신은성Eun Sung Shin,최지용Ji Yong Choi,이동훈Dong Hoon Lee

DOI: Vol.17(No.2) 137-146, 2001

For issues of integrated water quality management, a thorough investigation on both point source and non-point source of pollution loaded from streamlets to rivers should be conducted. Also, it is necessary to investigate the relationship between land use, pollutant discharge from non-point sources, and the unit load and its contribution to total pollution loadings. The objectives of this study is to estimate the unit load by land use and livestock breeding level in order to promote effective management of the non-point source of pollution in rural areas. The watershed under investigation consists of eleven sub-basins(smaller than 500ha) located in Chunchon city in Kangwon Province. Flow and quality parameters, such as biochemical oxygen demand(BOD), chemical oxygen demand(COD), suspended solids(SS), total nitrogen(T-N), and total phosphorous(T-P), are determined. The results are summarized below: 1. Annual runoff loading of SS. BOD, COD, T-P, and T-N were estimated to be 423.4, 20.0, 56.6, 2.6, 20.9㎏/ha.yr respectively. 2. Runoff loadings by landuse appeared to have following relationship. ·COD : L(㎏/yr) = 187.3 × Paddy + 110.1 × Field + 24.3 × Moun. (R² = 0.92) ·T-N : L(㎏/yr) = 77.8 × Paddy + 26.1 × Field + 11.1 × Moun. (R² = 0.96) ·T-P : L(㎏/yr) = 14.8 × Paddy + 4.3 × Field + 0.3 × Moun. (R² = 0.96) 3. Considering livestock breeding level, the runoff loading by land use were observed as below: ·COD : L(㎏/yr) = 173.6×Paddy+63.0×Field+24.8×Moun.+14.7LU(R² = 0.93) ·T-N : L(㎏/yr) = 74.3×Paddy+l4.0×Field+11.2×Moun. + 3.8LU(R² = 0.97) ·T-P : L(㎏/yr) = 7.7×Paddy+ 4.2×Field+ 0.3×Moun. + 0.3LU(R² = 0.98)

이현동Hyun Dong Lee,안재환Jae Hean Ahn,김운지Woon Ji Kim,배철호Chul Ho Bae

DOI: Vol.17(No.2) 147-156, 2001

This study carried out to identify the runoff characteristics of non-point source(NPS) pollution in the Paldang reservoir watershed. Several sub-basins were selected and used as the study sub-basins in which major landuse types were different each other. Rainfall, water quality and flow rate were observed by landuse types in the study sub-basins. Peak time of storm water runoff and pollutant concentration showed big differences depending on landuse and rainfall conditions at each corresponding sub-basins. Although slight differences in storm flow rate were observed depending on rainfall, sudden increase and decrease in flow rate were, however, noted in forest/resort and urban areas. While in agricultural areas, the slope of the hydrograph of storm runoff flow increased and decreased gradually. The variation of pollutant concentrations in terms of BOD, COD, SS and T-P was large depending on the flow rate of stormwater. On the other hand, little change of T-N concentration in stormwater was appeared. In forest/resort areas, the BOD load discharged was 1.53 ㎏/ha/day for total rainfall of 140.4 ㎜ during three rainfall. The BOD loading from agricultural areas was 1.93 ㎏/ha/day for total rainfall of 84.9 ㎜. And BOD loading from urban areas was 22.84 ㎏/ha/day for total rainfall of 72.94 ㎜. Although the total rainfall in the urban areas was smaller than other areas, the BOD load attributed to NPS in urban areas was much greater.

윤춘경Chun Gyeong Yoon,전지홍Ji Hong Jeon,함종화Jong Hwa Ham

DOI: Vol.17(No.2) 157-168, 2001

Rating curve method and SWMM (Storm Water Management Model) were applied to estimate pollution loading from Hwa-Ong watershed in Kyunggi-Do. Sampling data from monitored sites were used to derive rating curves and calibrate SWMM, and they were applied to the whole watershed including non-monitored subcatchments. Overall, the results from these methods were comparable and the loadings were in the same range and the difference was acceptable considering complicated natural pollutant loading processes. However, inconsistency was observed among the subcatchments. The pollutant loading estimates from two subcatchments with similar area were almost identical in rating curve methods, while the difference was significant in SWMM methods. Rating curve method can be a reliable tool to estimate pollutant loading from watershed if it is fully monitored, but it may generate large error during extrapolation to non-monitored area. SWMM is a comprehensive hydrologic model with great diversity that it can incorporate watershed characteristics like land use effects which is not available in rating curve methods. Therefore, it is recommended to use reasonable watershed model rather than rating curve and unit loading methods for the estimation of pollutant loading from watershed

이정규Jung Ku Lee,이상봉Sang Bong Lee,김동윤Dong Yun Kim

DOI: Vol.17(No.2) 169-177, 2001

Powdered activated carbon(PAC) is widely used to control 2-MIB and geosmin causing earthy-musty odor in water supplies. when PAC is added at the just before or rapid mix, incorporation of PAC into coagulants floc particle may affect adsorption rate and capacity. To investigate the effect of coagulant on the PAC`s ability to adsorb 2-MIB and Geosmin, a series of experiments was carried out to show 1) the effect of presence of coagulant on the 4-hr adsorption capacity and the rate of adsorption of PAC to adsorb 2-MIB and Geosmin from Lake Heodong water. 2) the effect of adding point of PAC with coagulant adding point at rapid mix. As a result of experiment, presence of coagulant no effect on the 4-hr adsorprion capacity to adsorb 2-MIB and geosmin. Adsorption rate of 2-MIB and geosmin is slightly reduced by coagulant addition. According to variation of PAC addition condition(point), the order of removal efficiency is PAC only(at rapid mix) 〉 slow mix after 5min 〉 slow mix 〉 PAC and coagulant simultaneously added at rapid mix.

남은정Eun Jung Nam,조일형Il Hyoung Cho,최종욱Jong Wook Choi,이민환Min Hwan Lee,이홍근Hong Keun Lee

DOI: Vol.17(No.2) 179-190, 2001

This study was performed to evaluate the application of TiO₂ photocatalysis for treating humic acid and heavy metals dissolved in water. The optimum condition of operating parameters such as UV illumination, pH. TiO₂ dosage, humic acid concentration and addition of H₂O₂ was suggested for removal of humic acid and heavy metals simultaneously. The results of study were as follows: The removal rate of humic acid and heavy metals by TiO₂ photocatalysis was higher than by UV illumination and by TiO₂ adsorption, therefore it was complied that TiO₂ photocatalysis was more practical method for treating humic acid and heavy metals in water. The removal rate of heavy metals increased more in mixed solution of humic acid and heavy metals than in solution of heavy metals only. The supply of nitrogen gas for reducing high oxygen concentration which restricts the reduction reaction of heavy metals did not influence to heavy metals except Hg(II), but that of nitrogen gas decreased the oxidation rate of humic acid. The increase of UV intensity removed more humic acid and heavy metals because of active photocatalytic reaction, but the removal rate began to decrease with more than 9㎽/㎠ of UV intensity. The decrease of pH increased the removal rate of humic acid due to oxidation reaction, while the increase of pH increased the removal rate of heavy metals except Cr(VI) due to reduction reaction. The removal rate of humic acid and heavy metals generally increased with increase of TiO₂ dosage, but that of heavy metals reduced with more than 0.5g/l of TiO₂ dosage. The increase of humic acid concentration with fixed heavy metal concentration removed more heavy metals effectively, while the removal of heavy metals decreased with more than 30㎎/l of humic acid concentration. The addition of H₂O₂ as an oxidant increased the removal rate of humic acid and heavy metals because of active photocatalytic reaction, while the removal rate of humic acid and heavy metals did not increase with more than 300㎎/l of H₂O₂.

황갑수Gap Soo Hwang,김강주Kang Joo Kim,신형선Hyung Seon Shin,여성구Sung Koo Yeo,김진삼Jin Sam Kim

DOI: Vol.17(No.2) 191-200, 2001

This study was carried out to investigate heavy metal contamination in the burrowing mussels. So1en strictus Gould, from coastal tidal flat in Western coast. Korea and to clarify the biological availibility of heavy metals according to shell size. The sizes of the collected mussels were linearly related to their dry weights of soft parts. The heavy metal levels of the mussels decrease as their dry weights increase. Only Cd levels were the exception indicating its relatively strong tendency of accumulation in organisms. The mussels sampled from a site (S5) showed considerably higher concentration levels than those from elsewhere. However, the mussels from a nearby site (S6) that is about 200m apart from S5 to the north did not show such high levels. Statistical analysis showed that Cr and Ni (Cu and Zn) levels in the mussels are strongly correlated with each other.

신정이Shin Joung Yi,박석순Seok Soon Park

DOI: Vol.17(No.2) 201-213, 2001

This paper presents the results from a study on the nutrient removal potential of aquatic plants. Phragmites japonica and Salix gracilistyla, which are dominant species in riparian zone of the Suip Stream, a tributary of the North Branch of Han River. Both plants were obtained from the field survey and hydrocultured in a laboratory aquarium specially designed for this experiment after short period of acclimination. The nutrient removal potentials of both plants were determined as a functions of hydraulic retention time as well as influent nutrient concentrations. The nutrients include ammonia-nitrogen, nitrate-nitrogen, and dissolved inorganic phosphorus. Based on the results of determined removal potential and in-situ biomass, removal capacity was estimated in the reach of 6 km in the Suip Stream. The nutrient removal potentials of both plants were significantly affected by hydraulic retention time and inflow concentration. The potential was much higher at short period of hydrualic retention time and high concentrations of nutrient. The removal potential of Phragmites japonica is much higher than that of Salix gracilistyla. Multiple regression was performed to describe the removal potential as a function of hydraulic retention time and influent nutrient concentration. From this study, it was estimated that ammonia-nitrogen of 0.8∼22.3 ㎏/day, nitrate-nitrogen of 12.9∼577.2 ㎏/day, and dissolved inorganic phosphorus of 11.4∼38.6 ㎏/day, would be removed by both plants in the study reach of the Suip Stream. Since this study did not include removal effect by soil micro-organisms, the removed amounts of all three nutrients in real system would be much higher than those determined in this study.

김영웅Young Ung Kim,손희종Hee Jong Son,유명호Myung Ho Yu,김영희Yeong Hee Kim,정종문Jong Moon Jung,김철Chul Kim

DOI: Vol.17(No.2) 215-227, 2001

The photo catalytic oxidation using TiO_2 with UV light was tested to remove odorous and toxic by-products by algae. Among various kinds of photo catalytic oxidations, rotating disc system with coated TiO_2 on glass surface showed higher-removal efficiency with long term stability. To reduce the retention time of solution, higher rotation speed of disc was needed. 10 ㎍/L of geosmin and 2-MIB, and 4.0 ㎍/L of microcystin-LR were completely oxidized in 90 min and 120 min of the operation, respectively and 80% of 330 ㎍/L of chlorophyll-a was removed in 240 min of the operation.

김동한Dong Han Kim,김성홍Seong Hong Kim,정태학Tai Hak Chung

DOI: Vol.17(No.2) 229-240, 2001

Dissolved oxygen (DO) is an essential variable to accomodate the aerobic environment for the removal of organics, nitrogen, and phosphorus in a biological nutrient removal process. The proportional-integral-derivative (PID) controller has been commonly used to control DO in a wastewater treatment plant due to simplicity and robustness. However, it is difficult to tune gains of the controller and it can not reflect uncertainties, nonlinearities, and time-varying parameters sufficiently. Especially, DO dynamics in a sequencing batch reactor (SBR) highly varies because of batch operation and the SBR process has little buffer capacity for surplus aeration in the secondary aeration period. The PID controller shows the poor control performance for DO in the secondary aeration period and great maximum overshoot, oscillations, and root mean square error. The autoregressive with exogenous input (ARX) controller of the first order of inputs shows the good performance, but a little unstability due to the control law of minimum variance in the latter period of the first aeration, in which DO dynamics highly varies. The ARX of the second order of inputs shows the better control performance, stability, and softening the control actions. By applying an adaptive control strategy of the dual set-point in the control of DO, the reduced air flow and enhanced denitrification could be obtained.

윤현식Hyun Sik Yoon,최용수Yong Su Choi,이영대Young Dae Lee,홍석원Seok Won Hong,정익재Ik Jae Chung

DOI: Vol.17(No.2) 241-250, 2001

In general a waste activated sludge is biologically stabilized by either aerobic or aerobic digestion. Typical problems associated with these two processes include high energy requirement, capital cost, and high load to the main wastewater treatment process due to returned digestion supernatant. To overcome these problems in conventional digestion processes, the intermittently aerated sludge digestion, which is operated under combined aerobic and anoxic condition, has been studied for another alternative. In order to understand the behaviors of nutrients in a supernatant of sludge digestion, intermittently aerated batch and continuous digestion experiments were investigated in this study. In a batch digestion, it is shown that nitrogen and phosphorus concentration in the intermittently aerated digestion are less than those in controlled batch digestions: anaerobic digestion without air supply and aerobic digestion with continuous air supply. The endogenous nitrate respiration following the nitrification and the P-uptake by the residual microbes are alternatively occurred in the intermittently aerated digestion. In the continuous digestion, nitrogen and phosphorus concentration in the effluent were examined under air on/off operating condition.

이상민Sang Min Lee,신항식Hang Sik Shin,남세용Se Yong Nam

DOI: Vol.17(No.2) 251-260, 2001

The MAP precipitation was studied as a way of removing simultaneously ammonia nitrogen and phosphorus using various magnesium sources. The operational parameters of pH, mixing time, and the magnesium molar ratio were investigated to find optimal conditions of the MAP precipitation using synthetic wastewater. The removal efficiency of ammonia and phosphorus increased with pH up to 10.5. By MAP precipitating of the synthetic wastewater, 83% of the ammonia nitrogen and 97% of the phosphorus were eliminated at pH 10.5. It was found that at least 10 minutes` mixing time was required and 20 minutes` mixing time was recommended for efficient ammonia and phosphorus removal. High efficiency removal of ammonia nitrogen was possible when the magnesium molar ratio was 1.0-2.0. The comparative study of different magnesium sources showed that bittern was the more efficient coagulant than sea water or magnesium salt. The result showed that 72% of ammonia nitrogen and 98% of phosphorus, respectively, were removed when bittern was used for the MAP precipitation of coke wastewater.

박승국Seung Kook Park,김병군Byung Goon Kim,서인석In Seok Seo,이상일Sang Ill Lee

DOI: Vol.17(No.2) 261-271, 2001

Recently, major concerns in the area of environmental engineering have been the effective treatment of waste, and removal of nutrients for public health. Therefore, this study was initiated to evaluate the potential utilization of fermented food waste as external carbon sources for nitrogen and phosphorus removal in wastewater, eventually recycling of useful sources from wastes. Especially, we evaluated the effects of the environmental parameters on the production of fermented organic acids and the denitrification and phosphorous removal by addition of the fermented food waste. Initial concentration of total solid (TS) contained in the diluted food wastes was 78,000 ㎎/L. It was observed that the mixing and adjustment of pH in fermentation process were major factors in producing the fermented organic acids. When fermented organic acids were used as external carbon sources, total denitrification and phosphorous release rates were 5.62 ㎎NOx-N/gVSS ·hr and 3.89 ㎎PO₄-P/gVSS ·hr, respectively. These rates were similar to, or even higher than those in the case of acetate. Especially, the fermented food wastes having more than 200 of C/N ratio after fermentation proved to be excellent external carbon sources. Furthermore, it seems that the same sources of external carbon can be used in removing N and P of wastewater.

최의소Eui So Choi,호재호Ho Jae Ho

DOI: Vol.17(No.2) 273-281, 2001

Piggery waste represents low COD/TKN ratio of 3.6 resulting in poor nitrogen removal because of limited carbon source. This study was aimed to apply nitrite nitrification to save oxygen and carbon source when denitrify from nitrite. Two stages of nitrite oxidation units with intermediate denitrification unit were utilized for this purpose. Successful nitrite nitrification could be obtained at loading rates of 0.2 ㎏ NH₄-N/㎥/d (SRT = 3.3 d) for lst oxidation unit and 0.15 ㎏NH₄-N/㎥/d (SRT=2.3d) for the 2nd oxidation unit, respectively with addition of alkalinity. Carbon requirements for denitrification from the effluent of nitrite nitrification units were 1.8 to 2.1 ㎏COD/㎏NOxN. Overall economic analysis indicated this process could save about 10 % oxygen and 45 to 50 % carbon requirement in comparison to nitrate nitrification process. However, additional effluent treatment was required in order to meet the current regulatory limit.