윤양호Yang Ho Yoon

DOI: Vol.17(No.1) 1-13, 2001

Field survey on the distributional characteristics of water quality and environmental factors on the variation of the phytoplankton biomass in Mokpo coastal waters, southwestern Korea were carried out at the 30 stations in November 1991 and in February 1992. I made an analysis on biological factor as chlorophyll a concentration as well as water quality such as dissolved oxygen(DO). chemical oxygen demand(COD), suspended solid(SS) and nutrients: ammonia. nitrite, nitrate, dissolved inorganic nitrogen, phosphate. N/P ratio, silicate and Si/P ratio. In the Mokpo coastal waters, the high productivity in photic layer were supported by high nutrients concentration from the runoff of freshwater and the input of outside seawater in low temperature season. The high concentrations of suspended solid in straits had a bad influence upon marine primary production. Mokpo coastal waters had a sufficient nutrients for primary production during a year. Especially the dissolved inorganic nitrogen were high, the other side. silicate and phosphate was very low. The source of nitrogen supply depended on runoff of freshwater including urban waste water. On the other hand, silicate and phosphate were input of outside seawater. Phosphate and silicate seemed to become a limiting factor for primary production in low temperature season. Phytoplankton biomass as measured by chlorophyll a concentration was very high in low temperature season, and it was controlled by the combination of several environmental factors, especially of phosphate, Si/P ratio and physical factor such as intensity of illumination.

이승룡Seung Ryong Lee,한명수Chul Woo Jung,박갑성Lim Seok Kang

DOI: Vol.17(No.1) 15-23, 2001

Optimum conditions of coagulation of organic matters in raw water were found to be ozone contact time of 3min, ozone dosages of 0.5㎎ O₃/㎎ TOC, and coagulant dosage of 0.15mM as AI. In addition, preozonation was used as an aid to removal of UV_(254), DOC at optimum condition of coagulant dosage. Hydrophobic fractions were transformed into hydrophilic fraction by ozonation, more DOC. THMs and THMFP were removed by only ozonation than by combination of chlorination and ozonation. From the results of the batch experiments under different oxidation methods, oxidation potential in combination of chlorine and ozone was decreased with increasing chlorine dosages. Because the ozone reacts with free aqueous chlorine present as hypochlorite ion(OCl^-), preozonation could not improve the removal of organics in the water treatment processes in the presence of chlorine.

한명수Myung Soo Han,이동석Dong Seok Yi,박갑성Kap Song Park

DOI: Vol.17(No.1) 25-33, 2001

Chlorophyll a standing crops of phytoplankton, photosynthesis-irradiance curve (P-I curve). primary productivity, and physico-chemical environmental factors were measured at Kwangdong bridge of Kyeongan Stream from April 3 to November 21 in 1997. The studied area was characterized as a stream-lake system where the physico-chemical environmental factors had abruptly fluctuated depending on precipitation. Variations in environmental factors except for water temperature showed little seasonal trend. Kyeongan Stream was a strongly eutrophicated, often showing high concentration of nutrient and chl-a. Standing crops of phytoplankton ranged from 628-144,500 cells/ml. The highest values of standing crops were 10^5 cells/㎖ when Cyanophyceae, Microcystis sp. and Aphanizomenon flos-aquae were bursting in the fall. Daily productivity was changed from 384 to 3.713 ㎎ C/㎡/d, which were almost similar to that of Nakdong River which was well known as a eutrophicated area. The monthly readings of P-I curve were divided into four types based on the values of P-max (maximum photosynthesis rate) and a (photoadaptive rate). These four types of P-I curve were a reflective of a change of dominant species, which were effected by seasonal variations of environmental factors such as irradiance. water temperature, nutrients and hydrodynamics. High primary productivity of dominant species such as Stephanodiscus sp., Cryptomonas erosa. Micractinium pursillum var. elegans and Aphanizomenon flos-aquae was maintained seasonally in Kyeongan Stream.

조일형Il Hyoung Cho,김현용Hyun Yong Kim,성기석Gi Seok Sung,박경렬Kyung Yeul Park,이홍근Hong Keun Lee

DOI: Vol.17(No.1) 35-46, 2001

The removal of heavy metal and EDTA was done by a solar photocatalytic oxidation and reduction. EDTA is industrial agent to form stable heavy metal-EDTA complex with toxic metals such as Cr(VI), Ni(II), Zn(II). Hg(II). Cu (II). Cd(II). In this experiment, comparison solar photolysis. TiO₂ adsorption, and solar/TiO₂ photocatalysis as well as the effect of reaction conditions such as solar light intensity, TiO₂ dosage and H₂O₂ concentration on the removal of heavy metal-EDTA were done in a tubular type reactor. The results of this study were as follows: 1) With both solar light and TiO₂ present, heavy metal-EDTA was more effectively removed than either solar light or TiO₂ alone. It was found that solar light application to the photocatalytic oxidation and reduction of heavy metal-EDTA was possible. 2) Photocatalytic removal efficiency of heavy metal-EDTA increased with solar light intensity. 3) Photocatalytic removal efficiency of heavy metal-EDTA increased with TiO₂ dosage. However, the efficiency approached to a saturation level over 1.5g/L of TiO₂ dosage. 4) Addition of H₂O₂ enhanced the efficiency of photocatalytic oxidation and reduction of the heavy metal-EDTA but the removal efficiency was similar or decreased over some level of H₂O₂ concentration.

김시준Shi Jun Kim,김정숙Jeong Sook Kim

DOI: Vol.17(No.1) 47-52, 2001

Endocrine disruptors(EDs) consist of synthetic and naturally occurring chemicals that affect the balance of normal hormonal functions in animals. Depending on their activity that they may be characterized as estrogen modulators or androgen modulators. Estrogenic activity of endocrine disruptors was assayed with fluorescence polarization system. 17β-estradiol, nonylphenol, bisphenol A and benzophenone that estrogenic activity is suspected were used for the competition assay. Because, there is much detection frequency in a municipal wastewater as compared with other endocrine disruptors in Japan. Fluorescence polarization in high concentration of 5,000nM of the endocrine disrupters which were 17β-estradiol, nonylphenol, bisphenol A and benzophenone were 100.8mP, 162.6mP. 288.6mP and 330.2mP respectively. The IC_(50)(50% inhibition concentration) of 17β-estradiol, nonylphenol, bisphenol A and benzophenone were 25nM. 3,000nM, 5 × l0⁴nM and 2 × l0^6nM respectively. As a results. It was estimated that strength of estrogenic activity of the endocrine disrupters was the order of 17β-estradiol, nonylphenol, bisphenol A and benzophenone.

정용찬Yong Chan Chung,정명훈Myung Hoon Chung

DOI: Vol.17(No.1) 53-61, 2001

During the electrolysis of water, hydroxide and proton ions are generated at cathode and anode, respectively. Hydroxide ions from cathode can be used for the hydrolysis of toxic chemicals such as pesticides or nerve agent simulants, and proton ions around anode make aqueous solution strongly acidic enough to kill microorganisms. In addition, chloride ions from NaCl added as an electrolyte can be oxidized to hypochlorite ions which are very strong oxidant and whitening agent so that organic wastes can be decolorized and degraded. Commercial pesticides (Parathion. Paraquat, and Cartap), nerve agent simulants (PNPDPP, and PNPA). and 1-bromooctane can be deactivaed by more than 90 % in an hour, and Cyfluthrin takes at least 100 min. for the same degree of hydrolysis. But Chlorothalonil (10 hrs) and 1-bromotetradecane (5 hrs) are not easily decomposed. After the sewage water from Suwon area is treated by the electrolytic system, the quality of water can be significantly improved, judging from the reduction of COD, deodorization, and inhibition of fungal growth. The mechanism and applicability of the electrolytic hydrolysis system for the deactivation of toxic chemicals in aqueous system is thoroughly studied in this paper.

조민석Min Seok Cho,최상규Sang Gue Choi,김승재Seung Jai Kim,김진환Jin Hwan Kim

DOI: Vol.17(No.1) 63-73, 2001

Organic chlorides are very toxic and easy to accumulate within human bodies and most of them are known to be potential carcinogens. Since the contaminated water by these compounds causes serious problems for providing potable water, the effective separations of chlorinated organics from water are required. In order to separate trace organic chlorides from aqueous solutions, poly (dimethylsiloxane) (PDMS) membrane and zeolite-filled PDMS membranes were prepared and the permeation characteristics of chlorinated organics were investigated by the experiments of sorption, diffusion and pervaporation at the temperature of 25℃. Seven chlorinated organics such as dichloromethane(DCM), chloroform(CF), perchloromethane(PCM), dichlroethylene(DCE), trichloroethylene (TCE), perchloroethylene(PCE) and chlorobenzene(CB) have been selected as representitive compounds for the current study and methanol(MeOH) was also used for comparison. Compared to the zeolite-free PDMS membrane, the permeation fluxes of organic chlorides through zeolite/PDMS membranes were reduced, while the fluxes of methanol were enhanced. However, the permeation selectivities for both organic chlorides and methanol were improved. The decreased fluxes of organic chlorides were resulted from the decreases of both sorptions and diffusion coefficients in the zeolite/PDMS membrane, but the enhanced fluxes of methanol were due to the increase of sorptions. The permeate flux of organic chlorides through zeolite/PDMS membrane was 17∼24 g/㎡hr and permeation selectivity ranged from 4,500 to 12,600.

김강주Kang Joo Kim,이지선Ji Sun Lee,오창환Chang Whan Oh,황갑수Kab Soo Hwang,유재연Jae Yeon Yu,김진삼Jin Sam Kim,여성구Seong Ku Yeo,김영규Yeong Kyoo Kim,이광식Kwang Sik Lee

DOI: Vol.17(No.1) 75-86, 2001

The goal of this study is to evaluate the possibility of using the chemical species dissolved in the WTP effluent as tracers for stream flow measurements. For this study, the effluents from Chonju WTP and the nearby streams were sampled and analyzed twice in the summer of 1999. It was revealed that the water chemistry of the effluent is distinct relative to the stream waters, especially, in concentrations of inorganic anions. The chemistry of those streams was strongly influenced by mixing with the treated water being discharged from the plant. Because of this reason. the conservative species such as chloride, sulfate, and EC were linearly correlated with high r² values. However, alkalinity and nitrate did not show such a relationship with respect to the conservative species, indicating modification of their concentrations by various chemical reactions. In this study, Streams flows were calculated by observing water chemistry of streams lower than the discharge point of Chonju WTP. The stream flows estimated from the chloride and sulfate concentrations, and EC were nearly the same at least for the immediate downstream of the discharge point. This consistency indicates the validity of the method suggested in this study.

최동진Dong Jin Choi,박희경Hee Kyung Park

DOI: Vol.17(No.1) 87-98, 2001

For control and automation of biological wastewater treatment process. lack of reliable on-line sensors to measure water quality parameters is one of the most important problems to be overcome. The accuracy of many hardware sensors is not sufficient and maintenance problems such as electrode fouling often give trouble. This article deals with development of software sensor technique which estimates the target water quality parameter from other parameters using the correlation between water quality parameters. We propose a hybrid neural network that combines conventional statistical methods as a software sensor inferring wastewater quality parameter. Multivariate regression, artificial neural networks (ANN), and the hybrid technique that combines principal component analysis (PCA) as a preprocessing stage are applied to data from industrial wastewater process. The proposed hybrid ANN technique shows an enhancement of prediction capability and reduces the overfitting problem of neural networks. The result shows that hybrid ANN technique can be used to extract information from noisy data and to describe the nonlinearity of complex wastewater treatment process.

유대환Dae Hwan Rhu,박종복Jong Bok Park,이재진Jae Jin Lee,이원권Won Kwon Lee

DOI: Vol.17(No.1) 99-107, 2001

The biological nutrient removal from wastewater with low C/N and C/P is difficult. This study was carried to remove nitrogen and phosphorus from wastewater by using the 5-stage BNR process with denitrifying phosphorus removing bacteria(DPB). The 5-stage BNR process could achieve stable phosphorus and nitrogen removal with less substrate consumed. These laboratory experiments revealed that step feed with DPB showed a possibility of biological nitrogen and phosphorus removal from low organic municipal wastewater. With DPB, specific denitrification rate was 1.3 ㎎NO₃-N/gVSS/hr and specific phosphorus utilizing rate was 2.0 ㎎SP/gVSS/hr.

최영균Young Gyun Choi,정태학Tai Hak Chung

DOI: Vol.17(No.1) 109-117, 2001

An experimental study was conducted to investigate the effects of soil particles upon the settling properties of the biosolids using humus soil (HS) powder and fresh activated sludge. Settling properties of the biosolids were altered remarkably by the presence of the HS particles. An attempt was made to identify the physical effect and the chemical effect of the HS particles addition. Cation mixtures equivalent to the cations leaching from the HS were introduced for estimation of only the chemical effect. The physical effect was then isolated by subtracting the chemical effect. Based on the results of the batch settling tests and the microscopic observations it may be concluded that the chemical effect takes part in 30∼50% of the overall improvement of the settling properties and the physical effect, mainly by floc density increase. is more important in the improved settling properties by the HS addition.

권재현Jae Hyun Kwon,구석본Sek Bon Koo,곽복식Bok Sik Kwak,류성호Sung Ho Ryu

DOI: Vol.17(No.1) 119-127, 2001

This study was conducted to illuminate the effectiveness of dual-conditioning compared with that of conventional mono-conditioning. In this method, both cationic and anionic polymer were successively dosed into water treatment plant sludge for dewaterability improvement. As results, sludge dewaterability was more enhanced by dual-conditioning method than any other mono-conditioning method using cationic polymer as well as anionic polymer. As sludge pH increased using NaOH. sludge properties including turbidity, viscosity, particle size and zeta-potential were more deteriorated. This made poor dewaterability and also increased optimal polymer dosage. Sludge properties, especially zeta-potential affected the effectiveness of dual-conditioning as well. In case zeta potential became under about -20㎷, dewatering performance by dual-conditioning method was similar to that by mono-conditioning method even though dosage of dual polymer was more lower compared with that of mono polymer. Therefore, dual-conditioning method adapted in this study might be less expensive than conventional mono-polymer conditioning method as depended on zeta-potential.

차기철Gi Cheol Cha,정태영Tae Young Jeong,권택훈Taek Hoon Kwon,정형근Hyung Keun Chung,김동진Dong Jin Kim

DOI: Vol.17(No.1) 129-136, 2001

The kinetic of metabolism was investigated by using the submerged hollow fiber membrane separation activated sludge process, with HRT of 8 hours which the food wastewater was fed as a substrate. The kinetic model was studied under the unsteady state and the steady state condition. The concentration of MLVSS was increased by the time course and maintained about 10,000㎎/L after the first 70days. The yield factor(Y) and decay coefficient(K_d) were calculated as 0.7218㎎ VSS/㎎ COD and 0.1666day^(-1) at the unsteady state condition, respectively. At the steady state condition. Y and kd were calculated as 0.00068㎎ VSS/㎎ COD and 0.0002day^(-1), respectively. The resistance values of R_c, R_g, R_f, and R_m were calculated as 25.97×10^7m^(-1), 1.97×10^7m^(-1), 0.29×l0^7m^(-1) and 0.02×10^m^(-1), respectively.