Upflow Anaerobic Sludge Blanket Reactor Research Articles

Simultaneous hydrogen and methane production by tequila vinasses dark fermentation in series with anaerobic digestion

Biofuels production from agro-industrial residues is a promising alternative for obtaining energy from renewable resources. Here, vinasses (tequila manufacture waste) were used as substrate to an anaerobic system comprised by a Continuous Stirred Tank Reactor (CSTR) with biomass carriers and an Upflow Anaerobic Sludge Blanket reactor (UASB) connected in series. The effect of the organic loading rate on the hydrogen and methane generation was evaluated through increase in fed vinasse concentration. Maximum volumetric production rates of 2.2 L H2/L-d in the CSTR and 0.12 L CH4/L-d in the UASB were obtained when feeding 20 g chemical oxygen demand per liter from vinasse diluted to 60 % of its original concentration. Feeding more concentrated vinasses provoked a decrease in the production of hydrogen and methane, coinciding with a 5 g/L-peak in reducing sugars in the CSTR, suggesting overload and acidification as reasons of the diminished performance. The highest hydrogen and methane equivalent energy obtained in the anaerobic system was estimated to be 2.6 kJ/L-d.

Effect of hydraulic retention time on sulfide production with sludge from hydrothermal vent sediments and its utilization on the removal of Cu, Zn, and Al

The present work aimed to evaluate the production of sulfide through the application of different hydraulic retention times (HRT) and different sulfate loading rates in an up-flow anaerobic sludge blanket (UASB) reactor utilizing acetate-butyrate as electron donors and the coupling of the reactor to a crystallizer to remove metals. The sulfidogenic sludge for the UASB was generated from hydrothermal vent sediments and this was operated at room temperature (18-22 ºC). The sulfate reduction process was linked to the precipitation of Cu2+, Zn2+ and Al3+ in a crystallizer coupled to the UASB reactor (two-stage system) to avoid the toxicity of the metals to the sludge. The concentration of dissolved sulfide increased with the HRT up to 312.9 mg HS–/L at 3 d of HRT. As the sulfate loading rate was increasing, the maximum sulfide concentration obtained was of 376.8 mg HS–/L at 500 mg SO4–2/L/d (1500 mg/L), whereas the concentration of Cu2+, Zn2+ and Al3+ was up to 150, 100, and 100 mg/L, respectively. The removal efficiencies of Cu2+, Zn2+, and Al3+ were higher than 98% when they were fed separately. When a mixture of metals was added, the removal efficiency was close to 80%. Recovery of metals was lower than 57% in all cases. The sulfide production was supported with acetate-butyrate, being the former commonly accumulated because of the oxidation of higher organic compounds; in this case, its utilization sustained sulfate reduction. This process could be controlled by parameters such as HRT and sulfate loading rate to improve the performance of the bioreactor in the treatment of the effluents contaminated with metals in a two-stage system.

Biogas production by integrating lava rock, red clay & ceramic bio ring as support carrier in treatment of landfill leachate with liquidised food waste

To evaluate the feasibility of co-digestion of landfill leachate and liquidised food waste, batch experiments were conducted to explore the optimal mixing ratio and support carrier integration in up-flow anaerobic sludge blanket reactors. Continuous experiments were conducted to evaluate the long-term effects of support carriers on methane generation and digestate characteristics. To compare biogas accuracy, Biomethane Potential Tests 1 and 2 data were used to build artificial neural networks using feed-forward backpropagation and support vector machines using linear function. Red clay bio ring, ceramic bio ring and lava rock support carriers were used in the modified reactors. Significant improvement in the anaerobic process was observed during the co-digestion, along with the addition of a ceramic bio ring with biogas production (2150 mL/d), specific methane production (293.30 mL CH4/gCODadded, >66.10% compared to the conventional reactor), and chemical oxygen demand removal (>80%) at an organic loading rate of 6 g/L/day. The Brunauer-Emmett-Teller method demonstrates that ceramic bio ring has a higher specific surface area (7.87 m2/g). The support vector machine model had superior predicted accuracy in biogas production with an R2 of 0.986, indicating it is more robust for large-scale applications. Thus, utilising a suitable proportion of substrates and selecting an appropriate support carrier can stimulate methanogenic activity, which can boost methane production, a promising renewable energy source, and produce higher-quality effluent.

Study of two approaches for the process water management from hydrothermal carbonization of swine manure: Anaerobic treatment and nutrient recovery

Hydrothermal carbonization (HTC) is a promising alternative to transform biomass waste into a solid carbonaceous material (hydrochar) and a process water with potential for material and energy recovery. In this study, two alternatives for process water treatment by conventional and acid-assisted HTC of swine manure are discussed. Process water from conventional HTC at 180 °C showed high biodegradability (55% COD removal) and methane production (∼290 mL STP CH4 g−1 CODadded) and the treatment in an upflow anaerobic sludge blanket reactor allowed obtaining a high methane production yield (1.3 L CH4 L−1 d−1) and COD removal (∼70%). The analysis of the microbiota showed a high concentration of Synergistota and Firmicutes phyla, with high degradation of organic nitrogen-containing organic compounds. Acid-assisted HTC proved to be a viable option for nutrient recovery (migration of 83% of the P to the process water), which allowed obtaining a solid salt by chemical precipitation with Mg(OH)2 (NPK of 4/4/0.4) and MgCl2 (NPK 8/17/0.5), with a negligible content of heavy metals. The characteristics of the precipitated solid complied with the requirements of European Regulation (2019)/1009 for fertilizers and amendments in agricultural soils, being a suitable alternative for the recycling of nutrients from wastes.

Preliminary Study of Up-Flow Anaerobic Sludge Blanket (UASB) Technology for Energy Recovery from Domestic Wastewater

New efforts are increasingly oriented towards the search for sustainable Waste Water Treatment Plant (WWTP) designs. The use of anaerobic digestion processes allows energy production during the treatment of wastewater. However, this technology has been poorly implemented for domestic wastewater due its low organic matter content. In this work, the generation of biogas from municipal wastewater has been studied through anaerobic digestion treatment. UASB effluent has been fed to a membrane photobioreactor (MPBR) where developed indigenous microalgae-bacteria consortia contributes to organic matter and nutrients recovery from digested wastewater and membrane allows continuous regenerated wastewater production as permeate stream. The study was performed at pilot scale making use of an Y configuration UASB, operated under psychrophilic conditions. In addition, the energy production potential of different valorisable substrates, which are residual streams from different treatment processes, was studied at lab scale: concentrate from direct ultrafiltration (DUF) membrane and sludge from conventional membrane bioreactors (MBR), in order to define the potentiality of technological trains with UASB reactors. Anaerobic digestion yields interesting results that should be considered, such as the fact that energy recovery in MBR is lower than that achieved in DUF, where a higher concentration of organic matter is obtained, and therefore, a greater energy obtainment is achieved.

Evaluation of upflow anaerobic sludge blanket (UASB) performance in synthetic vinasse treatment

Vinasse is one of the major sources of environmental pollution because of high organic matter and toxic compound levels (e.g., sulfates and phenols). The more the vinasse treatment is, the less the environmental pollution will be. This study aimed to evaluate the effect of a low-cost and simple anaerobic pretreatment on the COD removal efficiency of the UASB reactor for the treatment of synthetic vinasse. In addition, this system was evaluated through organic loading rate (OLR), hydraulic retention time (HRT), upflow velocity (Vup), mixed liquor volatile suspended solid (MLVSS), mixed liquor suspended solids (MLSS), and pH. In a 155-day trial, the system was fed by synthetic vinasse with an organic loading rate (OLR) ranging from 2.5 to 20.5 kgCOD/m3.d. The results indicated that when a UASB reactor was used for synthetic vinasse treatment, the average COD removal efficiency and methane production were about 80.45% and 56%, respectively. However, the use of an anaerobic unit as a less expensive and simple pretreatment increased COD removal efficiency to 88.4% and methane production to 62.5% (684.6 L/kgCOD). The study result suggested that anaerobic pretreatment is suitable for reducing the environmental pollution of vinasse and can be used as an economical system for real vinasse treatment on an industrial scale.

Análise de desempenho dos sistemas de esgotamento sanitário do Sul do Brasil

ABSTRACT This study assesses the influent and effluent characteristics and the removal efficiency of 56 wastewater treatment plants (WWTPs) operating in Brazil’s southern region, in the Rio Grande do Sul state. The analysis encompasses the main secondary wastewater treatment processes used in the country, such as septic tank and anaerobic filter, activated sludge with sequencing batch reactor and with extended aeration, upflow anaerobic sludge blanket reactor followed by trickling filter, anaerobic and facultative ponds, and the combination of anaerobic, facultative, and maturation ponds. The parameters evaluated were biochemical oxygen demand (BOD), chemical oxygen demand (COD), ammoniacal nitrogen (NNH3), total phosphorus (TP), total suspended solids (TSS), and Escherichia coli. The influent concentrations of BOD, COD, and TSS were considerably lower than other values reported in studies in Brazil, indicating that the analyzed WWTPs operate with a diluted influent, with respective average ranges of 38–189, 203–416, and 75–242 mg∙L−1. The effluent concentrations were also lower than the reference values, although the differences were not as pronounced as in the influent. No significant distinctions were observed between the removal efficiencies obtained and other results in the literature, except for TSS, which had a weaker performance. Concerning the technologies, lower performance was observed for BOD, COD, and TSS removal in the septic tank and higher removal rates of TP for the activated sludge systems. This study represents the first comprehensive dataset on the performance of WWTPs in Brazil’s southern region, contributing to the understanding of wastewater management practices in the country by indicating potential points for improvement.

Inorganic carbon as a key factor governing competition between methanogens and acetogens in high-rate anaerobic treatment of methanol wastewater

The anaerobic treatment of methanolic wastewater has become a crucial issue. Sodium bicarbonate (NaHCO3), as a typical representative of inorganic carbon substances, not only provides alkalinity in the anaerobic treatment of methanol but also governs the competition between methanogens and acetogens. However, a suitable dosage has rarely been mentioned. In this study, we demonstrate the crucial role of NaHCO3 in the anaerobic treatment of methanol using a long-term operated up-flow anaerobic sludge blanket (UASB) reactor and batch tests. The UASB results revealed that by adding 3 to 5 g/L of NaHCO3 to the influent at a high organic loading rate of 50 gCOD/L/d, a significant accumulation of acetic acid was detected, with a maximum value of up to 1400 mg/L. In the context of microbial community evolution, this study profiled substrate competition between the acetogens Acetobacterium and Methanomethylovorans, which directly utilize methanol, as well as the synergistic effects of Acetobacterium and acetoclastic Methanosaeta. Abundance analysis of genes encoding relevant pathway enzymes also revealed that the acetic acid production pathway was significantly enhanced when more NaHCO3 was added. According to the dose–response mechanism in the batch test based on kinetic analysis, an acceptable threshold prediction scheme was beneficial in reasonably adding NaHCO3 to improve acid production capacity and rapid methanol degradation, and ensuring that the generated acetate could be rapidly degraded without inhibition, in the high-rate anaerobic treatment of methanolic wastewater.

Investigation of denitrification to Anammox phase transformation performance of Up-Flow anaerobic sludge blanket reactor

For investigating the microbial community and nitrogen removal performance during the transformation from heterotrophic denitrification (HtDn), mixotrophic denitrification (MtDn), and autotrophic denitrification (AtDn) to anaerobic ammonia oxidation (Anammox), an up-flow anaerobic sludge blanket reactor was constructed by changing the influent substrates and their ratios. The reactor got a total nitrogen removal efficiency (TNRE) of 98.0 % at the molar ratio of carbon, nitrogen, and sulfur sources was 5:8:4 in the MtDn process. In the last phase, the conversion of AtDn to Anammox was successful in 33 days, and a stable TNRE was 87.7 %. The dominant functional bacteria of the microbial communities were Thauera and unclassified_Comamonadaceae in the HtDn process; Thiobacillus, Thauera, Denitratisoma, and Pseudoxanthomonas in the MtDn process; Thiobacillus and Sulfurimonas in the AtDn process; and unclassified_Gemmatimonadaceae, unclassified_SBR1031, and Candidatus_Brocadia in the Anammox process.

Start Up And Operation Of A UASB Rector With Molasses As A Preferred Substrate – A Case Study

Anaerobic digestion followed by aerobic treatment has gained wide acceptability for many of the wastewater treatment. Several novel bio-reactors have been developed. All these reactors pose a problem of shock loading, when the high COD organic industrial waste is fed in to the reactor. Further, the normal substrates like glucose, sewage, citric acid may result in addition of a large volume of the substrate solution for a given organic loading. Both these problems are solved by adopting molasses, a typical by-product from the sugar industry. Among the bio-reactors to treat high strength waste waters, the Up-flow Anaerobic Sludge Blanket Reactor (UASBR), has received wide popularity for the treatment of domestic waste waters as well as for a variety of industrial wastewaters. This paper is to present a cogent and a clear picture of the startup and steady state operation of an UASB Reactor with molasses as the initial startup substrate for the development of well settleable sludge granules, the major feature of an UASB Reactor. The UASB reactor was fabricated in transparent Plexiglas. The reactor had a working volume of 9.75 liters with provision of ports for input, output, collection of samples, and collection of gas. Inside the settler, a gas-liquid-solid separation system using a glass funnel and a gas pressurizing plexiglass tube was provided. The aim was to granulate the sludge and acclimatizing it completely to take high organic loading. The feed was supplemented with a fixed COD: N: P ratio by adding urea for nitrogen and KH2PO4 for phosphorous. The HRT was fixed to be 8 hours. The reactor temperature was maintained at 35 ± 20oC. In about 55 days, the buttery seed sludge got granulated at an OLR of 8 g COD/l.day. The SEM of the granules exhibited a mixed morphology on the surface of the granules while filamentous Methanothrix proliferation could be clearly seen in the interior of the granule. Methanoceata and Methanothrix are the two dominant species found in the granules.

A Cost Analysis of Two-Stage Thermophilic-Mesophilic Anaerobic Wastewater Treatment Systems

Anaerobic bacteria have displayed great potential as a wastewater treatment method because of their efficiency, high methane yield, and low input requirements. In the past, studies have investigated various aspects of these systems, including their chemical oxygen demand (COD) removal efficiency, methane yield, and retention times. However, they have mostly focused on single stage high rate anaerobic (HRAA) reactors such as the upflow anaerobic sludge blanket (UASB) reactor. In this paper, we aim to synthesize the results of these studies to investigate the advantages of building upon the UASB via a two-stage thermophilic-mesophilic (T-M) reactor system with an anaerobic filter (AF) as the acidification tank. The key constraint for adopting two-stage anaerobic systems is primarily related to construction and O&M costs. Therefore, we propose adjusting pH levels and influent flow rates to enhance energy generation and cost-efficiency. This approach aims to encourage greater utilization of two-stage anaerobic systems for wastewater treatment by lowering costs and increasing profits.

Polyhydroxyalkanoates production in purple phototrophic bacteria ponds: A breakthrough in outdoor pilot-scale operation

The versatile capacity of purple phototrophic bacteria (PPB) for producing valuable bioproducts has gathered renewed interest in the field of resource recovery and waste valorisation. However, greater knowledge regarding the viability of applying PPB technologies in outdoor, large-scale systems is required. This study assessed, for the first time, the upscaling of the phototrophic polyhydroxyalkanoate (PHA) production technology in a pilot-scale system operated in outdoor conditions. An integrated system composed of two up-flow anaerobic sludge blanket (UASB) reactors (for fermentation of wastewater with molasses), and two high-rate algal ponds retrofitted into PPB ponds, was operated in a wastewater treatment plant under outdoor conditions. UASB's adaptation to the outdoor temperatures involved testing different operational settings, namely hydraulic retention times (HRT) of 48 and 72 h, and molasses fermentation in one or two UASBs. Results have shown that the fermentation of molasses in both UASBs with an increased HRT of 72 h was able to ensure a suitable operation during colder conditions, achieving 3.83 ± 0.63 g CODFermentative Products/L, compared to the 3.73 ± 0.85 g CODFermentative Products/L achieved during warmer conditions (molasses fermentation in one UASB; HRT 48 h). Furthermore, the PPB ponds were operated under a light-feast/dark-aerated-famine strategy and fed with the fermented wastewater and molasses from the two UASBs. The best PHA production was obtained during the summer of 2018 and spring of 2019, attaining 34.7 % gPHA/gVSS with a productivity of 0.11 gPHA L−1 day−1 and 36 % gPHA/gVSS with a productivity of 0.14 gPHA L−1 day−1, respectively. Overall, this study showcases the first translation of phototrophic PHA production technology from an artificially illuminated laboratory scale system into a naturally illuminated, outdoor, pilot-scale system. It also addresses relevant process integration aspects with UASBs for pre-fermenting wastewater with molasses, providing a novel operational strategy to achieve photosynthetic PHA production in outdoor full-scale systems.

Biogas and photovoltaic solar energy as renewable energy in wastewater treatment plants: A focus on energy recovery and greenhouse gas emission mitigation

Globalization has led to a rapid rise in energy consumption, making climate change one of the world's most pressing issues. As wastewater treatment plants (WWTPs) contribute to climate change by emitting greenhouse gases (GHGs), this study estimated the total GHG emissions of WWTPs by classifying them as either direct or indirect carbon emissions. The effectiveness of the use of solar photovoltaic systems and biogas produced by WWTPs in increasing energy recovery and reducing GHG emissions was investigated. This study demonstrated that the use of an up-flow anaerobic sludge blanket (UASB) reactor with a biogas flow of 9 120.77 m3/d and an activated sludge processing system (ASPS) reactor with a biogas flow of 14 004 m3/d, in addition to the energy production from the UASB reactor (6 421.8 MW⸱h per year) and the ASPS reactor (9 860.0 MW⸱h per year), yielded a reduction of 3 316.85 and 5 092.69 t of CO2 equivalent per year, respectively. Furthermore, the co-design of wastewater processes could be utilized to optimize biogas energy recovery. Moreover, the use of solar photovoltaic systems reduced GHG emissions from WWTPs. This is important to the transition to renewable energy because it resulted in a 10%–40% reduction in carbon emissions from WWTPs. Integrating renewable energy sources, biogas, and solar energy could provide up to 88% of the annual energy requirements of WWTPs. Recommendations are provided for further research considering the limited availability of integrated resources for studying the simultaneous utilization of photovoltaic and biogas systems.

Significant enhancement of biomethane recovery in up-flow anaerobic sludge blanket reactor treating starch wastewater through oyster shells conditioning

The up-flow anaerobic sludge blanket (UASB) reactor for treating starch wastewater exhibits poor resistance to organic loading rate shocks and low efficiency in biomethane recovery. This study proposed a solution to address this issue by using oyster shells as an alternative conditioner. Results indicated that the UASB reactor with oyster shells conditioning exhibited a significant increase in methane production from 243 to 435 mL/g-chemical oxygen demand (COD)removed, as the organic loading rate increased from 2.5 to 7.1 kg-COD/(m3·d). This value surpassed that of the control reactor, which experienced a sharp decline in performance. Furthermore, it also exceeded the majority of reported methane yields ranging from 150 to 330 mL/g-CODremoved. The pH adjustment and additional supply of carbon dioxide from oyster shells was primarily responsible for the substantial increase in methane production. Moreover, oyster shell conditioning also resulted in improvements in specific methanogenic activity, extracellular polymeric substances protection, and settling capacity of anaerobic granular sludge, as well as the enrichment in Methanosaeta abundance, and strengthening of methanogenic functional activity. All these factors contributed to the successful methanogenesis of starch wastewater in UASB reactor through oyster shell conditioning. These findings highlighted the potential of using oyster shells as a favorable conditioner for optimizing UASB treatment of easily acidified wastewater (e.g., starch wastewater), which presented promising practical applications.

Enhancing Anaerobic Digestion with an UASB Reactor of the Winery Wastewater for Producing Volatile Fatty Acid Effluent Enriched in Caproic Acid

The production of Volatile Fatty Acids (VFAs) from wastewater holds significant importance in the context of biorefinery concepts due to their potential as valuable precursors for various bio-based processes. Therefore, the primary objective of this research is to investigate the fermentation of Winery Wastewater (WW) in an Upflow Anaerobic Sludge Blanket (UASB) reactor to generate VFAs, with particular emphasis on Caproic Acid (HCa) production and the dynamics of the microbiota, under varying Hydraulic Retention Time (HRT) periods (8, 5, and 2.5 h). The change from an 8 h to a 5 h HRT period resulted in an approximately 20% increase in total VFA production. However, when the HRT was further reduced to 2.5 h, total VFA production decreased by approximately 50%. Concerning the specific production of HCa, expressed in grams of Chemical Oxygen Demand (gCOD), the maximum yield was observed at around 0.9 gCOD/L for a 5-h HRT. Microbial population analysis revealed that Eubacteria outnumbered Archaea across all HRTs. Population dynamics analysis indicated that the Firmicutes Phylum was predominant in all cases. Within this phylum, bacteria such as Clostridium kluyveri and Clostridium sp., known for their ability to produce HCa, were identified. Based on the results obtained, the application of the UASB reactor for WW treatment, within the biorefinery framework, has the potential to provide a practical alternative for HCa production when operated with a 5 h HRT.

Sewage treatment in cities of the state of Minas Gerais, Brazil, that use the UASB reactor as the only biological treatment: A case study

This article analyzed the performance of four Wastewater Treatment Plants (WWTP) in three cities in the state of Minas Gerais, Brazil, which use the UASB (Upflow Anaerobic Sludge Blanket) reactor as the only stage of biological treatment. When evaluating the characteristics of treated wastewater, it was verified that the WWTPs were not efficient enough to meet the disposal standards established by environmental agencies. Most of the sewage samples from Ipatinga municipality did not meet the minimum removal for BOD5 of 60 % and COD of 55 %, being 56 % and 46 % the average removals, respectively. These results suggest the need for improvements in the current biological treatment and/or the adoption of a polishing step. The raw sewage had high biodegradability (BOD5/COD>0.4) and the UASB reactors reduced this biodegradability (ranging from 0.2 to 0.43) by removing the content of easier degradation. A strong linear correlation (R2 = 0.85) was observed between COD and DBO5 data for the raw sewage from Timóteo municipality, making it possible to estimate the second parameter as a function of the first. When compared with wastewater characterized and used in fertigation studies, the treated sewage samples of the present study show potential for application in agricultural practices.

Performance of Microbial fuel cell as a post treatment unit of UASB reactor for distillery spent wash

Post treatment of Up-flow anaerobic sludge blanket reactor (UASBR) effluents by a duel chambered Microbial fuel cell (MFC) was evaluated for high strength distillery spent wash. Bench scale UASBR (5 L capacity) and MFC (1 L capacity) with carbon electrodes having proton exchange membrane were used to elucidate the energy generation potential and substrate (COD) removal efficiency. Step by step, the influent COD concentration of UASB-MFC unit was increased. The MFC shows increasing trend of open circuit voltage, COD removal and substrate degradation rate with increase in influent COD concentration. The maximum COD removal (73.79%) and open circuit voltage (1.1 V) were achieved at 20600 mg/L of COD. At maximum COD concentration, MFC showed power density (maximum), substrate degradation rate and power yield as 61.61mW/m2, 1.086 kg COD/m3day and 0.041 W/kg CODR respectively. UASB-MFC combined unit gave maximum COD removal of 90%. The experimental data revealed the potential of MFC as feasible, economic (cost saving) and sustainable option.

Corn ethanol production with thin stillage anaerobic digestion for bioenergy recovery: A technical and economic evaluation

The generation of bioenergy from thin stillage in a corn ethanol mill provides a new perspective for the use of by-products in a circular economy concept. Alternative technological routes for the corn ethanol by-products energy and nutrients recovery must be investigated to assess present and future decision-making toward economic and environmental indicators. The theoretical biogas production from an up-flow anaerobic sludge blanket (UASB) reactor in a corn-ethanol mill and the potential thermal and electrical power generation along with the avoided greenhouse gas (GHG) emissions were estimated for a large-scale industrial facility. This work aimed to assess the anaerobic digestion (AD) contribution to techno-economic indicators of a corn ethanol mill in three scenarios: 1) Standard corn-to-ethanol mill; 2) AD-CHP - thin stillage AD to produce biogas and its burning in a combined heat and power (CHP) system; 3) AD-BU - biogas purification to obtain and commercialize biomethane. The existent Brazilian market and fuels and biofuel policies place the system without AD in a slightly better position when analyzing financial indicators related to investment return. In contrast, the global energy and mass balances considering thin stillage AD showed that in the AD-CHP scenario, processing 1 ton of thin stillage would produce 10.37 m³ of biogas, which could generate 119.9 MJ of heat and 24.7 kWh of electricity in a CHP system, favoring a greener energy scenario. The energy recovered from biogas returns to the industry, supplying 7.15% of the heat required for steam production and 52.74% of the electricity requirement for industrial processing. As a renewable energy source, biogas would replace fossil sources for energy generation avoiding GHG emissions. Extrapolating the results of the present work to the Brazilian national scale, the biogas yield from the corn-to-ethanol industry would be 179.68 million m³ , the thermal energy generation from biogas could mitigate 125,574.42 ton CO2eq, and the electricity replacement could mitigate 58,193.02 ton CO2eq. Besides the mentioned energy generation and environmental benefits, the financial indicators for the examined scenarios showed that the Brazilian market and public policies related to biogas/biomethane are constraints to overcoming to larger adoption of AD by the corn-to-ethanol industry.

Distillery Plant Upflow Anaerobic Sludge Blanket Reactor comparision of Energy regime in Mesophilic and Thermophilic conditions

In this study, comparison of energy regime analysis of mesophilic and thermophilic condition upflow anaerobic sludge blanket (UASB) reactor treating distillery effluent is studied. Percentage COD reduction in thermophilic condition was more by 6.96% than mesophilic condition due to which biogas production increased by 0.1 m3/kg COD removed. In thermophilic temperature condition, methenogenesis was more than acidification than in mesophilic temperature condition; effluent VFA concentration in mesophilic condition was more in thermophilic condition. Stability of thermophilic reactor was more than mesophilic reactor from VFA/ Alkalinity ratio. Waste water treatment plant consumes 2.10 kWh/m3 total energy which comprises of electrical, mechanical and manual energy in mesophilic temperature condition. Input given in the form of electrical energy was 2.07 kWh/m3 and energy recovered in the form of biogas was 185 kWh/m3. Total energy input in thermophilic temperature condition was 1.82 kWh/ m3 and biogas recovery was 211 kWh/m3 in the form of energy. Net saving in energy input was 0.28 kWh/m3 (12.98%) and biogas production increased by 25.9 kWh/m3 (14%) in the form of energy in thermophic temperature condition. Treatment of distillery wastewater in thermophilic temperature condition can be a good option as compared to mesophilic temperature conditions considering the aspect of energy and it seems feasible due to the availability of elevated temperature of the feed for UASB.

Internal driving mechanisms of microbial community and metabolism for granular activated carbon enhancing anaerobic digestion of high-strength sulfate organic wastewater

In this study, the feasibility of enhancing high-strength sulfate organic wastewater anaerobic digestion by adding granular activated carbon (GAC) and the internal driving mechanisms were investigated in up-flow anaerobic sludge blanket (UASB) reactors. The UASB reactor with GAC (GAC reactor) was more stable in COD removal efficiency and CH4 production than that without GAC (non-GAC reactor). When the influent COD concentration increased to 12,000 mg/L with a COD/SO42− ratio of 4.0, the COD removal efficiency and CH4 yield increased by 10.45 % and 20.50 %, respectively. Under inhibition condition with sulfides of 800 mg/L, specific methanogenic activity of GAC reactor sludge increased by 41.8 % compared to that of non-GAC reactor sludge. Electron transport system and microbial community results showed that GAC enhanced microbial activity and improved direct interspecies electron transfer (DIET) between potential electroactive microorganisms and Methanosaeta. Functional enzyme gene analysis demonstrated that GAC enhanced microbial metabolic activity, covering glycolysis, pyruvate metabolism, sulfate reduction, and methanogenesis. Therefore, the enrichment of key microorganisms, the promotion of DIET methanogenesis, and the improvement of functional metabolism activity may be the important reasons for GAC reactor sludge with higher methanogenic activity. Furthermore, synergistic promotion of sulfate-reducing metabolism and methanogenesis may be due to the establishment of potential syntrophic partnership between sulfate-reducing bacteria (Desulfovibrio) and Methanosaeta. This study deciphered internal driving mechanisms of microbial community and metabolism for GAC enhancing anaerobic digestion of high-strength sulfate organic wastewater.