• Journal of Environmental Science International
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• v.25 no.9
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• pp.1233-1239
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• 2016

This study aimed to evaluate changes in the TN and TP removal efficiencies, depending on whether or not a settling process is applied, in a sequencing batch reactor (SBR) process with a membrane bioreactor (MBR). Nutrient removal was considered in terms of developing an advanced water treatment system for ships in accordance with water quality standards set forth by 227(64). For these purposes, the TN and TP concentrations in the inflow and outflow water were measured to calculate the TN and TP removal efficiencies, depending on whether or not a settling process was used. Water discharged from a bathroom, which was constructed for the experiment, was used as the raw water. The experiment that included a settling process was conducted twice, and the operating conditions were: aeration for 90 min, settling for 30 min, agitation for 15 min, and settling for 15 min for one experiment; and aeration for 150 min, settling for 45 min, agitation for 15 min, and settling for 15 min in the other. Operating conditions for the experiment that did not include a settling process were: aeration for 180 min and agitation for 60 min. The concentration of the mixed liquor suspended solids (MLSS) in the reactor was 3,500 mg/L, while the aeration rate was 121 L/min and the water production rate was 1.5 L/min. For the two experiments where a settling process was applied, the average TN removal efficiencies were 44.39% and 41.05%, and the average TP removal efficiencies were 47.85% and 46.04%. For the experiment in which a settling process was not applied, the average TN removal efficiency was 65.51%, and the average TP removal efficiency was 52.51%. Although the final nutrient levels did not satisfy the water quality standards of MEPC 227(64), the TN and TP removal efficiencies were higher when a settling process was not applied.

• Journal of the Korea Organic Resources Recycling Association
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• v.18 no.1
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• pp.89-97
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• 2010

In this study, to investigate the effect of chemical pretreatment for livestock wastewater, laboratory scale test for ozonation and linked treatment of sewage were conducted. and the results were obtained as follows. The ozonation of livestock wastewater showed the COD removal rate per hour to be 17%, 78% and 62% at each pH 4, 7 and 10, respectively. With transformation of NBDCOD to biodegradable BDCOD by ozonation, the ratio of SCODcr/TCODcr was increased from 26% to 38%. Accordingly, pretreatment of livestock wastewater affected to the biological post treatment process to elevate removal efficiency by transformation of nonbiodegradable mass to biodegradable mass. As the results of linked treatment of pre-ozonated livestock wastewater and sewage in the MLE process, the treatment efficiencies of TCODcr 93.8%, T-N 74.3%, T-P 89.7%, SS 97.5% were earned at 100% of internal recycle rate. When the internal recycle rate was increased to 150%, the treatment efficiencies of TCODcr 94.5%, T-N 54.5%, T-P 70.8%, SS 98.5% were earned. Also the removal efficiencies of TCODcr 92.6%, T-N 83.1%, T-P 81.9%, SS 98.5% were earned as the internal recycle rate was increased to 200%. Especially, nitrogen removal efficiency in the linked treatment showed 74.3%, 54.5%, 83.1% at 100%, 150% and 200% of internal recycle ratio, respectively, which revealed the tendency of higher removal efficiency than that of sewage treatment.

• Journal of Korean Society on Water Environment
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• v.24 no.1
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• pp.86-90
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• 2008

Water reuse of effluent is limited, due to bacteria and chromaticity or turbidity which may result in low perception of water quality. Consequently, this study showed a method in the reuse of treated wastewater by a diversified treatment method, with separation of centralized reformation of aeration tank into pre-treatment with minimum installation of facilities, and post-treatment, applying advanced oxidation treatment. A pilot plant experiment was performed using Sym-Bio process adopting an NADH Sensor without modification of the exiting aeration tank. The Dissolved Ozone Flotation process, which is an advanced oxidation process, to treat the remaining organics, nutrients, chromaticity, turbidity and bacteria. As a result in the Sym-Bio process, the biological treatment, even on the condition of single stage reaction tank, the treatment efficiencies of BOD, $COD_{Mn}$, $COD_{Cr}$, SS and T-N were 96.6%, 84.6%, 88.25%, 95.1% and 71.0%, respectively, while that for T-P was 25.0%, which required further treatment. In the Dissolved Ozone Flotation process, the advanced oxidation treatment, the treatment efficiencies of BOD, $COD_{Mn}$, $COD_{Cr}$, SS, T-N, T-P, chromaticity, turbidity, bacteria, coliforms were 78.9%, 34.6%, 28.7%, 48.0%, 70.4%, 82.4%, 84.0%, 74.5%, 99.8% and 99.4%, respectively.

• Journal of the Korean Society for Marine Environment & Energy
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• v.7 no.3
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• pp.116-121
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• 2004

Treatability tests were conducted to study the feasibility of EMMC process as a recycling-water treatment system in high density seawater aquaculture farm. To study the effect of organic and ammonia nitrogen loading rate on system performance, hydraulic retention time was reduced gradually from 12hr to 10min. The conclusions are can be summarized as follows. When the system HRT was reduced from 12hr to 2hr gradually, there was little noticeable change(reduction) in ammonia nitrogen removal efficiencies. However, removal efficiencies were decreased dramatically when the system was operated under the HRT of less than 2hr. In case of organics(COD), there was no dramatic change in removal efficiencies depending on HRT reduction. COD removal efficiencies were maintained successfully higher than 9％ when the system was operated at tile HRT of 10 min. System performances depending on media packing ratio in the reactors were also evaluated. There were little differences in each reactor performances depending on media packing ratio in reactor when the reactors were operated under the HRT of longer than 1hr. However, differences in reactor performances were considerably evident when the reactors were operated under the HRT of shorter than 1hr. When comparing reactor performance among 25％, 50％,7 5％ packed reactor, it can be judged that media packing ratio more than 50％ plays no significant role in increasing reactor performance. For this reason, packing the media less than 50％ is more reasonable way in view of economic. Such a tendency shown in COD removal efficiencies well agreed with the variation of ammonia-nitrogen removal efficiencies according to the media packing ratio in reactors at each HRT. Difference in effluent ammonia-nitrogen concentration between 50％ media packing reactor and 75％ media packing reactor was negligible. When comparing with the results of 25％ packing reactor, difference was not so great.

• Journal of Environmental Health Sciences
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• v.41 no.3
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• pp.203-215
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• 2015

Objectives: This study was designed to evaluate the filtration efficiencies and pressure drops of five commercial cloth masks (4 plate type, 1 cup type) in comparison to the performance of a class 1 disposable respirator (reference respirator). A further objective was to evaluate the effects of the number of layers and wash treatment independently on filtration efficiencies and pressure drops. Methods: Polydisperse NaCl aerosols were generated in an aerosol chamber and their concentrations were measured by an optical particle counter (OPC) in the size range of $0.3{\sim}10{\mu}m$ (five channels). Results: The filtration efficiencies of the five cloth masks and the reference respirator were D: 9.5%, C: 18.5%, E: 23.6%, A: 28.5%, B: 29.7% and R: 91.1%, respectively, and the pressure drops through them were C, D: 0.8 Pa, E: 1.7 Pa, B: 6.4 Pa, A: 42.7 Pa and R: 19.3 Pa, respectively. The filtration efficiencies of the cloth masks and reference respirator were below the class 1 respirator criterion (${\geq}94.0%$) of the Ministry of Employment and Labor (MOEL) and Ministry of Food and Drug Safety (MFDS). The pressure drops satisfied the class 1 respirator criterion (${\leq}70Pa$) of MOEL and MFDS. When the cloth masks were folded into two and four layers, the filtration efficiencies of cloth masks A, B, C, D (plate type) increased 1.7-4.6 times, and 2.3-6.8 times, respectively, compared to the efficiencies of the same products in a single layer. Pressure drops increased as the number of layers was increased. The filtration efficiency of cloth mask E with a liner was 1.3 times higher than that of the same mask without a liner, and the pressure drop was lower in the no-liner configuration. After a single washing, the filtration efficiencies of all the cloth mask products decreased 1.04-4.0 times compared to those of the same products intact. For the cloth masks C and E, their filtration efficiencies were significantly decreased after washing (p<0.05). The pressure drops of all cloth masks were 1.2-2.0 times lower after washing. Conclusions: The filtration efficiencies of the five cloth masks were below 30% and did not improve greatly by increasing the number of layers. After a single washing, their performances decreased. Considering the above and other issues identified with cloth masks, such as poor fit and stretched fibers through use, people should not expect protection against particulate matters from the cloth masks on the market.

• Journal of Environmental Science International
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• v.22 no.10
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• pp.1353-1361
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• 2013

The objectives of this paper are the characterization of the pretreatment of wastewater by microfiltration (MF) membranes for river maintenance and water recycling. This is done by investigation of the proper coagulation conditions, such as the types and doses of coagulants, mixing conditions (velocity gradients and mixing periods), pH, etc., using jar tests. The effluent water from a pore control fiber (PCF) filter located after the secondary clarifier at Kang-byeon Sewage Treatment Plant (K-STP) was used in these experiments. Two established coagulants, aluminum sulfate (Alum) and poly aluminum chloride (PAC), which are commonly used in sewage treatment plants to treat drinking water, were used in this research. The results indicate that the optimal coagulation velocity gradients (G) and agitation period (T) for both Alum and PAC were 200-250 $s^{-1}$ and 5 min respectively, but the coagulation efficiencies for both Alum and PAC were lower at low values of G and T. For a 60 min filtration period on the MF, the flux efficiencies ($J/J_0$ (%)) at the K-STP effluent that were coagulated by PAC and Alum were 92.9 % and 79.9 %, respectively, under the same coagulation conditions. It is concluded that an enhanced membrane process is possible by effective filtration of effluent at the K-STP using the coagulation-membrane separation process.

• Journal of Korean Society of Water and Wastewater
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• v.11 no.4
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• pp.63-70
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• 1997

The objectives of this study were to find out the optimum treatment conditions for removing nitrogen in a synthetic wastewater by using microorganisms immobilized with PVA-Freezing method. The samples used as influents to the laboratory scale treatment units were a synthetic wastewater. The experiments in this study were mainly directed to collect the data of nitrogen and organic matter removal efficiencies for the different hydraulic and internal recycle rates conditions, temperature and influent C/N ratios. The removal efficiencies of nitrogen and organic matters were investigated for the operating conditions of HRT 2~12hours, internal recycle rates 50~400%, temperatures $15{\sim}30^{\circ}C$ and C/N ratios 2.5~7.5. The adequate internal recycle rate for removing T-N and $BOD_5$ in the synthetic wastewater was found to be about 300% at the temperature of $30^{\circ}C$ when the ratio of carbon contents to the nitrogen (C/N) in the influent was around 5.5. Under these conditions, the final effluent concentrations of T-N and $BOD_5$ were 8.7 and 8.4 mg/l, respectively.

• Journal of environmental and Sanitary engineering
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• v.18 no.1
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• pp.15-22
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• 2003

Treatability tests were conducted using EMC process to study the feasibility of applying this process as recycling-water treatment system in high density seawater aquaculture farm. To study the effect of organic and ammonia nitrogen loading on system performance, hydraulic retention time of reactor was reduced gradually from 12hr to 10min. The conclusions are can be summarized as follows. When the system HRT was reduced from 12hr to 10 min gradually, there was little noticeable change(reduction) in ammonia nitrogen removal efficiencies until 2hr of HRT, however, removal efficiencies were decreased dramatically when the system was operated under the HRT of less than 2hr. In case of organics(COD), there was no dramatic deterioration in removal efficiencies depending on HRT reduction. More than 90% of removal efficiencies were maintained successfully when the system was operated at the HRT of 10 min. In case of system performance depending on media packing ratio in reactor, there was little difference in each reactor performance depending on media packing ratio in reactor when the reactors were operated under the HRT of longer than 1hr, however, differences in reactor performances were considerably evident when the reactors were operated under the HRT of shorter than 1hr. That is, the more reactor was packed, the better reactor performed. When comparing reactor performance among 25%, 50%, 75% packed reactor, it can be judged that media packing ratio more than 50% plays no significant role in increasing reactor performance. For this reason, packing the media less than 50% is more reasonable way in view of economic. Such a tendency well agreed with the variation of ammonia-nitrogen removal efficiencies according to the media packing ratio in reactors at each HRT. Difference in effluent ammonia-nitrogen concentration between 50% media packing reactor and 75% media packing reactor was negligible. When comparing with the results of 25% packing reactor, difference was not so great.

• Journal of The Korean Society of Grassland and Forage Science
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• v.10 no.2
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• pp.102-109
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• 1990

This experiment was carried out to study the effect of pure mineral nitrogen fertilizing on dry matter yield of grassland and the advisable mineral nitrogen amounts in long duration under practical conditions at the "Federal Institute for Agriculture in the Alps" in Austria. The application rates were 0, 30, 60,90 and 120 kg N/ha/cut, the cutting regimes 3-, 4-, 5- and 6-cuts/year. In order to explain the nitrogen-profitability were determined that 1 kg pure mineral nitrogen have to produce 8 - 16 kg DM/kg N in dependence on cutting regimes and requiring of nitrogen efficiencies. The results were as follows: 1. With only PK-fertilizaing average dry matter yields from 4.0 to 7.6 tons per ha and year were obtained. 2. Within all applied cutting regimes 60 kg min. Nlhalgrowth have proved to be the most efficient application rate witn 13 - 24 kg DM/kg N in dependent of cutting regimes. Comapred with only PK-treatment the DM yields increased by 3.9 - 4.7 t/ ha nad year. 3. By the sigmaformed process of Input-Output curve the highest marginal yield (the "most efficient" Ndressing rate) per ha and year was calculated: 152 kg N at 3-cut regimes, 204 kg N at 4-cut regimes, 220 kg N at 5-cut regimes and 240 kg N/ha/year at 6-cut regimes. 4. With required efficiencies of 16 and 12 kg DM/kg N 240 - 300 kg N per ha and year respectively would have to be applied at 3-cut regimes; with required efficiencies of 12 and 10 kg DM/kg N at 4-cut regimes the appropriate figures ranged from 320 to 420 kg N/ha and year, at 5- and 6-cut regimes and efficiencies of 10 and 8 kg DM/kg N results of 360 - 460 kg N and 380 - 500 kg N respectively were obtained. 5. At the relatively dry location Piber the highest dressing rates were needed in order to obtain the efficiencies from 8 to 16 kg DM/kg N, about 30 - 60 kg N/ha/year more than at the relatively moist location Admont.ist location Admont.

• Membrane Journal
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• v.23 no.1
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• pp.70-79
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• 2013

The $N_2$ back-flushing period (FT) and time (BT) were investigated in hybrid process of ceramic microfiltration and PES (polyethersulfone) beads loaded with titanium dioxide ($TiO_2$) photocatalyst for advanced drinking water treatment in viewpoints of membrane fouling resistance ($R_f$), permeate flux (J), and total permeate volume ($V_T$). As decreasing FT and increasing BT, $R_f$ decreased and J increased, and finally the maximum $V_T$ could be acquired at FT 10 min and BT 30 sec. In FT effect experiment, treatment efficiencies of turbidity and dissolved organic matters (DOM) were the highest at no back-flushing (NBF) because of dramatic membrane fouling. As result of BT effect, the treatment efficiencies were the maximum at BT 30 sec, which was different with the FT result. Because the photocatalyst beads could be cleaned effectively as decreasing FT and increasing BT, turbidity treatment efficiency increased a little from 95.4% to 97.5% as decreasing FT, and from 95.9% to 98.5% as increasing BT. Also DOM treatment efficiency increased from 70.8% to 80.6% as decreasing FT, and from 75.1% to 85.8% as increasing BT. The optimal condition, where the treatment efficiencies and $V_T$ were the maximum, should be FT 10 min and BT 30 sec in our experimental range.