Upflow Anaerobic Sludge Blanket Research Articles

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.

Efficient nitrogen removal from real municipal wastewater and mature landfill leachate using partial nitrification-simultaneous anammox and partial denitrification process

Anaerobic ammonia oxidation (anammox) of municipal wastewater is a research focus, especially the combined treatment with mature landfill leachate is a current research hotspot. In this study, municipal wastewater was treated by partial nitrification via sequencing batch reactor (SBR), and its effluent and mature landfill leachate were then mixed into an up-flow anaerobic sludge blanket (UASB) for simultaneous anammox and partial denitrification reaction. Through partial nitrification, a high nitrite accumulation rate (93.0 ± 3.8 %) was achieved by low dissolved oxygen (0.5–1.6 mg/L) and controlled aerobic time (3.5 h) in SBR. The UASB system was responsible for 78.8 ± 2.1 % nitrogen removal of the entire system with a hydraulic reaction time (HRT) of 3.8 h, accompanied by the anammox contribution up to 89.4 ± 6.0 %. The overall partial nitrification-simultaneous anammox and partial denitrification (PN-SAPD) system was controlled at a total COD/TIN of 2.8 ± 0.3 and a total HRT of only 10.2 h, achieving the nitrogen removal efficiency and effluent TIN were 95.2 ± 2.2 % and 3.4 ± 1.5 mg/L, respectively. The qPCR results showed functional genes (hzsA(B), hdh) associated with anaerobic ammonia-oxidizing bacteria (AnAOB), whose high gene copy abundance and transcription expression ensured the removal of major nitrogen from municipal wastewater and mature landfill leachate. 16S amplicon sequencing showed that the Ca. Brocadia (9.72–12.6 %) was further enrichment after sodium acetate was added, and the transcription expression of Thauera (0.5–7.0 %) caused nitrate to nitrite. The high abundance of related enzymes (hao, hzs, hdh, narGHI) involved in anammox and partial denitrification processes were found in the macrogenomic sequencing, and only Ca. Brocadia was involved in multi-pathway nitrogen metabolism in AnAOB. Based on the efficient nitrogen removal by AnAOB and denitrifying bacteria, this modified PN-SAPD process provides a new option for the co-treatment of mature landfill leachate in municipal wastewater treatment plants.

Assessment of the Feasibility of Converting the Liquid Fraction Separated from Fruit and Vegetable Waste in a UASB Digester.

Anaerobic digestion of food waste still faces important challenges despite its world-wide application. An important fraction of food waste is composed of organic material having a low hydrolysis rate and which is often not degraded in digesters. The addition of this less hydrolysable fraction into anaerobic digesters requires a longer hydraulic residence time, and therefore leads to oversizing of the digesters. To overcome this problem, the conversion of the highly biodegradable liquid fraction from fruit and vegetable waste in a up-flow anaerobic sludge blanket (UASB) digester is proposed and demonstrated. The more easily biodegradable fraction of the waste is concentrated in the liquid phase using a 2-stage screw press separation. Then, this liquid fraction is digested in a 3.5 L UASB digester at a high organic loading rate. A good and stable performance was observed up to an organic loading rate (OLR) of 12 g COD/(Lrx.d), with a specific methane production of 2.6 L CH4/(Lrx.d) and a degradation of 85% of the initial total COD. Compared to the conversion of the same initial waste with a continuously stirred tank reactor (CSTR), this new treatment strategy leads to 10% lower COD degradation, but can produce the same amount of methane with a digester that is twice as small. The scale-up of this process could contribute to reduced costs related to the anaerobic digestion of food waste, while reducing management efforts associated with digestate handling and increasing process stability at high organic loading rates.

Development of partial denitrification process in upflow-anaerobic sludge blanket and effect of electric field on partial denitrification performance

Partial denitrification (PD) is an alternative to providing NO2– for the anaerobic ammonium oxidation (anammox) process. In this study, three upflow anaerobic sludge blankets (UASB) were used to investigate the effect of an external electric field on PD performance. The results indicated that the maximum nitrite transformation ratio (NTR) reached 76.3 %, with an average NTR of 54.1 %, in the presence of external electric field, whereas the average NTR of the control was only 49.8 %. The fitted maximum specific nitrate reduction rates of PD1, PD2, and PD3 were 83.7, 90.5, and 92.3 mg N g−1VSS h−1, respectively, according to the Haldane model analysis. Microbial community analysis demonstrated that the abundance of Thauera, Comamonas, and Accumulibacter increased with electric assistance. In summary, UASB reactor with electrodes set in the upper region was most feasible for the stable PD process, providing an alternative for developing a coupled PD-anammox process.

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.

Enhancing anammox process at moderate temperature via employing anammox granular sludge reactor effluent addition

The anaerobic ammonium oxidation (anammox) application on mainstream wastewater treatment is limited by the ambient environment and slow growth rate of anammox bacteria. Bulk liquid in established anammox granular sludge bioreactors naturally contains active factors that could potentially boost anammox process under suboptimal conditions. In this study, effluent of a granular sludge-based anammox up-flow anaerobic sludge blanket treating ammonium-rich wastewater was harvested (the effluent is named as UAE) and continuously added into a bioreactor treating low-strength wastewater at 25 °C to study the effects and mechanisms on enhancing the anammox process. The NH4+-N removal efficiencies increased from 6.5% - 32.5% to 89.7% – 93.8%, and anammox genera accounted from 0.1% to 12.1% of microbial community in the receiving reactor with UAE addition. Coupled partial denitrification and dissimilatory nitrate reduction to ammonium (DNRA) processes with anammox were stimulated by UAE addition. Metagenomic analysis showed that the acyl-homoserine lactone-dependent quorum sensing molecules synthesis pathway was enhanced and an increased concentration of C8-HSL from 2.59 ng/L to 4.62 ng/L was observed in the UAE-receiving reactor. Selective amino acid transportation, amino acids biosynthesis and energy metabolic pathways of microbial community were upregulated with UAE addition. We demonstrate UAE as anammox biocatalyst and facilitate a deeper understanding for synergistic effect of active factors in UAE modified microhabitat for anammox metabolism in the UAE-receiving reactor.

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.

Exploration of Microalgae-Activated Sludge Growth Performance in Lab-Scale Photobioreactors under Outdoor Environmental Conditions for Wastewater Biotreatment

Increasing the volume of untreated and inadequately treated municipal wastewater undermines the circular economy potential of wastewater resources, particularly in low-income regions. This present study focused on and evaluated the performance of native microalgae-activated sludge (MAS) growth for tertiary treatment of anaerobically digested wastewater from an up-flow anaerobic sludge blanket (UASB) in an outdoor lab-scale photobioreactor (2.2 L). Three conditions with distinct MAS inoculum concentrations alongside three controls were operated in batch mode for 5 days hydraulic retention time (HRT) at 11.5:12.5 photo-hours. The MAS inoculum concentration influenced the treatment outcome. The best performance was observed when the MAS concentration was 0.10/0.20 g L−1, and the cell density was 1.60 × 107 cells mL−1, total biomass productivity of 0.10 g TSS L−1 d−1, total phosphorus uptake of 85.1%, and total nitrogen uptake of 66.1%. Logarithmic removal (Log-Re) of bacterial pathogens (water quality indicators) showed Log-Re 3.4 for total coliforms (1.37 × 102 CFU 100 mL−1) and 4.7 for Escherichia coli (0.00 × 100 CFU 100 mL−1). The results revealed optimum remediation performance and nutrient recovery potential with appropriate inoculum concentration, in admiration to advancing the science of circular economy.

Domestic and industrial wastewater generation and its energy recovery potential in Bangladesh

A sizable amount of wastewater is produced every day. Wastewater treatment is required to safeguard the environment, human health, flora, and aquatic life. However, wastewater treatment is an expensive operation on one hand, but on the other hand, wastewater contains five to ten times the energy needed for treatment in the form of chemical energy. This energy is accessible via biological processes. Wastewater contains potential and kinetic energy in addition to chemical energy, and it can be harnessed to generate hydropower. Any country must have a central inventory of wastewater in order to harvest this energy. To harness renewable energy from wastewater sector, it is necessary to have a central database for wastewater generation with type of wastewater and its parameters. Unfortunately, Bangladesh lacks a reliable inventory of national wastewater generation, composition, and attributes that may be utilized for estimating wastewater's potential energy output. Therefore, the aim of this research is to estimate the annual total domestic and industrial wastewater output in Bangladesh and estimate its energy recovery potentials. To estimate domestic wastewater (DWW) and industrial wastewater (IWW), an income-based estimating technique and industry-based reports/literature, respectively have been used. Few novel technologies, such as up-flow anaerobic sludge blankets (UASB), anaerobic digestion (AD), and micro hydropower plants (MHP), and five scenarios using only half of the total wastewater (DWW & IWW) have been considered for estimating the energy recovery potential of wastewater. For the hydropower evaluation using MHP, the unit total head is assumed, whereas the average chemical oxygen demand (COD) has been considered for the energy potential assessment of the UASB and AD. Techno-economic analysis (TEA) steps have been also discussed. Results indicate that the expected annual output of DWW and IWW is 4874 million m3 /yr. and 452 million m3 /yr., respectively. In terms of energy potential, scenario 2 has the highest (1986 Giga watt-hour equivalent (GWh)/yr.)), followed by scenario 1 (1857 GWh/yr.), scenario 5 (1770 GWh/yr.), scenario 3 (1401 GWh/yr.), and scenario 4 (976 GWh/yr.). This rigorous research will open up new horizons by attracting the attention not only of Bangladeshi researchers, but also of the international community.

Role of sulfate in regulating performance and metabolic mechanisms of bioelectrochemical up-flow anaerobic sludge blanket fed with methanolic wastewater

To investigate the impact of sulfate (SO42−) on the performance of bioelectrochemical up-flow anaerobic sludge blanket (BE-UASB), the COD/SO42− ratio of sulfate-containing methanolic wastewater was gradually decreased from 20 to 3. The results showed that BE-UASB maintained higher COD and SO42− removal (i.e., 91% and 70%, respectively) with methane production rate of 278.7 mL/Lreactor/d at COD/SO42− ratio from 10 to 5, ensuring efficient energy recovery. Sulfidogenesis enabled the sludge re-granulation while bioelectrocatalysis further contributed to the growth/proliferation of biomass with interwoven filaments, rods, and spherical microorganisms. 16 S rRNA gene analysis demonstrated that bioelectrocatalysis promoted the diversity of methane-producing archaea (MPA), including Methanomethylovorans, Methanosaeta, Candidatus_Methanofastidiosum, and Methanobacterium. Sulfate-reducing bacteria (SRB), mainly comprising G_norank_f_Syntrophobacteraceae, Desulfomonile, and Syntrophobacter, tended to be enriched on bioelectrodes, which not only eased the competition with MPA but also achieved simultaneous removal of COD and SO42− in synergy with MPA.

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.

Bacterial community composition in a two-stage anaerobic membrane bioreactor for co-digestion of food waste and food court wastewater

This study investigated the microbial community of a two-stage anaerobic membrane bioreactor (2S-AnMBR) co-digesting food waste and food court wastewater. The hydrolysis reactor (HR) was dominated by Bacteroidetes and Firmicutes phylum, with genus Lactobacillus enriched due to food waste fermentation. The up-flow anaerobic sludge blanket (UASB) was dominated by genus such as Methanobacterium and Methanosaeta. The presence of Methanobacterium (91 %) and Methanosaeta (7.5 %) suggested that methane production pathways inevitably undergo both hydrogenotrophic and acetoclastic methanogenesis. Hydrogen generated during hydrolysis fermentation in the HR contributed to methane production in the UASB via hydrogenotrophic pathways. However, the low abundance of Methanosaeta in the UASB can be attributed to the limited inffluent of volatile fatty acids (VFA) and the competitive presence of acetate-consuming bacteria Acinetobacter. The UASB exhibited more excellent dispersion and diversity of metabolic pathways compared to the HR, indicating efficient methane production.