• International journal of advanced smart convergence
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• v.5 no.2
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• pp.18-23
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• 2016

Cell walls of microalgae consist of a polysaccharide and glycoprotein matrix providing the cells with a formidable defense against its environment. Anaerobic digestion (AD) of microalgae is primarily inhibited by the chemical composition of their cell walls containing biopolymers able to resist bacterial degradation. Adoption of pre-treatments such as thermal, thermal hydrolysis, ultrasound and enzymatic hydrolysis have the potential to remove these inhibitory compounds and enhance biogas yields by degrading the cell wall, and releasing the intracellular algogenic organic matter (AOM). This paper preproposal stage investigated the effect of different pre-treatments on microalgae cell wall, and their impact on the quantity of soluble biomass released in the media and thus on the digestion process yields. This Paper present optimum approach to degradation of the cell wall by ultra-sonication with practical design specification parameter for ultrasound based pretreatment system. As a result of this paper presents, a microalgae system in a wastewater treatment flowsheet for residual nutrient uptake can be justified by processing the waste biomass for energy recovery. As a conclusion on this result, Low energy harvesting technologies and pre-treatment of the algal biomass are required to improve the overall energy balance of this integrated system.

• 수도
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• v.24 no.5 s.86
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• pp.29-44
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• 1997

Sewage sludge produced in Korea was 1,275,800 tons (dewatered sludge cake) per year in 1996, which is 3,495 tons per day, 0.303% of 11,526,100 tons per day of sewage treated in 79 sewage treatment plants. Sludge production has been and will be increasing in accordance with construction of new facilities for sewage treatment. Most of the sludge is currently disposed by landfill and ocean dumping, but it is becoming difficult to find suitable sites for landfill, particularly in big cities such as Seoul. In addition, rapid increase of landfill cost is anticipated in a near future. Current trend for sludge disposal in advanced countries is land application. Over the past 10 to 20 years in the United States, sludge management practices have changed significantly, moving from disposal to beneficial use. They use biosolid for utilization instead of sludge for disposal. Under the Clean Water Act of 1972, amended in 1987 by Congress, the U.S. EPA was required to develop regulations for the use and disposal of sewage sludge. The EPA assessed the potential for pollutants in sewage sludge to affect public health and the environment through a number of different routes of exposure. The Agency also assessed the potential risk to human health through contamination of drinking water sources or surface water when sludge is disposed on land. The Final Rules were signed by the EPA Administrator and were published (Federal Register, 1993). These rules state that sewage sludge shall not be applied to land if the concentration of any pollutant in the sludge exceeds the ceiling concentration. In addition, the cumulative loading rate for each pollutant shall not exceed the cumulative pollutant loading rate nor should the concentration of each pollutant in the sludge exceed the monthly average concentration for the pollutant. The annual pollutant loading rate generally applies to applications of sewage sludge on agricultural lands. The most popular beneficial use of sewage sludge is land application. The sludge has to be stabilized for appling to land. One of the stabilization process for sewage sludge is lime stabilization process. The stabilization process is consisted of the stabilizing process and the drying process. Stabilization reactor can be a drum type reactor in which a crossed mixer is equipped. The additive agents are a very reactive mixture of calcium oxide and others. The stabilized sludge is dried in sun drier or rotary kiln.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.3
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• pp.269-275
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• 2014

The objective of this study was to investigate the performance characteristics of an inline mixing and coagulation system for water treatment based on the process intensification concept. Three-stage inline mixing and coagulation system was composed of the reservoirs of source wastewater, the fixed quantity injection pumps of coagulants, the mixing and coagulation tubes, a sedimentation tank and a control panel. In the equal dosage of coagulant and coagulant aids, the turbidity removal with increasing the dosage of coagulant aids was about 3 times higher than that with increasing the dosage of coagulant. In the condition of the equal mixing and coagulation time, the turbidity removal of inline mixing and coagulation system was about 4.6 times higher than that of mechanical type.

• Textile Coloration and Finishing
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• v.19 no.3
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• pp.26-36
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• 2007

This study was carried out to treat the aqueous solutions containing reactive dyes(RB19, RR120 and RY179) by the Ozone demand flask method and adsorption process using activated carbon fiber(ACF) which are one of the main pollutants in dye wastewater. Ozone oxidation of three kinds of the reactive dyes was examined to investigate the reactivity of dyes with ozone, competition reaction and ozone utilization on various conditions for single- and multi-solute dye solution. Concentration of dyes was decreased continuously with increasing ozone dosage in the single-solute dye solutions. Competition quotient values were calculated to investigate the preferential oxidation of individual dyes in multi-solute dye solutions. Competition quotients(CQi) and values of the overall utilization efficiency, ${\eta}O_3$, were increased at 40mg/l of ozone dosage in multi-solute dye solutions. ACF(A-15) has much larger specific surface area$(1,584m^2/g-ACF)$ in comparison with granular activated carbon adsorbent (F400, $1,125m^2/g-GAC$), which is commonly used, and most of pores were found to be micropores with pore radius of 2nm and below. It was found that RB19 was most easily adsorbed among the dyes in this study. In the case of PCP (p-chlorophenol) and sucrose, which are single component adsorbate, adsorption capacities of ACF(A-15) were in good agreement with the batch adsorption measurement, and saturation time predicted of ACF columns for these components was also well agreed with practically measured time. But in the case of reactive dyes, which have relatively high molecular weight and aggregated with multi-components, adsorption capacities or saturation time predicted were not agreed with practically measured values.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.3
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• pp.645-654
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• 1994

Photocatalytic oxidation conditions of reactant recirculation flow rate 275 mL/min, aeration rate 2 LPM and $UV+TiO_2+H_2O_2$(500 mg/L) proved to be appropriate for water including organic materials treatment. With increasing turbidity and suspended solids concentration, at turbidity 10 NTU-suspended solids concentration 29 mg/L the phenol degradation efficiency increased, which in turn decreased at turbidity 50 NTU-suspended solids concentration 170 mg/L, however no significant differences were observed, demonstrating similar results with those obtained at zero turbidity and suspended solids concentration. The degradation efficiency of phenol decreased with increasing influent phenol concentrations. The $UV+TiO_2+H_2O_2$ photocatalytic advanced oxidation process conducted is considered to be possibly applied to the drinking water treatment, and the post-treatment process of biological wastewater treatment.

• Journal of Korean Society of Water and Wastewater
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• v.27 no.1
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• pp.101-112
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• 2013

Integrated process with coagulation and microfiltration as an advanced water treatment has been expanded its application in recent years due to its superb removal of particles and natural organic matter. In usual, effectiveness of coagulation sometimes determines performance of the whole system. Several new polymeric coagulants introduced to water utilities for better efficiency were studied in this paper. Three polymeric coagulants (i.e., PACl, PACs, and PAHCs) along with alum were evaluated for removal of natural organic matter, especially for reduction of trihalomethane formation potential, for which regulation has become stringent. Turbidity removal was closely related to pH variation showing the reduced turbidity removal by PACs due to the decreases in the pH of supernants at high doses. The four coagulants showed different organic matter removal during coagulation and affected the removal in microfiltration. For instance, DOC concentration was not reduced by microfiltration when PAHCs were used however 10 % of DOC removal was observed by microfiltration with alum coagulation. Coagulation pretreatment also impacted the THM removals, i.e., approximately 30 % of THMs and 13 % of DOC was removed by microfiltration only, but 40 to 67 % of THMs and 30 % of DOC was removed by the integrated process. Strategies on selection of coagulants are needed depending on characteristics of target pollutants in raw waters.

• Membrane Journal
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• v.28 no.1
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• pp.31-36
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• 2018

The purpose of this study is to investigate the changes of sludge characteristics according to the changes of influent sewage flowrate in the advanced wastewater treatment processes including MBR, SBR, and $A_2O$. The ratio of the actual sewage flowrate to the design flowrate is decreased from 100% to 70, 40%, and 10%, and the specific denitrification rate and ammonia oxidation (nitrification) rate was measured. The specific nitrification rate of the sludge collected from the aeration tank of each process was measured at a similar value ($0.10gNH_4/gMLVSS/day$) in all three process under the condition of 100% of sewage flowrate. It has tended to decrease significantly as the sewage flowrate decreased from 70% to 40%. The specific denitrification rate was also decreased by ~50% as the sewage flowrate decreased. However, considering the total nitrogen concentration in the influent and the microbial concentration in the reactor, the changes in kinetic parameter did not affect overall nitrogen removal. Therefore, it can be concluded that stable nitrogen removal will be possible under low influent flowrate condition if the MLVSS concentration is kept high.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.1
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• pp.97-104
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• 2010

At present, the biological nutrient removal (BNR) process for removal of nitrogen and phosphorus is being constructing to keep pace with the reinforced standard of effluent quality and the traditional activated sludge process of preexistence is being promoting to retrofit. At the most case of retrofitting, processes are subjected to be under consideration as alternative BNR process for retrofitting. However, process evaluation methods are restricted to compare only treatment efficiency. Therefore, when BNR process apply, process evaluation was needed various method for treatment efficiency as well as sludge production and aeration cost, and all. In this study, the evaluation method of alternative process was suggested for the case for retrofitting S wastewater treatment plant which has been operated the standard activated sludge process. Three BNR processes for evaluation of proper alternatative process were selected and evaluated with suggested method. The selected $A^2$/O, VIP and DNR processes were evaluated using the mathematical model which is time and cost effective as well as gathered objective evaluation criteria. The evaluation between 5 individual criteria was possible including sludge production and energy efficiency as well as treatment performance. The objective final decision method for selection of optimal process was established through the fuzzy inference.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.3
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• pp.212-221
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• 2011

Wastewater treatment plants (WWTPs) are required to meet the reinforced discharge standards which are differentiated as 0.2, 0.3 and 0.5 mg-TP/L for the district I, II and III, respectively. Although most of WWTPs are operating advanced biological phosphorus removal system, the supplementary phosphorus treatment facility using chemical addition should be required almost at all WWTPs. Therefore, water quality data from several exemplary full-scale plants operating phosphorus treatment process were analyzed to evaluate the reliability of removal performance. Additionally, a series of jar tests were conducted to find optimal coagulants dose for phosphorus removal by chemical precipitation and to describe characteristics of the reaction and sludge production. Chemical costs and the increasing sludge volume in physicochemical phosphorus removal process were estimated based on the results of jar tests. The minimum coagulant (aluminium sulfate and poly aluminium chloride) doses to keep TP concentration below 0.5 and 0.2 mg/L were around 25 and 30 mg/L (as $Al_2O_3$), respectively, in the mixed liquor of activated sludge. In the tertiary treatment facility, relatively lower coagulant doses of 1/12~1/3 the minimum doses for activated sludge were required to achieve the same TP concentrations of 0.2~0.5 mg/L. Increase in suspended solids concentration due to chemical precipitates in mixed liquor was estimated at 10~11%, compared to the concentration without chemical addition. When coagulant was added into mixed liquor, chemical (aluminium sulfate) cost was estimated to be 4~10 times higher than in secondary effluent coagulation/separation process. Sludge production to be wasted was also 4~10 times higher than secondary effluent coagulation/separation process.

• Journal of Korean Society on Water Environment
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• v.23 no.3
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• pp.319-323
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• 2007

The Advanced Oxidation Process (AOP) is being increasingly used to oxidize complex organic constituents in treated effluents from domestic wastewater treatment plants. Generally, ${NO_3}^--N$ concentrations ranges between 5 and 8 mg/L for biologically well-treated effluents. However, nitrate ions, ${NO_3}^-$, affects on oxidation as not only a well-known strong absorber of UV light below 250 nm of wavelength but also as an OH radical scavenger. The objective of this study was to evaluate the AOP systems for degradation of 2,4-DCP, and to delineate the effect of nitrate ions on UV oxidation of 2,4-DCP by conducting a bench-scale operation at various reaction times and initial concentrations of $H_2O_2$. The experimental results indicated that 2,4-DCP could be completely oxidized by $UV/H_2O_2$ process with an initial $H_2O_2$ concentration of 20 mg/L at a retention time of 1.0 min or longer. Nitrate ions did not show any adverse effect on 2,4-DCP oxidation at this high $H_2O_2$ concentration, and the practical initial $H_2O_2$ concentration and reaction time for the 80% oxidation turned out to be 5 mg/L and 1.0 min, respectively.