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Seokhwan Hwang – One of the best experts on this subject based on the ideXlab platform.

  • Temporal variation in bacterial and methanogenic communities of three full-scale Anaerobic Digesters treating swine wastewater
    Environmental Science and Pollution Research, 2019
    Co-Authors: Seung Gu Shin, Seokhwan Hwang

    Abstract:

    To investigate the effects of temporal variations of process parameters on microbial community structures in the two types of full-scale Anaerobic digester treating swine wastewater, three full-scale Anaerobic Digesters were monitored. An Anaerobic filter (AF)-type digester located in Gong-Ju (GJ) showed the highest COD removal among three Digesters and maintained stable efficiency. A digester in Hong-Seong (HS) was of the same type as it GJ and showed improved efficiency over the sampling period. A continuously stirred tank reactor (CSTR)-type digester in Soon-Cheon (SC) showed decreasing efficiency due to a high residual concentration of VFAs and NH_4^+. These process efficiencies were closely correlated to the Simpson indices of the methanogenic communities. Genera Bacillus , Methanosaeta , and Methanospirillum that have filamentous morphology were dominant in both AF-type Digesters, but genera Acholeplasma , Methanosarcina , and Methanoculleus that have spherical or coccoid morphology were dominantly abundant in the CSTR-type digester. Correlation between populations suggests a possible syntrophic relationship between genera Desulfobulbus and Methanosaeta in Digesters GJ and HS.

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  • bacteria and archaea communities in full scale thermophilic and mesophilic Anaerobic Digesters treating food wastewater key process parameters and microbial indicators of process instability
    Bioresource Technology, 2017
    Co-Authors: Seung Gu Shin, Seokhwan Hwang

    Abstract:

    Abstract In this study, four different mesophilic and thermophilic full-scale Anaerobic Digesters treating food wastewater (FWW) were monitored for 1–2 years in order to investigate: 1) microbial communities underpinning Anaerobic digestion of FWW, 2) significant factors shaping microbial community structures, and 3) potential microbial indicators of process instability. Twenty-seven bacterial genera were identified as abundant bacteria underpinning the Anaerobic digestion of FWW. Methanosaeta harundinacea, M. concilii, Methanoculleus bourgensis, M. thermophilus, and Methanobacterium beijingense were revealed as dominant methanogens. Bacterial community structures were clearly differentiated by Digesters; archaeal community structures of each digester were dominated by one or two methanogen species. Temperature, ammonia, propionate, Na+, and acetate in the digester were significant factors shaping microbial community structures. The total microbial populations, microbial diversity, and specific bacteria genera showed potential as indicators of process instability in the Anaerobic digestion of FWW.

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  • correlations between bacterial populations and process parameters in four full scale Anaerobic Digesters treating sewage sludge
    Bioresource Technology, 2016
    Co-Authors: Seung Gu Shin, Taewoan Koo, Joonyeob Lee, Gyuseong Han, Kyungjin Cho, Woong Kim, Seokhwan Hwang

    Abstract:

    Process parameters and bacterial populations were investigated in four full-scale Anaerobic Digesters treating sewage sludge. Although the four Digesters were operated under similar conditions, Digesters A and B had higher pH (7.2-7.4) and lipid removal efficiencies (>50%) than C and D (pH 6.1-6.4; average lipid removal <16%). Bacterial richness, diversity, and evenness were higher in Digesters C and D. Among the top-populated genera, ten (group I) were more abundant in Digesters A and/or B; they were putative syntrophic fatty acid or protein/amino acid-utilizers. In contrast, fifteen others (group II) were less abundant in A and/or B and included potentially dormant/dead cells originated from activated sludge. Despite the overall richness trend, the presence of the 25 genera in groups I/II was greater in Digesters A and B (24) than in C and D (17); this observation suggests that group I bacteria might be essential in AD of sewage sludge.

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Sarina J Ergas – One of the best experts on this subject based on the ideXlab platform.

  • review of small scale tubular Anaerobic Digesters treating livestock waste in the developing world
    Renewable & Sustainable Energy Reviews, 2016
    Co-Authors: Maureen N Kinyua, Laurel E Rowse, Sarina J Ergas

    Abstract:

    Small-scale tubular Anaerobic Digesters are an attractive technology for treatment of livestock waste in the developing world. These systems produce biogas (a mixture of CH4 and CO2) that is mainly used for cooking. Digester effluent is rich in nutrients (nitrogen and phosphorus) and can be used as a soil amendment. These systems also assist in mitigating deforestation by providing an alternative fuel source, reducing water pollution due to runoff of untreated livestock waste, decreasing air pollution from biomass combustion and promoting gender equality. However, for these benefits to be significant, the effects of design, substrate characteristics and operating parameters on system performance must be understood. This review provides a detailed summary of the research that has been conducted on tubular Anaerobic Digesters treating livestock waste in developing countries. Links between successful digester performance and energy, environmental, public health and social benefits are also provided. In addition, this review discusses governmental policies that have successfully increased adoption of livestock waste Anaerobic digestion systems in Africa, Asia and Latin America.

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  • use of physical and biological process models to understand the performance of tubular Anaerobic Digesters
    Biochemical Engineering Journal, 2016
    Co-Authors: Jie Zhang, Maureen N Kinyua, Fabricio Camachocespedes, Andres E Tejadamartinez, Sarina J Ergas

    Abstract:

    Abstract Tubular Anaerobic Digesters are used in developing countries to produce biogas from livestock waste. In this research, field measurements and physical and biological process modeling studies were used to investigate transport and transformation mechanisms for particulate and soluble organic matter in household-scale tubular Digesters in the Monteverde region of Costa Rica. Greater than 75% removal of volatile solids and biochemical oxygen demand (BOD5) were observed. The high effluent quality was attributed to the formation of a biologically active floccular sludge layer, which allowed for separation of hydraulic and mean cell residence times (HRT and MCRT). A reduced order transport model was developed and validated using field tracer study data. Key assumptions of the reduced order model were verified via computational fluid dynamics (CFD) analysis. The mean HRT predicted by the reduced order model was 23 days and was in good agreement with the tracer experiment. A simplified floccular sludge biological process model was developed and used to estimate an average MCRT of 115 days. The results showed that household-scale tubular Anaerobic Digesters can provide enough biogas to meet households’ cooking energy needs, which was consistent with field results. This is the first study to combine mathematical modeling with field studies of tubular Anaerobic digester performance.

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  • semi continuous mesophilic Anaerobic digester performance under variations in solids retention time and feeding frequency
    Bioresource Technology, 2015
    Co-Authors: Nathan D Manser, James R Mihelcic, Sarina J Ergas

    Abstract:

    The goal of this research was to understand the effect of solids retention time (SRT) and feeding frequency on the performance of Anaerobic Digesters used to recover bioenergy from swine waste. Semi-continuous mesophilic Anaerobic Digesters were operated at varying SRTs and feeding frequencies. Performance metrics included biogas and methane production rates, biomass robustness and functionality and removals of volatile solids, soluble chemical oxygen demand, the fecal-indicator bacteria Escherichia coli, and the human pathogen Salmonella. Biochemical methane formation potential and specific methanogenic activity assays were used to demonstrate biomass robustness and functionality. Results indicated that Anaerobic Digesters fed weekly had higher average methane yields (0.20 vs. 0.18m(3)CH4/kg-VSadded), specific methanogenic activities (40 vs. 35ml/day), and fecal indicator bacteria destruction (99.9% vs. 99.4%) than those fed every-other day. Salmonella, soluble COD, and VS destruction did not change with varied feeding frequency; however, higher removals were observed with longer SRT.

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Seung Gu Shin – One of the best experts on this subject based on the ideXlab platform.

  • Temporal variation in bacterial and methanogenic communities of three full-scale Anaerobic Digesters treating swine wastewater
    Environmental Science and Pollution Research, 2019
    Co-Authors: Seung Gu Shin, Seokhwan Hwang

    Abstract:

    To investigate the effects of temporal variations of process parameters on microbial community structures in the two types of full-scale Anaerobic digester treating swine wastewater, three full-scale Anaerobic Digesters were monitored. An Anaerobic filter (AF)-type digester located in Gong-Ju (GJ) showed the highest COD removal among three Digesters and maintained stable efficiency. A digester in Hong-Seong (HS) was of the same type as it GJ and showed improved efficiency over the sampling period. A continuously stirred tank reactor (CSTR)-type digester in Soon-Cheon (SC) showed decreasing efficiency due to a high residual concentration of VFAs and NH_4^+. These process efficiencies were closely correlated to the Simpson indices of the methanogenic communities. Genera Bacillus , Methanosaeta , and Methanospirillum that have filamentous morphology were dominant in both AF-type Digesters, but genera Acholeplasma , Methanosarcina , and Methanoculleus that have spherical or coccoid morphology were dominantly abundant in the CSTR-type digester. Correlation between populations suggests a possible syntrophic relationship between genera Desulfobulbus and Methanosaeta in Digesters GJ and HS.

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  • bacteria and archaea communities in full scale thermophilic and mesophilic Anaerobic Digesters treating food wastewater key process parameters and microbial indicators of process instability
    Bioresource Technology, 2017
    Co-Authors: Seung Gu Shin, Seokhwan Hwang

    Abstract:

    Abstract In this study, four different mesophilic and thermophilic full-scale Anaerobic Digesters treating food wastewater (FWW) were monitored for 1–2 years in order to investigate: 1) microbial communities underpinning Anaerobic digestion of FWW, 2) significant factors shaping microbial community structures, and 3) potential microbial indicators of process instability. Twenty-seven bacterial genera were identified as abundant bacteria underpinning the Anaerobic digestion of FWW. Methanosaeta harundinacea, M. concilii, Methanoculleus bourgensis, M. thermophilus, and Methanobacterium beijingense were revealed as dominant methanogens. Bacterial community structures were clearly differentiated by Digesters; archaeal community structures of each digester were dominated by one or two methanogen species. Temperature, ammonia, propionate, Na+, and acetate in the digester were significant factors shaping microbial community structures. The total microbial populations, microbial diversity, and specific bacteria genera showed potential as indicators of process instability in the Anaerobic digestion of FWW.

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  • correlations between bacterial populations and process parameters in four full scale Anaerobic Digesters treating sewage sludge
    Bioresource Technology, 2016
    Co-Authors: Seung Gu Shin, Taewoan Koo, Joonyeob Lee, Gyuseong Han, Kyungjin Cho, Woong Kim, Seokhwan Hwang

    Abstract:

    Process parameters and bacterial populations were investigated in four full-scale Anaerobic Digesters treating sewage sludge. Although the four Digesters were operated under similar conditions, Digesters A and B had higher pH (7.2-7.4) and lipid removal efficiencies (>50%) than C and D (pH 6.1-6.4; average lipid removal <16%). Bacterial richness, diversity, and evenness were higher in Digesters C and D. Among the top-populated genera, ten (group I) were more abundant in Digesters A and/or B; they were putative syntrophic fatty acid or protein/amino acid-utilizers. In contrast, fifteen others (group II) were less abundant in A and/or B and included potentially dormant/dead cells originated from activated sludge. Despite the overall richness trend, the presence of the 25 genera in groups I/II was greater in Digesters A and B (24) than in C and D (17); this observation suggests that group I bacteria might be essential in AD of sewage sludge.

    Free Register to Access Article