최경식Kyoung Sik Choi,나은혜Eun Hye Na,박석순Seok Soon Park

DOI: Vol.16(No.5) 565-572, 2000

This paper describes the application of a distributed non-point source model called AGNPS(Agricultural Non-Point Sources) to Bulno Cheon watershed. Deagu, Korea. All the required databases (soils, land use and topography) were assembled at 1: 250.000 scale. The study watershed was discretized into 85 grids, of which size is 500m x 500m. The model was calibrated and verified with the measured data. including the runoff flow, chemical oxygen demand, and total nitrogen. The model results displayed a good agreement with the field measurements for both calibration and verification. The validated model was utilized to predict an impact of urbanization on the runoff flow and pollution loads. The predicted results indicated that an urbanization would cause the runoff flow to increase significantly, but the pollution loads to somewhat decrease if all the livestock feedlots are eliminated from the study watershed with urbanization.

황병기Byung Gi Hwang,조미영Mi Young Cho,최경식Kyoung Sik Choi

DOI: Vol.16(No.5) 573-583, 2000

An intergrated water-quality management system for Masan Bay has been developed using ArcView GIS with a system language Avenue. A water-quality model is linked with environmental databases in the system. The model WASP/EUTRO5 for eutrophication analysis of the bay is included within the system. The databases are mainly composed of data for land use, watershed information, concentration and flow of inflowing pollutants due to runoff, and concentration for water-quality items of seawaters and sediments. The system runs on a personal computer under the Windows environment and provides extensive Graphic User Interface(GUI) for user-friendly assessment. The graphic include a site map and plots of model results such as spatial and temporal variations of pollutants in seawater. Using the pull-down menus provided by the GUI panel, the user is able to operate the system by pointing and clicking the icon to identify the state of water quality at locations concerned. As this system utilized the water-quality model and can predict the current and future state of water quality, it could serve as a useful tool for the decision means of policy-maker

김혜선Hye Sun Kim,윤제용Je Yong Yoon,염철민Cheol Min Yeom

DOI: Vol.16(No.5) 585-594, 2000

Few researches relative to the occurrence of the enteric protozoan parasites Cryptosporidium oocysts and Giardia cysts were reported in Korea, despite of the increasing importance of public health in supplying drinking water. Hence. the occurrence of Cryptosporidium oocysts and Giardia cysts was investigated in the raw waters of Han and Kum River for drinking water and the effluent of L wastewater treatment plant in Han River between Jan. 1999 and Jul. 1999. The method for the isolation and enumeration of oocysts and cysts used was American Standards for Testing Methods. Both Cryptosporidium oocysts and Giardia cysts were detected in 11 and 10 out of total 14 raw water samples, respectively. The concentrations of both Cryptosporidium oocysts and Giardia cysts were similar, ranging to 0-350 oocysts/100 L. Much higher concentration of Cryptosporidium was found in the effluent of L wastewater treatment plant. Approximately, this level of Cryptosporidium oocysts and Giardia cysts concentration lies between the pristine water source and the heavily contaminated watershed as compared to literature values.

이목영Mok Young Lee,김도연Do Yeon Kim,조은주Eun Ju Cho,이의광Eu Kwang Lee,오세종Sea Jong Oh,이채근Chae Keun Lee,하영칠Yung Chil Hah

DOI: Vol.16(No.5) 595-608, 2000

Giardia cysts and Cryptosporidium oocysts in water samples were detected simultaneouly using 1623 Method, which combined capsule/membrane filtration and immunomagnetic separation with immunofluorescence assay. In this study, raw water samples from 6 intakes, finished and tap water samples supplied from Kueui Water Treatment Plants in Seoul, and Wangsuk creek water samples were tested from April 1999 to February 2000, to estimate the prevalence of two protozoa in Seoul drinking water supplies. Giardia cysts were found in 25∼75% of water samples from 6 intakes in the range of 0∼9.7/10L. Cryptosporidium oocysts were found in 0∼50% of six intake water samples in the range of 0∼4/10L. Raw water samples from Kueui. Jayang, Pungnap intakes showed significantly higher concentration and more frequent incidence of Giardia than that from Paldang, Kangbuk. Amsa intakes. It seemed that Wangsuk creek acts as an important source of Giardia pollution in Kueui, Jayang. Pungnap intakes because all samples from Wangsuk creek, flowing in upstream of Kueui intakes, contained 19∼109/l0L of Giardia cysts. No Cryptosporidium and Giardia were found in all finished and tap water sample. We concluded that Giardia cysts are more often found in raw surface waters of Seoul than Cryptosporidium oocysts, although two protozoa were not detected in treated water samples of Kueui Water Treatment Plant.

A . R . Khan , Kyung Sok Min , Yong Jum Jung

DOI: Vol.16(No.5) 609-620, 2000

Rhodococcus rubra, being a slow growing filamentous species, is a proven stable foam forming actinomycete in wastewater treatment systems. This paper examines the growth characteristics of this species, its biosurfactant production and its foaming characteristics in comparison to sludge samples from both foaming and non-foaming plants. In continuation of our previous work, growth studies of Rhodococcus rubra were investigated at 37˚C using Czapek as growth medium. The results indicate that increasing the growth temperature from 28 to 37℃, neither the cell surface activity nor the yield of the biopolymer was enhanced. Nostocoida limicola dominated samples, although, showed a marked decrease in surface tension and higher foaming potential, yet the stability of these foams was less marked compared to the Nocardia dominated ones. Critical values of surface tension have been determined, above which, foaming is unlikely. These values can be used as a tool to assess the foaming condition in a plant prior to its aggravation.

유대환Dae Hwan Rhu,최의소Eui So Choi

DOI: Vol.16(No.5) 621-631, 2000

Evaluation of sludge mass produced by substrate removal is important to operate biological wastewater treatment plant. Sludge production depends on the yield coefficient of the bacteria metabolizing substrates. It is indispensible for predicting the sludge production to evaluate accurate yield coefficient. Especially. It is supposed that anoxic yield coefficient be different to that of oxic condition due to different reaction condition in BNR process. Yield coefficients were evaluated by measuring electron acceptors at oxic and anoxic conditions. The average oxic yield coefficient was about 0.5g cell COD/gCOD removed independent to temperature. The anoxic yield coefficient was various with temperature: 0.2 at 20℃, 0.3 at 10℃ and 0.5g cell COD/gCODremoved at 5℃.

최은주Eun Ju Choi,주대성Dae Sung Joo,박희경Hee Kyung Park

DOI: Vol.16(No.5) 633-647, 2000

Development of a dynamic SBR simulation model for biological nitrogen removal. based on the Activated Sludge Model No.l, is presented. An experimental study for the calibration and validation of the model was carried out using a pilot scale SBR which treated the wastewater of KAIST. Thirteen water quality components and twenty model parameters are incorporated into this model. In this study, the model components and parameters are evaluated using the simple respirometer. The fractions of organic matter are used for mathematical modelling as the model components. The fractions include readily biodegradable(S_S), inert soluble(S_I), slowly biodegradable(X_S). inert particulate(X_I) substrates and active biomass(X_H) in the wastewater. In this study, the model components and parameters are evaluated using the simple respirometer which measures the biological oxygen consumption rate under well-defined experimental conditions. The fractions of S_S, S_I. X_S. X_I and X_H were 0.1. 0.04. 0.417, 0.11 and 0.28 of TCOD respectively. Also the sensitive model parameters. Y_H(0.53gCOD/gCOD), Y_A(0.208gCOD/gN),_(μH)(2.36/d)._(㎂)(0.936/d), K_(NH)(2.185㎎N/ ℓ), η_g(0.88) and η_n(0.7857) were evaluated using the simple respirometer. Using the SBR model simulation, two operating strategies are suggested. First, the optimization of the total cycle time and the phase distribution is developed in order to minimize the effluent nitrogen concentration. The existing operating cycle for SBR is 8hr/cycle(1.5hr agitation - 3.5hr aeration - 1.5hr agitation - lhr settle - 0.5hr idle). It is thought that extended aeration caused shortage of the carbon source in the anoxic period and high DO concentration at the end of the aeration period. As the result, these are inhibition factors on denitrification in the anoxic period. The simulation result shows that the new cycle phase distribution with shortened cycle time (6hr/cycle, lhr agitation - 2hr aeration - 1.5hr agitation-lhr settle - 0.5hr idle) is more effective than the old one. Secondly, in order to maintain constant DO concentration in the aeration period, step-aeration was suggested. As a result of model simulation, it is thought that the step-aeration accelerates the nitrification and denitrification and reduces the effluent nitrogen compounds concentration.

최의소Eui So Choi,박홍근Hong Keun Park,유대환Dae Hwan Rhu

DOI: Vol.16(No.5) 649-659, 2000

Sequencing batch reactors operating with weak sewage have a tendency of poor phosphorus removal due to inhibition of oxidized nitrogen. To minimize this inhibition, nitrate storage tank was utilized in this study. Phosphorus removal was successful with nitrate storage tank. With influent BOD 100 ㎎/L and VFA 30 ㎎/L, a total of the maximum removable nitrogen and phosphorus was about 30 ㎎/L with 8 to 9 hr HRT. VFA utilized for phosphorus removal was about 5 ㎎COD/㎎P. The concentrations of effluent nitrogen and phosphorus were generally 11 and 1 ㎎/L, respectively.

선용호Yong Ho Seon,장윤영Yoon Young Chang,황경엽Kyung Yub Hwang

DOI: Vol.16(No.5) 661-670, 2000

We carried out a preliminary study for development of high-pressure oxidation process with respect to toxic, biologically refractive, high level organic wastewater using a continuous tubular reactor, which consists of a vertical sieve tray column. The oxidation process was tested for phenol, leachate from landfill, and dyeing wastewater using H₂O₂ as an oxidant. The results of the experiment with injection of 145mL of H₂O₂(35%) per 1L of phenol solution(l0g/L) at 130℃ and 4 atm showed the removal efficiencies for phenol and COD. 98% and 45% at the retention time of 10 min. 99% and 98% at the retention time of 20 min. 99% and 98% at the retention time of 30 min. The results for refractive wastes, leachate and dyeing wastewater, showed 90% and 70% of COD removals at 150℃, 4 atm and the retention time of 30 min, feeding H₂O₂ according to the mole ratio of the oxidation equation. But, after adjusting pH to 1.3, the removal efficiency for dyeing wastewater was increased to 80%.

황규대Gye Dae Whang,황선진Sun Jin Hwang,장준기Jun Gi Jang

DOI: Vol.16(No.5) 671-683, 2000

The objective of this study was to examine the effects of solid concentrations of influent on the removal efficiency of organic matter and nitrate and on the biological kinetic coefficients. Each set of experiments consists of three bench scale anoxic reactors which were operated under different SRT to determine the biological kinetic coefficients and the optimum operating conditions for COD and nitrate removal. In anoxic reactors operated with 18hr of HRT, with the organic loading ranging 2.81∼4.70㎏TCODcr/㎥/day and TSS loading ranging 0.40∼2.49㎏TSS/㎥/day the removal efficiency of TCOD_(cr) and SCOD_(cr) were in the range of about 72∼83% and 62∼85%, respectively. Influent TSS concentration affects the removal efficiency of organic matter and nitrate. With high influent TSS concentration, COD removal efficiency was decreased and nitrate efficiency was increased slightly. To improve the removal efficiency of nitrate. HRT should be increased properly to extend the reaction time of denitrifying microorganism. SRT does not affect the COD removal efficiency and sludge settling characteristic. COD requirement for NO₃^--N removal was ranged from 2.19 to 3.34㎎SCOD_(cr)/㎎NO₃^-N_((Removed)), and was influenced by the influent TSS. Specific denitrification rates were ranged from 0.08 to 0.15㎎N/㎎MLVSS/day. Biological kinetic coefficients Y-t and K-d value of reactor Run-1 which received influent of high TSS concentration were 2.19㎎MLVSS/㎎COD_(cr) and 0.29day^(-1). These coefficients decreased to 0.50㎎MLVSS/㎎COD_(cr) and 0.l0day^(-1) for reactor Run-2 which received influent of low TSS concentration.

박미란Mi Ran Park,김병욱Byoung Ug Kim,임재영Jay Myoung Rim

DOI: Vol.16(No.5) 685-693, 2000

This study was performed to investigate nutrient removal characteristics of swine wastewater using duckweed as floating aquatic plant, and growth characteristics of duckweed with retention time. As the result of experiments. nutrient removal efficiency was very high in a retention time of 3 days, and was more than 90 % on the all operation conditions in a retention time of 10 days. Growth rate was most effected by the change of retention time. Growth rate was very high as 0.280 day^(-1) in a retention time of 3 days. Growth rate decreased gradually as retention time increased, so it was very low as 0.084 day^(-1) when a retention time was 10 days. Crude protein content was very high with ranges of from 23.9 % to 37.6 % as dry content during operating periods. Consequently, duckweed can be used to treat the swine wastewater and its biomass can be used for the alternative protein source as animal food, very effectively.

김병욱Byoung Ug Kim,박미란Mi Ran Park,임재명Jay Myoung Rim

DOI: Vol.16(No.5) 695-702, 2000

This study aims to treat anaerobic digested effluent of high strength swine wastewater using duckweed as aquatic macrophyte and observe growth characteristics of duckweed according to variable influent loadings. Nutrient removal characteristics with influent loadings are as follows. In the case of nitrogen, removal efficiency was above 70 % and effluent concentration was below 10.0 ㎎/L when the influent ammonia loading was about 1.0gN/㎡/day. In the case of phosphorus, when the influent ortho phosphate loading was about 0.15gP/㎡/day, effluent concentration was below 2.0㎎/L and removal efficiency was above 55%. Also, crude protein and phosphorus content of duckweed biomass increased from 15.6% to 41.6% and from 0.8% to 1.6% with as increase of influent nutrient concentration, respectively. In general, duckweed could vegetate at high organic loadings as about 30 gTCOD/㎡/day, and organic removal rate was range of 30∼75% during operating periods.

김원기Won Ky Kim,강선홍Seon Hong Kang

DOI: Vol.16(No.5) 703-709, 2000

Since phosphorus can play an important role in eutrophication as well as nitrogen, pollution due to phosphorus has been issued globally. To remove phosphorous in water and wastewater, chemical precipitation has been generally used. However, this method needs high cost and further treatment to remove chemical sludge. In this work it was studied whether loess can be used as an adsorbent to remove phosphorous in wastewater. Synthetic wastewater was made in the laboratory. To investigate phosphorus removal efficiency, loess dosage, particle size, temperature, and pH were varied. To investigate adsorption efficiency of loess, results were applied to Freundlich and Langmuir Isotherm. As a result of this study, removal efficiency of phosphorus increased as dossage of loess and temperature increased. When loess was used in removing phosphorus in wastewater, the removal efficiency was lower than that of CaO or Ca(OH)₂. But the removal rate was higher than that of CaCO₃ or CaCl₂ · 2H₂O at 2% as weight/volume base. Isotherm experiments results using phosphorus were reasonably suitable to Freundlich and Langmuir isotherm respectively. As a conclusion, loess has a potential value as an adsorbent to remove phosphorus in wastewater.