Young-Chae Song

Performance of UASB reactor treating leachate from acidogenic fermenter in the two-phase anaerobic digestion of food waste.

This study was conducted to investigate the performance of the upflow anaerobic sludge blanket (UASB) reactor treating leachate from acidogenic fermenter in the two-phase anaerobic digestion of food waste. The chemical oxygen demand (COD) removal efficiency was consistently over 96% up to the loading rates of 15.8 g COD/l d. The methane production rate increased to 5.51/l d. Of all the COD removed, 92% was converted to methane and the remaining presumably to biomass. At loading rates over 18.7 g COD/l d, the COD removal efficiency decreased due to sludge flotation and washout in the reactor, which resulted from short HRT of less than 10.6 h. The residual propionate concentration was the highest among the volatile fatty acids (VFA) in the effluent. The specific methanogenic activity (SMA) analysis showed that the VFA-degrading activity of granule was the highest for butyrate, and the lowest for propionate. Typical granules were found to be mainly composed of microcolonies of Methanosaeta. The size distribution of sludge particles indicated that partially granulated sludge could maintain the original structure of granular sludge and continue to gain size in the UASB reactor treating leachate from acidogenic fermenter.

Influence of applied voltage on the performance of bioelectrochemical anaerobic digestion of sewage sludge and planktonic microbial communities at ambient temperature.

The influence of applied voltage on the bioelectrochemical anaerobic digestion of sewage sludge was studied at ambient temperature (25±2°C). The stability of the bioelectrochemical anaerobic digestion was considerably good in terms of pH, alkalinity and VFAs at 0.3V and 0.5V, but VFA accumulation occurred at 0.7V. The specific methane production rate (370mLCH4/L.d) was the highest at 0.3V, but the methane content (80.6%) in biogas and the methane yield (350mLCH4/gCODr) were higher at 0.5V, significantly better than those of 0.7V. The VS removal efficiency was 64-66% at 0.3V and 0.5V, but only 31% at 0.7V. The dominant species of planktonic microbial communities was Cloacamonas at 0.3V and 0.5V, but the percentage of hydrolytic bacteria species such as Saprospiraceae, Fimbriimonas, and Ottowia pentelensis was much higher at 0.7V. The optimal applied voltage for bioelectrochemical anaerobic digestion was 0.3-0.5V according to digestion performance and planktonic microbial communities.

Multi-Step Sequential Batch Two-Phase Anaerobic Composting of Food Waste

This study was conducted to evaluate the newly devised process, called MUlti-step Sequential batch Two-phase Anaerobic Composting (MUSTAC). The MUSTAC process consisted of several leaching beds for hydrolysis, acidification and posttreatment, and a UASB reactor for methane recovery. This process to treat food waste was developed with a high-rate anaerobic composting technique based on the rate-limiting step approach. Rumen microorganisms were inoculated to improve the low efficiency of acidogenic fermentation. Both two-phase anaerobic digestion and sequential batch operation were used to control environmental constraints in anaerobic degradation. The MUSTAC process demonstrated excellent performance as it resulted in a large reduction in volatile solids (VS) (84.7%) and high methane conversion efficiency (84.4%) at high organic loading rates (10.8 kg VS m−3 d−1) in a short SRT (10 days). Methane yield was 0.27 m3 kg−1 VS, while methane gas production rate was 2.27 m3 m−3 d−1. The output from the post-treatment could be used as a soil amendment, which was produced at the same acidogenic fermenter without troublesome moving. The main advantages of the MUSTAC process were simple operation and high efficiency. The MUSTAC process proved stable, reliable and effective in resource recovery as well as waste stabilization.

A Model for Evaluation of Anaerobic Degradation Characteristics of Organic Waste: Focusing on Kinetics, Rate-Limiting Step

A kinetic study for an anaerobic batch reactor was performed to evaluate quantitatively the effect of substrate characteristics on the anaerobic degradation of organic waste. The kinetic behavior of anaerobic degradation was described as a first order series reaction that is a consecutive reaction of acidogenic- and methanogenic-fermentation. DR (Determinant of Rate limiting step) that is based on balancing between the rates of the reaction steps was defined, that is the logarithmic difference between maximum acidification rate and maximum methanation rate. Anaerobic degradation characteristics, such as the kinetic and rate limiting step, could be evaluated by the value of DR. DR depended on PR (Pivotal Ratio) that is a ratio of ultimate methane yield to maximum methane production rate. PR could be obtained easily by using a first order kinetic analysis for overall anaerobic degradation, and it was considered as a useful parameter to estimate approximately the characteristics of anaerobic degradation for ...

Effects of starvation on morphometric characteristics of olive flounder, Paralichthys olivaceus

An experiment was conducted for 12 weeks to determine the effect of feeding and starvation on truss and classical parameters in the external body of olive flounder, Paralichthys olivaceus. There was an increase in the truss dimension of body depth in the trunk region of the fed group at the end of the experiment (P < 0.05). In the olive flounder, the trunk region dimensions, including body depth measurements, are likely to be compromised by variability related to differences in the feeding of fish from different habitats. Classical dimensions in relation to the anterior–posterior body axis decreased and classical dimensions of head characteristics increased upon starvation but decreased upon feeding (P < 0.05). These results suggest that these morphometric parameters may be a useful index of nutritional status in olive flounder.

Bioelectrochemical enhancement of direct interspecies electron transfer in upflow anaerobic reactor with effluent recirculation for acidic distillery wastewater

Methane production in the upflow anaerobic bioelectrochemical reactor (UABE) treating acidic distillery wastewater was compared to the upflow anaerobic sludge blanket reactor (UASB), and the electron transfer pathways for methane production were also evaluated in the effluent recirculation. The methane productions from reactors were influenced by the low pH of influent wastewater. However, the methane production rate and yield of the UABE were 2.08L/L.d and 320mL/g CODr, which were higher than the UASB. The effluent recirculation containing alkalinity neutralized the acidic influent and increased the upflow velocity in both reactors, and improved the direct interspecies electron transfer more in the UABE. When the effluent recirculation ratio was 3.0 in the UABE, the methane production rate and yield were reached up to 3.88L/L.d and 501.0mL/g CODr, respectively. The UABE requires electrode installation and electrical energy for operation, but the benefits from increased methane production are much higher.

Influence of Applied Voltage for Bioelectrochemical Anaerobic Digestion of Sewage Sludge

The bioelectrochemical anaerobic digestion for sewage sludge was attempted at different applied voltages ranged from 0.2 V to 0.4 V. At 0.3 V of the applied voltage, pH and VFAs were at 7.32 and 760 mg COD/L, respectively, which were quite stable. The methane production rate was , and the methane content in biogas was 73.8%, indicating that the performance of the bioelectrochemical anaerobic digestion could be considerably improved by applying a low voltage. At 0.4 V of the applied voltage, however, the contents of the minor VFA components including formic acid and propionic acid were increased. The methane production rate was reduced to and the biogas methane content was also reduced to 72.4%. At 0.2 V of the applied voltage, the pH was decreased to 6.3, and VFAs was accumulated to 5,684 mg COD/L. The contents of propionic acid and butyric acid in the VFAs were considerably increased, The performances in terms of the methane production rate and the biogas methane content were deteriorated. The poor performance of the bioelectrochemical reactor at 0.2 V of the applied voltage was ascribed to the thermodynamic potential lack for the driving of the carbon dioxide reduction into methane at cathode.

Effect of Epoxy Mixed with Nafion Solution as an Anode Binder on the Performance of Microbial Fuel Cell

The composite anodes of exfoliated graphite (EG) and multiwall carbon nanotube (MWCNT) were fabricated by using the binders with different content of epoxy in Nafion solution. The influence of the epoxy content in the anode binder on the performance of microbial fuel cell (MFC) was examined in a batch reactor. With the increase in the epoxy content in the anode binder, increase in physical binding force was observed, but at the same time an increase in the internal resistance of MFC was also observed. This was due to the increase in activation and ohmic resistance. For the anode binder without epoxy, the maximum power density was 1,892 mW/m, but a decrease in maximum power density was observed with the increase in the epoxy content in the anode binder. With the epoxy content of 50% in the anode binder, a decrease in the maximum power density to 1,425 mW/m was observed, which about 75.3% of the anode binder without epoxy is. However, the material consisting of the same amount of epoxy and Nafion solution is a good alternative for anode binder in terms of durability and economics of MFC.

Electroactive microorganisms in bulk solution contribute significantly to methane production in bioelectrochemical anaerobic reactor

The role of anaerobic microorganisms suspended in the bulk solution on methane production was investigated in a bioelectrochemical anaerobic reactor with the electrode polarized at 0.5 V. The electron transfer from substrate to methane and hydrogen were 25% and 7.5%, respectively, in the absence of the anaerobic microorganisms in the bulk solution. As the anaerobic microorganisms increased to 4400 mg/L, the electrons transferred to methane increased to 83.3% but decreased to 0.3% in hydrogen. The electroactive microorganisms (EAM), including exoelectrogens and electrotrophs, enriched in the bulk solution that confirmed by the redox peaks in the cyclic voltammogram was proportional to the anaerobic microorganism. The methane yield based on COD removal was dependent on the anaerobic microorganisms in the bulk solution rather than on the bioelectrode surface. The EAM suspended in the bulk solution are enriched by the polarized electrode, and significantly improve methane production in bioelectrochemical anaerobic reactor.

Performance of Upflow Anaerobic Bioelectrochemical Reactor Compared to the Sludge Blanket Reactor for Acidic Distillery Wastewater Treatment

The performance of upflow anaerobic bioelectrochemical reactor (UABE), equipped with electrodes (anode and cathode) inside the upflow anaerobic reactor, was compared to that of upflow anaerobic sludge blanket (UASB) reactor for the treatment of acidic distillery wastewater. The UASB was stable in pH, alkalinity and VFAs until the organic loading rate (OLR) of 4.0 g COD/L.d, but it became unstable over 4.0 g COD/L.d. As a response to the abrupt doubling in OLR, the perturbation in the state variables for the UABE was smaller, compared to the UASB, and quickly recovered. The UABE stability was better than the UASB at higher OLR of 4.0-8.0 g COD/L.d, and the UABE showed better performance in specific methane production rate (2,076 mL CH4/L.d), methane content in biogas (66.8%), and COD removal efficiency (82.3%) at 8.0 g COD/L.d than the UASB. The maximum methane yield in UABE was about 407 mL/g CODr at 4.0 g COD/L.d, which was considerably higher than about 282 mL/g CODr in UASB. The rate limiting step for the bioelectrochemical reaction in UABE was the oxidation of organic matter on the anode surface, and the electrode reactions were considerably affected by the pH at 8.0 g COD/L.d of high OLR. The maximum energy efficiency of UABE was 99.5%, at 4.0 g COD/L.d of OLR. The UABE can be an advanced high rate anaerobic process for the treatment of acidic distillery wastewater.