• Journal of the Korea Organic Resources Recycling Association
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• v.16 no.2
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• pp.57-65
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• 2008

Wastewater containing strong organic matter is very difficult to treat by utilizing general sewage treatment plant. but the wastewater is adequate to generate biomass energy (bio-gas; methane gas) by utilizing anaerobic digestion. EcoDays Plug Flow Reactor (E-PFR), which was already proved as an excellent aerobic wastewater treatment reactor, was adapted for anaerobic food wastewater digestion. This research was performed to improve the efficiency of bio-gas production and to optimize anaerobic wastewater treatment system. Food wastewater from N food waste treatment plant was applied for the pilot scale experiments. The results indicated that the efficiency of anaerobic wastewater treatment and the volume of bio-gas were increased by applying E-PFR to anaerobic digestion. The structural characteristics of E-PFR can cause the high efficiency of anaerobic treatment processes. The unique structure of E-PFR is a diaphragm dividing vertical hydraulic multi-stages and the inversely protruded fluid transfer tubes on each diaphragm. The unique structure of E-PFR can make gas hold-up space at the top part of each stage in the reactor. Also, E-PFR can contain relatively high MLSS concentration in lower stage by vertical up-flow of wastewater. This hydraulic flow can cause high buffering capacity against shock load from the wastewater in the reactor, resulting in stable pH (7.0~8.0), relatively higher wastewater treatment efficiency, and larger volume of bio-gas generation. In addition, relatively longer solid retention time (SRT) in the reactor can increase organic matter degradation and bio-gas production efficiency. These characteristics in the reactor can be regarded as "ideal" anaerobic wastewater treatment conditions. Anaerobic wastewater treatment plant design factor can be assessed for having 70 % of methane gas content, and better bio-gas yielding and stable treatment efficiency based on the results of this research. For example, inner circulation with generated bio-gas in the reactor and better mixing conditions by improving fluid transfer tube structure can be used for achieving better bio-gas yielding efficiency. This research results can be used for acquiring better improved regenerated energy system.

• Journal of the Korea Organic Resources Recycling Association
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• v.8 no.2
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• pp.130-139
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• 2000

Serial basic tests were conducted for the determination of fundamental kinetics and for the actual application of kinetic parameter to food waste digestion with precise measurement of methane production under a thermophilic condition. The effects of food particle size, sodium ion concentration, and volatile solid (VS) loading rate on the anaerobic thermophilic food waste digestion process were investigated. Results of serial test for the determination of fundamental kinetic coefficients showed the value of k (maximum substrate utilization rate coefficient) and KS (half-saturation coefficient) as $0.24hr^{-1}$ and $700mg/{\ell}$, respectively, for non-inhibiting organic loading range. No inhibition effect was shown until $5g/{\ell}$ of sodium ion concentration was applied to a serum bottle reactor. However, the volume of methane gas was decreased gradually when the concentrations of more than $5g/{\ell}$ of sodium ion applied. All sizes of food waste particle showed the same constants (A : 0.45) but the maximum substrate utilization rate constant ($k_{HA}$) was inversely proportional to particle size. As an average particle size increased from 1.02 mm to 2.14 mm, $k_{HA}$ decreased from $0.0033hr^{-1}$ to $0.0015hr^{-1}$. The result reveals that particle size is one of the most important factors in anaerobic food waste digestion. There was no inhibition effect of sodium ion when VS loading rate was $30g/{\ell}$. And maximum injection concentration of VS loading rate was determined about $40g/{\ell}$.

• Journal of Korean Society of Environmental Engineers
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• v.37 no.7
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• pp.404-411
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• 2015

In this study, the effects of empty bed contact time (EBCT) and water temperature on the biodegradation of 9 halonitromethanes (HNMs) in biological activated carbon (BAC) process were investigated. Experiments were conducted at three water temperatures ($10^{\circ}C$, $15^{\circ}C$ and $25^{\circ}C$) and three EBCTs (5, 10 and 15 min). Increasing EBCT and water temperature increased the biodegradation efficiency of HNMs in BAC column. Dibromochloronitromethane (DBCNM) and tribromonitromethane (TBNM) showed the highest biodegradation efficiency, but chloronitromethane (CNM) and dichloronitromethane (DCNM) were the lowest. The kinetic analysis suggested a pseudo-first-order reaction model for biodegradation of 7 HNMs at various water temperatures and EBCTs. The pseudo-first-order biodegradation rate constants ($k_{bio}$) of 7 HNMs ranged from $0.0797{\sim}0.7657min^{-1}$ at $10^{\circ}C$ to $0.1245{\sim}1.8421min^{-1}$ at $25^{\circ}C$. By increasing the water temperature from $10^{\circ}C$ to $25^{\circ}C$, the biodegradation rate constants ($k_{bio}$) were increased 1.6~2.4 times.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.2
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• pp.151-157
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• 2005

A one-dimensional numerical model was developed to simulate vertical profiles of electron acceptors and their reduced species in benthic sediments. The model accounted for microbial degradation of organic matter and subsequent chemical reactions of interest using stoichiometric relationships. Depending on the dominant electron acceptors utilized by microorganisms, the benthic sediments were assumed to be vertically subdivided into six zones: (1) aerobic respiration, (2) denitrification, (3) manganese reduction, (4) iron reduction, (5) sulfate reduction, and (6) methanogenesis. The utilizations of electron acceptors in the biologically mediated oxidation of organic matter were represented by Monod-type expression. The mass balance equations formulated for the reactive transport of organic matter, electron acceptors, and their corresponding reduced species in the sediments were solved utilizing an iterative multistep numerical method. The ability of model to simulate a freshwater sediments system was tested by comparing simulation results against published data obtained from lake sediments. The simulation results reasonably agreed with field measurements for most species, except for ammonia. This result showed that the C/N ratio (106/16) in the sediments is lower than what the Redfield formula prescribes. Since accurate estimates of vertical profiles of electron acceptors and their reduced species are important to determine the mobility and bioavailability of trace metals in the sediments, the model has potential application to assess the stability of selected trace metals in the sediments.

• Journal of the Korea Organic Resources Recycling Association
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• v.25 no.3
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• pp.55-62
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• 2017

In this study, we investigated the effect of seaweed (SW) addition on the anaerobic digestion of food waste (FW). Anaerobic batch experiments were carried out at various substrate concentrations (2.5 to 10.0 g VS/L) and mixing ratios (FW:SW=100:0, 75:25, 50:50, 25:75 and 0:100 on VS basis) of FW and SW. The methane yield of FW alone was 394, 377, 276, $49mL\;CH_4/g\;VS_{added}$ at each substrate concentration (2.5 to 10.0 g VS/L). In cases of co-digestion, methane yield decreased (up to 15 %) with increasing mixing ratio of SW at low substrate concentration (2.5 to 5.0 g VS/L), while it increased (up to 240 %) at high substrate concentration (7.5 to 10.0 g VS/L). The synergistic effect was calculated based on the amount of methane generated from the single-feedstock digestion of FW and SW. The synergistic effect was not found at 2.5 and 5.0 g VS/L. However, the synergistic effect increased (up to 25% = synergistic increment/total methane production at 10.0 g VS/L, FW:SW=50:50) with increasing the ratio of seaweed at 7.5 and 10.0 g VS/L. At 10.0 g VS/L of FW alone, the accumulated amount of organic acids was 7,426 mg COD/L, which was decreased to 2,346 mg COD/L by seaweed (FW:SW=50:50) addition. The reason for the synergistic effect was to control the production rate of the organic acids by adding SW that has a relatively lower biodegradability compared to FW.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.12
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• pp.2197-2204
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• 2000

Lignin is a major component of wastewater generated in the chemical processing of wood. Because it is recalcitrant, it inhibits biological treatment of wastewater of pulp manufacturing, especially high concentration of lignin may inhibit the anaerobic digestion. The objective of this study was to evaluate the toxicity of high molecular hardwood lignin (lignosulfonate, MW $\geq$ 20,000) on aceticlastic methanogens in the batch reactors at different temperatures with different sludge concentrations, using anaerobic serum bottles. The hardwood lignin was found to inhibit anaerobic conversion of acetate to methane and carbon dioxide, shown with a long lag-phase before methanogenesis started. The methanogens assumed not to be able to acclimate to the lignin were found to be acclimated slowly in the batch experiments, finally reaching non-toxic levels in which methane production could start. The hardwood lignin was found not to be bacteriocidal but bacteriostatic to aceticlastic methanogens. Hardwood lignin(lignosulfonate) at 1.3, 2.6, and 3.9%(w/w) inhibited the acetateutilizing methanogens of anaerobic digester sludge by 14.5, 17.8, 21.1 days(in noninhibitory condition it took 10 days) to produce the same amount of methane. The inhibitory effect of lignin was examined at temperature ranges of $30^{\circ}C$ to $50^{\circ}C$. When 2.6% of lignin was contained in wastewater, methane production was highest at $30^{\circ}C$ during initial 8 days. At $4^{\circ}C$, methane production rapidly increased after 12 days of digestion, the value became higher than that at $30^{\circ}C$ after 14 days. However, the methane production was completely inhibited during whole digestion period at $50^{\circ}C$. High ratio of lignin concentration to initial anaerobic sludge concentration gave tolerance to the inhibition. In this experiment, high molecular hardwood lignin was not degraded and decolorized.

• Journal of the Korea Organic Resources Recycling Association
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• v.2 no.2
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• pp.3-17
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• 1994

The inhibitory effect of sodium ion on the anaerobic degradation of food waste was studied by an anaerobic batch toxicity assay and inhibition model. The anaerobic degradation activity of food waste spiked with over $2g\;Na^+/L$ of sodium ion was severely inhibited at the initial stage of the exposure. The inhibition response of anaerobic microorganisms on the sodium ion estimated from the methane production was differed according to the concentration of sodium ion. The relative acclimation time(RAT) and methanation rate(RMR), defined as the ratios of initial lag time and maximum methane production rate of the sample spiked with sodium ion to the control. respectively, were used to evaluate the acclimation and inhibitory effects quantitatively on the anaerobic microorganisms. When sodium ion was increased from $2g\;Na^+/L$ to $20g\;Na^+/L$, the RAT was exponentially increased from 18.9 to 90. but the RMR was linearly decreased from 0.97 to 0.02. The effects of sodium ion for the maximum methanation rate, first order kinetic constant and ultimate methane production were well evaluated by a generalized nonlinear expression model. it could be described by the uncompetitive inhibition mode. The sodium ion concentration causing 50% inhibition of methanation activity was about $11g\;Na^+/L$, and the critical sodium ion beyond to compelete inhibition was 20 to $21g\;Na^+/L$. The presented results could be used to obtain the design or operation parameters of the anaerobic process treating food waste of high salt.

• Clean Technology
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• v.25 no.3
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• pp.223-230
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• 2019

This research was performed to evaluate the characteristics of food waste from 5 areas in Gangwon Province, Korea and to predict the $CH_4$ gas production rate. Food wastes were sampled in July and September, 2017. The amount of methane gas generation was evaluated through the biochemical methane potential (BMP) test and a calculation method using chemical composition. Average bulk density and pH of the food wastes were in the range of $0.758{\sim}0.850g\;cm^{-3}$ and 4.29 ~ 4.75, respectively. By physical composition, vegetables were the highest with 56.43 ~ 72.81% with fruits recording 5.31 ~ 8.95%, cereals 1.60 ~ 18.73%, fish and meat 4.47 ~ 12.11%, and filtrate 1.76 ~ 3.64%. The average water content was 69.30 ~ 75.87%, and VS and ash content were 22.50 ~ 27.98% and 1.63 ~ 2.48%, respectively. In addition, $BOD_5$, $COD_{Cr}$, and $COD_{Mn}$ were in the ranges of $17,690.3{\sim}33,154.9mg\;L^{-1}$, $106,212.3{\sim}128,695.5mg\;L^{-1}$, and $51,266.1{\sim}63,426.3mg\;L^{-1}$, respectively. The NaCl content ranged from 0.81 to 1.17%. The results of elemental analysis showed that the contents of C, H, O, N, and S were 44.87 ~ 48.1%, 7.12 ~ 7.57%, 40.13 ~ 43.78%, 3.22 ~ 4.14%, and 0.00 ~ 0.02%, respectively. In a comparison of the methane production yield per VS mass of food waste, there was no significant difference between the cumulative amount (${0.303{\sim}0.354m_{CH4}}^3\;{kg_{VS}}^{-1}$) by the BMP test and the theoretical amount (${0.294{\sim}0.352m_{CH4}}^3\;{kg_{VS}}^{-1}$) calculated by chemical composition.

• Journal of the Korea Organic Resources Recycling Association
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• v.16 no.1
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• pp.31-38
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• 2008

Animal carcasses have always been and continue to be a major burden in animal production. The main aim of this study is to evaluate the feasibility of thermophilic anaerobic digestion for animal carcasses. A batch test using ground meat and organ as the model substrate showed that animal carcasses arehighly biodegradable at thermophilic anaerobic condition. The volatile solids (VS) destruction and $CH_4$ yieldranged from 52.7 to 58.5% and from 220 to 243 mL/g VS, respectively, at initial substrate VS in the range of 1.5~7.7%. However, high ammonia concentration inhibited continuous operation at substrate VS above 2.5%. As ammonia is formed during the degradation of proteineous organic materials, the major constituent of animal carcasses, the only way to reduce the ammonia concentration would be dilution. Co-digestion with other waste stream without high nitrogen content is recommended as an economically feasible approach for thermophilic digestion of animal carcass.

• Journal of the Korean Chemical Society
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• v.35 no.1
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• pp.3-15
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• 1991

The gaseous mixtures of iso-propanol of 10 torr with carbon dioxide of 0∼1990 torr were irradiated with Co-60 gamma radiation up to 50 kGy, and the products such as carbon monoxide, acetone, methane, ethane, C$_3$H$_a$, C$_4$H$_b$ and tert-butanol were analyzed by gas chromatography. G(CO) value of 4 was obtained from the gas mixtures containing more than 490 torr of carbon dioxide. The production rates of the organic products and the decomposition rate of iso-propanol increased linearly with the pressure of carbon dioxide, and G(-iso-Propanol) and G(Acetone) values increased by 4 and 2, respectively, with each 10 torr increment of carbon dioxide pressure. The mechanisms of the radiolytic decomposition of iso-propanol and the production of carbon monoxide and organic materials are discussed on the basis of the experimental results of the present study.