Anaerobic Treatment of Industrial Biodiesel Wastewater by an ASBR for Methane Production

A mechanically stirred anaerobic sequencing batch reactor (5 L, 30 °C) containing granular biomass was used to treat the effluent of an industrial biodiesel production process with the purpose to produce methane. Process stability and efficiency were analyzed as a function of applied volumetric organic load (AVOL of 1,000 to 3,000 mgCOD/L), reactor feed time, and cycle length (8-h cycles with 10-min or 4-h feeding and 4-h cycles with 10-min or 2-h feeding). Batch operations (B) with 1,000 to 3,000 mgCOD/L involved 10-min feeding/discharge: (1) 1.0-L influent with 4-h cycle and (2) 2.0-L influent with 8-h cycle. Fed-batch operations (FB) with 1,000 to 3,000 mgCOD/L involved 10-min discharge and the following feeding: (1) 1.0-L influent in 2 h with 4-h cycle and (2) 2.0-L influent in 4 h with 8-h cycle. At 1,000 mgCOD/L (AVOL of 18 to 1.29 gCOD/L?day), kinetic parameter values were 1.03 and 0.92 h^-1 at conditions B-1000-4 h and FB-1000-8/4 h, respectively. At both conditions, removal efficiency was 88 %, and cycle length could be reduced to 3 h (B-1000-4 h) and 5 h (FB-1000-8/4 h). At 2,000 mgCOD/L (AVOL of 2.38 to 2.52 gCOD/L?day), kinetic parameter values were 1.08 and 0.99 h^-1 at conditions B-2000-4/2 h and FB-2000-8/4 h, respectively, and removal efficiencies were 83 and 81 %. Cycle length could be reduced to 3 h (B-2000-4/2 h) and 6 h (FB-2000-8/4 h). At 3,000 mgCOD/L (AVOL of 3.71 to 3.89 gCOD/L?day), conditions allowing stable operation were B-3000-4 h, FB-3000-8/4 h, and FB-3000-4/2 h. Stability could not be obtained at condition B-3000-8 h, and the best results were obtained at condition FB-3000-8/4 h. Specific methane production ranged from 41.1 to 93.7 NmLCH₄/gCOD, demonstrating reactor application potential and operation flexibility.     

Dry Anaerobic Co-digestion of Cow Dung with Pig Manure for Methane Production

The performance of dry anaerobic digestions of cow dung, pig manure, and their mixtures into different ratios were evaluated at 35?±?1 °C in single-stage batch reactors for 63 days. The specific methane yields were 0.33, 0.37, 0.40, 0.38, 0.36, and 0.35 LCH₄/gVS_r for cow dung to pig manure ratios of 1:0, 4:1, 3:2, 2:3, 1:4, and 0:1, respectively, while volatile solid (VS) and chemical oxygen demand (COD) removal efficiencies were 48.59, 50.79, 53.20, 47.73, 46.10, and 44.88 % and 55.44, 57.96, 60.32, 56.96, 53.32, and 50.86 %, respectively. The experimental results demonstrated that the co-digestions resulted in 5.10–18.01 % higher methane yields, 2.03–12.95 % greater VS removals, 2.98–12.52 % greater COD degradation and so had positive synergism. The various mixtures of pig manure with cow dung might persuade a better nutrient balance and dilution of high ammonia concentration in pig manure and therefore enhanced digester performance efficiency and higher biogas yields. The dry co-digestion of 60 % cow dung and 40 % pig manure achieved the highest methane yield and the greatest organic materials removal efficiency than other mixtures and controls.     

Methane Production Characteristics of an Anaerobic Co-Digestion of Pig Manure and Fermented Liquid Feed

Methane production characteristics of anaerobic co-digestion of pig manure (PM) and fermented liquid feed (FLF) were investigated in a continuous digester under mesophilic conditions. The experiment followed three phases. PM alone was digested in phase I. In phases II and III, PM and FLF were mixed in a ratio of 95:5 and 90:10 (% v/v), respectively. The specific methane yields (SMYs) during phases I, II, and III were 238, 278, and 326.8 mLCH₄·gVS⁻¹-added, respectively. It was due to the effect of balancing the feedstock carbon-to-nitrogen ratio by adding FLF. This improvement can also be attributed to the readily biodegradable compounds in the FLF. The higher SMY obtained in this study showed a positive synergistic effect in the anaerobic co-digestion of PM and FLF. The results also indicate that adding the FLF positively affected and maintained a constant pH level, avoiding volatile fatty acid accumulation and ammonia inhibition in the anaerobic digestion (AD). Thus, this study provides valuable information regarding the usage of unused or wasted FLF as a co-substrate for the practical AD of PM. The production of fermented liquid additives such as FLF to improve the methane production from the AD of PM is a potential novel alternative to food waste recycling in Japan, besides compost and animal feeding.     

Fed-batch Anaerobic Valorization of Slaughterhouse By-products with Mesophilic Microbial Consortia Without Methane Production

This work aimed at setting up a fully instrumented, laboratory-scale bioreactor enabling anaerobic valorization of solid substrates through hydrogen and/or volatile fatty acid (VFA) production using mixed microbial populations (consortia). The substrate used was made of meat-based wastes, especially from slaughterhouses, which are becoming available in large amounts as a consequence of the growing constraints for waste disposal from meat industry. A reconstituted microbial mesophilic consortium without Archaebacteria (methanogens), named PBr, was cultivated in a 5-L anaerobic bioreactor on slaughterhouse wastes. The experiments were carried out with sequential fed-batch operations, including liquid medium removal from the bioreactor and addition of fresh substrate. VFAs and nitrogen were the main metabolites observed, while hydrogen accumulation was very low and no methane production was evidenced. After 1,300 h of culture, yields obtained for VFAs reached 0.38 g/g dry matter. Strain composition of the microbial consortium was also characterized using molecular tools (temporal temperature gradient gel electrophoresis and gene sequencing).     

零价铁耦合厌氧微生物法在废水处理中的应用

零价铁(ZVI)与厌氧微生物的耦合是一项很有前景的技术,在难降解有机废水的去除中得到了广泛关注.该耦合技术将ZVI技术的高效性与厌氧生物技术的经济性有效融合,在多元微电场和厌氧微生物协同作用下,有效降低难降解有机物的生物抑制性和毒性.本文综述了此技术处理工业废水的潜在机理、实际应用中主要操作参数及影响条件以及处理含氯化...     

Growth of Chlorella vulgaris on Sugarcane Vinasse: The Effect of Anaerobic Digestion Pretreatment

Microalgae farming has been identified as the most eco-sustainable solution for producing biodiesel. However, the operation of full-scale plants is still limited by costs and the utilization of industrial and/or domestic wastes can significantly improve economic profits. Several waste effluents are valuable sources of nutrients for the cultivation of microalgae. Ethanol production from sugarcane, for instance, generates significant amounts of organically rich effluent, the vinasse. After anaerobic digestion treatment, nutrient remaining in such an effluent can be used to grow microalgae. This research aimed to testing the potential of the anaerobic treated vinasse as an alternative source of nutrients for culturing microalgae with the goal of supplying the biodiesel industrial chain with algal biomass and oil. The anaerobic process treating vinasse reached a steady state at about 17 batch cycles of 24 h producing about 0.116 m³CH₄ kgCOD_vinasse ^?1. The highest productivity of Chlorella vulgaris biomass (70 mg l^?1 day^?1) was observed when using medium prepared with the anaerobic digester effluent. Lipid productivity varied from 0.5 to 17 mg l^?1 day^?1. Thus, the results show that it is possible to integrate the culturing of microalgae with the sugarcane industry by means of anaerobic digestion of the vinasse. There is also the advantageous possibility of using by-products of the anaerobic digestion such as methane and CO₂ for sustaining the system with energy and carbon source, respectively.     

Immobilized Cells in Anaerobic Digestion for Methane from Poultry Manure

The two-stage immobilized microbe waste processor designed for sewage treatment by Messing has been modified to process poultry manure. The Messing reactor of 120-mL volume was modified and scaled up to a 4-L volume. Three different carrier materials have been investigated. Temperatures for each of the two stages were examined, and residence time as well as feed concentration were explored. Analytical data has been computer analyzed using multiple variable correlations and the results of this analysis have indicated directions for optimization.     

Steam Plasma Methane Reforming for Hydrogen Production

Reactions of methane with water and CO₂ in thermal plasma generated in a special plasma torch with a water-stabilized arc were investigated. Steam plasma with very high enthalpy and low mass flow rate was produced in a dc arc discharge which was in direct contact with water vortex surrounding the arc column. Composition of produced gas, energy balance of the process and its efficiency were determined from measured data. The output H₂/CO ratio could be adjusted by a choice of feed rates of input reactants in the range 1.1–3.4. Depending on experimental conditions the conversion of methane was up to 99.5%, the selectivity of H₂ was up to 99.9%, and minimum energy needed for production of 1 mol of hydrogen was 158 kJ/mol. Effect of conditions on process characteristics was studied. Comparison of measured data with results of theoretical computations confirmed that the reforming process produces gas with composition which is close to the one obtained from the thermodynamic equilibrium calculations. Relations between process enthalpy, composition of produced syngas and process characteristics were determined both theoretically and experimentally.     

Anaerobic Digestion of Sugarcane Vinasse Through a Methanogenic UASB Reactor Followed by a Packed Bed Reactor

The anaerobic treatment of raw vinasse in a combined system consisting in two methanogenic reactors, up-flow anaerobic sludge blanket (UASB) + anaerobic packed bed reactors (APBR), was evaluated. The organic loading rate (OLR) was varied, and the best condition for the combined system was 12.5 kg COD m^?3day^?1 with averages of 0.289 m³ CH₄ kg COD r^?1for the UASB reactor and 4.4 kg COD m^?3day^?1 with 0.207 m³ CH₄ kg COD r^?1 for APBR. The OLR played a major role in the emission of H₂S conducting to relatively stable quality of biogas emitted from the APBR, with H₂S concentrations <10 mg L^?1. The importance of the sulphate to COD ratio was demonstrated as a result of the low biogas quality recorded at the lowest ratio. It was possible to develop a proper anaerobic digestion of raw vinasse through the combined system with COD removal efficiency of 86.7% and higher CH₄ and a lower H₂S content in biogas.     

Monoclinic KNbO_3 Nanowires for Photocatalytic Methane Production and Dye Degradation

The room temperature stabled monoclinic KNbO_3 nanowires were found to act as photocatalyst for photocatalytic methane production and dye degradation in this work. Higher activities have been observed for monoclinic phase compared to the reference(orthorhombic phase). In the photoreduction of CO2 reaction, the monoclinic KNbO_3 nanowires exhibited a CH_4 evolution rate of 0.025 μmol·g~(-1)·h~(-1), which was higher than 0.021 μmol·g~(-1)·h~(-1) of orthorhombic KNbO_3 nanowires. In the photodegradation of rhodamine B(Rh B), almost all the Rh B were degraded after 90 min light illumination for monoclinic KNbO_3 nanowires. But for orthorhombic KNbO_3 nanowires, the concentration of Rh B only decreased to 62% of the initial value.     

ASBR Applied to the Treatment of Biodiesel Production Effluent: Effect of Organic Load and Fill Time on Performance and Methane Production

The effect of organic matter and fill time on anaerobic sequencing batch reactor (5 L, 30°C, 8-h cycles, 50 rpm) efficiency has been analyzed. Organic matter was increased by the influent concentration. Fill times investigated were in the batch mode and fed-batch followed by batch. In the batch mode organic matter removal were 93%, 81%, and 66% for influent concentration of 500, 1,000, and 2,000 mgCOD/L (0.6, 1.29, and 2.44 gCOD/L.d), respectively. At 3,000 mgCOD/L (3.82 gCOD/L.d) operational stability could not be achieved. Removal efficiency was improved by increasing the fill time, and was 85% for the 1,000 mgCOD/L condition and fill times of 2 and 4 h, and 80 and 77% for the 2,000 mgCOD/L condition and fill times of 2 and 4 h, respectively. Hence, gradual feeding seemed to improve and to smooth the profiles of organic matter and volatile acids along the cycle with 78 to 96 NmLCH₄/gCOD.     

催化裂解甲烷制备氢气和碳纳米纤维

采用浸渍法制备了Ni/MgO与Ni/O-D(氧化金刚石)催化剂,分别研究了反应温度和空速对甲烷催化裂解转化率的影响,并利用XPS、SEM、EDS等测试技术对催化剂进行了表征. 结果表明,33Ni/O-D和41Ni/MgO分别在500与650 ℃能长时间维持其催化活性,前者在150 min内的甲烷转化率＞8%,后者则在120 min内的甲烷转化率＞25%;甲烷初始转化率随裂解反应温度升高而增大,但温度过高导致催化剂迅速失活;降低空速有利于提高甲烷的转化率,但却会降低氢气产量;甲烷裂解生成的碳产物形貌取决于载体和催化反应条件,较低温度(500和550 ℃)下,Ni/O-D表面的裂解碳呈现出纤维状,在650 ℃以上则表现为板结颗粒堆积并将Ni完全覆盖,但该温度下的Ni/MgO表面仍能形成碳纤维,并随空速降低存在直径增加的趋势.     

Plasma Treatment of Ni Catalyst for Partial Oxidation of Methane

The 10%Ni/Al2O3 catalyst for partial oxidation of methane was treated by DBD (dielectric barrier discharge) plasma in a continuous system under atmospheric pressure and room temperature by flowing He. It was found that 10%Ni/Al2O3 catalyst treated by plasma presents a higher catalytic activity and an enhanced stability than the catalysts prepared without plasma treatment. The methane conversion over the catalyst treated by plasma is 3%-5% higher than the catalysts untreated by plasma. Moreover,the enhanced dispersion of the catalyst can be achieved by plasma treatment, which can improve the interaction between active species and supports, catalytic activity and the resistance to carbon deposition.     

Bioremediation of Perfluoroalkyl Substances (PFAS) by Anaerobic Digestion: Effect of PFAS on Different Trophic Groups and Methane Production Accelerated by Carbon Materials

Per- and polyfluoroalkyl substances (PFAS) are recalcitrant pollutants which tend to persist in soils and aquatic environments and their remediation is among the most challenging with respect to organic pollutants. Anaerobic digestion (AD) supplemented with low amounts of carbon materials (CM), acting as electron drivers, has proved to be an efficient process for the removal of organic compounds from wastewater. This work explores the impact of PFAS on different trophic groups in anaerobic communities, and the effect of carbon nanotubes (CNT), activated carbon (AC), and oxidized AC (AC-HNO₃), as electron shuttles on the anaerobic bioremoval of these compounds, based on CH₄ production. The inhibition of the specific methanogenic activity (SMA) exerted by perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), at a concentration of 0.1 mg L⁻¹, was below 10% for acetoclastic and below 15%, for acetogenic communities. Hydrogenotrophic methanogens were not affected by the presence of PFAS. All CM reduced the negative impact of PFAS on the CH₄ production rate, but AC was the best. Moreover, the methanization percentage (MP) of sewage sludge (SS) increased 41% in the presence of PFOS (1.2 g L⁻¹) and AC. In addition, AC fostered an increase of 11% in the MP of SS+PFOS, relative to the condition without AC. AC promoted detoxification of PFOA- and PFOS-treated samples by 51% and 35%, respectively, as assessed by Vibrio fischeri assays, demonstrating the advantage of bringing AD and CM together for PFAS remediation.     

Viability of Using Glycerin as a Co-substrate in Anaerobic Digestion of Sugarcane Stillage (Vinasse): Effect of Diversified Operational Strategies

Vinasse, from sugar and ethanol production, stands out as one of the most problematic agroindustry wastes due to its high chemical oxygen demand, large production volume, and recalcitrant compounds. Therefore, the viability of using glycerin as a co-substrate in vinasse anaerobic digestion was tested, to increase process efficiency and biogas productivity. The effect of feeding strategy, influent concentration, cycle length, and temperature were assessed to optimize methane production. Glycerin (1.53% v/v) proved to be a good co-substrate since it increased the overall methane production in co-digestion assays. CH₄ productivity enhanced exponentially as influent concentration increased, but when temperature was increased to 35 °C, biogas production was impaired. The highest methane productivity and yield were achieved using fed-batch mode, at 30 °C and at an organic loading rate of 10.1 kg COD m⁻³ day⁻¹: 139.32 mol CH₄ m⁻³ day⁻¹, 13.86 mol CH₄ kg COD_applied, and 15.30 mol CH₄ kg COD_removed. Methane was predominantly produced through the hydrogenotrophic route. In order to treat all the vinasse produced by a mid-size sugar and ethanol plant, nine reactors with 7263.4 m³ each would be needed. The energy generated by burning the biogas in boilers would reach approximately 92,000 MW h per season and could save up to US$ 240,000.00 per month in diesel oil demand.

     

甲烷催化制氢气的研究进展

氢气作为二次能源将成为未来主要能源之一。用甲烷作原料制备氢气有重要意义。本文论述了目前国内外甲烷制氢技术的研究进展,分别对制氢的各种技术方法、反应器的分类、所用催化剂的种类及性能,以及目前解决催化剂结炭问题的研究成果等方面进行了详尽的论述。     

Methane Pyrolysis for Hydrogen Production: Specific Features of Using Molten Metals

Russian Journal of Applied Chemistry - Published data on noncatalytic pyrolysis of natural gas in molten metals are analyzed. The most illustrative results obtained in the past two decades are...