理系统中影响PAEs降解的可能因素.结果表明: 在污泥厌氧发酵系统中,DBP在6 d内降解率达99.6%, DEHP在整个14 d的培养期间也降解了46.1%;在发酵产氢系统中,在14 d培养过程DBP的降解率仅为19.5%,DEHP则没有明显的降解.与厌氧消化系统相比,PAEs在发酵产氢系统中的降解受到明显抑制,这与发酵产氢过程中微生物量下降、革兰氏阳性菌/革兰氏阴性菌(G⁺/G^-)和真菌/细菌变小及挥发性脂肪酸(包括乙酸、丙酸及丁酸)浓度升高有关.     

Responses of the biogas process to pulses of oleate in reactors treating mixtures of cattle and pig manure

The effect of oleate on the anaerobic digestion process was investigated. Two thermophilic continuously stirred tank reactors (CSTR) were fed with mixtures of cattle and pig manure with different total solid (TS) and volatile solid (VS) content. The reactors were subjected to increasing pulses of oleate. Following pulses of 0.5 and 1.0 g oleate/L, the most distinct increase in volatile fatty acid (VFA) concentrations were observed in the reactor with the lowest TS/VS content. This suggests a higher adsorption of oleate on the surfaces of biofibers in the reactor with the highest TS/VS and a less pronounced inhibition of the anaerobic digestion process. On the other hand, addition of 2.0 g oleate/L severely inhibited the process in both reactors, and a significant increase in all VFA concentrations combined with an immediate drop in methane production was noticed. However, 20 days after the reactors had been exposed to oleate both reactors showed a lower VFA concentration along with a higher methane production than before the pulses. This indicates that oleate had a stimulating effect on the overall process. The improved acetogenic and methanogenic activity in the reactors was confirmed in batch activity tests. In addition to this, toxicity tests revealed that the oleate pulses induced an increase in the tolerance level of acetotrophic methanogens towards oleate. When evaluating the usability of different process parameters (i.e., VFA and methane production) as indicators of process recovery, following the inhibition by oleate, propionate was found to be most suitable.     

Short-term and long-term effects of increasing temperatures on the stability and the production of volatile sulfur compounds in full-scale thermophilic anaerobic digesters

This study compares the effect of a rapid increase of the digester temperature (from 54 degrees C to 58 degrees C in 2 weeks) with a slow increase (from 53.9 degrees C to 57.2 degrees C at a rate of 0.55 degrees C per month) on full-scale thermophilic anaerobic digestion at Hyperion Treatment Plant. The short-term test demonstrated that rapidly increasing the digester temperature caused elevated production of volatile sulfur compounds, most notably methyl mercaptan, but volatile solids destruction and methane production were not significantly affected. The increase of the volatile fatty acid to alkalinity ratio from 0.1 to over 0.3 indicated a transient change in digester biochemistry, which was reversed by lowering the temperature. In the long term-test, a slow increase of digester temperature, the production of hydrogen sulfide increased above temperatures of 56.1 degrees C, but was controlled by increased injection of ferrous chloride. Methyl mercaptan was detected in trace amounts at the highest temperature tested (57.2 degrees C). This test showed insignificant effects on other digestion parameters, although some temperature-independent changes were observed that could have been seasonal effects over the year that the long-term test lasted. Thus a slow temperature increase was preferable. This observation contrasts with previous results showing the desirability of a rapid temperature rise to first establish a thermophilic culture when converting from mesophilic operation. Further research is warranted on temperature limits and process changes to optimize thermophilic anaerobic digestion.     

Combined removal of nitrate and carbon in granular sludge: Substrate competition and activities

Granular sludge from an upflow anaerobic sludge blanket reactor treating synthetic waste water containing a mixture of volatile fatty acids and nitrate showed a removal efficiency of nearly 100% for both nitrogen and carbon. This activity was achieved by a combined process of denitrification and methanogenesis under conditions of surplus carbon. Under batch conditions the two processes proceeded clearly separated in time with first denitrification dominating and excluding methanogenesis. However, as soon as nitrate was depleted, methane production was initiated, showing that the inhibition of methanogenesis by nitrate was reversible. Of the volatile fatty acids supplied to the reactor, i.e. acetate, propionate, and butyrate, the denitrifying population clearly preferred butyrate and propionate even though acetate could also be metabolized. Consequently, growth of syntrophic volatile fatty acid degraders was suppressed by the denitrifiers in cases of low C:N ratios in the medium, leaving acetate as the major substrate for methanogenesis.Abbreviations UASB upflow anaerobic sludge blanket - COD chemical oxygen demand - VFA volatile fatty     

Lactate and ethanol as intermediates in two-phase anaerobic digestion

The thermodynamics of the various anaerobic digestion patterns of hexose to methane are compared. It appears that by directing the hexose-hydrolysis phase towards ethanol and lactic acid production, methanogenesis can be enhanced because the syntrophic bacteria are allocated more potentially available energy. This hypothesis was confirmed in a series of laboratory test runs. They revealed that lactic acid and ethanol as intermediates, in comparison to lower volatile fatty acids, give rise to a considerably higher effluent quality and a slightly larger biogas production.     

Anaerobic digestion: microbial and biochemical aspects of volatile acid production

Summary The production of organic acids has been tested with bacterial flora selected from a municipal sludge digestor. In order to elucidate the basic mechanisms by which glucose is converted to volatile fatty acids, the examination of non-methanogenic bacteria was attempted. Both lactate-producers and lactate-utilizers were found among these bacteria. When mixed isolates were used as the inoculum, the accumulation of lactic acid and its further conversion to propionic and butyric acids was demonstrated at a carbon conversion rate of about 0.75. It is therefore suggested that this metabolic sequence may occur as a normal process in acidogenic fermentation, which is the first step in anaerobic digestion.