外源葡萄糖对麦秸厌氧发酵产沼气的影响

为进一步阐释混合厌氧发酵的内在机制,在中温(35±1)℃条件下,以麦秸为原料,以葡萄糖为外源易分解有机碳,采用批式发酵方式,进行了葡萄糖不同添加量和不同添加方式对秸秆厌氧发酵产沼气影响试验。结果表明,在试验初始添加葡萄糖可提高日产气量,但葡萄糖添加量太少对提高秸秆总固体(TS)产气量无促进作用,当葡萄糖添加量为秸秆TS质量的6%时获得最大秸秆TS产气量,为303.13 m L·g-1,继续增加葡萄糖添加量,秸秆TS产气量反而降低;在秸秆厌氧发酵日产气量下降阶段一次性或者分次添加葡萄糖对促进秸秆厌氧发酵产沼气均无效果,仅在试验初始一次性添加秸秆TS质量6%的葡萄糖时对秸秆厌氧发酵产沼气有促进作用,秸秆TS产气量较对照提高9.24%;添加葡萄糖对秸秆厌氧发酵过程产气中甲烷含量无明显影响,但提高累积产气中甲烷平均含量,且在日产气量下降后添加葡萄糖的效果更好,但这种促进效果与对照间差异并不显著。综合以上结果,在试验初始一次性添加秸秆TS质量6%的葡萄糖可以获得最佳的产气效果。     

pH值调控对秸秆两阶段厌氧发酵产沼气的影响

两阶段厌氧发酵产沼气是秸秆沼气化利用的重要方式之一。秸秆厌氧发酵过程包括水解产酸和产甲烷两个阶段,水解产酸是秸秆沼气化的限速步骤,也是目前的研究重点。pH值是影响物料水解产酸的重要因素,目前的研究多集中于酸性环境对物料水解产酸的影响,碱性环境对物料水解产酸的影响还未见研究报道。在实验室条件下,每天调节水解产酸反应器发酵液pH值至8.0(T1)、9.5(T2)和11.0(T3),CK在实验过程中不调节水解产酸反应器发酵液pH值,水解产酸反应器排出的水解酸化液直接用蠕动泵泵入产甲烷反应器内产甲烷,分析了发酵过程中水解产酸反应器日产气量、甲烷含量、水解酸化液pH值、COD浓度以及产甲烷反应器产气特性的变化。结果表明:在不调节水解产酸反应器水解酸化液pH值条件下,秸秆两阶段厌氧发酵可以正常进行,秸秆干物质(TS)产气量为281.28mL·g-1,平均甲烷含量为47.36%;T1水解产酸反应器内水解酸化液pH值稳定在7左右,系统累积产气量、总产甲烷量和平均甲烷含量分别较CK大幅增加了24.51%、29.39%和2.5个百分点;T2和T3水解产酸反应器产气明显受到抑制,水解酸化液后续产甲烷亦受到明显抑制,产甲烷反应器累积产气量分别仅为CK的89.97%和17.48%,总产气量仅为T1的67.67%和10.20%;维持水解产酸反应器至碱性条件促进了秸秆中半纤维素的溶出和木质素的破坏,但不利于纤维素的溶出,TS损失率的结果与产气的结果一致。综合以上结果,调节水解产酸反应器水解酸化液pH值至8.0对提高秸秆两阶段厌氧发酵产沼气有明显的促进作用。     

互花米草不同部位厌氧发酵特性

在中温条件下(35±1)℃,对互花米草茎、叶和整株分别进行批式中温厌氧消化实验,分析发酵过程中日产气量、累积产气量、甲烷含量、pH值、VFA、TS、VS及固形物的元素变化.结果表明:在TS负荷为6%的条件下,互花米草茎、叶、整株厌氧发酵均具有很好的产气特性.产气率为:叶(399ml.g-1TS)整珠(374m.lg-1TS)茎(366ml.g-1TS),甲烷含量为:茎(69.11%)整珠(68.87%)叶(66.21%).pH值、VFA、TS、VS及固形物的元素的变化特征差异不大.叶中可能含有更多被微生物利用的物质,成分的差异是造成这种结果的重要原因.     

麦秸与奶牛场废水高固体混合厌氧发酵产甲烷研究

在实验室条件下,以麦秸和奶牛场废水为原料,设计麦秸与奶牛场废水质量比1∶4(T1)、1∶3(T2)和1∶2(T3)以及对照(麦秸与水质量比1∶4(T4))4个处理,研究发酵过程中日产气量、甲烷含量、发酵前后麦秸理化特性和结构的变化.结果表明,奶牛场废水与麦秸在中温、高固体条件下,厌氧发酵可以正常进行,且产气期延长2周以上,对甲烷含量的影响不大;厌氧发酵初始TS浓度对系统产气的影响较大,麦秸产气量随TS浓度的增加而降低,以T1的产气效果最好,麦秸TS产气量为0.41 L.g-1,较T4提高了17.14%,平均甲烷含量为48.78%;厌氧发酵后,麦秸半纤维素含量大幅降低,纤维素含量少许降低,降低幅度均为T1>T2>T4>T3,木质素含量稍有增加,各处理间无显著差异(P>0.05);FTIR和XRD的结果表明,厌氧发酵后,麦秸纤维素结晶区的相对含量增加,混合发酵可以促进厌氧微生物对麦秸纤维素结晶区的破坏.将麦秸与奶牛场废水(质量比)1∶4混合发酵产沼气是可行的,且促进了厌氧微生物对麦秸有机物的分解破坏,提高了麦秸产气量.     

两相厌氧发酵互花米草的特性

利用两相(固态水解酸化相+湿式发酵产甲烷相)发酵互花米草,通过尿素的添加来调整厌氧发酵互花米草的碳氮比,考察两相厌氧发酵互花米草的特性;并利用FTIR考察水解发酵前后互花米草结构的变化.研究结果表明,由于固态水解渗滤液对尿素的淋滤,产生高浓度的氨氮溶液,抑制了湿式发酵产甲烷反应器中的甲烷菌;通过53 d的两相发酵互花米草,单位挥发性固体(VS)累积产气量仅为98.6 mL.g-1(0℃),转化率是理论产气量的17.5%;游离性氨(FA)浓度超过55 mg.L-1,就会严重抑制高温甲烷菌;红外光谱分析表明,石灰堆沤预处理对互花米草结构改变较小;只有大幅度的强化预处理,才能显著提高互花米草发酵的产气量.     

沼液全量连续回流对稻秸厌氧发酵特性的影响

秸秆厌氧发酵沼气工程中合理的沼液回流可减少沼液排放量,降低后续沼液处置利用成本。以稻秸为底物,采用完全混合搅拌反应器(CSTR)半连续发酵方式,研究沼液全量连续回流对稻秸厌氧发酵特性的影响,旨在为明确沼液全量回流对秸秆厌氧发酵的影响机制、改进沼液全量回流技术提供科学依据。结果表明:在100%沼液回流条件下连续回流50 d时系统运行稳定,总固体(TS)产气率、挥发性固体(VS)产气率及容积产气率分别稳定在245 m L·g-1、300 m L·g-1及0.74 L·L-1·d-1。但随着运行时间延长,回流天数达85 d时,虽然发酵液pH值和沼气中φ(CH4)无明显变化,但系统产气效率明显受到抑制。产气受抑制阶段与产气稳定阶段相比,TS产气率、VS产气率及容积产气率分别下降到186 m L·g-1、226 m L·g-1及0.56 L·L-1·d-1,下降幅度达24%。进一步分析表明,沼液中ρ(NH4+-N)下降到185 mg·L-1,下降幅度为71%;主要金属离子总质量浓度增加到4.13 g·L-1,增加幅度为342%。初步判断沼液全量连续回用会因氮含量严重下降和盐分积累致系统产气量下降,但真实原因还有待进一步研究。     

不同时间NaOH预处理对玉米秸秆中温厌氧发酵的影响

通过自行设计的厌氧发酵装置,采用0‰、4‰和12‰的NaOH溶液对玉米秸秆预处理3、7、14、21 d和28 d,研究不同时间NaOH预处理对玉米秸秆中温(35℃)厌氧发酵的影响,旨为玉米秸秆在沼气生产中的高效应用提供理论依据。结果表明,采用NaOH预处理可以提高玉米秸秆中温厌氧发酵时的产气量和产气速率,其中4‰NaOH预处理的效果好于0‰和12‰,而且以预处理7 d的效果最好。以16.0 g玉米秸秆为发酵原料时,111 d产气停止,总产气量为7 411.00 m L,若以累积产气量达到总产气量的90%以上作为发酵完成标准,则78 d发酵完成,可累积产气6 672.60 m L,日均产气85.55 m L,干物质累积产气量为417.04 m L·g~(-1)。最优组合预测模型同样显示,4‰NaOH预处理效果最好,最佳预处理时间为9.48 d,84.00 d发酵完全,产气速率为60.29 m L·d-1,最大干物质累积产气量为316.52 m L·g~(-1),这与实测值具有良好的一致性。综合判断,在玉米秸秆中温厌氧发酵时,通过适当延长预处理时间来减少碱液用量是可行的,其中以4‰NaOH预处理9.48 d效果最好。     

不同预处理方式对玉米秸秆结构及产气特性的模拟研究

以玉米秸秆为原料,在25℃条件下,分别采用沼液及不同含量的NaOH溶液对秸秆进行预处理,研究NaOH投加量与秸秆纤维结构、预处理料液理化性质以及产能特性之间的关系。结果表明,采用4 mg·g-1NaOH溶液预处理7 d后,料液中COD浓度已基本稳定,溶液pH值在7~8之间,可直接装罐发酵。利用扫描电镜观测预处理后秸秆结构变化状况,发现经4 mg·g-1NaOH溶液预处理后的秸秆表层结构粗糙、多孔,有助于厌氧微生物与可发酵底物的接触,产气量是未经预处理玉米秸秆的5.5倍,其干物质产气率为225.8 mL·g-1。综合考虑产气效率、生产成本及工程操作,采用4 mg·g-1NaOH溶液预处理秸秆更利于工程推广应用。     

压滤处理对水葫芦不同部位厌氧发酵的影响

为提高水葫芦的厌氧产气性能,将水葫芦整株、茎和根压滤,分别将压滤前后的水葫芦根、茎和整株以及压滤液接种进行中温批式厌氧消化实验,考察了发酵过程中产气量、pH值和挥发性脂肪酸的变化情况.结果表明,压滤处理明显提高了水葫芦各部位的厌氧产气能力,压滤后的水葫芦整株、根和茎的TS产气量分别为271.93、87.29和330.83 ml·g-1TS,较压滤前分别提高了75.33%、92.04%和72.95%;压滤处理对水葫芦各部位发酵过程中pH和挥发性脂肪酸含量的影响不大;水葫芦各部位压滤液的厌氧产气能力均较差,不适合进行厌氧发酵产气.因此,将水葫芦压滤后厌氧发酵是一种提高水葫芦厌氧生物转化率的可行的方法.     

餐厨垃圾与污泥联合两步厌氧发酵产酸阶段条件优化试验

以污水处理厂活性污泥为接种物,以餐厨垃圾为发酵底物进行两步厌氧发酵产气试验,考察了产酸阶段初始pH值、温度及发酵物的预处理方法对两步发酵产气的影响.结果表明,产酸阶段的初始pH值以5.0最佳,气体的累计产气量最大,为13.69 mL·g-1TVS,产酸阶段的温度以65℃最佳,产气的累计产气量最大,为74.35 mL·g...     

皇竹草厌氧发酵产沼气特性

在中温(35℃)条件下,采用批量厌氧发酵对生长期为35 d和68 d的皇竹草的发酵特性进行研究.实验结果表明,两组不同生产期的皇竹草C/N均较低,分别为14.75和17.52.经过45 d的厌氧发酵处理,生长期为35 d的皇竹草产气率为243.77ml.g-1VS,在第1天和第15天出现两个产气高峰,第45天的产气结束;生长期为68 d的皇竹草产气率为247.06 ml.g-1VS,出现4次产气高峰,第45天日产气量为512ml.生长期为35 d和68 d的皇竹草发酵液中乙酸、丙酸、丁酸含量分别为48.48%—72.71%、5.64%—22.99%、6.84%—26.71%和42.51%—64.17%、5.83%—34.20%、10.98%—34.41%,丙酸型发酵和丁酸型发酵交替进行.发酵液的pH值均先降低后升高最后保持相对稳定.皇竹草适合作为沼气发酵的原料加以利用.     

添加剂对污泥厌氧消化性能的影响

在间歇培养条件下,研究了还原型辅酶Ⅱ（NADPH）、乙酰辅酶A（Acetyl Co A）和对氨基苯甲酸（PABA）3种添加剂对污泥厌氧消化性能的影响.结果表明,3种微生物活性促进剂均能促进污泥厌氧消化产气.其中,NADPH的促进效果最为显著,消化第35 d,产甲烷量比对照组高15.90%.在污泥含固率为3%、未调初始pH（pH=6.7）和温度35℃的厌氧消化条件下,NADPH的最佳添加量为50 mg.L-1,消化第36 d,污泥累积产甲烷量127.13 mL.g-1VSS.在含固率3%、初始pH=8.5、温度55℃和NADPH添加量为50 mg.L-1的工艺条件下,污泥厌氧产气效果最佳,消化第30 d时累积产甲烷量达158.02 mL.g-1VSS.     

Use of gamma-irradiation pretreatment for enhancement of anaerobic digestibility of sewage sludge

The effects of γ-irradiation pretreatment on anaerobic digestibility of sewage sludge was investigated in this paper. Parameters like solid components, soluble components, and biogas production of anaerobic digestion experiment for sewage sludge were measured. The values of these parameters were compared before and after γ-irradiation pretreatment. Total solid (TS), volatile solid (VS), suspended solid (SS), volatile suspended solid (VSS), and average floc size of samples decreased after γ-irradiation treatment. Besides, floc size distribution of sewage sludge shifted from 80–100 μm to 0–40 μm after γ-irradiation treatment at the doses from 0 to 30 kGy, which indicated the disintegration of sewage sludge. Moreover, microbe cells of sewage sludge were ruptured by γ-irradiation treatment, which resulted in the release of cytoplasm and increase of soluble chemical oxygen demand (SCOD). Both sludge disintegration and microbe cells rupture enhanced the subsequent anaerobic digestion process, which was demonstrated by the increase of accumulated biogas production. Compared with digesters fed with none irradiated sludge, the accumulated biogas production increased 44, 98, and 178 mL for digesters fed sludge irradiated at 2.48, 6.51, and 11.24 kGy, respectively. The results indicated that γ-irradiation pretreatment could effectively enhance anaerobic digestibility of sewage sludge, and correspondingly, could accelerate hydrolysis process, shorten sludge retention time of sludge anaerobic digestion process.     

Effect of different gas releasing methods on anaerobic fermentative hydrogen production in batch cultures

Decreasing hydrogen partial pressure can not only increase the activity of the hydrogen enzyme but also decrease the products inhibition, so it is an appropriate method to enhance the fermentative hydrogen production from anaerobic mixed culture. The effect of biogas release method on anaerobic fermentative hydrogen production in batch culture system was compared, i.e., Owen method with intermediately release, continuous releasing method, and continuous releasing+ CO₂ absorbing. The experimental results showed that, at 35°C, initial pH 7.0 and glucose concentration of 10 g·L^-1, the hydrogen production was only 28 mL when releasing gas by Owen method, while it increased two times when releasing the biogas continuously. The cumulative hydrogen production could reach 155 mL when carbon dioxide in the gas stream was continuously absorbed by 1 mol·L^-1 NaOH. The results showed that acetate was dominated, accounting for 43% in the dissolved fermentation products in Owen method, whereas the butyrate predominated and reached 47%–53% of the total liquid end products when releasing gas continuously. It is concluded that the homoacetogenesis could be suppressed when absorbing CO₂ in the gas phase in fermentative hydrogen production system.     

猪场废水厌氧消化过程中的除磷效果

采用序批式半连续厌氧消化试验方法,研究猪场废水厌氧消化过程中磷的去除情况。结果表明,水力停留时间（HRT）为1、3、6和9 d的厌氧反应器平均除磷率分别为65.0%、81.1%、82.7%和83.0%,而COD平均去除率分别为54.5%、82.3%、87.0%和85.9%。厌氧反应器除磷能力随沼气产量的增加而增加,说明厌氧反应器中磷的去除与产甲烷过程密切相关。对厌氧消化前后的污泥进行浸提后发现,厌氧消化过程中,化学反应生成磷酸盐沉淀的除磷作用十分显著,污泥中正磷酸盐,与铁结合的磷化合物（Fe-RP）,还原可溶性磷,与钙、镁离子结合的磷化合物（Ca-RP、Mg-RP）以及无机或有机聚合磷增加量分别为0.027 8～0.101 5、0.013 5～0.081 0、0.2165～0.430 5、23.4～54.8和7.2～21.5 mg.g-1;且总体而言,HRT越长,污泥中与不同金属结合的磷增加量就越大。从HRT、磷和有机物的去除效果以及沼气产气速率3个方面综合考虑,猪场废水厌氧消化反应器的HRT控制在3 d为宜。     

Influencing mechanism of high solid concentration on anaerobic mono-digestion of sewage sludge without agitation

High-solids anaerobic digestion of sewage sludge was a promising process, but high solid concentration negatively influenced methane production. The influencing mechanism was systematically analyzed in this study through a series of static anaerobic digestion experiments at total solids (TS) contents of 3%–15%. The results showed that TS 6% was the boundary between low-solids and high-solids anaerobic digestion, and the accumulative methane yield decreased exponentially when TS increased from 6% to 15%. The performance of anaerobic digestion was directly determined by the efficiency of mass transfer, and the relation between methane yield and sludge diffusive coefficients was well described by a power function. Thus, the increasing TS resulted in an exponential increase in sludge viscosity but an exponential decrease in diffusive coefficient. The blocked mass transfer led to the accumulation of volatile fatty acids (VFAs) and free ammonia. Acetic metabolism was the main process, whereas butyric and propionic metabolisms occurred at the initial stage of high-solids anaerobic digestion. The concentration of VFAs reached the maximum at the initial stage, which were still lower than the threshold influencing methanogens. The concentration of free ammonia increased gradually, and the methanogenesis was inhibited when free ammonia nitrogen exceeded 50 mg·L⁻¹. Consequently, the deterioration of high-solids anaerobic digestion was related to the blocked mass transfer and the resulting ammonia accumulation.     

低浓度溶解氧下猪粪固体有机物水解产酸研究

本文以猪粪为发酵原料,通过批式实验研究不同溶解氧(DO)浓度(0—0.26 mg.L-1)、发酵时间(3—12 d)和挥发性固体(VS)浓度(11.14—111.35 g.L-1)对猪粪固体水解酸化过程的影响,确定了低DO浓度下固体有机物优化水解产酸工艺条件:中温35℃,初始VS浓度37.11 g.L-1,初期的DO浓度0.1—0.26 mg.L-1.在此条件下,发酵时间3 d,DO浓度下降到0.10 mg.L-1以下.猪粪发酵液pH值由7.45±0.10降低到5.86±0.17,VS降解率(25.67±1.20)%,挥发性脂肪酸(VFA)中乙酸(3895±91)mg.L-1、丙酸(2313±82)mg.L-1、正丁酸(1361±17)mg.L-1、正戊酸(540±11)mg.L-1.优化条件下的猪粪水解酸化液进行厌氧产甲烷发酵,发酵10 d内产气停止,低溶解氧水解酸化和厌氧产甲烷发酵累计时间仅为13 d,甲烷体积分数(69.5±0.2)%,VS产气率为(0.282±0.011)L CH.4g-1VS.研究结果表明,适当延长发酵时间能够增加VFA中乙酸的含量,初始VS浓度差异对发酵液VFA浓度和VS降解率的影响较显著,低溶解氧能够促进猪粪固体有机物水解过程.     

Solid state biomethanation of fruit wastes.

Overtones of fruit wastes accumulate daily in the city of Chennai, India and there is an urgent need to develop, assess and use ecofriendly methods to dispose them. Presently an attempt has been made to study solid state biomethanation of fruit wastes using a laboratory scale anaerobic digester Fruit wastes containing 3%, 4% and 5% solids were used for experimentation. Daily and cumulative production of biogas produced during the study was recorded. Increase in nitrogen, phosphorus and potassium content in the feed was observed during the digestion. During the study the biogas generation increased with increase in total solids. While the gas generation was 0.006 m3/day/m3 of the reactor volume when the solid content was 3% the corresponding values for 4% and 5% solids were 0.27and 0.35 m3 respectively Varying TS 3% to 4% has no effect on fermentation stability and pH remained between 6.8 and 7.4, but an inhibition of methanogenic bacteria was observed for TS 5%. The overall performance of the reactor was depressed by changing feed concentration from 3% to 5%. Experiments with 4% initial solid contend was ideal for solid-state biomethanation.