猪粪中温单级与高温-中温两级厌氧消化效率比较分析

为探究畜禽粪便两级厌氧消化的产气性能及厌氧消化效率,以总固体含量为10.0%的猪粪作为原料,研究猪粪高温（55℃）-中温（37℃）两级厌氧消化工艺的长期连续运行性能,并与中温（37℃）单级厌氧工艺进行比较。结果表明,在近600天长期试验的前期（1～100 d）,高温反应器酸化反应占主导地位,甲烷含量仅为36.3%,两相工艺挥发性固体（VS）的甲烷产率达0.314 L/g,VS去除率达到60.2%,比单相工艺提高了16%。在长期试验的后期（215～575 d）,高温反应器甲烷化效果增强,甲烷含量达到55.9%,pH也升高到7.51,挥发性脂肪酸浓度相较前期下降了220%。该阶段两级工艺的甲烷产率为0.294 L/g,比同时期的单级厌氧提升了19%,对应的VS去除率提高了41%。猪粪在长期的两级工艺运行中,第一级的高温罐并不能维持长期的酸化状态,反而长时间呈现出较为明显的产甲烷效果,但第二级的中温罐长期处于相对稳定的产甲烷状态。总体而言,高固体猪粪两级厌氧消化工艺比单级厌氧工艺具有更高的甲烷产率及更好的有机物去除效果。     

玉米秸秆两级CSTR厌氧消化工艺动力学性能研究

文章采用物料衡算模型、微生物衡算模型和一级动力学模型对两级CSTR厌氧消化系统的运行性能进行了研究。研究结果表明:两级厌氧消化系统HRT(20+20)d和HRT(30+10)d的产甲烷系数分别比单级厌氧消化系统HRT40d增加了5.38%和5.99%;HRT(20+20)d和HRT(30+10)d的第一级反应器的一级动力学常数高于HRT40d以及HRT(20+20)d和HRT(30+10)d的第二级反应器的一级动力学常数;HRT40d,HRT(20+20)d和HRT(30+10)d的微生物产率系数分别为0.003 8,0.016 6和0.020 4;在不同有机负荷率下,HRT(20+20)d,HRT30+10d和HRT40d的平均微生物浓度分别为0.221~0.350,0.275~0.447,0.047~0.076 g/L。     

接种量对稻草厌氧消化产气性能影响

文章考察了不同接种量对稻草厌氧消化性能的影响。结果表明:当接种量为30 g/L(TS)时,只出现一个产气高峰,且累积产甲烷量达到最大值,为9 025 m L,比其他组提高了13.11%~51.75%;TS和VS去除率均最高,分别为48.53%和59.61%;纤维素和半纤维素去除率分别达到60%和40%。Gompertz方程拟合结果显示,接种量为30 g/L(TS)时,厌氧消化速率最快。     

机械搅拌转速对稻草厌氧消化性能的影响

以稻草为原料,采用批式厌氧消化,研究了4种搅拌转速(40,80,120,160 r/min)对稻草厌氧消化产气情况、组分变化和系统稳定性参数(pH值、碱度和氨氮)等的影响。结果表明,搅拌转速对稻草厌氧消化的产气性能有显著影响。80 r/min的厌氧消化效果最好,单位VS产气量为430.6 ml/g,分别比40,120和160 r/min提高了23.6%,11.4%和18.3%;80 r/min和160 r/min的消化时间T80均为46 d,分别比40 r/min和120 r/min缩短了20 d和3 d。搅拌转速为80 r/min时,厌氧消化反应器既能保证良好的物料混合效果,又能维持系统的稳定和较高的微生物活性,其TS,VS降解率均高于其他搅拌转速的反应器,产气性能最好。     

有机垃圾高温厌氧消化中试验研究

采用高温厌氧消化处理方法对城市生活有机垃圾进行了中试试验研究.其有机垃圾产气量73.4m3/t,产气速率0.52m3/m3.d,COD去除率48.8%.结果表明,高温厌氧消化处理是城市生活有机垃圾较好的处理方式之一.有机垃圾不仅可以得到处理,最大限度地减少其污染环境;同时,还可以产生一定的经济效益和巨大的环境效益.这种垃圾处理方式值得应用和推广.     

有机负荷对厨垃圾厌氧消化系统稳定性的影响

厌氧消化是餐厨垃圾产业化处理的主流方式,酸化是影响餐厨垃圾厌氧消化过程稳定的关键,单位有机负荷是引起酸化的最主要因素.系统研究了不同单位体积有机负荷的产气情况.试验结果表明,在2.5～2.8kg TVS/(m3·d)单位体积有机负荷水平,全混合厌氧消化系统可以获得稳定的高产气率,达到2.55～2.68m3/(m3·d).当单位体积有机负荷进一步提高,系统内挥发性脂肪酸总量、pH值、碱度和沼气中甲烷含量急剧下降,体系迅速转向酸化.     

餐厨垃圾两相厌氧消化制沼气研究进展

我国餐厨垃圾产量日益增加,其资源化处理越来越受到人们重视。两相厌氧消化工艺中水解酸化阶段和产甲烷阶段相对独立,具有更多的优势。本文介绍了两相厌氧消化工艺的发展过程和餐厨垃圾的特性,研究了国内外餐厨垃圾两相厌氧消化制沼气技术的进展情况,以期为我国餐厨垃圾的快速高效处理提供参考。     

餐厨垃圾高效厌氧消化稳定产气研究

厌氧消化是餐厨垃圾产业化处理的主流方式,厌氧系统单位体积有机负荷和单位体积产气率是评价厌氧系统产业化能力的重要指标.实验研究了搅拌频率、物料投加方式和不同单位体积有机负荷情况下厌氧系统的产气情况.结果表明,在选择连续式投加物料情况下,维持60min/3hrs搅拌频率和2.8kg TVS/(m3.d)单位体积有机负荷水平,全混合厌氧消化系统可以获得稳定的高产气率,达到(2.69±0.03)m3/(m3·d),甲烷体积分数(65.2±1.3)％.     

CSTR反应器鸡粪厌氧消化中试启动研究

在中温(37℃)条件下,利用全混式厌氧(CSTR)反应器进行鸡粪废水厌氧消化启动的实验室模拟,将试验分为4个阶段(Ⅰ,Ⅱ,Ⅲ,Ⅳ),逐级增加进料负荷量,研究分析各阶段影响因素。结果表明:CSTR反应器能够正常启动鸡粪废水厌氧消化,当试验各阶段(Ⅰ∶Ⅱ∶Ⅲ∶Ⅳ)进料比为1∶2∶2.67∶3.33时,相应的最高产气速率之比约为1∶1.76∶2.04∶2.46;在进料COD为25 496 mg/L,HRT为31 d时,氨氮最高浓度为2 122 mg/L左右,COD去除率为(57.5±1.93)%,每日甲烷产量(单位质量VS)为(301±6)mL/g。试验4 d后,CSTR反应器产生的沼气中CH4含量稳定在61.8%～70.1%。     

超声波促进污泥厌氧消化的研究

介绍了超声波的作用机理，指出在污泥厌氧消化过程中，污泥水解是限速步骤，在厌氧消化前，对污泥进行超声波破解预处理，促使细胞壁破裂，细胞内含物溶出，可以加速污泥的水解过程，从而达到缩短消化时间，减少消化池容积，提高沼气产量的目的。     

搅拌对麦秸厌氧消化性能影响的试验研究

研究了搅拌对麦秸厌氧消化性能的影响。考察了4种搅拌频率对厌氧消化日产气量、单位TS和VS变化、pH值和氨氮等参数的影响。结果表明:日产气量随着搅拌频率的增加有上升的趋势。不同搅拌情况下的pH值始终维持在7.4~7.5,搅拌对pH值影响不明显。氨氮随消化时间的增加产生累积,搅拌越频繁,累积越明显,搅拌频率为每1 h搅拌一次时厌氧消化效果最好。此研究结果将为大中型秸秆沼气工程提供设计依据。     

Hydrogen and methane production from untreated rice straw and raw sewage sludge under thermophilic anaerobic conditions

Bioenergy produced from co-digestion of sewage sludge (SS) and rice straw (RS) as raw materials, without pretreatment and additional nutrients, was compared for the one-stage system for producing methane (CH₄) and the two-stage system for combined production of hydrogen (H₂) and CH₄ in batch experiments under thermophilic conditions. In the first stage H₂ fermentation process using untreated RS with raw SS, we obtained a high H₂ yield (21 ml/g-VS) and stable H₂ content (60.9%). Direct utilization of post-H₂ fermentation residues readily produced biogas, and significantly enhanced the CH₄ yield (266 ml/g-VS) with stable CH₄ content (75–80%) during the second stage CH₄ fermentation process. Overall, volatile solids removal (60.4%) and total bioenergy yield (8804 J/g-VS) for the two-stage system were 37.9% and 59.6% higher, respectively, than the one-stage system. The efficient production of bioenergy is believed to be due to a synergistically improved second stage process exploiting the well-digested post-H₂ generation residues over the one-stage system.     

Improving methane content and yield from rice straw by adding extra hydrogen into a two-stage anaerobic digestion system

This study was aimed to increase both the methane content and yield from rice straw by adding extra H₂ into a two-stage anaerobic digestion system. The results showed that the efficiency of H₂ utilization was 36.43%. Of the total amount of H₂ used, 47.3% was converted to CH₄, thereby increasing the CH₄ content and yield by 45% and 101%, respectively. This conversion was performed at a H₂/CO₂ ratio of 4/1 and a recycling frequency of two times a day in an up-flow reactor (UR). Due to the different ways of CH₄ production in continuously stirred tank reactor (CSTR) and UR, ethanol and acetate were produced as intermediaries, accounting for 65% and 87% of total intermediaries, respectively. Moreover, the pH values in CSTR and UR were 6.7 and 8.1, respectively. The results of the microbial community structures showed that the archaea genera of Methanosaeta and Methanobacterium were the most dominant in CSTR, whereas, Methanosaeta was the most dominant in UR. In terms of the bacterial community, Clostridia was the most abundant class in UR. Based on the results mentioned above, it is feasible to simultaneously improve both the CH₄ content and yield from rice straw by adding extra H₂ into the two-stage anaerobic digestion system.     

Synergistic effect in anaerobic co-digestion of rice straw and dairy manure - a batch kinetic study

Methane yield of seven co-digestion mixture proportions (1:0, 5:1, 3:1, 1:1, 1:3, 1:5, and 0:1) of rice straw and dairy manure was investigated at a total solids (TS) loading of 8%. Methane yield was improved by 50–57% and 9–10% with co-digestion at mixture proportions of 1:1,1:3 and 1:5 compared to mono digestion of rice straw and dairy manure, respectively. The modified Gompertz model accounted well for the kinetic behavior of methane yield with an R² of 0.99 and Root Mean Square Error of 0.06–1.70. It was observed that the co-digestion caused a reduction in lag phase time and improvement in the maximum methane production rate. The positive synergistic effects are a result of nutrient balance with the co-digestion of dairy manure and rice straw.     

Effect of agitation pretreatment on anaerobic digestion of swine manure

This study evaluated the effect of mechanical agitation pretreatment on anaerobic digestion (AD) of swine manure (SM). The results showed a remarkable increase in soluble polysaccharides, soluble proteins, and soluble chemical oxygen demand (SCOD) by 82.42%, 121.17%, and 114.89%, respectively, after the SM being agitated for 22 h. No improvement in the volatile fatty acids (VFAs) yield was observed during the agitation pretreatment. Apparently, agitation significantly accelerated the hydrolysis of SM, while it did not seem to enhance the acidification step. Batch AD experiments showed an improved accumulative methane yield by 77.89% with the pretreated SM compared to raw SM.     

Kinetic and performance study of a batch two-phase anaerobic digestion of fruit and vegetable wastes

Anaerobic digestion of a simulated organic fraction of the waste of a central market selling fruit and vegetables was carried out in two-phase digesters in the mesophilic range of temperatures. Batch digestion was prolonged until no biogas was produced (33 days). With digested pig manure as inoculum, maximum biogas production was obtained around day 10, and within 3 weeks the digestion was almost complete. A kinetic analysis was carried out using first-order, Monod and Chen-Hashimoto models. The Chen-Hashimoto model represents the best fit, whereas a first-order model was not consistent with the experimental results.     

Physicochemical changes of rice straw after lime pretreatment and mesophilic dry digestion

A better understanding of the physicochemical properties of the material, its changes and the effects of anaerobic digestion, will help to improve methane production efficiency. The physicochemical changes of rice straw after solid-state lime pretreatment and dry digestion were investigated. Those changes were revealed by the composition of the substrate before any treatment, from samples of the material during the process and by the final product. Such compositions were studied with X-ray, Fourier transform infrared spectroscopy and thermogravimetric analyzes. The obtained results showed that low mass transfer limited the lignin modification and polysaccharide decomposition, resulted in a low biogas yield; and that after pretreatment and 60 days of mesophilic dry digestion, the concentration of cellulose decreased (23.4%) as well as hemicellulose (13.1%). In the opposite case, the concentration of lignin increased (59%) as well as ash (108%). The crystallinity index increased by 5.4% after pretreatment and decreased by 4.8% after digestion. The FTIR spectrogram of the raw sample included a peak reflecting absorption of ester linkages. This peak was absent from FTIR spectra of pretreated and digested samples, indicating that such linkages are broken during pretreatment and then digested by the microorganisms during the anaerobic fermentation. Furthermore, lime pretreatment and dry digestion significantly changed the decomposed profiles and rate, the distribution of pyrolysis product. The obtained data showed that polysaccharides and lignin were decomposed during pretreatment and digestion phases, leading to changes in structural and thermal properties.     

Effect of lime loading on the performance of simultaneous lime treatment and dry anaerobic digestion of smooth cordgrass

The effects of lime loading on simultaneous lime treatment and dry digestion (SLTDD) of smooth cordgrass (SC) were evaluated at 35°C by batch reactors and leaching bed reactors (LBRs). Biogas yields of 1.5%, 3%, and 5% (w/w) lime loadings decreased by 7.1%, 20%, and 75.7%, respectively, compared with no-lime treatment with 198.0 mL/g total solids (TS) by batch reactors. The LBRs with liquid recycling and pH adjustment enhanced biogas production with 148.1–236.1 mL/g TS. The inhibition occurred SLTDD may be ascribed to be high pH and temperature from lime hydration at the initial stage. The activity for methanogenic bacteria was more inhibited than other anaerobic bacteria.     

Pilot-scale high solids thermophilic anaerobic digestion of municipal solid waste with an emphasis on nutrient requirements

A pilot study was conducted to assess the biodegradable organic fraction of municipal solid waste (BOF/MSW) as a substrate in a high-solids anaerobic digestion process. Results obtained indicate that a typical BOF/MSW in the United States is deficient in most macro and micro-nutrients required for robust and stable digestion. The BOF/MSW was supplemented with nutrient-rich organic wastes such as wastewater treatment plant sludges, dairy manure, and synthetic chemical solutions to correct nutritional deficiencies. The combined addition of wastewater treatment plant sludge and dairy manure to a typical BOF/MSW significantly elevated the gas production rate and enhanced the process stability. Microbial nutrient requirements are identified and nutrient concentrations for stable operation are quantified.