• Journal of Korean Society of Water and Wastewater
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• v.18 no.2
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• pp.191-200
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• 2004

DAF process has been designed considering raw water quality characteristics in Korea. Although direct filtration is usually operated, DAF is operated when the freshwater blooms occut or raw water turbidity become high. Pre-sedimentation iS prepared in case when raw water turbidity is very high by rainstorms. A main feature of this plant is that the operation mode can be changed (controlled) based on the characteristics of raw water to optimize the effluent quality and the operation costs. Treatment capacity (surface loading rate) and efficiency of DAF was found to be better than conventional sedimentation process. Moreover, low-density particles (algae and alum flocs) are easily separated while it is difficult to remove in sedimentation. One of the main concerns in adoption of DAF (Dissolved Air-Flotation) process is a high raw water turbidity problem. That is, DAF is not adequate for raw water, which is more turbid than 100NTU. In order to avoid this problem, pre-sedimentation basins are prepared in DAF plant to decrease the turbidity of DAF influent. For simulation of the actual operation, bench and full-scale tests were performed for highly turbid water conditions. Consequently, DAF process coupled with sedimentation is suggested that pre-sedimentation with optimum coagulation prior to DAF would be appropriate.

• Journal of Korean Society of Water and Wastewater
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• v.24 no.5
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• pp.581-593
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• 2010

The objectives of this study were to investigate the effects of raw water pH and basicity of coagulants on turbidity removal with several raw waters having different level of turbidity, alkalinity and pH. Raw waters were sampled from M, S and B water treatment plants(WTP) located at Miryang, Nakdong, Han river, respectively. Six coagulants which have different levels of basicity and aluminum contents were used for this evaluation. High basicity of the coagulant helped to properly control coagulation processes for treating turbid and low alkali raw water. It was difficult for operators to determine optimum coagulant dose for high basicity coagulants, since residual turbidity tended to decrease continuously as coagulant dose increased. Turbidity removal efficiencies with high basicity coagulants(E and F) were higher than the other coagulants at ambient pH for the M WTP. Turbidity removal efficiencies, however, at adjusted pH 7.0 showed similar among six coagulants. Residual turbidity kept low at excess dosages with high basicity coagulants. Optimum coagulant dosages at adjusted pH 7.0 showed higher than those at ambient pH in M WTP. On the contrary in B WTP, optimum coagulant dosage at ambient pH were higher than that at adjusted pH 7.0.

• Journal of Korean Society of Water and Wastewater
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• v.32 no.6
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• pp.517-526
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• 2018

Climate adaptation strategies for water utilities including 16 water treatment plants(WTPs) in Jeju were investigated. Drought, heat wave, and heavy rain were among the most significant climate factors affecting water utilities in Jeju. Heat wave increases water temperature, which in turn increases the concentration of algae, color, and odor materials. Some adaption strategies for the heat wave can be strengthening water monitoring and introducing advanced water treatments. Heavy rain increases raw water turbidity in surface water. The 7 WTPs that take raw water from streams or springs had a maximum turbidity of less than 50 NTU under heavy rain. However, due to concerns of turbidity spike in treated water, some WTPs discontinued intaking raw water when raw water turbidity increased more than 2 NTU. They instead received treated water from other WTPs which took groundwater for water supply. This happens because of the low skills of employees. Thus, there needs to be an increase in operator competency and upgrade of water facilities for the adaption of heavy rain. To improve adaption for the drought, there should be an increase in the capacity of intake facilities of surface water as well as a decrease in water loss. In addition, water consumption per person should be decreased.

• Journal of Korea Water Resources Association
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• v.49 no.1
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• pp.1-9
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• 2016

A correlation analysis between raw water turbidity at two wide-area water treatment plants and hydrological data was conducted for efficient water supply, design and management of water treatment plant. Both correlation analysis and principal component analysis were conducted using hydrological time series data such as inflow discharge, outflow discharge, and rainfall at dam basin of intake station of wide-area water treatment plants. And, forecasting of change in turbidity was conducted using regression equation for turbidity prediction. The raw water turbidity of two water treatment plants was strongly related to time series of discharge. The raw water turbidity of Chungju water treatment plant is strongly related to outflow discharge at Chungju dam (0.708). Whereas, the raw water turbidity of Wabu water treatment plant is strongly related to inflow discharge at Paldang dam (0.805). Similar trends between turbidity forecasting result using regression equation and calculation result using estimation equation on Korea water supply facilities standard were obtained. The result of this study can provide basic data for construction and management of water treatment plant.

• Journal of Korean Society of Water and Wastewater
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• v.23 no.1
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• pp.39-46
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• 2009

A method to improve water treatment efficiency by coagulant overdosing for high pH raw water at a drinking water treatment plant (WTP) which had no pH adjusting facilities was investigated. Poly aluminum chloride (PACl) was used for coagulant, and turbidity removal efficiency was evaluated as a function of PACl dosage increases. pH and turbidity of supernatant of jar-tester were 7.10 and 0.50 NTU respectively, when the turbidity, pH, alkalinity, water temperature, conductivity of raw water were 1.75 NTU, 9.38, 46.5 mg/L, $6.4^{\circ}C$, $400{\mu}s/cm$, respectively. Turbidity of settled water was reduced from 2.18 NTU to 0.28 NTU (87% reduction) when PACl dosage was increased from 16 mg/L to 45 mg/L at a full scale WTP. This can be attributed to the recovery of coagulant efficiency by pH reduction with the increase of coagulant dose, however coagulation efficiency was reduced with the formation of Al(OH)4- by PACl addition at higher pH. Coagulant overdosing was proven to be a rapid and effective method for high pH raw water, which can be applied at drinking WTP.

• Journal of Environmental Science International
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• v.11 no.9
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• pp.955-960
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• 2002

The recycled washwater, which has different water quality and is produced about 5 to 20% of the total water volume treated, affects the unit operation of water treatment, especially coagulation process. However, the effects of recycled washwater on unit operation of water treatment have not been fully investigated. In this study, effects of recycled washwater on coagulation process were investigated to find the optimum coagulation condition by analyzing turbidity, $UV_{254}$, TOC removal efficiencies. In addition, effects of recycled washwater on residual Al after coagulation were studied by analyzing soluble and particulate Al. The size distribution and fractal dimension of coagulated also analyzed. The recycled washwater was lower pH than the raw water. And the recycled washwater had higher $UV_{254}$, TOC and residual Al concentration than the raw water. Residual Al concentration of recycled washwater was about 50 times higher than that of raw water. Optimum coagulant dosages on the blending recycled washwater and the raw water for turbidity, $UV_{254}$ and Al removal were lower than that on the raw water. However, TOC removal increased by increasing coagulant dosage. The size and fractal dimension of coagulated particle produced in the blending recycled washwater were larger, which imply faster settling velocity, than those produced in the raw water only.

• Journal of Korean Society of Water and Wastewater
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• v.11 no.4
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• pp.118-125
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• 1997

Conventional sedimentation method has some limitations for turbidity removal in water treatment because drinking water sources are getting polluted. Removal rates of turbidity using DAF and sedimentation process were compared for various water conditions to know whether DAF is effective to improve sedimentation process. Water samples were clay(gravity 2.65) water 100mg/l, H raw water, mixed water of H raw water and clay 100mg/l, and mixed water of HA(Humic Acid) 5mg/l and clay 100mg/l. Other parameters were temperature, coagulants(Alum, $FeCl_3$), and treatment time. Water temperature greatly affected in removal rates of turbidity for sedimentation and DAF. Generally DAF was more effective in removal rates of turbidity than sedimentation at the same experimental condition. Removal rates of $UV_{254}$ were high to over 90%, and independent of temperature and coagulant.

• Journal of Korean Society of Environmental Engineers
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• v.34 no.9
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• pp.644-650
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• 2012

The purpose of this study is to evaluate the applicability of Horizontal Flow Fins Inclined Plate (HFIP) for the removal of high-turbidity raw water in water treatment plant. As an experimental result, treated water quality and removal efficiency were 0.34 NTU and 90.45% by the application of HFIP for low-turbidity raw water and for the high-turbidity influent resulted 0.75 NTU and 97.27% in removal efficiency. In view of stability for discharge water NTU, the standard deviation were found as 0.12 NTU for low-turbidity and 0.75 NTU for high-turbidity raw water indicating low fluctuations. Result of flow analysis using CFD (Computational Fluid Dynamic) that the addition of HFIP improves the turbidity treatment followed by the stabilization of flow velocity distribution and increases in settling velocity.

• Journal of Korean Society of Water and Wastewater
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• v.21 no.4
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• pp.503-508
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• 2007

Small scale D-water treatment plant(WTP) where has slow sand filtration was using raw water containing high concentration of manganese (> 2mg/l). The raw water was pre-chlorinated for oxidation of manganese and resulted in difficulty for filtration. Thus, sometimes manganese concentration and turbidity were over the water quality standard. Two stage rapid manganese sand filtration pilot plant which can treat $200m^3/d$ was operated to solve manganese problem in D-WTP. The removal rate of manganese and turbidity were about 38% and 84%, respectively without pH control of raw water. However, when pH of raw water was controlled to average 7.9 with NaOH solution, the removal rate of manganese and turbidity increased to 95.0% and 95.5%, respectively and the water quality of filtrate satisfied the water quality standard. Manganese content in sand was over 0.3mg/g which is Japan Water Association Guideline. The content in upper filter was 5~10 times more than that of middle and lower during an early operation but the content in middle and lower filter was increased more and more with increase of operation time. This result means that the oxidized manganese was adsorbed well in sand. Rapid manganese sand filter was backwashed periodically. The water quality of backwash wastewater was improved by sedimentation. Thus, turbidity and manganese concentration decreased from 29.4NTU to 3.09NTU and from 1.7mg/L to 0.26mg/L, respectively for one day. In Jar test of backwash wastewater with PAC(Poly-aluminum chloride), optimum dosage was 30mg/L. Because the turbidity of filtrate was high as 0.76NTU for early 5 minute after backwash, filter-to-waste should be used after backwash to prevent poor quality water.

• Journal of Korean Society of Water and Wastewater
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• v.19 no.2
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• pp.135-143
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• 2005

It was evaluated that the effect of turbidity removal by Pore Controllable Fiber Filter(PCF) installed in NS(Naksang) small water treatmant plant(system) using under flow water as raw water in the study. The results of the study are as the followings. Firstly, the removal efficiency of turbidity by PCF without coagulation(in operation mode not using coagulants) was mostly below 20 percent. On the other hand, when operation using proper coagulants, that of turbidity was mostly over 80 percent. Secondly, slow sand filtration after PCF, total turbidity removal efficiency of final treated water was 84.3 percent, and the contribution by PCF was 57.1 percent and that of slow sand filtration was 27.7 percent. Therefore the introduction of PCF as pre-treatment process would be helpful to reduce the loading of high turbidity of slow sand filtration. Thirdly, the results of particle counter measurements showed that when operated PCF with coagulants, fine flocs captured or adsorbed at the pore of PCF were flow out into the effluents from 120 minutes after backwashing because of the increase of headloss of PCF. Therefore the decision of backwashing time should made consideration into the outflow of fine flocs from PCF. Fourth, coagulant dosages on PCF at the same turbidity was largely variable because of the effect of the raw water characteristics and the turbidity increase velocity at rainy days, therefore flexible coagulant dosages should be considered rather than fixed coagulant dosage by the influent jar-test result.