박석순Seok Soon Park,박선영Sun Young Park

DOI: Vol.17(No.4) 439-449, 2001

This paper presents trend analyses of algal growth in the 12 major lakes of Korea, which include Paldang, Chungiu, Soyang, Chuncheon, Euiam, Cheongpyeong, Andong, Imha, Namgang, Hapcheon, Daecheong, and Oakjung. The parameter tested in this study is the monthly data of chlorophyll-a measured from 1990 to 1997. The normality of data was examined by the chi-square goodness-of-fit test and the skewness test. The seasonality was examined by the Kruskal-Wallis test. The long term trend was analyzed by the seasonal Mann-Kendall test. Water temperature was considered as an exogenous variable in the trend analysis of a few lakes where a significant correlation between temperature and chlorophyll-a was observed. Removal of variance in chlorophyll-a due to exogenous variables increased the power and efficiency of the trend analysis. The results indicated that there were no significant trend of chlorophyll-a concentrations in most studied lakes except for Euiam, Daecheong, and Hapcheon lake. For Euiam lake and Daecheong lake, there were upward trends. On the other hand, there was a downward trend in Hapcheon lake.

배은영Eun Young Bae,류동춘Dong Choon Ryu,김상구Sang Goo Kim,손희종Hee Jong Son,나영신Young Shin Na,송미정Mi Jeong Song,최동훈Dong Hoon Choi

DOI: Vol.17(No.4) 451-464, 2001

We have researched removal of organic matters as DOC, THMFP and UV254 with pre-ozonation. filtration, post-ozonation and 3 kinds of granular activated carbon(GAC) by using the Nakdong river`s water for evaluating removal characteristics of organic matters on each treatment process. UV-254/DOC(SUVA) and THMFP/DOC(STHMFP) can be valuable parameters for evaluating each processes and finding more effective process by comparing the removal of specific organic and DOC before and after treatment. The removal of DOC. THMFP and UV-254 by pre-ozonation are 0%, 25%, 30% and by filtration are 33%, 52%, 46% and by post-ozonation are 7%, 7%, 36% and residual rate of SUVA and STHMFP by pre-ozonation are 0.68. 0.75 and by filtration 0.8, 0.79 and by post-ozonation 0.69, 1.0 respectively. The reason of higher removal of THMFP and UV-254 than DOC is hydrophobic organic matters are more easily removed by ozonation and coagulation than hydrophilic organic matters. The removal of DOC are 21%, 26%, 21% and THMFP are 27%, 40%. 30% and UV-254 are 22%, 26%, 14% and residual of SUVA are 1.0, 0.91, 1.1 and STHMFP are 0.97, 0.83, 0.93 by coconut, coal, wood base GAC. Residual of SUVA are over than 1.0 by coconut, wood base GAC treatment because UV-254 could not be easily removed by biomass on the surface of GAC but residual of SUVA is lower than 1.0 treated by coal base GAC treatment because UV-254 can be easily adsorbed into the residual pore.

윤제용Je Yong Yoon,변석종Seok Jong Byun,김해심Hae Shim Kim,조순행Soon Haing Cho

DOI: Vol.17(No.4) 465-475, 2001

Ammonia is sometimes considered as a indicator parameter for organic pollution in fresh water. The presence of ammonia in fresh water could be harmful to aqueous ecosystem, depending upon its concentration and pH. In addition, the reaction of ammonia with chlorine may produce organic chloramines causing taste and odor problems in treated water. We investigated the characteristics of ammonia concentration (NH₃-N) in raw water and treated water in Korea. The water quality data during 5 years (1994-1998) were collected from the Ministry of Environment. The number of ammonia data in raw water and treated water was 7,091 from 592 raw water monitoring sites, and 34,134 from 600 water treatment plants, respectively. Ammonia was detected in 37.6% out of 7,091 raw water monitoring data. 88.4 out of the ammonia detected samples were below 0.1 ㎎/L. The frequency of ammonia detection in both raw water and treated water has been gradually decreased for last five years. The number of data exceeding 0.5 ㎎/L was 283(3.6%) and many of these samples occurred in winter. It is attributed to the lack of nitrification of ammonia due to low temperature.

박병흔Byung Heun Park,남귀숙Gui Sook Nam,이광식Kwang Sik Lee

DOI: Vol.17(No.4) 477-484, 2001

The objectives of this study were to analyze the efficiencies of constructed wetlands under high hydraulic loadings. Constructed wetlands used for this study were composed of 5 planted wetlands in series. The system was operated with the condition of low concentrations and high hydraulic loadings. Average removal efficiencies(%) of pollutants in the wetlands were 49.2(BOD), 16.5(COD), 23.9 (T-N), 27.4 (T-P) and 51.5(Chl-a). And, average removal rates(g/㎡/d) were 3.71(BOD), 2.22(COD), 0.56 (T-N), 0.07 (T-P). Comparing this system with other wetlands operated at low hydraulic loadings and high level of water quality, the former could remove greater amount of pollutants by unit area than the latter, and vice versa in the case of removal efficiencies due to different hydraulic loadings. Pollutant removal rates were considered to be increased as influent loads got higher from the regression analysis for influent pollutant loads and removal rates. From these results, constructed wetlands are considered to have potential for removing pollutants even though hydraulic loadings were high. Therefore, constructed wetlands are thought to be a practical alternative to improve polluted stream water quality and non-point source pollution management.

서보인Bo In Seo,정철우Chul Woo Jung,한승우Seung Woo Han,강임식Lim Seok Kang

DOI: Vol.17(No.4) 485-491, 2001

This study was performed to determine the effectiveness of optimized coagulation for the removal of particles and organic matters when optimized coagulation (optimizing the pH of coagulation) was compared with conventional treatment. To determine optimized coagulation treatments, coagulants tested included alum, FeCl₃, and polyaluminum chloride (PACl). In addition, fractionation of organic matters was performed to characterize the changes in organic fractions according to the coagulation treatment conditions. Jar-test results indicate that the FeCl₃ coagulant was more effective than aluminum-based coagulant(Alum, PACl) in removing natural organic matter. The removal of organic carbon was enhanced at optimized coagulation conditions. In addition, optimizing coagulation pH can reduce coagulant dosage by as much as 72 percent compared with convention coagulation treatment. The strong hydrophobic acids(e.g.humic acid, fulvic acid) had more amenable to coagulation than the other nonhumic fractions. The fulvic acid of hydrophobics played a significant role in operation organic matters in raw water.

한인섭Ihn Sup Han,조용균Yong Kyun Cho

DOI: Vol.17(No.4) 493-503, 2001

Filtrasorb 400 GAC preloaded with phenol was chemically and thermally regenerated and the regenerated GAC was used for investigation on the change of adsorption capacities. The experiments were carried out at pH 7 and 23±1℃ under the oxic condition. Isotherm, rate and extraction experiments were conducted using virgin GAC and isotherm experiments were using preloaded GAC after regeneration and/or drying. The data obtained from the isotherm experiments were well fitted by Freundlich isotherm. i) Isotherm, rate and extraction for phenol and DNT using virgin GAC Freundlich isotherm equations were q_e=35.8C_e^(1/0.357) and q_e=129.7C_e^(l/0.283) for phenol and DNT, respectively. The adsorption capacity for DNT was larger than that of phenol. It required a longer contact time for phenol to get an equilibrium. probably due to transformation of phenol on the GAC surface in the presence of DO. Extraction efficiencies from GAC for adsorbed phenol were decreased with increasing contact time, but for DNT such a trend was not observed. ii) Isotherm using preloaded GAC and repeatedly regenerated GAC. There existed in difference of adsorption capacities depending on the regeneration method. Thermal regeneration was better than chemical regeneration in the viewpoint of adsorption capacity. The decrease in adsorption capacity for phenol was larger than that for DNT in comparison of the adsorption capacity of virgin GAC. As the contact time increased for preloading, the adsorption capacity for preloaded DNT decreased. Dried GAC after preloading showed a little adsorption capacity, possibly due to the desorption of sorbed phenol by heat during drying. Such trends were double-checked through the results obtained using repeatedly-regenerated GAC. It was possibly explained by the deduction that active adsorption sites for phenol and DNT are different.

한인섭Ihn Sup Han,조용균Yong Kyun Cho

DOI: Vol.17(No.4) 505-516, 2001

Preloaded GAC with phenol and HA and virgin GAC were used for investigating the change of adsorption capacities and the effects of DO and NOM. The experiments were conducted at pH 7 and 23±1℃ under the anoxic condition. All the experimental procedures for anoxic experiments were performed in an anaerobic chamber except tumbling the samples. Specifically, preloaded GAC with HA under the anoxic condition was used for the oxic and anoxic adsorption experiments after regeneration by thermal or chemical methods. i) Adsorption of phenol and DNT with virgin GAC Freundlich isotherm equations were q_e=23.8C_e^(1/0.420) and q_e=119.5C_e^(1/0.274) for phenol and DNT, respectively, whose adsorption capacities were smaller than those of the oxic experiment. It was observed that adsorption capacity for phenol decreased more than that for DNT depending on the presence/absence of DO. It was possibly due to transformation (or oxidative coupling(s)) reactions) on the GAC surface in the presence of DO. To get the equilibrium between liquid and solid phases, it required one week or shorter and the trend observed in the oxic experiments that the longer contact time, the less extraction efficiencies, was not shown. ii) Adsorption of phenol and DNT with preloaded GAC. Depending on the regeneration methods and preloading compounds, the differences of adsorption capacities were observed. Regenerated GAC after preloading with phenol showed approximately 10 to 20% decrease in adsorption capacities for phenol and 5 to 15% decrease for DNT. Adsorption capacity was larger after thermal regeneration, especially for HA-polluted GAC. Re-adsorption capacity (that is, adsorption capacity after regeneration) was greatly affected by the preloading materials.

장훈Hoon Jang,강선홍Seon Hong Kang

DOI: Vol.17(No.4) 517-524, 2001

The applicability of cow bone as a seed material in hydroxyapatite crystallization was investigated in this research. Seed crystal used for the experiments was prepared by the calcination of cow bone. The effects of initial calcium concentration, pH, alkalinity, reaction temperature condition, and calcination temperature were examined for synthetic solution by batch experiment. The experimental results showed that a good phosphorus removal could be achieved by cow bone crystal seeding. The phosphorus removal rate with various calcium concentrations and pHs could be predicted from high relationships between residual phosphorus concentration and pH (after reaction). The effects of alkalinity, reaction temperature condition, and calcination temperature were also examined by rate constant analysis.

김도희Do Hee Kim,이상엽Sang Youp Lee,이홍주Hong Joo Lee,문승현Seung Hyeon Moon,조재원Jae Weon Cho

DOI: Vol.17(No.4) 525-537, 2001

Various membrane tests were conducted to determine transport characteristics of natural organic matter (NOM) in ion exchange (IX) membranes. Both pH and ion strength could affect the adsorption of NOM on the membrane surface. The amount of the adsorbed NOM mass on the membrane surface under an alkaline (pH 10) condition was approximate 3.0 times larger than that under an acid condition (pH 4) when the dissolved organic carbon (DOC) concentration of NOM was 10 ㎎-C/L. Zeta potential was characterized to demonstrate the effect of IX membrane fouling with NOM on the membrane surface charge. The major transmitted NOM fraction through electrodialysis membrane was anticipated to be the hydrophobic NOM due to its high negative charge density. However, the molecular size of the hydrophobic NOM was too large to pass thorough the IX membrane pores, providing its accumulation or adsorption on the membrane surface.

윤조희Cho Hee Yoon,김학준Hark Joon Kim

DOI: Vol.17(No.4) 539-548, 2001

Electrochemical decolorization from secondary effluent of livestock wastewater treated with biological process was carried out and investigated in this study. The bipolar packed-bed metal electrode reactor as the electrochemical process has been employed for the test. Operating variables of this process including different packing electrode materials, current density, flow rate to the reactor, temperature and additive were considered to determine their respective effect of color removal. From the test results, PbO₂ electrode as anode electrode was found to be suitable for this process among various materials and optimal current density was 1.48 A/dm². The total theoretical voltage obtained from voltage-current curve was 45 V in reactor and 4.5 V per unit layer bipolar cell. And the effect of an aqueous solution(17 mM, pH 9) with the added NaCl on color removal from secondary effluent was observed to be actually more effective than without the added NaCl. Color removal increased with an increase in temperature over 50 ℃. However, increasing the flow rate decrease color removal efficiency and the value of maximum efficiency 96% when flow rate 60 mL/min at various flow rate.