1,721,013 research outputs found
Biogas desulfurization using autotrophic denitrification process
No full textThe aim of this study was to evaluate the performance of an autotrophic denitrification process for desulfurization of biogas produced from a chicken manure digester. A laboratory scale upflow fixed bed reactor (UFBR) was operated for 105 days and fed with sodium sulfide or H2S scrubbed from the biogas and nitrate as electron donor and acceptor, respectively. The S/N ratio (2.5 mol/mol) of the feed solution was kept constant throughout the study. When the UFBR was fed with sodium sulfide solution with an influent pH of 7.7, about 95 % sulfide and 90 % nitrate removal efficiencies were achieved. However, the inlet of the UFBR was clogged several times due to the accumulation of biologically produced elemental sulfur particles and the clogging resulted in operational problems. When the UFBR was fed with the H2S absorbed from the biogas and operated with an influent pH of 8-9, around 98 % sulfide and 97 % nitrate removal efficiencies were obtained. In this way, above 95 % of the H2S in the biogas was removed as elemental sulfur and the reactor effluent was reused as scrubbing liquid without any clogging problem
Continuous flow membrane-less air cathode microbial fuel cell with spunbonded olefin diffusion layer
No full textThe power production performance of a membrane-less air-cathode microbial fuel cell was evaluated for 53 days. Anode and cathode electrodes and the micro-fiber cloth separator were configured by sandwiching the separator between two electrodes. In addition, the air-facing side of the cathode was covered with a spunbonded olefin sheet instead of polytetrafluoroethylene (PTFE) coating to control oxygen diffusion and water loss. The configuration resulted in a low resistance of about 4 Omega and a maximum power density of 750 mW/m(2). However, as a result of a gradual decrease in the cathode potential, maximum power density decreased to 280 mW/m(2). The declining power output was attributed to loss of platinum catalyst (8.26%) and biomass growth (38.44%) on the cathode. Coulombic efficiencies over 55% and no water leakage showed that the spunbonded olefin sheet covering the air-facing side of the cathode can be a cost-effective alternative to PITE coating. (C) 2011 Elsevier Ltd. All rights reserved
A hybrid dry-fermentation and membrane contactor system: Enhanced volatile fatty acid (VFA) production and recovery from organic solid wastes
No full textAnaerobic dry-fermentation of food wastes can be utilized for the production of volatile fatty acids (VFA). However, especially for high load fermentation systems, accumulation of VFAs may result in inhibition of fermentation process. In this study, separation of VFAs from synthetic mixtures via a vapor permeation membrane contactor (VPMC) system with an air-filled polytetrafluoroethylene (PTFE) membrane was assessed at various temperatures and permeate solution concentrations. In addition, a pioneering integrated leach-bed fermentation and membrane separation system was operated with undefined mixed culture for the purpose of enhanced VFA production along with its recovery. Hybrid system resulted in 42% enhancement in total VFA production and 60% of total VFAs were recovered through the VPMC system. The results of this study revealed that integrated system can be exploited as a means of increasing organic loading to fermentation systems and increasing the value of VFA production. (c) 2021 Elsevier Ltd. All rights reserved
A hybrid membrane gas absorption and bio-oxidation process for the removal of hydrogen sulfide from biogas
No full textA study was conducted on hydrogen sulfide (H2S) removal from biogas using a novel hybrid polydimethylsiloxane (PDMS) membrane bioscrubber. The effect of absorption liquid pH, biogas flowrate and DO concentration on H2S selectivity, removal efficiency and sulfide oxidation were investigated. The process performance at pH 7 was better than pH 8.5 in terms of H2S removal capacity and selectivity. Desulfurization selectivity of H2S/CO2 and H2S/CH4 increased along with the increase of gas flowrate (32 l/d) and reached 3.5 and 63, respectively. The calorific value of the biogas significantly increased due to the raising of CH4 content by 21%. During the long-term operation, air diffusion through the membrane into the biogas was not observed. Almost complete H2S removal (> 97%) and high conversion ratio to S (> 74%) were achieved when volumetric loading rate and DO concentration were kept below 148 g H2S/m(3)d and 1 mg/l, respectively. Partial oxidation of sulfide to S (1 mg/l) rather than sulfate (4 mg/l) reduced the caustic consumption by half. Even though S and inorganics were detected on membrane surface with SEM-EDS analysis, fouling and wetting problems were not observed. The novel hybrid process developed in this study is a cost-effective and robust alternative to conventional biogas desulfurization
Dry anaerobic digestion of chicken manure coupled with membrane separation of ammonia
No full textIn this study, the anaerobic digestion of egg-laying hen manure combined with membrane-based ammonia separation was investigated. Long-term continuous experiments with and without ammonia separation were performed by increasing the organic loading rate (OLR). Although the control digester was completely inhibited at an OLR and influent total Kjeldahl nitrogen (TKN) concentration of 3.85 kgVS/m(3).d and 8.2 g/l, respectively, an average methane yield of 0.30 +/- 0.02 m(3)/kgVS was achieved with a membrane-integrated digester at an OLR and influent TKN concentration of 6.0 kgVS/m(3).d and 15 g/l, respectively. When the ammonia concentration increased above 4000 mg/l, hydrogenotrophic methanogens Methanoculleus bourgensis and Methanobrevibacter sp. performed methane production via syntrophic acetate oxidation
Simultaneous nitrate and sulfide removal using a bio-electrochemical system
No full textThis study addresses the applicability of simultaneous nitrate and sulfide removal using two-chamber bioelectrochemical systems (BES). The anode and cathode chambers of a BES were fed with the effluent of a sulfate reducing reactor and a nitrate-rich groundwater as an electron donor and acceptor sources, respectively. BES has been found to be effective for simultaneous removal of sulfide and nitrate coming from different sources and without mixing them. As a result, 10 gS/m(3)/d of sulfide oxidation and 7.26 gN/m(3)/d of nitrate reduction rates were achieved. The number of electrons used for denitrification was more than that of delivered from the anode, especially when the anode chamber was fed with the SRR effluent and operated at pH 7-7.5. It was supposed that H2S was used for denitrification in the cathode by passing through the membrane. Another reason for this might be the electrons released from the corroding steel mesh current collector. (C) 2019 Elsevier B.V. All rights reserved
Effect of Operating Conditions on Separation of H2S from Biogas Using a Chemical Assisted PDMS Membrane Process
No full textHydrogen sulfide (H2S) is an undesirable impurity that has to be removed from biogas to avoid the corrosion of co-generation units. In the present study, we evaluated the potential of a gas-liquid membrane contactor process for selective removal of H2S from biogas. The effects of biogas retention time (GRT), membrane thickness and liquid absorbent pH were investigated. A dilute sodium hydroxide solution was used as absorbent. The results revealed that H2S removal efficiency (RE) improved with increasing GRT and absorbent pH, and decreased with increasing membrane thickness. When GRT reduced from 19 to 3.4min, the RE of H2S and CO2 decreased by over 2.5 and 5.2 times, respectively. In contrast, a higher desulfurization selectivity was observed with lower GRT and thicker membranes. The CH4 content of the treated biogas increased along with increasing GRT and was enriched from 60% to a maximum of 87% with only 4.68% loss. The SEM-EDS analysis confirmed the deposition of inorganics such as Ca, Mg, S and Si on the membrane surface. However, any membrane clogging and fouling problem was not observed. In summary, the novel gas-liquid polydimethylsiloxane membrane contactor tested in this study has performed well in selective removal of H2S from biogas and is expected to be a promising alternative to conventional desulfurization processes
Treatment of synthetic wastewater and cheese whey by the anaerobic dynamic membrane bioreactor
No full textThe aim of this study was to develop a laboratory-scale anaerobic dynamic membrane bioreactor (AnDMBR) for the treatment of high-strength synthetic and real cheese whey wastewater. We determined the appropriate pore size for a convenient type of support material (nylon mesh) to optimize cake layer formation. The performance of the AnDMBRs was measured in terms of chemical oxygen demand (COD) and solids removal efficiencies. During high-strength synthetic wastewater treatment, the 70-mu m pore size AnDMBR achieved COD removal efficiencies of 78% and 96% with COD loading rates of 4.03 and 2.34 kg m(-3) day(-1), respectively, while the 10-mu m pore size AnDMBR achieved 66% and 92% COD removal efficiencies at COD loading rates of 5.02 and 3.16 kg m(-3) day(-1). The 10 mu m pore size AnDMBR was operated in two periods: first period and second period (before and after physical cleaning) during high-strength synthetic wastewater treatment. The 10-mu m pore size AnDMBR removed 83% and 88% of suspended solids during period 1 and period 2, respectively. Furthermore, using a pore size of 10 mu m retained 72% of solids (973 mg L-1) in the reactor outlet. The 10-mu m pore size AnDMBR performed better than the 70-mu m pore size AnDMBR in terms of cake layer formation. The 10-mu m pore size AnDMBR was used to treat real cheese whey wastewater, resulting in COD removal efficiencies ranging from 59% (4.32 kg m(-3) day(-1)) to 97% (5.22 kg m(-3) day(-1)). In addition, 85% of suspended solids were removed from real cheese whey wastewater after treatment. The results show that dynamic membrane technology using a pore size of 10 mu m can be used to treat real industrial wastewater
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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