• Journal of Korean Society of Water and Wastewater
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• v.21 no.3
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• pp.341-348
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• 2007

The efficiency of powdered activated carbon (PAC) for removing taste and odor (T&O) in drinking water supplies is dependent on the contact time, quality of mixing, and the presence of competing compounds. All of these are strongly influenced by the stage in the treatment process at which the PAC is added. In conventional water treatment plants (WTPs), PAC is commonly added into the rapid mixing basin where chemicals such as coagulants, alkaline chemicals, and chlorine, are simultaneously applied. In order to prevent interference between PAC and other water treatment chemicals, alternative locations for addition of PAC, such as at transmission pipe in the water intake tower or into a separated PAC contactor, were investigated. Whatever the location, addition of PAC apart from other water treatment chemicals was more effective for geosmin removal than simultaneous addition. Among several combinations, the sequence 'chlorine-PAC-coagulant' produced the best result with respect to geosmin removal efficiency. Consequently, when PAC has to be applied to cope with T&O problems in conventional WTPs, it is very important to prevent interference with other water treatment chemicals, such as chlorine and coagulant. Adequate contact time should also be given for adsorption of the T&O compounds onto the PAC. To satisfy these conditions, installation of a separated PAC contactor would be the superior alternative if there is space available in the WTP. If necessary, PAC could be added at transmission pipe in the water intake tower and still provide some benefit for T&O treatment.

• Journal of Environmental Health Sciences
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• v.39 no.5
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• pp.391-407
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• 2013

Micropollutants emerge in surface water through untreated discharge from sewage and wastewater treatment plants (STPs and WWTPs). Most micropollutants resist the conventional systems in place at water treatment plants (WTPs) and survive the production of tap water. In particular, pharmaceuticals and endocrine disruptors (ECDs) are micropollutants frequently detected in drinking water. In this review, we summarized the distribution of micropollutants at WTPs and also scrutinized the effectiveness and mechanisms for their removal at each stage of drinking water production. Micropollutants demonstrated clear concentrations in the final effluents of WTPs. Although chronic exposure to micropollutants in drinking water has unclear adverse effects on humans, peer reviews have argued that continuous accumulation in water environments and inappropriate removal at WTPs has the potential to eventually affect human health. Among the available removal mechanisms for micropollutants at WTPs, coagulation alone is unlikely to eliminate the pollutants, but ionized compounds can be adsorbed to natural particles (e.g. clay and colloidal particles) and metal salts in coagulants. Hydrophobicities of micropollutants are a critical factor in adsorption removal using activated carbon. Disinfection can reduce contaminants through oxidation by disinfectants (e.g. ozone, chlorine and ultraviolet light), but unidentified toxic byproducts may result from such treatments. Overall, the persistence of micropollutants in a treatment system is based on the physico-chemical properties of chemicals and the operating conditions of the processes involved. Therefore, monitoring of WTPs and effective elimination process studies for pharmaceuticals and ECDs are required to control micropollutant contamination of drinking water.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.4
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• pp.651-657
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• 2016

The purpose of this research was to examine the possibility on the recycling of foodwaste leachate as external carbon sources using microbubble. The following operating conditions were selected: pressurizing tank 3 bar, circulation flow rate 3.65 LPM, and air flow rate 0.3 LPM with batch type. Microbubble contact time of 18 hours is optimal time to satisfy the recycling of foodwaste leachate as external carbon sources with batch type. HRT 18 hours came up to standard for external carbon sources, except for T-P concentration with continuous type. Coagulants need to be used for removal of dissolved phosphorus concentration by more than 88.5% of the total phosphorus concentration. The VFA was influenced by the organic decomposition rate and the concentration in the aerobic condition. It was considered that the VFA was needed for selection the optimal HRT or the addition of acid fermentation process in order to meet recycling standard of foodwaste leachate.

• Applied Biological Chemistry
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• v.37 no.6
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• pp.472-479
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• 1994

This study was conducted to determine the effective removal method of THMs and humic material in drinking water when the doses of oxidants, coagulants, and activated carbon, and the points of oxidants treatment were changed in the drinking water treatment process. The inhibition of THMs formation and the removal of humic matter were more effectively achieved by $ClO_2$ than by other oxidants, $Cl_2,\;NH_2Cl,\;KMnO_4\;and\;O_3$. By changing the point of oxidant treatment, the formation of THMs was reduced by about 36.7 to 8.2% on treatment after coagulation, but the content of humic matter was not affected. The coagulation efficiency of alum and ferric sulfate to coagulate organic materials in water was affected by the molecular weight of humic matter in drinking water. The treatment of activated carbon after filtration was found to be more effective than that before oxidation in inhibiting THMs formation and removing THMs.

• Environmental Engineering Research
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• v.13 no.1
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• pp.1-7
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• 2008

Recently a new technology called the flexible-fiber deep-bed filter (FDF) claimed to replace the conventional sand filter including coagulation and sedimentation filter (CSF) processes in the water treatment plant. Therefore the life cycle assessment (LCA) approach was applied for evaluating the life cycle impacts of FDF compared with those of CSF. The used LCA softwares were the Simapro 6 and PASS and their life cycle impact assessment (LCIA) methodologies were the Eco-indicator 99 and the Korean Eco-indicator, respectively. The goal of this LCA was to identify environmental loads of CSF and FDF from raw material to disposal stages. The scopes of the systems have been determined based on the experiences of existing CSF and FDF. The function was to remove suspended solids by filtration and the functional unit was $1\;m^3$/day. Both systems showed that most environmental impacts were occurred during the operation stage. To reduce the environmental impacts the coagulants and electricity consumptions need to be cut down. If the CSF was replaced with the FDF, the environmental impacts would be reduced in most of the impact categories. The LCA results of Korean Eco-indicator and Eco- indicator99 were quite different from each other due to the indwelling differences such as category indicators, impact categories, characterization factors, normalization values and weighting factors. This study showed that the life cycle assessment could be a valuable tool for evaluating the environmental impact of the new technology which was introduced in water treatment process.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.8
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• pp.775-780
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• 2008

Sludge conditioning is widely used to improve aggregation and dewaterability of waste sludge in sludge treatment processes. The study aims to examine quantitative correlations between coagulant dosage and sludge cake dewaterability using three kinds of coagulants, such as an aluminum sulfate, a ferric chloride, and a poly aluminum chloride(PAC). When an aluminum sulfate, a ferric chloride, and a PAC were injected with 0.79$\sim$1.19 mmol/g, 0.61$\sim$1.25 mmol/g TSS, and 0.21$\sim$0.39 mmol/g TSS, respectively, specific resistances to filtration of the sludge were decreased at 95.0% or more. This study shows that the correlation between coagulant dosage per g sludge(D) and normalized specific resistance to filtration(R) could be expressed by the exponential functions.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.3
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• pp.2321-2327
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• 2015

Three coagulants, alum sulfate(alum), poly aluminum chloride(PAC) and poly aluminum silicate chloride (PASC), were used to remove low to high turbidity and TOC in surface and ground blended water. Laboratory experiments and pilot plant experiments were carried out to evaluate the optimal coagulant and its dosage. To determine the optimized coagulant and its dosage, the turbidity, TOC and pH were measured. The experimental results showed the best removal performance using PASC. The optimal dosage of PASC between 3-20 NTU was found to be 15 mg/L in the jar test. In the pilot test, a 15 mg/L PASC dosage was applied and resulted in the efficient removal of turbidity and TOC between 3.6-27 NTU. The removal efficiency of PASC increased with increasing turbidity and TOC.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.12
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• pp.2227-2238
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• 2000

The interfacial features of suspension system made of $CaCO_3$ particles have been investigated for the purpose of designing its effective treatment process. For the examination of variation of electrokinetic potential as a function of pH. the value of potential was observed to shift in the negative direction, which was thought to be due to the adsorption of hydroxide ion on the particle surface. Adsorption of surfactant on suspended particles resulted in the change of surface charge and shift in electrokinetic potential, which was dependent upon the sign of head charge and concentration of surfactant. Addition of inorganic salts affected stability of suspension greatly and sedimentation rate of suspension was influenced by the electric valence and amount of ions produced by dissolution of inorganic coagulants. DLVO theory made it possible to construct a energy profile diagram and a close correlation was found between experimental result and theoretically derived consequences. Non-specific adsorption of indifferent electrolyte resulted in the compression of electrical double layer and specific adsorption induced the shift of IEP and PZC in the opposite direction.

• Journal of environmental and Sanitary engineering
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• v.20 no.3 s.57
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• pp.36-43
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• 2005

Prior to the study of the sewage treatment methods, water quality for Gwangju sewage of fluent was investigated from January to December, 2004 for sewage water reuse. Monthly mean values of BOD, SS, turbidity, total phosphorus and color were 4.1 mg/L, 2.9 mg/L, 0.8 NTU, 1.3 mg/L, and 27 unit, respectively. Jar-test was performed to investigate the removal efficiency of pollutants under the coagulation conditions of fast mixing for 5 min, slow mixing for 15 min and precipitation for 1hr. Here, alum and polyaluminium chloride (PAC) were used as coagulants to reduce color, turbidity, total phosphorus (TP) and total organic carbon (TOC) in sewage effluents. The results showed that PAC gave better efficiency in removing turbidity and dissolved phosphorus than alum. It was also found from the relative molecular weight (RMW) distribution analysis that organic matter over 1,000 Dalton (Da) was easily removed by coagulation and subsequently MF treatment, while it was not effective for less than 500 Da. Based on tis result, Natural organic matter (NOM) with lower molecular weight (< 500 Da) may cause harmful disinfectant by-product (DBP) after chlorine treatment. Thus, activated carbon adsorption seems to be required for the complete removal of DBP in the hybrid system.

• Journal of Trauma and Injury
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• v.28 no.4
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• pp.266-271
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• 2015

Reports on a posttraumatic isolated superior mesenteric artery (SMA) dissection are rare. Recently, endovascular stent placement via percutaneous access, instead of vascular surgery, has been widely accepted as the initial treatment for a patient with an isolated SMA dissection or its complications. A 60-year-old female patient was transferred to our hospital due to an isolated SMA dissection after a car accident. The SMA dissection was 8.5 cm in length, and it involved the true lumen, which was severely compressed by the thrombosed false lumen. The patient was closely observed because she did not complain of any specific visceral pain. On the seventh hospital day, she underwent computed tomography (CT) to decide on a further treatment plan, irrespective of the presence of the abdominal symptom. The findings of the follow-up CT showed no difference compared to those of the previous CT. She was discharged with anti-coagulants. One month later, the follow-up CT revealed focally progressing dissecting aneurysms in the false lumen of the dissected SMA and a more severely compressed true lumen. Two self-expandable metallic stents were successfully placed in the true lumen of the dissected SMA, covering two aneurysmal lesions. Herein, we report a successful endovascular treatment with stent placement for treating focally progressing dissecting aneurysms and a severely compressed true lumen in a patient with a posttraumatic isolated SMA dissection.