• Journal of Korea Water Resources Association
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• v.41 no.12
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• pp.1187-1198
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• 2008

Many reservoirs in Korea and their downstream environments are under increased pressure for water utilization and ecosystem management from longer discharge of turbid flood runoff compared to a natural river system. Turbidity($C_T$) is an indirect measurement of water 'cloudiness' and has been widely used as an important indicator of water quality and environmental "health". However, $C_T$ modeling studies have been rare due to lack of experimental data that are necessary for model validation. The objective of this study is to validate a coupled three-dimensional(3D) hydrodynamic and particle dynamics model (ELCOM-CAEDYM) for the simulation of turbid density flows in stratified Daecheong Reservoir using extensive field data. Three different groups of suspended solids (SS) classified by the particle size were used as model state variables, and their site-specific SS-$C_T$ relationships were used for the conversion between field measurements ($C_T$) and state variables (SS). The simulation results were validated by comparing vertical profiles of temperature and turbidity measured at monitoring stations of Haenam(R3) and Dam(R4) in 2004. The model showed good performance in reproducing the reservoir thermal structure and propagation of stream density flow, and the magnitude and distribution of turbidity in the reservoir were consistent with the field data. The 3D model and turbidity modeling framework suggested in this study can be used as a supportive tool for the best management of turbidity flow in other reservoirs that have similar turbidity problems.

• Journal of the Korea Organic Resources Recycling Association
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• v.2 no.1
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• pp.87-98
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• 1994

Sludge minimization in an water treatment plant can be achieved by optimizing a main water treatment process as well as by enhancing a thickening and a dewatering facilities. In this study, dewatering and drying techniques for reducing the quantity of the water sludge generated from the conventional water treatment plant in the local states were investigated by reducing its water content. Not only the types and dosages of polymers but also the mixing intensity of the mixtures of a concentrated sludge and polymers on the different pH were evaluated for the optimum dewatering conditions of the water sludge. Weight reduction of the water sludge was also tested at a given temperature range. The dewatering efficiency of the water sludge was not affected by the types of polymer but by mixing intensity(GT value) in this study. pH effect on dewaterbility of the water sludge took a major role at the neutral pH range. The optimal polymer dose was 1.5 mg-polymer/g-TSS(about 40mg/L as polymer). Dewaterability was enhanced at a lower mixing intensity(GTbelow 10,000 sec-1). Free water in the void of sludge cake was dried around $100^{\circ}C$, chemical bound water was evaporated around $320^{\circ}C$, and organic material was burned out at the range of 300 to $600^{\circ}C$. Ignition losses of the water sludge were varied 15 to 40 % as the raw water quality. The ignition loss due to the chemical bound water was 10-20% and the loss due to the organic material was 4-20% of the total ignition loss.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.3
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• pp.240-248
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• 2006

In this study, a retrofitting BNR process that was modified for the economical applicability was proposed and evaluated in the pilot plant($50m^3/d$). At the same time the bacterial community structure was investigated in the pilot plant by using FISH(fluorescent in situ hybridization) method. Economically 16% of the initial construction cost for the proposed process(introduction of a biological nutrient removal process of $60,000m^3/d$ scale basis) was reduced due to the absence of a bioreactor. Water treatment efficiencies and maintenance facilities of the modified process were satisfied with the strengthened discharge permits in Korea throughout a long term pilot plant operating including a winter season. Bacterial populations in the pilot plant and in the control plant(A2/O process, B SIP(Sewage Treatment Plant)) were remained uniformly during the test period, but bacterial structure in the bioreactor was changed drastically. Proportions of ${\beta}$-proteobacteria group including soil bacteria which play a important role in wastewater treatment increased $25{\sim}607%$ in population.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.37 no.1
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• pp.73-82
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• 2017

In Korea, previous certification of water supply infrastructure was mainly focused on economical and physical aspects. Recently, hygienic safety of water supply service has become a sensitive and important issue to our people for evaluating the water quality with growth of economy and education system. According on water quality in 497 Korean water supply facilities, pH values in the supplied water have ranged between 5.8-8.5. However, little is known about metal leachability at the pH conditions observed in the real water supply systems because a fixed pH condition (pH 7.0) has been used in the current standard method, 'Hygienic Safety Testing Method', in water supply. In this work, we examined the effects on heavy metal leachability with pH differences in the water supply pipes which are typically used in Korea. As a result, the amounts of metal leachability were tended to increase when pH levels were decreased. Especially at pH 5.8, Cu leachability from Cu pipes was found to exceed the public health standard level even after applying a normalization factor (NF) given by the current Korea standard method. The Cr and Cu leached from stainless steel pipes, Cd, Pb, Cu, and Zn from Cu-based pipe fittings, and Zn from Zn-based pipe fittings were exceeded the Korean hygienic safety standards while, after applying the NF, concentrations of the leached metals were satisfied with the current Korean standard. The findings from this work provide implications on the needs of reforming the current hygienic safety standard methodology.

• Journal of agricultural medicine and community health
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• v.36 no.4
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• pp.218-226
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• 2011

Objectives: Paraquat (PQ) is a widely used ionic pesticide that is fatal when ingested accidentally or for suicidal purposes. It is thought that chronic exposure of PQ is related with the development of Parkinson's disease, but epidemiological studies have not yet confirmed that theory. This study attempted to estimate the possibility of environmental PQ exposure through soil and water. Materials and Methods: We analyzed the amount of decomposed PQ solution in wet soil after exposure to ultraviolet light. An artificial rainfall condition was simulated over soil sprayed with PQ to measure the amount of eluted PQ. In addition, PQ was diluted in water from three differently rated rivers and the changes in PQ concentration were measured after ultraviolet exposure over one month. High performance liquid chromatography/ultra violet detection was used to analyze the concentrations of PQ. Results: In the method we used, the recovery rate of PQ showed a precision rate less than 5%, an accuracy greater than 88%, and the calibration equation was y=5538.8x-440.01($R^2$=0.9985). There were no significant differences in the concentrations of PQ obtained from the three specimens over a 1-week period. From the PQ-sprayed soil, the artificial rainfall conditions showed no PQ elution over a 1-month period, and there was no significant differences in PQ concentrations according to ultraviolet exposure among the three samples. Conclusions: PQ remains well adsorbed naturally in soil. However, it may still exist in an integrated state for a long time in the hydrosphere, so the possibility of PQ exposure through drinking water cannot be disqualified.

• Journal of the Korean Society of Marine Environment & Safety
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• v.16 no.1
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• pp.31-41
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• 2010

Harmful dinoflagellate, Cochlodinium polykrikoides, has always occurred in southern coastal waters every year during summer, but it did not occur in 2009. A comparative study on outbreak in 2007/2008 and non-outbreak of C. polykrikoides in 2009 was performed based on environmental parameters and phytoplankton appearances. Samples were obtained at 13 stations from Yeosu to Wando waters in 2007-2009. The heavy rainfall was associated with the decrease of surface water temperature below $20^{\circ}C$ in July, the decrease of salinity below 31psu in August and increase of pH to 8.4 in Augus, 2009. concentration of DIN in 2009 was approximately too times as high as those of 2007 and 2008, and the ratioes of N:P and Si:N in 2009 showed Redfield ratio to be above the value of 16. This indicates that Redfield ratioes were significantly different between 2007/2008 and 2009. Dominant species during the field survey were shown to be Chaetoceros spp., Skeletonema costatum and Thalassiosir spp. in diatoms and to be Ceratium spp. in dinoflagellate. In partiuclar, Gonyaulax polygramma occurred in August, 2009 instead of C. polykrikoides. Consequently, the massive rainfall and shortage of sunshine contributed to considerable variation in environmental parameters which were associated with delay in the timing of rapid growth phase of C. polykrikoides.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.1
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• pp.159-167
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• 2000

In recent years, combined and separated sewer overflows (CSOs, SSOs) have been recognized as a significant pollution problem. To solve this problem a series of experiments were performed in a small scale Rapid Floc Settler (RFS) device to determine its ability in removing micro particles and dissolved materials from polluted waters. The RFS device is a compact physico-chemical wasterwater treatment system. Polyacrylamide (PAM) is used as a coagulant for treating stormwater in the RFS. The results of Jar test showed that PAM could be an excellent coagulant as compared with aluminum sulfate. and ferric chloride. In several experimental conditions, the influence of different variation parameters was tested to measure the efficiency of the RFS. Tests have been carried out with typical CSOs concentrations (50~1.000mg SS/L). The treatment efficiency with regard to SS and COD, which can be obtained at an overflow rate of $130m^3/m^2/day$, are 90% and 80%, respectively. Comparing other sedimentation technologies with RFS, the overflows rate of RFS is ten times faster. The distribution of particle size and number were analyzed. The RFS is suitable for the treatment of CSOs and also the removal of settleable and dissolved materials in urban stormwater runoff.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.1
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• pp.1-10
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• 2000

An experimental study regarding the effect of emulsions on RO is presented. Heavy oil was added to the sea water and the distilled water separately and treated for 30 minutes by a homogenizer to make emulsions. For the case of the sea water without heavy oil the permeate decreased from the beginning of the experiment. Chloride and conductivity increased with time, due to the fouling occurring as the suspended solids in the sea water accumulated on the membrane surface. Rejection rate of salt was 99.6~99.7%. As for the sea water containing heavy oil, the permeate decreased slowly from the beginning of the experiment. This result was the same for the case of the sea water only. However. chloride and conductivity increased significantly when heavy oil was added. In the second experiment with sea water containing heavy oil, the operation time of RO was reduced considerably. With addition of oil, the chloride increased greatly, while the permeate reduced comparatively. In the experiment where emulsion of $0.3{\sim}0.8mg/{\ell}$ was supplied to RO. oil concentration was about 10ppb in the permeate at the end of the experiment. In case of the distilled water containing heavy oil. the conductivity increased. However. the permeate reduced to 30% compared to the case of the sea water containing heavy oil. The case of sea water containing heavy oil showed an opposite result, but the effect of the addition of oil on RO was significant. Oil caused fouling of the RO and the contamination of the whole system, and as the result the system could not be operated properly. As a result the membrane capacity, the amount and water quality of permeate deteriorated significantly.

• Journal of Korean Society of Environmental Engineers
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• v.34 no.9
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• pp.597-603
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• 2012

To investigate the effects of weir construction on sediment characteristics of river bed, we conducted sediments sampling on the 9 locations near the weir, Kangchun, Yuju and Ipo in Namhan-River. Physical and chemical characteristics of sediments were analyzed by measuring particle size distribution, water content, Ignition loss, COD (Chemical Oxyzen Demand), TOC (Total Organic Carbon), TP (Total Phosphorus), SRP (Soluble Reactive Phosphorus) and TN (Total Nitrogen). Particle classification of all three weir sediments showed sandy loam that was caused by the river bed dredging. Due to the presence of weir, Ignition loss, COD, TOC, TP, SRP and TN showed similar trend such as the concentrations of upward weir had higher than those of downward weir. For the case of SRP concentration and C/N ratio, however, there is not much difference in the sediment characteristics compared to the those of sediments before weir construction. Therefore, It can be predicted that there are little effects of weir construction on sediment characteristics. However, weir construction could influence water quality of the river by controlling the transport and the accumulation of suspended materials from rainfall. Therefore, more intensive monitoring is required to examine the magnitude and patterns of sediment accumulation which could influence overlying water quality.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.10
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• pp.694-702
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• 2013

The purpose of this study is to evaluate a de-watering filtrate treatment and the possibility of securing biological treatment capacity by changing the structure of the secondary clarifier. Accordingly, the column test was conducted to determine the effect of polymer in the de-watering filtrate on sludge sedimentation. Also, the characteristics of de-watering filtrate processing was evaluated through batch test and continuous processing operation. The results showed that sludge settling velocity increased with higher polymer concentration, and that effluent SS concentration was found to decrease. Regarding processing characteristics of de-watering filtrate, the removal efficiency of TSS and TBOD5 increased as the length of secondary clarifier was longer. Also, comparing injections into anoxic tank and secondary clarifier, de-watering filtrate by continuous infusion treatment process showed stability in both conditions. Therefore, by modifying the structure of secondary clarifier, efficient processing of de-watering filtrate is expected to be possible and processing capacity of small sewage treatment plants is considered to be improved.