• Journal of Environmental Health Sciences
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• v.23 no.1
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• pp.95-104
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• 1997

The objectives of this study are to investigate the effect of media on the removal efficiency of nitrate-nitrogen and the biofilm thickness in the fluidized bed biofilm reactor(FBBR) used for the high rate denitrification of nitric acid wastewater. Granular activated carbon(GAC) of 1.274 mm diameter and sand of 0.455 mm diameter were used as the media in the FBBR of 0.05 m diameter and 1.5 m height. As the nitrate-nitrogen concentration of the influent was increased stepwise from 600 to 4800 mg/l, the nitrate- and nitrite-nitrogen concentration of the effluent, biofilm thickness and biofilm dry density were measured to study the effects of media on the denitrification efficiency. The biofilm thickness increased with the substrate loading rate, and the biofilm dry density decreased with the increase of the biofilm thickness. At the influent nitrate-nitrogen concentration of 2400 mg/l, the removal efficiency in the FBBR with GAC was 88%, while that in the FBBR with sand was 99.6%. The biofilm in the FBBR with GAC was so thick, 754.9 $\mu$m, as to increase the mass transfer resistance, compared to that, 143.7 $\mu$m, in the FBBR with sand. The maximum specific denitrification rate in the FBBR with GAC was 15.0 kg-N/m$^3\cdot$ day, while that in the FBBR with sand was 18.0 kg-N/m$^3\cdot$ day. The biomass concentration in the FBBR with sand exhibited the high value 37 kg/m$^3$.

• Transactions of the Korean hydrogen and new energy society
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• v.25 no.5
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• pp.459-467
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• 2014

The catalytic steam reforming of toluene, a major component of biomass tar, was studied using several catalysts at various temperatures $400-800^{\circ}C$, kind of metal, and metal loading content. Ru and K promoted Ni-base catalyst were prepared, and used for steam reforming of toluene with steam/toluene molar ratio of 25. Concentration of toluene in reactant flow is $30g/Nm^3$ that is usual content of tar from biomass gasifier. The result from experiments showed that $H_2$ content in product gas and toluene conversion increased with temperature. Where in high temperature range, CO and $CO_2$ content in product gas were affected mainly by Boudouard reaction. Ni/Ru-K(3wt%)/$Al_2O_3$ catalyst showed best performance on steam reforming of toluene than used catalysts in this study at whole temperature. Catalysts have been characterized by XRD, TG. XRD analysis displayed that Ni particle size on Ni/Ru-K (3wt%)/$Al_2O_3$ catalyst was 29.4nm. Activation energy of Ni/Ru-K (3wt%)/$Al_2O_3$ catalyst was calculated 36.8kJ/mol by Arrhenius plot.

• Journal of environmental and Sanitary engineering
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• v.10 no.1
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• pp.45-65
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• 1995

Seasonal occurrences and dynamics on the freshwater algae were examined in the upstream of the Yongsan river system with the Kwangju service water area from 1993 to 1994. Three hundred and three taxi were totally collected and composed of 6 classes, 15 orders, 7 suborders, 31 families, 74 genera, 248 species, 48 varieties and 7 forma. Compositions in each algal class were divided in 136 taxi of Chlorophyceae(44.8% ), 109 taxi of Bacillariophyceae(36.0% ), 30 taxa of Cyanophyceae(10.1% ), 21 taxa of Euglenophyceae(6. 9% ),4 taxi of Chrysophyceae(1.3% ) and 3 taxa of Dinophyceae(1.0% ). The occurrence of taxa was a markedly decrease(-62) between summer and autumn, the critically increase(+43) between spring and summer. And also, it was indicated that the high frequency of taxa in summer, but the high standing biomass In winter in spite of low taxi. In general, it has much algal biomass in station 9 and 10, but low in station 4, 5 and 11, relatively. Through this survey, the major dominant taxa in algal biomass, Microcystis aeruginosa, Melosira varians, Synedra ulna and Navicula cryptocephala, they were all above 2.1×10$^{6}$ce11s/1, 13.2% of totals. There are about 10% of new emigrated taxa by season and they showed a remarkable succession. We may suggested that this system was well sustained for the habitat of freshwater algal community with low dominance and high diversity. Twenty three of nuisance algae including of Microcystis aeruginosa, Peridinium willei and Anabaena flos-aquae were distributed as if had low appearance. Of course, many of them were saprobiontic taxa, extraordinary growttung groups depend on organic loading in water system and also it was not showed severe algal blooming phenomenon.

• Journal of Korean Society of Water and Wastewater
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• v.14 no.1
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• pp.37-44
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• 2000

Laboratory experiments were conducted to investigate the performances of anaerobic filters packed with ceramic tube and pall-ring media treating a dairy waste. The media packing volume was 65% of effective volume of anaerobic filter. Organics removals of anaerobic filters were maintained above 80% even at an organics loading rate of $10kgCOD/m^3/d$, and this was comparable to aerobic treatment of organic wastes. Organics removals of the ceramic tube anaerobic filters were always lower than those of the pall-ring anaerobic filters due to intrinsic physical property of ceramic tube, especially lower void space which caused to clogging and entrapment of biogas, substrate transfer limitation, and irregular evolution of biogas leading to loss of solids and biomass. This was clearly observed in higher concentration of TSS in the effluent from the ceramic tube anaerobic filter despite of higher retention capacity of TSS compared with pall-ring media. Vertical distribution of organics and solids in the filters showed above 90% of organics and solids in influent were removed below 20% of reactor height, and 50% of remaining organics and solids were removed though media packing zone. Effluent quality from the anaerobic filter was heavily depended on media itself as well as suspended biomass formed below media. It is therefore concluded that the type of media played an important role in biomass accumulation arid gas-liquid-solid separation efficiency. Type of media did not affect the start-up behaviors of the anaerobic filter, and supernatant from anaerobic digested sludge showed a good performance as a seeding materials.

• Journal of the Korean Association of Geographic Information Studies
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• v.15 no.1
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• pp.184-196
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• 2012

Biomass burning activities(BBA) are caused by both natural and anthropogenic origins. Due to emissions of greenhouse gases and atmospheric aerosols during the burning process, BBA has been known to be one of important sources of atmospheric pollution and the climate change. However, the monitoring of BBA and its effects on atmospheric environment are not simple. This study evaluates the trends of BBA and its impact on atmospheric environment by using earth observing satellite. The results show that the most BBA were found over ever green, green vegetation types, and irrigated land cover types in study region. The trends of BBA and aerosol optical thickness which represents relative aerosol loading in the atmosphere, show similar pattern. Aerosol increases caused by BBA highlight the effectiveness of these mechanisms and would affect the regional atmospheric environment and climate change.

• Korean Chemical Engineering Research
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• v.49 no.4
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• pp.470-474
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• 2011

Rice straw is the main grain straw and is produced in large quantities every year in Korea. Pretreatment of lignocellulosic biomass using soaking process was carried out mild conditions at atmospheric pressure and temperature of $60^{\circ}C$. We found enzymatic hydrolysis condition of pretreated biomass. In case of a rice straw, compared with previous lignocellulosic biomass, we found that hydrolysis time was a shorter than others. Hydrolysis of SAA-treated rice straw has shown conversion rate was higher at $50^{\circ}C$. Hydrolysis was ended between 40~48 hour. Glucose conversion rate was higher when enzyme loading is 65 FPU/ml and 32 CbU/ml. When substrate concentration was 5%(w/v), it was that conversion rate was 83.8% after hydrolysis for 72 hr. In simultaneous saccharification and fermentation(SSF) experiment about SAA-treated rice straw, ethanol productive yield was highest from $40^{\circ}C$. The yield of that time was 33.05% from 48 hour.

• Journal of environmental and Sanitary engineering
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• v.8 no.1
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• pp.107-116
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• 1993

This study is conducted to investigate treatability by activated sludge process for wastewater from acetaldehyde manufacturing plant. The optimum hydraulic retention time in aeration tank for removal of high strength substrate were measured. The removal efficiency were checked out by hydraulic retention time : 35hr., 40hr. and 45hr., respectively. $COD_{Cr}$, like substances were removed in all hydraulic retention time zone directed for efficiency, but non-biodegradable substances were remained. $COD_{Cr}$ biomass loading was 0.81kg $COD_{Cr}/kgMLVSS$ . day at 35hr. of retention time, 0.34 kg$COD_{Cr}$/kg MLVSS . day at 40hr., and O.l9kg$COD_Cr$/kgMLVSS . day at 45hr. And the mean $COD_{Cr}$, removal efficiency was 65.5%, 81.6% and 83.0%, respectively. And also $COD_{Cr}$, volume loading was 1.01kg$COD_{Cr}/m^3$ day, 0.87kg$COD_{Cr}/m^3$ - day, and 0.79kg$COD_{Cr}/m^3{\cdot }$day, respectively. The basic design parameter obtained is as fallows. The value of Specific substrate removal rate coefficient (k), Yield coefficient(Y) and Decay coefficient($k_d$) was $0.0013day^{-1}$, $0.505kgMLVSS/kgCOD_{Cr}$ and $0.040day^{-1}$, respectively.

• KSBB Journal
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• v.7 no.3
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• pp.235-245
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• 1992

A number of experiments to treat wastewater of a dye plant were conducted to investigate the basic design parameters and effluent characteristics for aerobic fixed biofilm reactor upon the variation of organic loading rate. The media used for this study were SARAN 4000 D with specific surface area $153m^2/m^3$, and 1000 D with specific surface area $307m^2/m^3$. The influent COD concentration ranged from 1250 to 4080 mg/L. Substrate removal and variation of biomass concentration were observed. At the beginning, the effluent quality was poor but improved as the time passed. However the effluent quality became seriously deteriorated when the media clogged. At influent COD of 1250mg/L, the effluent COD varied little, even if the organic loading rate increased from 0.63 to 2.5kg COD/$m^3$/day. It was also noted that the design parameters for activated sludge process could be applied to an aerobic fixed biofilm process under the experimental conditions.

• Journal of Korean Society on Water Environment
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• v.18 no.2
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• pp.113-122
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• 2002

A bench-scale anoxic membrane bioreactor (MBR) system, consisting of a bioreactor coupled to a ceramic crossflow ultrafiltration module, was evaluated to treat a synthetic wastewater containing alkaline hydrolysis byproducts (hydrolysates) of RDX, The wastewater was formulated the same as RDX hydrolysates, and consisted of acetate, formate, formaldehyde as carbon sources and nitrite, nitrate as electron accepters. The MBR system removed 80 to 90% of these carbon sources, and approximately 90% of the stoichiometric amount of nitrate, 60% of nitrite. The reactor was also operated over a range of transmembrane pressures, temperatures, suspended solids concentration, and organic loading rate in order to maximize treatment efficiency and permeate flux. Increasing transmembrane pressure and temperature did not improve membrane flux significantly. Increasing biomass concentration in the bioreactor decreased the permeate flux significantly. The maximum volumetric organic loading rate was $0.72kg\;COD/m^3/day$, and the maximum F/M ratio was 0.50 kg N/kg MLSS/day and 1.82 kg COD/kg MLSS/day. Membrane permeate was clear and essentially free of bacteria, as indicated by heterotrophic plate count. Permeate flux ranged between 0.15 and $2.0m^3/m^2/day$ and was maintained by routine backwashing every 3 to 4 day. Backwashing with 2% NaOCl solution every fourth or fifth backwashing cycle was able to restore membrane flux to its original value.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.10 no.1
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• pp.173-184
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• 1990

This study is an experimental research on the treatment of phenolic wastes by Rotating Biological Contactors(RBC). The objective of this study is to determine the optimum range of influent phenol concentration and organic loading rate. Organic removal rates were analyzed with increasing organic loading and influent phenol concentration, together with the observation of microorganism. Biomass, SCOD, and phenol concentration were measured under the steady state after a step change of influent phenol concentration. As the result, at the phenol concentration less then 98.8 mg/L there were no evidence of substrate inhibition. As the results, organic removal rates in each stage at various organic loading, were decreased with increasing phenol concentration. First order kinetic was observed on the removal of SCOD for which phenol concentration is within the range of substrate inhibition. And also, microorganisms were changed with influent phenol concentration. Namely, at low influent phenol concentration, thin biofilm with filamentous growth was produced. To the contrary, thick biofilm with nonfilamentous growth was produced at high influent phenol concentration.