微好氧预处理对市政污泥厌氧消化产甲烷的影响

针对目前市政污泥处理资源化与减量化效率低的问题,利用微好氧预处理技术进行预处理,提高其甲烷产量。利用有机物溶出效率、VSS减量、甲烷产量3项指标对预处理效果进行了评价;研究了不同参数条件下微好氧预处理对市政污泥厌氧消化产甲烷的影响;探讨了微好氧预处理对污泥胞外聚合物的影响。结果表明,微好氧预处理可以促进污泥溶解性有机物释放、提高VSS去除率;在最佳反应条件下(曝气强度0.30 m³·(min·m³)⁻¹、预处理时间12 h),相对于未经过预处理的工况,甲烷产量可提高26.77%;微好氧预处理对剩余污泥活性细胞的影响主要发生在胞外聚合物部分,同时也存在对活性微生物的破解作用。市政污泥经过微好氧预处理后,可有效提升后续中温厌氧消化或高温厌氧消化的甲烷产量。     

木薯酒精废水高温厌氧发酵产氢研究

以木薯酒精废水为厌氧发酵产氢底物,以中温(37℃)厌氧颗粒污泥作为接种物.研究了高温条件(60℃)下厌氧发酵产氢的可行性;并比较了60～80℃条件下的累积产氢量,产氢速率和液相发酵产物组成,以确定温度对木薯酒精废水厌氧发酵产氢的影响以及不同温度下厌氧发酵产氢菌的代谢类型.结果表明,60℃时累积产氢量为383 mL(木薯酒精废水用量140 mL)、产氢率为70.0 mL(以每克挥发性固体(VS)计),中温厌氧颗粒污泥适合作为高温条件下木薯酒精废水厌氧发酵产氢的接种物;从60℃升高到80℃时,累积产氢量逐渐下降,最大产氢速率逐渐降低,80℃时产氢完全受到抑翩.70℃为产氢的临界点,低于70℃时厌氧发酵产氢菌的代谢类型属典型的丁酸型发酵,此过程中伴随着大量氢气产生,大于等于70℃时,正丁酸生成受到严重抑制,累积产氢量迅速降低;氢气的产生主要来自于溶解性碳水化合物的分解.     

挥发性脂肪酸对厌氧干式发酵产甲烷的影响

为了提高中温干式厌氧间歇发酵效率,研究了发酵过程中间产物———挥发性脂肪酸对产甲烷的影响。实验分2批进行,第1批在牛粪发酵过程中分别添加乙酸、丙酸和丁酸,第2批发酵添加易产生挥发酸的厨余垃圾混合发酵。结果显示,添加单一挥发酸的发酵过程中,添加丙酸的产甲烷速度较慢,因为丙酸降解生成乙酸的速度较慢,减慢了甲烷的形成;混合发酵过程厨余垃圾产甲烷速度比牛粪快,发酵过程产生2个产气高峰;牛粪和厨余垃圾固体物质含量比在11∶1到5∶1范围内较好,比牛粪单独发酵产气多,产酸高但不酸败,产生的挥发酸主要是乙酸和丙酸,其中比例为7∶1混合发酵的产甲烷速率最大,为4.89 mL/(g VS·d)。实验表明,牛粪厌氧干式发酵过程添加一定量的厨余垃圾可加快挥发酸的产生并提高挥发酸产量,从而提高甲烷的产量,但是总挥发酸长时间超过10 000 mg/L,pH降到不适于产甲烷菌生长的范围时,将抑制甲烷的生成,挥发酸积累导致厌氧发酵酸败。     

长链脂肪酸对餐厨垃圾厌氧消化产甲烷的影响

为研究中温条件下长链脂肪酸（LCFA）的含量及代谢对餐厨垃圾厌氧消化过程的影响,考察了LCFA添加量分别为0、0.6、1.2、1.8、2.4、3和3.6 g·L-1条件下产沼气量、累积甲烷产量以及代谢中间产物挥发性脂肪酸/乙醇的浓度和组成。结果表明：在中温餐厨垃圾厌氧产甲烷的过程中,虽然LCFA也能够被微生物代谢转化生成甲烷,但LCFA的存在会对产甲烷过程造成一定程度的抑制作用;当其含量较低时抑制作用较为微弱,当其含量较高（>2.4 g·L-1）时,甲烷产量及产甲烷速率都会受到较大影响;特别是当LCFA含量高于3.6 g·L-1时,体系出现较强的抑制现象。通过实验累积值与理论甲烷产率的对比可以发现,LCFA含量越高的反应器中实验累积值/理论值的比值越低,表明有机物的转化效率越低。通过对厌氧过程中间产物的检测可知,LCFA含量越多的反应器中初期累积的挥发性脂肪酸浓度越高,当反应体系的LCFA浓度超过2.4 g·L-1时,累积的乙酸和丙酸浓度较高,丙酸降解过程和乙酸代谢产甲烷的过程受到一定程度的延滞和抑制作用,降解速率低于正常水平,厌氧发酵的能力和效率受到影响。     

Effect of potassium inhibition on the thermophilic anaerobic digestion of swine waste.

The inhibition effects of high potassium concentration on thermophilic anaerobic digestion of swine waste were studied. A continuous stirred tank reactor (CSTR), operated at a hydraulic retention time of 10 days and chemical oxygen demand loading of 7.2 to 7.5 g/L/d, was used to digest swine waste and cultivate thermophilic anaerobic microorganisms. To evaluate the toxicity of potassium, batch inhibition tests were also conducted. Without acclimation to potassium, the inhibition threshold beyond which methane production decreased significantly was 3 g K+/L. Volatile fatty acids accumulation was observed during the decline of methane production. Propionic acid was the dominant fatty acid, indicating that propionic acid utilizers were more sensitive to potassium inhibition than acetoclastic methanogens. To test the effect of acclimation on potassium inhibition, the potassium concentration in the CSTR was increased to 6 and 9 g K+/L. Acclimation to 6 g K+/L increased the tolerance of anaerobic inocula to potassium inhibition without significantly reducing the methanogenic activity. The inhibition threshold was increased from 3 g K+/L for unacclimated inocula, to 6 g K+/L for inocula acclimated to 6 g/L of potassium. Acclimation of inocula to 9 g/L potassium further increased the inhibition threshold to 7.5 g K+/L. However, the overall methanogenic activity in the last case was lower than that of unacclimated and 6 g K+/L acclimated inocula.     

Implications of urine-to-feces ratio in the thermophilic anaerobic digestion of swine waste.

Thermophilic anaerobic digestion of swine manure represents a potential waste treatment technology to address environmental concerns, such as odor emissions and removal of pathogenic microorganisms. However, there are concerns relative to the stability of this process when swine manure is the sole substrate. In this study, the potential of biogas production from swine manure as the sole substrate under thermophilic (50 degrees C) conditions was investigated in the laboratory, to determine whether separation of urine and feces as part of the waste collection process would benefit anaerobic digestion. Effluent from a continuously stirred tank reactor was used as the inoculum for batch tests, in which the substrate contained three different concentrations of urine (urine-free, as-excreted urine-to-feces ratio and double the as-excreted urine-to-feces ratio). Inocula were acclimated to these same urine-to-feces ratios to determine methane production. Results show that both urine-free and as-excreted substrates were not inhibitory to anaerobic inocula. Anaerobic microorganisms can be readily acclimated to substrate with double the as-excreted urine concentration, which contained nitrogen concentrations up to 7.20 g/L. Cumulative methane production reached similar levels in the batch tests, regardless of the substrate urine concentration.     

Influence of staging, mean cell residence time, and thermophilic temperature on the thermophilic anaerobic digestion process.

As Class B biosolids land application has become less acceptable to many local jurisdictions, low-cost processes to achieve Class A standards have become more popular. Prominent among these low-cost processes is thermophilic anaerobic digestion. As a result, thermophilic anaerobic digestion is now a popular topic in wastewater treatment literature, but quantifiable methods for selecting a particular thermophilic process have not been offered. To provide for this need, an empirical model was developed from data collected in thermophilic anaerobic digestion studies conducted using East Bay Municipal Utility District's (Oakland, California) primary and waste activated sludge to feed both bench- and full-scale digesters. The model predicts at which thermophilic temperature and mean cell residence time (MCRT) one process will outperform or equal another, with respect to fecal coliform reduction. The different disinfection efficiencies in the different thermophilic processes might be explained by the presence or absence of high volatile acid and/or un-ionized ammonia levels in the processes' digested sludges. Data from these studies also show an apparent relationship between increased thermophilic temperatures and volatile solids destruction, and between increased temperatures and specific volatile acids production, for digesters operating at a 13-day MCRT and higher, but not for digesters operating at a 2-day MCRT.     

热水解预处理对制药菌渣厌氧消化产甲烷性能的影响

针对我国发酵类制药行业生产过程中产生的菌渣难处理问题,以制药菌渣为研究对象,将制药厂综合污泥为对照,采用热水解(thermal hydrolysis)预处理技术,研究高含固率制药菌渣在170 ℃,800 000 Pa和30 min水解条件下的处理效果,并进行生物化学产甲烷潜能实验,考察热水解预处理对制药菌渣厌氧消化效率的提高程度。结果表明,VB12菌渣、青霉素菌渣、综合污泥在预处理后,SCOD分别增加了80.00%、-28.57%、275%,TN分别增加了76.98%、-76.53%、93.68%,TP分别增加了101.10%、-81.97%、167.86%。VB12菌渣、青霉素菌渣、综合污泥在厌氧消化后,VS去除率为82.52%、63.76%、61.07%。累计产甲烷量分别提高了258.23%、740.63%、190.75%,可见热水解预处理提高产甲烷性能效果显著。与现有填埋、焚烧处理技术相比,厌氧消化能实现菌渣的资源化处置。为热水解与厌氧消化组合工艺处理制药菌渣在我国制药行业的工程应用提供参考。     

污泥的高温微好氧消化-厌氧消化工艺研究

城市污泥含有大量有机物和病原菌,需要稳定化处理.采用新型工艺高温微好氧与中温厌氧两级消化工艺(ATMD-MAD)处理城市污泥,与全程厌氧消化工艺(MAD)相比,不仅回收能源气体甲烷,而且缩短稳定化停留时间.55℃高温微好氧消化停留时间为2 d,后接35℃中温厌氧消化共运行24 d.结果表明,在ATMD-MAD系统中污泥的挥发性悬浮固体VSS去除率能在22 d时达到污泥稳定化要求的40%以上.ATMD-MAD工艺的单位VSS甲烷产量最高为496 mL/g VSS高于MAD工艺.在消化的前14天,可溶性挥发有机酸VFA在ATMD-MAD系统中的总量比MAD高出20%;在消化的第2天,ATMD-MAD系统中可溶性COD(SCOD)高出MAD工艺43.8%.ORP的变化反映了ATMD-MAD工艺保持了较好的厌氧状态,消化开始时的头2天限量曝气并没有给厌氧带来冲击.     

Recurrence of fecal coliforms and Salmonella species in biosolids following thermophilic anaerobic digestion.

The U.S. Environmental Protection Agency (U.S. EPA) Part 503 Biosolids Rule requires the fecal coliform (indicator) or Salmonella species (pathogen) density requirements for Class A biosolids to be met at the last point of plant control (truck-loading facility and/or farm for land application). The three Southern Californian wastewater treatment plants in this study produced biosolids by thermophilic anaerobic digestion and all met the Class A limits for both fecal coliforms and Salmonella sp. in the digester outflow biosolids. At two plants, however, a recurrence of fecal coliforms was observed in postdigestion biosolids, which caused exceedance of the Class A limit for fecal coliforms at the truck-loading facility and farm for land application. Comparison of observations at the three plants and further laboratory tests indicated that the recurrence of fecal coliforms can possibly be related to the following combination of factors: (1) incomplete destruction of fecal coliforms during thermophilic anaerobic digestion, (2) contamination of Class A biosolids with fecal coliforms from external sources during postdigestion, (3) a large drop of the postdigestion biosolids temperature to below the maximum for fecal coliform growth, (4) an unknown effect of biosolids dewatering in centrifuges. At Hyperion Treatment Plant (City of Los Angeles, California), fecal coliform recurrence could be prevented by the following: (1) complete conversion to thermophilic operation to exclude contamination by mesophilically digested biosolids and (2) insulation and electrical heat-tracing of postdigestion train for maintaining a high biosolids temperature in postdigestion.     

生活垃圾厌氧堆肥产甲烷特性研究

为了更好地利用厌氧处理产生的气体,在介绍模拟厌氧堆肥试验的基础上,对厌氧堆肥产甲烷的基本特性进行了研究。结果表明,在厌氧堆肥开始阶段20d左右,甲烷只有7．8％（质量分数,下同）左右,远远低于32．8％的二氧化碳;而随着反应的进行,二氧化碳呈下降趋势,甲烷先升高后降低,直到反应进行到第70天左右时,甲烷才逐渐高于二氧化碳,片于第90天左右时达到最高值42．0％;此后二氧化碳及甲烷都逐渐降低,但甲烷始终高于二氧化碳。     

非混合接种对猪粪厌氧干发酵产气特性的影响

为达到缓解猪粪厌氧干发酵时有机酸的积累并能够同时提高产气性能的目的,采用小试批式实验,在中温(37 ℃)、总固体(TS)为20%的条件下研究了猪粪接种物全混合发酵、猪粪非混合接种发酵、猪粪玉米秸秆与接种物全混合发酵及猪粪玉米秸秆混合原料非混合接种发酵这4种方式对发酵体系的有机酸积累及产甲烷特性的影响。结果表明,猪粪接种物全混合发酵和猪粪玉米秸秆与接种物全混合发酵的总有机酸(TVFAs)质量浓度在发酵结束时分别为15.2和3.6 mg·g⁻¹,较对应底物的非混合接种发酵分别提高了6.3倍和5.0倍。在2种非混合接种发酵体系中,TVFAs质量浓度在21 d后迅速降低。其中,猪粪玉米秸秆混合原料非混合接种的TVFAs下降幅度更大,其第30天的TVFAs质量浓度低于1.5 mg·g⁻¹。猪粪玉米秸秆混合原料非混合接种厌氧发酵产气效果最佳,累积VS产甲烷量达到148.2 mL·g⁻¹。猪粪非混合接种发酵沼气中甲烷含量最高,达到75.1%。修正的Gompertz模型拟合结果显示,猪粪玉米秸秆混合原料非混合接种发酵和猪粪非混合接种发酵的迟滞期分别为10.6和12.4 d,较对应底物的混合接种发酵分别缩短了5.9和6.1 d;最大VS产甲烷速率分别提高了1.7倍和4.9倍,达到6.2和4.8 mL·(g·d)⁻¹。非混合接种能够缓解猪粪厌氧干发酵的酸抑制并同时提高其甲烷产率。     

有机砷对固态厌氧消化产甲烷的影响和动力学研究

通过高温(55℃)固态厌氧消化研究,发现添加洛克沙胂(ROX)会抑制固态厌氧消化产甲烷,ROX添加水平为0.5、1.0、1.5mmol/kg时,初始每克挥发性固体(VS)累积产甲烷量依次下降19.19%、94.04%、96.56%;添加3-氨基-4-羟基苯砷酸(HAPA)加快了系统前期产甲烷,最终累积产甲烷量与空白对照组相近,抑制效应不明显。一级动力学模型符合固态厌氧消化系统产甲烷动力学,其基本方程为G=G∞×(1-exp(-kt)),其中:G为试验检测得到的累积产甲烷量,mL;G∞为理想状态下基质完全降解时的累积产甲烷量,mL;k为产气一级反应速率常数,d-1;t为反应时间,d。一级动力学模型预测值与实测值的F检验以及P和r2说明,产甲烷动力学方程与实测数据拟合相关度很高,产甲烷动力学方程的回归是极显著的。     

Comparative mesophilic and thermophilic anaerobic digestion of palm oil mill effluent using upflow anaerobic sludge blanket

The effects of organic loading rate and operating temperature on the microbial diversity and performances of upflow anaerobic sludge blanket (UASB) reactors treating palm oil mill effluent (POME) were investigated. The following two UASB reactors were run in parallel for comparison: (1) under a mesophilic condition (37 degrees C) and (2) under a mesophilic condition in transition to a thermophilic condition (57 degrees C). A polymerase chain reaction (PCR)-based denaturing gradient gel electrophoresis (DGGE) analysis showed that the microbial population profiles significantly changed with the organic loading rate (OLR) and the temperature transition from the mesophilic to the thermophilic condition. Significant biomass washout was observed for the mesophilic UASB when operating at a high organic loading rate (OLR) of 9.5 g chemical oxygen demand (COD)/L.d. In contrast, the thermophilic UASB can be operated at this OLR and at a temperature of 57 degrees C with satisfactory COD removal and biogas production. The PCR-based DGGE analysis suggested that the thermophilic temperature of 57 degrees C was suitable for a number of hydrolytic, acidogenic, and acetogenic bacteria.     

Full-scale class A biosolids production by two-stage continuous-batch thermophilic anaerobic digestion at the hyperion treatment plant, Los Angeles, California.

The City of Los Angeles Hyperion Treatment Plant (HTP) (California) converted its anaerobic digesters to thermophilic operation to produce Class A biosolids. Phase IV tests demonstrated compliance of a two-stage, continuous-batch process with Alternative 1 of U.S. Environmental Protection Agency 40 CFR Part 503 (U.S. EPA, 1993), which defines the time-temperature requirement for batch treatment (T > or = 56.3 degrees C at 16-h holding). Fecal coliforms, Salmonella sp., viable helminth ova, and enteric viruses were not detected in biosolids in the postdigestion train, including the truck-loading facility and the farm for land application as the last points of plant control where compliance is to be demonstrated. The same results were achieved during Phase V tests, after lowering the second-stage holding temperature to 52.6 degrees C to reduce the elevated methyl mercaptan production that was observed during Phase IV. Hence, the Phase V process complied with Alternative 3 of 40 CFR Part 503. Currently, HTP operates its digesters under the same conditions as tested in Phase V. In 2003, monthly monitoring of the biosolids at the truck-loading facility and the farm for land application demonstrated consistent compliance with Alternative 3.     

生物炭和石墨的电化学性质对剩余污泥厌氧消化产甲烷的影响

以玉米秸秆为原料,分别在300、500和700 ℃的条件下热解制备生物炭(CS300、CS500、CS700),对其理化性质(pH、比表面积、灰分含量、元素组成)和电化学性质(电子供给能力(EDC)、电子接受能力(EAC)、导电率(EC))进行了表征,并将3种生物炭和导电型石墨分别加入消化反应器进行污泥中温厌氧消化批次实验。结果表明：CS300具有最高的EDC(0.598 mmol·g⁻¹),CS700具有最高的EAC(0.740 mmol·g⁻¹),石墨的导电性最强(2.0×10⁴ S·m⁻¹);4种碳材料对污泥厌氧消化产甲烷均有促进作用,CS300、石墨、CS500和CS700实验组的甲烷累积总产量比对照组分别提高了42.4%、38.9%、28.9%和11.2%。微生物群落结构分析结果表明：甲烷生成的主要代谢途径是CO₂还原代谢途径;3种生物炭材料均提高了Methanosarcina等氢营养型产甲烷古菌的相对丰度,CS300的富集能力最强,石墨的影响作用则不显著。冗余分析结果表明：4种碳材料的电化学性质对厌氧细菌群落组成变化的贡献度为52.7%,对厌氧古菌群落组成变化的贡献度为 64.4%;具有氧化还原活性的生物炭通过反复供给、接受电子大幅增加体系中微生物可用电子数量来提高互养微生物种间电子传递效率;而导电性能优秀的石墨则主要通过促进微生物的直接电子传递来提高甲烷产率。研究为解析具有电化学活性的碳材料对厌氧微生物菌群代谢特征和电子传递的影响规律提供了一定的理论支撑,对提高污泥厌氧消化效率、实现能源高效回收具有重要理论价值和现实意义。     

有机负荷对酒糟厌氧消化降解及甲烷产率的影响

为了探究有机负荷对酒糟中温厌氧消化运行的稳定性及产气性能的影响,启动了有机负荷分别为1.6、4.8和6.4 kg·（m3·d）-1的厌氧反应器R1、R2和R3,并以半连续方式运行100 d。单因素方差分析（ANOVA）的结果表明,3个反应器在60~90 d的VS降解率无显著性差异（p=0.19>0.05）,分别为（66.9±3.2）%、（68.1±2.7）%和（66.1±1.5）%,但产气率随着有机负荷的提高而升高,分别为（0.48±0.07）、（0.61±0.06）、（0.71±0.06）m3·kg-1,对应的甲烷比例为56.9%、60.9%和59.6%。虽然提高有机负荷促进了有机碳源利用效率,提高了甲烷比例和产量,但其稳定运行存在一定困难,R3在90 d后产气急剧下降,丙酸大量积累,产酸菌和产甲烷菌间的动态平衡受到破坏。因而,适宜的有机负荷是确保酒糟良好的厌氧消化稳定性能和产气性能的关键因素。     

腐熟蓝藻与厌氧污泥混合厌氧发酵特性

采用批次小试实验对不同腐熟程度的蓝藻进行厌氧发酵产沼气实验研究。结果表明,新鲜蓝藻在30-35℃时腐熟7 d后,可在35℃的厌氧温度下获得最高的产气速率和246 mL/g COD的产气量,产气潜力为354 mL/g（VS）。厌氧反应15 d后,累计产气量、COD和VFA浓度趋于稳定。淀粉酶和脱氢酶的活性在厌氧反应初期受到抑制,蛋白酶活性和辅酶F420浓度在厌氧系统中逐渐增加,分别在第6天达到27.66μmol/（g VS·min）和第15天达到0.62μmol/g（VS）。15-18d是腐熟蓝藻适宜的中温厌氧发酵时间,少于以新鲜蓝藻为基质的厌氧消化时间。蓝藻腐熟过程促进了厌氧反应,腐熟7 d的蓝藻厌氧系统具有更高的微生物活性和产甲烷能力。