The Microbial Metabolic Characteristics in the Course of Sulfate-Reduction

Acid-producing phase reactor of two-phase anaerobic treatment process has remarkable advantages treating sulfate-laden wastewater. In order to investigate SRB population‘s capability of utilizing substrate and the microbial acidification type formed during the course of sulfate reduction, continuous-flow and batch tests were conducted in a continuous stirred tank bio-film reactor supplied with sodium sulfate as electron acceptor. The experimental results demonstrated that the acidification type formed b...     

Anaerobic co-digestion of sewage and brewery sludge for biogas production and land application

In Thailand, sewage sludge production from the Bangkok metropolitan area can reach up to 63,000 ton/y by 2010. The Beer-Thai Company, Thailand, produces beer and generates lots of sludge as waste. Sewage sludge and brewery sludge can be used to generate energy which could be saved on the fossil fuels conventionally used as a source of energy. The possibility was explored to mix brewery sludge with sewage sludge at different mixing ratios for anaerobic digestion so that the energy can be generated as biogas and at the same time, digested sewage sludge can be used as fertilizer for agricultural applications. A batch anaerobic reactor under mesophilic condition for a digestion period of 40 days was used in the laboratory. The acrylic reactor was cylindrical with a working weight of 12 kg. The diameter was 23.7 cm and the height was 34.5 cm. Sludge mixtures at different ratios were fed into the reactors and the optimum mixing ratio was determined. Experimental results showed that the sludge mixture at ratio of 25:75 % by weight (sewage:brewery) yielded higher biogas production. A reduction in heavy metals and pathogens was observed at this ratio after the digestion indicating its safe use as fertilizer. Nitrogen content was about 4.95 % which is well above the commercial fertilizers. At optimum mixing ratio of 25:75, the amount of the generated biogas is 1.15×10⁶ m³/y. This large amount of biogas is equivalent to 1.44 million kWh/y of electricity, 561,000 L/y of diesel oil and 936,000 L/y of vehicle gasoline.     

Effects of co-substrate on biogas production from cattle manure: a review

This literature review surveys the previous and current researches on the co-digestion of anaerobic processes and examines the synergies effect of co-digestion with cattle manure. Furthermore, this review also pays attention to different operational conditions like operating temperature, organic loading rate (OLR), hydraulic retention time (HRT), chemical oxygen demand (COD) and volatile solid (VS) removal efficiency and biogas or methane production. This review shows that anaerobic mono-digestion of cattle manure usually causing poor performance and stability. Anaerobic studies were generally performed under mesophilic conditions maintained between 35 and 37 °C. Organic waste loading rate generally ranges from 1 to 6 g VS–COD L^?1 day^?1 stable condition in anaerobic digester. Generally, studies show that HRT for co-digestion of fruit–vegetables waste and industrial organic waste appears to exceed 20 days. However, the anaerobic co-digestion process is generally operated at HRT of between 10 and 20 days. VS and COD removal efficiency usually reaches up to 90 % due to co-digestion with different type organic waste. Methane–biogas production is generally obtained between 0.1 and 0.65 L CH₄–biogas g^?1 VS.     

超临界CO2参与下煤储层原位微生物甲烷化物理模拟研究

超临界CO₂能够破坏煤分子结构,提高生物甲烷的产量。为研究微生物在超临界CO₂参与的煤储层原位条件下的产气潜力,以新疆地区某煤层气区块目标煤层的初始储层压力、温度和气体组分作为原位储层条件,通过自主设计的煤储层原位厌氧发酵装置,模拟煤储层原位储层条件下的厌氧发酵过程,并对生物气产量、煤的官能团结构和微生物群落结构进行了分析。研究结果表明,在超临界CO₂参与的煤储层原位条件下,生物甲烷产量达到了32.9 mL/g,CO₂的生物转化率为17.4%。FTIR光谱表明,原位条件下微生物对苯酚、醇、醚、酯中含氧基团的降解能力要强于常规条件下的厌氧发酵。超临界CO₂参与下的储层原位厌氧发酵系统中,多种产甲烷代谢途径的产甲烷菌(氢营养型、乙酸营养型和甲基营养型)逐渐向单一的氢营养型产甲烷菌演化。高压环境下,细菌群落中芽孢杆菌Solibacillus silvestris成为水解产酸发酵阶段的优势菌。该研究为煤层气生物工程的现场实施和碳减排提供了实验基础。      

Effect of trace metals on halophilic and mixed cultures in anaerobic treatment

Trace metals are known to stimulate the activity of anaerobic methanogenic bacteria involved in the degradation of organic matter. The objective of this research was to investigate the effect of three trace metals, iron, nickel and cobalt on the activity of halophilic methanogens, digester sludge and a mixed culture of halophilic bacteria and digester sludge, at various salt concentrations. Iron slightly stimulated both initial and maximum specific methanogenic activity (SMA) of halophilic methanogens at all salt concentrations. Iron addition was also able to increase both initial and maximum SMA of the mixed culture. Iron could not stimulate either initial or maximum SMA of digester sludge at salt concentrations of more than 10 g/L. Adding cobalt showed no benefit on the initial and maximum SMA of halophilic methanogens. A slight increase in the initial SMA was observed in mixed culture when cobalt was injected to the system containing sodium concentrations of 10–30 g/L. At salt concentrations above 40 g/L, cobalt could stimulate the maximum SMA of mixed culture. No benefits were found when cobalt was added to the digester sludge at sodium concentrations higher than 20 g/L. Nickel was observed to increase the initial SMA of digester sludge at all salt concentrations, and the maximum SMA of mixed culture at salt concentrations of 30–50 g/L.     

The dominant acetate degradation pathway/methanogenic composition in full-scale anaerobic digesters operating under different ammonia levels

Ammonia is a major environmental factor influencing biomethanation in full-scale anaerobic digesters. In this study, the effect of different ammonia levels on methanogenic pathways and methanogenic community composition of full-scale biogas plants was investigated. Eight full-scale digesters operating under different ammonia levels were sampled, and the residual biogas production was followed in fed-batch reactors. Acetate, labelled in the methyl group, was used to determine the methanogenic pathway by following the ¹⁴CH₄ and ¹⁴CO₂ production. Fluorescence in situ hybridisation was used to determine the methanogenic communities’ composition. Results obtained clearly demonstrated that syntrophic acetate oxidation coupled with hydrogenotrophic methanogenesis was the dominant pathway in all digesters with high ammonia levels (2.8–4.57 g NH₄ ⁺-N L^?1), while acetoclastic methanogenic pathway dominated at low ammonia (<1.21 g NH₄ ⁺-N L^?1). Thermophilic Methanomicrobiales spp. and mesophilic Methanobacteriales spp. were the most abundant methanogens at free ammonia concentrations above 0.44 g NH₃-N L^?1 and total ammonia concentrations above 2.8 g NH₄ ⁺-N L^?1, respectively. Meanwhile, in anaerobic digesters with low ammonia (<1.21 g NH₄ ⁺-N L^?1) and free ammonia (<0.07 g NH₃-N L^?1) levels, mesophilic and thermophilic Methanosaetaceae spp. were the most abundant methanogens.     

Anaerobic co-digestion of sanitary wastewater and kitchen solid waste for biogas and fertilizer production under ambient temperature: waste generated from condominium house

Addis Ababa is one of the fastest growing cities where high urbanization has become a challenge. Consequently, housing shortage is a big problem of the city. The municipality has launched a huge Condominium Housing Programme in response to the problem. However, sanitary wastewater and solid waste management are the critical problems to those houses. The wastes were collected and evaluated for its biogas production and fertilizer potential to solve the foreseen waste management problems. The physicochemical characteristics of the collected wastes were determined. A laboratory scale batch anaerobic co-digestion of both wastes with different mix ratio of 100:0, 75:25, 50:50, 25:75, and 0:100 by volume [sanitary wastewater (TS = 7,068 mg/L):kitchen organic solid waste (TS = 56, 084 mg/L)]were carried out at ambient temperature for 30 days. The amount of biogas and methane produced over the digestion period for those mixing ratios were compared. The highest biogas yield obtained from a mix ratio of 25:75 was 65.6 L, and the lowest from a mix ratio of 100:0 was 9.5 L. The percentage of methane gas in the biogas was between 19.8 and 52.8 %. From the study results, it is evidenced that the mixing ratio 25:75 produced the maximum quantity of biogas and methane. With regard to the fertilizer potential of the digested sludge, composting and sun drying process were helpful for land application by inactivating the pathogen.     

Hydrous pyrolysis of New Albany and Phosphoria Shales: production kinetics of carboxylic acids and light hydrocarbons and interactions between the inorganic and organic chemical systems

Hydrous pyrolysis in flexible gold-bag autoclaves was used to study the production of carboxylic acids and light hydrocarbons from two marine type IIb source rocks (New Albany and Phosphoria Shales). Kerogen pyrolysis produced significant amounts of the monocarboxylic acids (acetic > propionic > butyric). The gases were dominated by CO₂ and methane, in that order, and progressively smaller amounts of the alkanes (ethane > propane > butane > pentane). Kinetic analyses of production rates for the New Albany Shale suggest mean activation energies (E) of 51-54 kcal/mol for both the light hydrocarbons and acids. Pressure had little effect on measured production rates for either shale over the pressure range investigated. Chemical thermodynamic speciation modeling suggests that in these experiments metal-organic acid anion complexation had little impact on aluminum speciation/solubility, but was important with respect to the alkaline earths.     

一株硫酸盐还原菌的分离及生理生态特性的研究

硫酸盐有机废水生物处理技术一直是人们关注的热点,该种废水处理的关键是如何在有效地去除COD的同时,高效地去除SO_4~(2-)厌氧生物处理系统中的硫酸盐还原菌(Sulfte-Reducing Bacteria,SRB)在一定的条件下可以有效地将SO_4~(2-)还原而从废水中去除。产酸脱硫反应器是一个复杂的生态学系统,在这个生态系统中,SRB起着最主要的生态学作用,要研究产酸脱硫反应器中的各种群的微生物的生理生态学,是非常复杂而且难以实现的。为了更方便地研究产酸脱硫反应器中的微生物生理生态学,比较好的做法是把在反应器中数量上占优势,并且起主要功能的种群分离出来,对它们进行单独和配合研究。本实验就是利用滚管法和改进的Hungate技术,在COD/SO_4~(2-)=3的稳定阶段,对产酸脱硫反应器中的SRB进行了分离,分离出在数量上占优势的SRB,命名为SRB-ZH07。在厌氧试管和三角瓶中,进行了SRB-ZH07生理生态学研究。pH值对SRB-ZH07的生长和硫酸盐去除率的影响,pH为7.0左右SRB-ZH07的生长状况最好,在34h,菌液的OD_(600nm)达到0.827,而其它pH下的OD_(600nm)...     

Anaerobic digester sludge as nutrient source for culturing of microalgae for economic biodiesel production

After decades of ‘living dangerously’, the human kind has paused to think of Mother Nature. Alternate energy sources are being developed as a part of this realization. The use of indigenous sources of nutrients would considerably bring down the cost of production. A mixed consortium of Chlorella vulgaris, Arthrospira platensis, and tap water-originated Scenedesmus dimorphus was cultured using natural seawater, anaerobic digester sludge, and its growth was compared with synthetic commercial media like Zarrouk’s media, NaNO₃ media, and NH₄Cl media. A spectrophotometric method was standardized for regular biomass estimation. The dry biomass of a 15-day pure, batch culture of Arthrospira was found to yield around 600 mg/L in anaerobic digester sludge, whereas the pure batch culture of chlorella’s growth was hindered mainly due to the presence of bacteria and grazers. Regular microscopic observation and biomass monitoring revealed a drastic reduction in grazing activity, with the use of autoclaved AD sludge, resulting in a strong and stable microalgal mixed consortia. The consortia growth in AD sludge was found to be better than with the synthetic media with no cost of nutrient. The mixed consortia yielded a biomass up to 600 mg/L and lipid of 21.18%. The lipid generated from AD sludge had around 95% unsaturates and contained around 5% omega-3 fatty acids. The use of anaerobic digester sludge in a non-sterile condition reduces the total cost of the biodiesel production process as a whole and introduces a decentralized system for waste water treatment as well.     

Dissolved organic carbon and volatile fatty acids in marine sediment pore waters

The results of a study of the contribution of microbial metabolic products to total dissolved organic carbon (DOC) levels in coastal sediments are presented. The data indicate that acidic volatile compounds make up a substantial fraction of pore water DOC's in both oxic and anoxic pore waters of coastal marine sediments. Formic, acetic and butyric acids are the principal volatile species identified at levels exceeding 10 μM. Acid concentrations are up to five times higher in anoxic pore waters than in oxic waters. Volatile organic acids show promise as indicators of diagenetic processes in marine sediments and of the ecological succession of microorganisms, in particular.     

褐煤生物产气规律及其液相体系中阳离子变化特征

为研究褐煤生物产气规律及其液相体系中常见阳离子变化特征,以内蒙古胜利褐煤为产气底物,寺河矿区煤层气井排采水中微生物作为发酵菌群,利用5 L厌氧发酵罐进行模拟生物产气实验,采用离子色谱仪对发酵液中的NH₄+、K+、Ca2+、Mg2+和Na+5种阳离子浓度进行动态监测。结果表明:煤模拟生物产气周期为33 d,分为缓慢增长期、快速增长期和平缓期3个阶段,33 d单位质量煤净产甲烷量最高达23 μmol/g;产气体系中NH₄+（741.5 mg/L）和K+（994.5 mg/L）离子质量浓度变化最为明显,Ca2+（26 mg/L）、Mg2+（10.7 mg/L）和Na+（72 mg/L）次之,表明发酵液中5种阳离子均参与了褐煤生物产气过程,且被不同程度地释放和利用;褐煤生物产气量与阳离子浓度有一定相关性,单位质量煤产气量与NH₄+和K+浓度呈正相关,与Ca2+、Mg2+浓度呈负相关。此外,NH₄+和K+以及Ca2+和Mg2+之间浓度呈显著正相关。由实验结果可知:褐煤生物产气液相体系中4+、K+、Ca2+、Mg2+和Na+5种阳离子会随着煤中有机组分的厌氧降解而缓慢释放、再吸附,同时可被微生物利用参与细胞内的生物化学反应。      

Comparison of the experimental and theoretical production of biogas by monosaccharides,disaccharides, and amino acids

The estimation of biogas production from organic monomers is very important for the optimal design, configuration, and efficient evaluation of the anaerobic digestion processes in a digester. The theoretical estimation of the biogas potential that is most used is that of Buswell and Boyle. In this work, we found that this estimate was much exaggerated compared to the real biogas potential determined in practice. For monosaccharides, we noted that the biogas potential of glucose was very low compared to that of fructose, even though the two substrates have the same chemical composition and molecular mass. The same result was observed for the disaccharides lactose and maltose. The amino acid valine produced more biogas than the amino acid cysteine did. The experimental potential remained lower than the calculated potential. An important difference existed between the experimental biogas potential of the six monomers investigated and the theoretical biogas potential. This indicated that the calculation of the biogas potential by the stereochemical equation of Buswell and Boyle was overstated and did not take into consideration the isometric form, spatial configuration, and intermediate metabolite produced by the monosaccharides in the four steps of anaerobic digestion. For the disaccharides, the theoretical calculations did not take into account the nature of the molecular components in carbohydrate, type of glycosidic bond, and intermediate metabolites of substrates for anaerobic digestion. Finally, for the amino acids, it does not take into account the ramification of the atomic components and the chemical nature of atoms in amino acids.     

Specific methanogenic activity of halophilic and mixed cultures in saline wastewater

Wastewater containing high concentrations of salt, are difficult to treat using biological treatment processes, especially anaerobic processes. Limited information is available on methanogenic activity in saline environments. The objective of this research was to investigate the activity of halophilic methanogens, digester sludge and a mixed culture of halophilic and methanogenic bacteria, at various levels of salinity, in terms of lag period and specific methanogenic activity (SMA) at two temperatures. For the halophilic bacteria at 35 °C, the initial SMA ranged from 0.46 to 0.90 g acetate/g VSSd, but decreased at higher salt concentrations. The maximum SMA varied from 1.2 to 2.08 g acetate/g VSSd. High sodium chloride concentrations had a significant adverse effect on digester sludge. At 25 °C, at salt concentrations of 30 g/l and above, the digester sludge could not acclimate even in 50 days. Little difference was observed in the maximum SMA of mixed culture and halophilic bacteria at high salt concentrations of40–50 g/l.     

Applicability of upflow anaerobic sludge blanket (UASB) reactor for typical sewage of a small community: its biomass reactivation after shutdown

In this study, the characteristics of sewage of small community were determined for 6 months to ascertain the type of treatment required in subtropical conditions. The results demarcated sewage of this community as a medium-strength wastewater (chemical oxygen demand: 475 mg/L, biochemical oxygen demand: 240 mg/L and total suspended solids: 434 mg/L). Chemical oxygen demand to sulphate ratio of the sewage (11.6) established that it was amenable to anaerobic digestion. The temperature, strength, biodegradability and components of sewage were suitable for anaerobic digestion, and thus, upflow anaerobic sludge blanket reactor (UASB) was selected for its treatment. These reactors are often shutdown in small communities due to environmental and/or socio-economic factors. The ability of two UASB reactors, seeded with cow dung (UASB_CD) and activated sludge of a dairy treatment plant (UASB_ASDIT) to restart after a long idle period of 12 months, was investigated along with sludge analysis by scanning electron microscope. Biomass in both reactors reactivated rapidly after shutdown period and within 30 days after substrate feeding achieved uniform removal efficiencies for chemical oxygen demand, total suspended solids, total dissolved solids, chloride and oil and grease. Chemical oxygen demand removal efficiency of both reactors became uniform and remained close to 80% after 30 days through reactivation of microbes in sludge bed due to adequate food and temperature conditions. During restart-up, at an average organic loading rate of 0.902 kg COD/m³ per day, methane yields of 0.091 and 0.084 m³/kg COD removed were achieved for UASB_CD and UASB_ASDIT reactors, respectively.     

Volatile organic acids and microbial processes in the Yegua formation,east-central Texas

Geochemical and microbiological evidence indicates that viable microorganisms produce and consume volatile organic acids (VOA) in the Yegua formation. Acetic and propionic acid concentrations in mudstones range from 200 to 1270 and 20 to 38 nmol·gdw⁻¹ respectively, whereas concentrations in sands are 50–200 and less than 20 nmol·gdw⁻¹. VOA concentrations in sediments and in laboratory incubations suggest net production of VOAs by microorganisms in mudstones, and net consumption of VOAs by SO₄ reducing bacteria (SRB) in sands. Notably, SRB activity is mostly confined to aquifer sands.Vertical diffusion and advection were modeled to estimate acetic acid transport from aquitard to aquifer. Assuming that SRB completely respire the acetic acid transported into the aquifer (3.2 μmol·l⁻¹·m·a⁻¹), the CO₂ production rate in the aquifer sands is 5.3 μmol·l⁻¹·a⁻¹. This slow mineralization rate of in situ organic matter is within the range for deep aquifers, and probably accounts for the long-term survival of microorganisms in oligotrophic environments. Finally, the microbial communities in Yegua sediments appear to exhibit a loose commensalism, with microorganisms in aquitards providing VOAs for respiratory processes (i.e., SO₄ reduction) in aquifers.     

Isotopic fractionation associated with biosynthesis of fatty acids by a marine bacterium under oxic and anoxic conditions

Shewanella putrefaciens (Strain MR-4), a gram negative facultative marine bacterium, was grown to stationary phase under both aerobic and anaerobic conditions using lactate as the sole carbon source. Aerobically-produced cells were slightly enriched in ¹³C (+1.5‰) relative to the lactate carbon source, whereas those from anaerobic growth were depleted in ¹³C (−2.2‰). The distribution of fatty acids produced under aerobic conditions was similar to that resulting from anaerobic growth, being dominated by C_16:1 ω7 and C_16:0 fatty acids with a lesser amount of the C_18:1 ω7 component. Low concentrations of saturated even numbered normal fatty acids in the C₁₄ to C₁₈ range, and iso-C_15:0 were synthesized under both conditions. Fatty acids from anaerobic cultures (average δ¹³C=−37.8‰) were considerably depleted in ¹³C relative to their aerobically-synthesized counterparts (−28.8‰). The distinct differences in isotopic composition of both whole cells and individual fatty acid components result from differences in assimilation pathways. Under aerobic conditions, the primary route of assimilation involves the pyruvate dehydrogenase enzyme complex which produces acetyl-CoA, the precursor to lipid synthesis. In contrast, under anaerobic conditions formate, and not acetate, is the central intermediate in carbon assimilation with the precursors to fatty acid synthesis being produced via the serine pathway. Anaerobically-produced bacterial fatty acids were depleted by up to 12‰ relative to the carbon source. Therefore, detection of isotopically depleted fatty acids in sediments may be falsely attributed to a terrestrial origin, when in fact they are the result of bacterial resynthesis.     

Enhanced bioremoval of refractory compounds from dyeing wastewater using optimized sequential anaerobic/aerobic process

The upflow anaerobic sludge blanket process followed by the biological aerated filter process was employed to improve the removal of color and recalcitrant compounds from real dyeing wastewater. The highest removal efficiency for color was observed in the anaerobic process, at 8-h hydraulic retention time, seeded with the sludge granule. In the subsequent aerobic process packed with the microbe-immobilized polyethylene glycol media, the removal efficiency for chemical oxygen demand increased significantly to 75 %, regardless of the empty bed contact time. The average influent non-biodegradable soluble chemical oxygen demand was 517 mg/L, and the average concentration in effluent from the anaerobic reactor was 363 mg/L, suggesting the removal of some recalcitrant matters together with the degradable ones. The average non-biodegradable soluble chemical oxygen demand in effluent from the aerobic reactor was 87, 93, and 118 mg/L, with the removal efficiency of 76, 74, and 67 %, at 24-, 12-, and 8-h empty bed contact time, respectively. The combined anaerobic sludge blanket and aerobic cell-entrapped process was effective to remove the refractory compounds from real dyeing wastewater as well as in reducing organic loading to meet the effluent discharge limits. This integrated process is considered an effective and economical treatment technology for dyeing wastewater.     

Treatability of landfill leachate by combined upflow anaerobic sludge blanket reactor and aerated lagoon

Continuous upflow anaerobic sludge blanket reactor performs more favorably at the higher organic loading rate than other anaerobic treatment. The treatment of municipal landfill leachate of Shiraz??s city investigated using continuous flow anaerobic reactor and subsequently aerated lagoon. Landfill leachate has chemical oxygen demand of 45,000?C90,000?mg/L and ammonia nitrogen at 1,000?C2,500 and heavy metals that can impact biological treatments. Capacity of anaerobic and aerobic reactors is 10 and 20?L that operated at detention time of 2 and 4?days, respectively. Organic loading rate of upflow anaerobic sludge blanket is between 0.5?C20?g chemical oxygen demand/L/day. Chemical oxygen demand removal efficiencies are between 57?C87, 35?C70 and 66?C94% in the anaerobic, aerobic and whole system, respectively. As the entry, leachate organic loading rate increased from 1 to 20?g/L/day, the chemical oxygen demand removal efficiency reached a maximum of 71% and 84% in the anaerobic reactor and whole system, respectively, at high organic loading rate. Ammonium removal efficiency was about 54% after the aerobic stage.     

Innovative anaerobic upflow sludge blanket filtration combined bioreactor for nitrogen removal from municipal wastewater

In this research, a novel laboratory scale anaerobic/upflow sludge blanket filtration combined bioreactor was designed and operated to improve the efficiency of the upflow sludge blanket filtration process for the simultaneous removal of phosphorus and nitrogen from wastewater. The anaerobic/upflow sludge blanket filtration technique was developed by adding an anaerobic reactor to its influent and operated by varying the main process parameters in order to gain the optimum conditions. The results showed that biological removal efficiency of nitrogen and preservation of sludge blanket strongly depend on wastewater characteristics, hydraulic retention time, sludge age and process controlling parameters. The combined bioreactor performed a total nitrogen removal efficiency of 96.6 % with the sludge age of 25 days, total hydraulic retention time of 24 h and optimum “chemical oxygen demand/nitrogen/phosphorus” ratio of 100/ 5/1. This ratio also improved the compaction quality of sludge blanket in the upflow sludge blanket filtration clarifier. The average specific nitrification and denitrification rates occurred during the process can be expressed as 4.43 mg NO_x-N produced/g VSS.d and 5.50 mg NOx-N removed/g VSS.d at the optimum ratio, respectively. To avoid sludge rising due to denitrification process, the optimum total hydraulic retention time of 16 to 24 h was achieved based on the effluent quality. This study suggested that the anaerobic/upflow sludge blanket filtration bioreactor at the optimum operational conditions can be an effective process for removal of nutrients from municipal wastewater.