• Journal of Korean Society of Environmental Engineers
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• v.35 no.1
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• pp.57-63
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• 2013

A combined process consisted of a biofilm reactor and a continuously stirred-tank reactor (CSTR) was investigated for highly loaded ammonium wastewater treatment via nitrite accumulation. To enhance ammonium oxidizing bacteria over nitrite oxidizing bacteria on the surface of carriers, the biofilm reactor was operated at temperature of $35^{\circ}C$ for more than three months but the influent ammonium (500 mg-N/L) was partially oxidized to nitrite (240 mg-N/L). As pH was increased from 7.5 to 8.0, nitrite accumulation was fully achieved due to the inhibition of nitrite oxidizing bacteria under high free ammonia concentration. The biofilm reactor performance was severely deteriorated at the hydraulic retention time of 12 hr, at which incomplete nitrification of ammonia was observed. Various solubilization methods were applied to sewage sludge for enhancing its biodegradability and the combined method, alkaline followed by ultrasonic, gave the highest solubilization efficiency (58%); the solubilized solution was used as the external carbon source for denitrification reaction in CSTR. FISH analysis showed that the dominant microorganisms on the carriers were ammonium oxidizing bacteria such as Nitrosomonas spp. and Nitrospirar spp. but low amounts of nitrite oxidizing bacteria as Nitrobacter spp. was also detected.

• Proceedings of the Membrane Society of Korea Conference
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• 1996.10a
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• pp.60-61
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• 1996

염색폐수를 처리하기 위하여, 일반적으로 물리.화학적 공정과 호기성 생물학적 공정을 조합한 방법들을 사용하고 있다. 하지만 호기성 생물학적 공정은 난분해성 물질의 제거능력이 낮고, 염색폐수의 주된 오염원인 염료분자가 호기성 미생물에 대한 에너지원으로 적합하지 않아 분해되기 어려우며, 물리.화학적 공정을 이용한 처리방법으로도 높은 처리효율을 얻을 수가 없다. 이러한 문제점을 극복하기 위하여 염색폐수 처리에 혐기-호기공정을 이용하며, 혐기성 공정에서 생물학적으로 분해되기 어려운 고분자 물질들을 가수분해하여 생물학적으로 분해가능한 저분자물질로 전환시키고, 호기성 공정에서 저분자 물질을 효과적으로 처라할 수 있기때문에 기존의 염색폐수 처리공정에 비하여 훨씬 높은 처리효율을 얻을 수 있다. 특히, 혐기성 미생물은 호기성 미생물에 비하여 난분해성 물질에 대한 분해력이 높고, 생물독성 물질에 대한 내성이 강하기 때문에 수중생물에 유해한 염료를 함유한 염색폐수의 색도제거에 효과적인 것으로 기대된다. 또한, 막분리 공정은 유기물 및 미생물이 막표면에 축적, 증식함으로써 막세공에 막힘현상을 초래하여 역세척 등의 물리적인 방법이나 화학약품을 이용한 화학적 세척 방법으로도 투과플럭스의 회복이 불가능한 상태를 유발함으로 막의 수명을 단축시키는 원인이 된다. 따라서, 혐기-호기공정과 조합하면 색도성분 제거 및 막 오염의 원인이 되는 유기물 및 용존성 고형물을 제거하고, 막 오염의 억제를 통한 후 수염의 연장은 물론, 처리수의 수질향상에 활용될 수 있을 것으로 사료된다.1로 강구와 함께 공구강 vial에 장입 후, Spex mixer/mill을 이용하여 기계적 합금화 하였다. 기계적 합금화 공정으로 제조한 분말에 대한 X-선 회절분석과 시차 열분석으로 합금화 정도를 분석하였다. (Bi1-xSbx)2Te3 및 Bi2(Te1-ySey)3 합금분말을 10-5 torr의 진공중에서 300℃∼550℃의 온도로 30분간 가압소결하였다. 가압소결체의 파단면에서의 미세구조를 주사전자현미경으로 관찰하였으며, 상온에서 가압소결체의 열전특성을 측정하였다. (Bi1-xSbx)2Te3의 기계적 합금화에 요구되는 공정시간은 Sb2Te3 함량에 따라 증가하여 x=0.5 조성에서는 4 시간 45분, x=0.75 조성에서는 5 시간, x=1 조성에서는 6 시간 45분의 vibro 밀링이 요구되었다. n형 Bi2(Te1-ySey)3 합금분말의 제조에 요구되는 밀링시간 역시 Bi2Se3 함량 증가에 따라 증가하였으며 Bi2(Te0.95Se0.05)3 합금분말의 제조에는 2시간, Bi2(Te0.9Se0.1)3 및 Bi2(Te0.85Se0.15)3 합금분말의 형성에는 3시간의 bivro 밀링이 요구되었다. 기계적 합금화로 제조한 p형 (Bi0.2Sb0.8)2Te3 및 n형 Bi2(Te0.9Se0.1)3 가압 소결체는 각기 2.9x10-3/K 및 2.1x10-3/K 의 우수한 성능지수를 나타내었다.ering)가 필수적이다. 그러나 침전법에서 얻게 되는 분말은 매우 미세하여 colloid를 형성하게 되며, 이러한 colloid 상태의 미세한 침전입자가 filte

• Journal of Environmental Health Sciences
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• v.20 no.1
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• pp.62-67
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• 1994

Introduction : Recently, water and environmental pollution becomes serious social problem and high technology makes this pollution accelerate. Hydrogen sulfide, the main subject of our research, is one of the most dangerous air pollutant like SO$_x$ and NO$_x$. The major contaminant in coal gasification is H$_2$S, which is very toxic, hazardous and extremely corrosive. Therefore, control of hydrogen sulfide to a safe level is essential. Although commercial desulfurization process called liquid scrubbing is effective for removal of H$_2$S, it has drawbacks, the loss of sensible heat of the gas and costly wastewater treatment. Many investigations are carried out about high-temperature removal ol H$_2$S in hot coal-derived gas using metal oxide or mixed metal qxide sorbents. It was reported that ZnO was very effective sorbent for H2S removal, but it has big flaw to vaporize elemental zinc above 600\ulcorner \ulcorner As alternative, metal oxides such as CaO, $Fe_2O_3$, TiO$_2$ and CuO were added to ZnO. Especially, different results are reported for $Fe_2O_3$ additive. Tamhankar et al. reported SiO$_2$ with 45 wt% $Fe_2O_3$ sorbent is favorable for removal of H$_2$S and regeneration.

• Journal of the Korea Organic Resources Recycling Association
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• v.20 no.4
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• pp.61-74
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• 2012

Industrial complexes in Korea have been vigorously established by economic development plan and development policy of industry in 1960s. Recently, Korean government has promoted Eco Industrial Park (EIP) project to recycle by-products and wastes in industrial park In this study, we analyzed the physical and chemical properties for the sludges discharged from A industrial complex. And we investigated the economic feasibility and environmental impact of sludge to energy facilities. The analysis results indicated that the petrochemical industry were 92% in sludge production, the highest treatment amount was landfill, followed by incineration and recycling and then ocean disposal. Wastewater sludge and process sludge samples are collected and analyzed to use as basic data on economic feasibility and environmental impact. Weighted average heating value of sludge samples was 3,891kcal/kg. Based on this data, installation and operation costs, operation returns of operating the drying facility are estimated, compared with cogeneration facility. And this study examines how the payback period of each simulation(total 8 case) with the important parameter changes. As a result, it was found that what needs the shortest payback period is 3years with connection of drying facility and cogeneration facility based on the government's financial subsidy system.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.5
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• pp.527-534
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• 2006

The purpose of this study is the development of more effective filter-type polymer adsorbent for removal of anionic pollutants from wastewater. In order to synthesize the polymer adsorbent that possesses anionic exchangeable function, carboxyl(-COOH) group of PP-g-AA nonwoven fabric was converted into amine($-NH_2$) group by the chemical modification using diethylene triamine(DETA). FT-IR data indicate that amine group was introduced into PP-g-AA through amidation of grafted acrylic acid by reaction with DETA. The degree of amination increased with increase in the reaction time and temperature of the chemical modification process, and was significantly improved by the pre-swelling treatment of PP-g-AA with solvent and addition of metal chlorides as a catalyst in following order as $NH_4OH>MeOH{\geq}HCl{\geq}H_2O\;and\;AlCl_3>FeCl_3{\geq}SnCl_2{\gg}ZnCl_2{\geq}FeCl_2$, respectively. However, the addition of catalyst limited the reusability of DETA, hence was less useful from the viewpoint of cost effectiveness and waste management. The anion exchange capacity of the aminated PP-g-AA(PP-g-AA-Am) increased with increase in the degree of amination, but it reached maximum value at the degree of amination as about $50{\sim}60%$. The anion exchange capacity of PP-g-AA-Am was higher than those of commercial anion resins.

• Journal of Korean Society on Water Environment
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• v.31 no.6
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• pp.599-609
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• 2015

In order to investigate why OSA (oxic-settling-anaerobic) process produces less sludge than CAS (conventional activated sludge) process, sequential cultivation through 1^st aerobic-anaerobic-2^nd aerobic conditions, were carried out. Then, the intracellular concentrations of adenosine triphosphate (ATP), nicotinamide adenine dinucleotide (NAD and NADH), and nicotinamide adenine dinucleotide phosphate (NADP and NADPH) were monitored for these three stages. Results showed that the concentrations of these energy substances rapidly decreased through time in both aerobic and anaerobic conditions but the anaerobic culture contained the lower energy level than aerobic culture. The 2^nd aerobic culture that experienced anaerobic condition showed lower concentration of these energy substances than those of the 1^st aerobic culture. Meanwhile, the anaerobic culture corresponding to the sludge holding stage of OSA was subjected to different soluble chemical oxygen demand (SCOD) levels, detention time, and temperature to evaluate the effects of these variations on the energy level difference between the 1^st and 2^nd aerobic stages. The lower the SCOD concentration, the longer detention time; and the higher temperature in the anaerobic stage tended to further reduce the intracellular level of the 2^nd aerobic culture. On the average, the intracellular energy level of the anaerobic and 2^nd aerobic stage were 57.73% and 39.12% of the 1st aerobic culture, respectively. These indicated that the insertion of an anaerobic stage between two aerobic stages could lower the intracellular energy levels, hence the lower the sludge in OSA than CAS process. Moreover, manipulation of the operating conditions of the intervening anaerobic stage can change intracellular energy levels thereby controlling sludge production.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.8
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• pp.673-678
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• 2009

High-rate phosphorous removal by PAC (poly aluminum chloride) coagulation of A2O effluent was investigate to meet the stringent requirement of wastewater discharge from municipal wastewater treatment plant. A series of jar tests were conducted to find optimum coagulation condition and to enhance removal efficiency. The optimum volumetric concentration of PAC was 30 ppm (2.81mol Al/mol P by mol ratio). Only 17.2% of soluble P was removed for 30 minutes' settling without PAC addition, while this increased to 30.3% by dosing 10ppm PAC. It even increased conspicuously from 49.3% to 88.4% by increasing PAC dose from 20 ppm to 30 ppm. 92.4% of total P was removed by 30 ppm PAC, and the effluent concentration (0.3 mg/L) was acceptable for discharge. The optimum value of coagulation time, settling time, and pH were 4minutes, 20 minutes, and 7.0, respectively. It was not necessary to control pH of raw sample whose pH was 7.0. Soluble P removal was remarkably enhanced at pH 7.0. This implied that sweep floc formation by $Al(OH)_3$ was the main mechanism of coagulation for soluble P removal. Influent and effluent of secondary clarifier were tested for coagulation, and the effluent was better for high-rate P removal. It resulted in 0.18 mg/L of P and 95.4% of P removal by coagulation. It was favorable to recycle the treated water to coagulation tank and the optimum recycle ratio was 0.3.

• Journal of Korean Society on Water Environment
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• v.22 no.6
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• pp.1101-1106
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• 2006

Many BNR (Biological Nutrient Removal) plants have experienced a bulking problem, mainly due to the growth of filamentous organisms, particularly during the winter months. This study investigated the problem of bulking due to the growth of M. parvicella both at a full-scale municipal wastewater treatment plant and a pilot scale plant located in the C city. The full-scale facility was operated at a flow rate of $51,000m^3/d$, an F/M (Food-to-Microorganism) ratio of 0.12 kgBOD/kgMLVSS/d and an SRT (Solids Retention Time) higher than 25 days, respectively. This plant experienced bulking and foaming problems at low temperatures below $15^{\circ}C$ since it was retrofitted with the BNR system in 2003. The pilot plant employed had an identical process configuration as the full scale one and used the same wastewater source. It was operated at a flow rate of $3.8m^3/d$, temperatures between 10 to $25^{\circ}C$ and SRTs between 10 and 25 days. At full scale, the M. parvicella growth and SVI (Sludge Volume Index) patterns were studied in conjunction with temperature variations. At pilot scale, DO and SRT variations were also explored, in addition to the filamentous bacteria growth and SVI patterns. During the full-scale investigation, over a 3 year period, it was noted that the SVI was maintained within acceptable operational values (i.e. under 160) during the summer months. Moreover settling in the secondary clarifiers was good and was not affected by the presence of M. parvicella. In contrast, at low mean temperatures during winter, the SVI increased to over 300. Overall, as the temperature decreased, the predominance of M. parvicella became apparent. According to this study, M. parvicella growth could be controlled and SVI could drop under 160 by a change in operational conditions which involved an increase in DO concentration between 2 and 4 mg/L and a decrease in SRT to less than 20 days.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.4
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• pp.797-806
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• 2000

The objectives were to compare the biodegradable threshold concentrations of phenol with the different composition of the influent carbon source and examine the SMA (Specific Methanogenic Activity)and the possibility of simultaneous removal of high-strength organics and nitrogen compounds in UASB(Upflow Anaerobic Sludge Blanket) - PBR(Packed Bed Reactor) process. The results showed that UASB reactors were efficient to remove phenol and phenol + glucose from synthetic wastewater. At phenol conc, of 600 mg/L and SCOD conc. of 2100 mg/L in UASB reactor(with only phenol as substrate), the removal efficiencies of phenol and SCOD were over 99% and 93% respectively, under MLVSS of 20 g. The activity of microorganism was $0.112g\;phenol/g\;VSS{\cdot}d$, $0.351g\;SCOD/g\;VSS{\cdot}d$. The gas production rate was $0.115L/g\;VSS{\cdot}d$ and $CH_4$ content in gas was about 70%. At phenol conc. of 760 mg/L and SCOD conc. of 4300 mg/L in UASB reactor( with phenol + glucose as substrates), the removal efficiencies of phenol and of SCOD were over 99% and 90% respectively, under MLVSS of 20 g. The activity of microoganism was $0.135g\;phenol/g\;VSS{\cdot}d$, $0.696g\;SCOD/g\;VSS{\cdot}d$. The gas production rate was $0.257L/g\;VSS{\cdot}d$ and $CH_4$ content in gas was about 70%. Serum bottle test showed that the activity of granule was inhibited over 1600 mg/L phenol conc, and denitrification and methanogenesis simultaneously took place in UASB granules under co-substrates conditions. PBR reactor packed with cilium type media, was efficient in nitrification. In condition of $0.038kg\;NH_4-N/m^3-media{\cdot}d$. 10~12 mg/L phenol conc. and 200~500 mg/L SCOD conc., nitrification efficiency was over 90% and phenol removal efficiency was over 98%.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.8
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• pp.831-838
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• 2008

This study investigated the characteristics of nitrogen removal and microbial community in a lab-scale A$_2$O activated sludge process filled with the fluidized media at an aerebic basin. The change of microbial community was monitored based on quinone profiles of activated sludge according to feeding sewage with/without external carbon source. Low C/N ratio(COD$_{Cr}$/T-N of 1.24) sewage was fed. The obtained results from this study were as follows; Ubiquinone(UQ) in the influent was in the descending order of UQ-8, UQ-10 and UQ-9. Menaquinone(MK) was simpler and much less than UQ. The ratio of UQ/MK was less than 0.41 and the dissimilarity was below 0.26. Without an external carbon source, MK-8 was the dominant species and there were 3 kinds of quinone species and low DQ and EQ values in an anaerobic basin. The ratio of UQ/MK increased to 2.3 in an anoxic basin. In an oxic basin, UQ-7 and UQ-8 were the dominant species. UQ-7 was dominating in suspended microorganisms, while UQ-8 was in attached microorganisms. With an external carbon source addition, MK-8 decreased but UQ-8 increased in an anaerobic basin. So did quinone species, DQ and EQ values. There was also a change in an anoxic basin with the improvement of denitrification. UQ-8 decreased instead, MK-7 and MK-8 increased. UQ/MK ratio decreased 2.3 to 1.4. It means that the dominant species change from Pseudomonas sp. to Bacillus and Micrococcus species. etc. In an oxic basin, UQ-8 replaced UQ-7 in suspended microorganisms and UQ-10 replaced UQ-8 in attached microbials. This seemed related with the growth of Nitrosomonas and Nitrobactor species.