유춘만Chun Man Yu, 위인선In Sun Wui, 이종빈Jong Bin Lee, 위성욱Sung Wook Wui

DOI: Vol.15(No.1) 127-134, 1999

In August, 1995, the water quality of offshore waters around the Korean East coast was evaluated by bioassay using gametes, embryoss and early development systems of a sea urchins species Scaphechinus brevis. The results showed that despite the inflows of several river systems, the East coast maintained the 2nd grade(II) quality. Site 2 in Cheungcho Lake of Sokcho were rated as 3rd grade(III). Site 1, 3 Sokcho shore, site 4, 5 Kanglung offshore, site 13 Wooljin offshore were all rated the lst grade(I). The other nine sites proved to be 2nd grade.

정현미Hyen Mi Chung, 윤제용Je Yong Yoon, 류재근Jae Keun Ryu

DOI: Vol.15(No.1) 1-11, 1999

N/A

김충환Chung Hwan Kim, 정혜원Hye Won Chung

DOI: Vol.15(No.1) 13-22, 1999

The effects of pH, temperature, boron concentration and NaCl concentration etc. in bench scale experimental on boron removal were studied to remove boron from permeate of an H area reverse osmosis desalination plant for drinking water production. The boron rejection by reverse osmosis membrane used here started to increase at pH=9 and reached 97%, 0.04㎎/ℓ, at pH=11. The boron rejection tends to increase with operating temperature and pressure but decrease with boron concentration. However, the NaCl concentration upto 2,000㎎/ℓ gave little effect on the boron rejection. When the recovery ratio was increased, the boron concentration in permeate increased because boron was continuously accumulated in the feed water container. The boron rejection from sea water could be improved by rising pH but it may cause scaling. The boron concentration of permeate at pH 8 and above in an H area reverse osmosis desalination plant was satisfied with Japan guidelines value, 0.2㎎/ℓ.

주대성Dae Sung Joo, 최동진Dong Jin Choi, 박희경Hee Kyung Park

DOI: Vol.15(No.1) 23-30, 1999

Currently determining the coagulant dosing rates depends on Jar-test results and the operators experience in many cases. The nature of these practices makes it difficult to timely cope with the rapid fluctuation of raw water quality mainly since it takes relatively long time to obtain Jar-test results. For promptly predicting required coagulant doses in response to water quality change, a number of researchers have attempted to use multi-variable regression (MVR) approach. However, it has been known that the prediction capability of the MVR. approach is not satisfactory. Artificial neural network (ANN) is known as an excellent estimator of nonlinear relationship between the accumulated input and output numerical data. Using this nature of the ANN, this study has attempted to predict the optimal coagulant dosing rate with accuracy and in time. The ANN used in this study consists of an input, a hidden and an output layer. The input and output relationship of a neural network can be nonlinear and linear, and its characteristics are determined by the weights assigned to the connections between nodes in two adjacent layers. Changing these weights will change the input/output behavior of the network. Systematic ways of determining the weights of the network to achieve a desired input/output relationship are referred to as a training or learning algorithm. In this study, quasi-Newton algorithm is used as a training method which is known most efficient for the unconstrained optimization. To train the ANN and deduce the MVR equation, a set of 142 data chosen from the 2-year operation of a water treatment plant was used. Another set of 72 data not used in training was also used to check the prediction capability of the trained ANN and MVR equation. Mean square root error(MSRE) has been used as a quantitative indicator of prediction capability. For the training data set and the raw data set, MSREs of the MVR equation are, respectively, 0.0143 and 0.0193 while those of the ANN 0.0058 and 0.0092, respectively. These results indicate that the ANN reduced the prediction error for the training data by about 59% and for the raw data by about 52%. Therefore, it can be said that the prediction capability of ANN for raw data is enhanced about twice as much as that of MVR. As the advancement of on-line monitoring techniques enables ANN to continuously update the weights periodically, its prediction capability can be also continuously enhanced. However, it is noted that since ANN can not reveal the direct mechanistic relationship between water quality parameters and required coagulant doses, the training data must be prepared correctly in advance to reliably use the ANNs prediction. Further research is necessary for improving correctness of the training data.

Sung Hyun Kwon, Jae Kwan Lee, In S . Kim

DOI: Vol.15(No.1) 31-36, 1999

Improper management of red water generated during the manufacture of trinitrotoluene (TNT) is an environmental concern because it can result in soil and groundwater contamination. Past methods for the management of this hazardous waste stream did not fully meet pollution compliance or were not cost-effective. The biodegradation of TNT by pure population under their optimum conditions has been studied, and its intermediates have been found to be toxic and mutagenic to microorganisms because they interact with cell membranes. Our observation by a mixed microbial population in digested sewage culture under strict anaerobic conditions revealed TNT (2,4,6-trinitrotoluene) was degraded effectively. An initial concentration of 110㎎/L of TNT was reduced to a non-detectable amount (>99% removal) in 6 days of incubation. Red color due to the electron charge of NO2 groups become colorless after 6 days of incubation, while the autoclaved control remained red in color. Due to the resistance of the transformed inhibitors, further stepwise deamination and subsequent mineralization by ring cleavage occurred by mixed vitro reductase which is created predominantly by many of the denitrifying bacteria in sewage culture.

김승건Seung Gun Kim, 이호원Ho Won Lee, 허목Mock Huh

DOI: Vol.15(No.1) 37-45, 1999

Hybrid process coupling ultrafiltration and adsorption was demonstrated to treat effluents from the night soil treatment to high quality product. The product water treated by hybrid process could be within the reinforced basis of effluent qualities. Removal efficiencies for COD, SS, T-N, T-P, TOC, and turbidity were 13.3%, 100%, 18.5%, 18.0%, 21.3%, and 80.7% by ultrafiltration, and 37.3%, 100%, 35.8%, 37.0%, 81.3%, and 84.9% by hybrid process. The performance for removal efficiencies was not nearly affected by run time. The permeate flux at the transmembrane pressure difference of 2.0Kg_f/㎠ was 49.8L/㎡/hr at initial operation, and decreased to 26.2L/㎡/hr after 7days, but it was restored to 99% of initial flux by chemical cleaning of organic foulants. It is expected that hybrid process coupling ultrafiltration and adsorption can be applied to treat effluents from the night soil treatment.

권동민Dong Min Kwon, 이병헌Byung Hun Lee, 박은정Eun Jung Park

DOI: Vol.15(No.1) 47-54, 1999

In the water treatment plant, chemical treatment process is increasingly used for reducing such impurities as suspended solids and organic materials. Many water treatment plants has been adapted chemical treatment process using alum as a primary coagulant. The use of alum is producing a waste commonly called alum sludge. Alum sludge is a bulky gelatinous substance composed of aluminium hydroxides, inorganic particles such as clay or sand, colloids, microorganisms, etc. It has relatively low solid content that is difficult to thicken and dewater. This study attempted to investigate the effect of thickening and dewatering of alum sludge in Duk-san water treatment plant through pretreatment using sulfuric acid, lime and polyacrylamide. The main results obtained in this study are summarized as follows: In case of alum sludge pretreated by sulfuric acid, the effect of thickening increased with proportion to concentration of aluminium extracted, while the dewaterability was mainly affected by the extraction ratio of aluminium and TOC concentration. Alum sludge pretreated by lime enhanced both thickening and dewaterability. It appeared that extracted aluminium and organics were adsorbed to non-dissolved lime and removed by co-precipitation. The thickening velocity and dewaterability increased by dosing polyacrylamide but the final effect of thickening was not appeared.

정팔진Paul Gene Chung, 이성우Sung Woo Lee, 김충환Chung Hwan Kim, 채선하Seon Ha Chae

DOI: Vol.15(No.1) 55-63, 1999

Membrane processes including microfiltration(MF), ultrafiltration(UF) and nanofiltration(NF) membrane have been recently applied to produce drinking water from river, lake and canal sources. In this study, dead-end MF membrane system was operated to treat polluted water from the downstream of Kum river. Permeate flux, removal of Fe, Mn, KMnO₄ consumed, THMFP were evaluated and compared with the effluent quality of conventional water treatment.- coagulation, sedimentation and sand filtration. Permeate flux and flux recovery after backwashing were monitored continuously. Initially permeate flux was 120ℓ/㎡/hr and then decreased to 70ℓ/㎡/hr which was stabilized after 60 days of operation. Turbidity of raw water was in the range of 2.8∼25.7NTU but the MF system gave the removal efficiency of over 99%, maintaining stable and good water quality which compared to the conventional process. Removal of KMnO₄ consumed and THMFP by MF process were 50% and 57.7% respectively. Fe was reduced to 96% and Mn was 30.5% since dissolved Mn in water is hard to be converted to colloidal Mn which can not pass through the membrane. The particle size distributions for raw water, sandfiltration and MF filtered water were obtained by counting particles in 2.0∼10.0㎛ range. The MF rejection for total particle number and particle number of 2.0∼4.0㎛ range was better than the conventional water treatment. Because of increasingly stringent regulations in the future, this technology has the potentiality of MF application to water treatment processes.

양형재Hyung Jae Yang, 신응배Eung Bai Shin, 정윤철Yun Chul Chung, 이재운Jae Woon Lee

DOI: Vol.15(No.1) 65-70, 1999

A bench-scale reactor using SBR process was experimented with a synthetic wastewater. The main purpose of this investigation was to evaluate applicability in the field and process removal efficiencies in terms of BOD and T-N, and its corresponding kinetic parameters. Removal rate of nitrogen was 71% in terms of total nitrogen. Effluent concentrations were 9.8㎎/ℓ BOD and 11.2㎎/ℓ T-N, and was maintained consistently stable concentration by controlling decant volume and operating cycles. During the anaerobic phase, corresponding to the end of denitrification, the pH profile shows a maximum due to the alkalinity production during the reactions. And during the aerobic phase, the pH shows a rapid increase due to the CO₂ stripping and pH starts to increase again when ammonia nitrogen reaches the minimum level. Microscopic examination revealed that microcytes observed predominantly in sludge were Vorticella, Epistilis, Opercularia, Aspidisca, Chilodonella that are protozoa and Philodina, Rotaria, Notommata, Nematoda that are rotatoria

이태진Tae Jin Lee, 한기훈Ki Hun Han, 이호상Ho Sang Yi, 김장규Jang Kyu Kim

DOI: Vol.15(No.1) 71-77, 1999

For the development of an electrochemical wastewater treatment system for municipal landfill leachate, the characteristics and performance of an electrocoagulation(EC) unit using iron electrode are studied. By proceeding an electrolytic oxidation of electrode, the organic pollutants are removed by the Fe^(n+) ion and iron hydroxide which come from electrolytic reaction through coagulation mechanisms. The electrocoagulation unit with Fe^(3+) ion shows higher organic removal efficiency than that with Fe^(2+) ion. The COD_(Cr), TOC, and SS removal efficiencies under the conditions of pH 5, 1,200 coulomb/L and 165㎎·H₂O₂/L are 45, 40, and 80%, respectively. From the results of the experiments, it is concluded that the landfill leachate can be treated by the EC process as a substitute of the conventional chemical coagulation process, and it is expected that the other wastewater would also be treated by the electrochemical method.

성동모Dong Mo Sung, 윤태일Tai Il Yoon

DOI: Vol.15(No.1) 79-88, 1999

The possibility of Hakic cheon municipal wastewater treatment by utilizing the alkali waste slurry from Oriental chemical company as a coagulant was investigated. Coagulants as the Lime, Alum, Ferric Chloride and waste slurry were tested in jar tester. The experimental results showed that the waste slurry could be used as a coagulant instead of lime. When the combined dose of waste slurry 5∼7.5% and ferric chloride 25㎎/ℓ obtained the optimum coagulation condition, and the analytical results showed that turbidity removal was 97%, T-P removal was 70% and COD_(Mn) removal was 30∼42%.

박석순Seok Soon Park, 이시진Si Jin Lee, 이용석Yong Seok Lee, 최경식Kyoung Sik Choi

DOI: Vol.15(No.1) 89-98, 1999

A water quality modeling study was performed for the Hantan River located at Yeoncheon-gun, Kyunggi-do, in order to predict the impact of a small dam for hydroelectric power generation. Model construction was based on QUAL2E which was developed by United States Environmental Protection Agency. The study area was divided into 12 reaches according to the hydraulic characteristics of the Hantan River. Each reach was then subdivided into uniform computational element of 0.25㎞. Five synoptic surveys were performed from March to November, 1996. Data from two of them were used for model calibration and verification. In most cases, there were reasonable agreements between the model results and the field measurements. The validated model was then used to predict the impact of the dam on water qualities. The deterioration of water qualities was found in the study area from the field surveys. From the modeling study, however, it was predicted that the dam does not cause a significant impact on water qualities, if the base flow would be discharged from the dam. The control of pollution sources located at the Youngpyung branch was suggested along with the maintenance of base flow from the dam for the water quality conservation of the Hantan River.

신동석D . S . Shin, 류재근J . K . Ryu

DOI: Vol.15(No.1) 99-105, 1999

Many computer models have been used for estimating the water quality and evaluating countermeasures. The models such as QUAL2E, STREAM, WASP, CE-QUAL have been applied in the waters so far. Some modeller assumed either that the flow of the waters is steady or that the storage change of the waters is negligible. And someone excluded hydraulic part from the quality simulation. It may cause inaccurate estimations of water flow and quality, particularly when the waters have seawards boundary and more inflow than outflow, etc. In order to show the velocity for water quality simulation of Paldang lake in dynamic condition, RMA-2 was performed with the monthly flow rate in 1997. The velocity was more sensitive to turbulence exchange coefficient than Manning`s n in Paldang lake. The results of simulation show that flows reverse around the Sonae island in late Summer because of less outflow than inflow and flows blocked by dam.

윤영삼Young Sam Yoon, 황종연Jong Yeon Hwang, 김인실In Sil Kim

DOI: Vol.15(No.1) 107-117, 1999

Adsorption isotherms of phenol(Ph), p-chlorophenol(PCP) and p-nitrophenol (PNP) from aqueous solution on granular activated carbon have been obtained. The aqueous phase adsorption experiment of phenols was studied in a batch adsorption vessel. Experimental studies and predictive models for adsorption rate were used to investigate the performance and adsorption characteristics of activated carbon in the removal of phenols in aqueous solution. The experimental data were analyzed by the surface and pore diffusion models. Both models could be applied to predict the adsorption phenomena. However, the pore diffusion model was slightly better than the surface diffusion model in representing the experimental data for the initial concentration changes. Therefore, the pore diffusion model was used to predict the change of operating variables such as the agitation speed and particle size of adsorbent which have influence on the film resistance and intraparticle diffusion.

양승태Seung Tae Yang, 정상섭Sang Sub Jung, 차상덕Sang Duk Cha

DOI: Vol.15(No.1) 119-126, 1999

A method for determining six phthalate esters by using SPE(solid phase extraction) and GC/MS is descrived. The SPE was performed with C_(18)-bonded silica in 6㎖ Supelclean LC-18 cartridge of Supelco. The optimal pH, volume and flow rate of sample through SPE cartridge were neutrality, 500㎖ and 8.3㎖/min, respectively. The GC analysis was performed with SPB-5 capillary column(30m × 0.25㎜ I.D. × 0.25 film thickness) with He as carrier gas operated with temperature programming from 100℃ (held for 1min) to 260℃ (held for l0min) at 10℃/min, and the detection was by MS-SIM in EI^+ ionization mode at m/z 40∼500. Average extraction recovery(%) was 79.6% for a 500㎖ volume of water spiked at 5㎍/ℓ. Each calibration curve on six phthalate esters was linear for 0.1∼25㎍/ℓ and method detection limit(MDL) was 0.06㎍/ℓ. The SPE was compared with LLE(liquid liquid extraction) in the extraction recovery(%). The procedure could be used for examinating effect of sample matrix on extraction recovery(%) and determining phthalate esters in the river.