• Journal of Korean Society of Water and Wastewater
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• v.34 no.6
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• pp.473-480
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• 2020

High-pressure membrane system like nanofiltration(NF) and reverse osmosis(RO) was investigated as a part of water treatment processes to produce high quality potable water with low organic matter concentration through membrane module tests and design simulation. River water and sand filtration permeate in Busan D water treatment plant were selected as feed water, and NE4040-90 and RE4040-Fen(Toray Chemical Korea) were used as NF and RO membranes, respectively. Total organic carbon(TOC) concentrations of NF and RO permeates were mostly below 0.5 mg/l and the average TOC removal rates of NF and RO membranes were 93.99% and 94.28%, respectively, which means NF used in this study is competitive with RO in terms of organic matter removal ability. Different from ions rejection tendency, the TOC removal rate increases at higher recovery rates, which is because the portion of higher molecular weight materials in the concentrated raw water with increasing recovery rate increases. Discharge of NF/RO concentrates to rivers may not be acceptable because the increased TDS concentration of the concentrates can harm the river eco-system. Thus, the idea of using NF/RO concentrate as the raw water for industrial water production was introduced. The design simulation results with feed water and membranes used in this work reveal that the raw water guideline can be satisfied if the recovery rate of NF/RO system is designed below 80%.

• Journal of Environmental Science International
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• v.2 no.4
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• pp.317-324
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• 1993

Effluent recycling effect on UASB reactor performances is known as an important operational factor. In the present study, the possibility of intermittent recycle in UASB process for saving the power consumption was examined at different organic loading and various operational modes in recycle time period. The organic removal efficiencies of the reactors operated with the intermittent effluent recycle were considerably higher compared to those without the effluent recycle. In the intermittent recycle mode, the organic removal efficiencies slightly decreased as the non-recycle time period in the operational mode increased. Proper ratio of recycle and non-recycle time period in the mode seemed to be required to prevent the produced biogas from accumulation in the sludge bed, which caused dead zone in the reactor and sludge loss when the gas was escaped from the bed at the certain pressure.

• Journal of Environmental Science International
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• v.8 no.2
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• pp.221-225
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• 1999

This study was conducted to evaluate the treatment efficiency including reaction kinetics and hydraulic characteristics of food processing wastewater by using an ejector-type aeration system (ETAS) in activated sludge process. The oxygen transfer efficiency in ETAS can be changed in accordance with the depth of reactor. However, the optimum air velocity was found less than 1.82 m/hr at a superficial liquid velocity of 634 m/hr. The ETAS process showed higher organic material removal efficiency than that of the existing activated sludge process under hydraulic detention time 6 to 12 hours. This process, which can maintain MLVSS highly, is able to have high organic material removal efficiency at short HRT and deal with variable organic material loading.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.04a
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• pp.183-185
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• 2004

In this study, the combined electrokinetic and ultrasonic remediation technique, ultrasonically enhanced electrokinetic technique, was studied for the removal of heavy metal and organic substance in contaminated soils. The electrokinetic technique has been applied to remove mainly the heavy metal and the ultrasonic technique has been to remove mainly organic substance in contaminated soil. The laboratory soil flushing tests combined electrokinetic and ultrasonic technique were conducted using specially designed and fabricated devices to determine the effect of these both techniques. A series of laboratory experiments involving the simple, electrokinetic, ultrasonic, and electrokinetic & ultrasonic flushing test were carried out. A soil admixed with sand and kaolin was used as a test specimen, and Pb and ethylene glycol were used as contaminants of heavy metal and organic substance. An increase in out flow, permeability and contaminant removal rate was observed in electrokinetic and ultrasonic flushing tests. Some practical implications of these results are discussed in terms of technical feasibility of in situ implementation of electrokinetic ultrasonic remediation technique.

• Journal of Environmental Health Sciences
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• v.27 no.3
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• pp.43-48
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• 2001

Terephthalic acid and ethylene glycol resulting form the weight-reduction process of polyester make trouble in the operation of activated sludge process. Also, polyester weight loss wastewater shows high pH, high organic strength and wide variation of organic loading. Therefore, this study was conducted in order to improve treatment efficiency by activated sludge process with Pseudomonas sp degrading components of polyester weight loss wastewater. The CO $D_{Mn}$ and BO $S_{5}$ of the waste wastewater were 560~3,000 mg/$\ell$ and 8000~3,000 mg/$\ell$, respectively. pH was 11.8~12.3. COD removal efficiency by activated sludge-coagulation process with Pseudomonas sp was 94.1~95.8% for 35 hr of hydraulic retention time. Total organic carbon removal efficiency was 97.1%. Ethylene glycol and terephthalic acid in the wastewater were completely degraded during 32 hr of hydraulic retention time.e.

• Journal of Environmental Health Sciences
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• v.27 no.3
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• pp.27-34
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• 2001

This paper discussed the shape effect of ceramic support carrier in order to facilitate biomass immobilization. The shape of ceramic support carrier was modified hollow pipe type into hollow gear type. After seeding, microorganisms were attached in crevices where protection from shear forces or surfaces where easy to contact with support carrier surface. In case of hollow gear type carrier, initial attachment rate was faster than that of hollow pipe type and obtained thick biofilm. Synthetic wastewater(COD:75~880 mg/L, organic loading rate:0.36~4.22 kgCOD/㎥.d) was treated aerobic fixed bed biofilm reactor where 100% of the volume was filled with the ceramic carrier. COD removal efficiency of reactor filled with gear type support carrier was a little high withing 70 days, and then showed similar removal efficiency. It was found that highly loaded operation with up to 4.22 kgCOD/㎥.d was possible in both reactor. Total biomass amounts of pipe type was higher than gear type, however, attached biomass of gear type was higher than that of pipe type.

• Environmental Engineering Research
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• v.19 no.1
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• pp.1-8
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• 2014

Natural organic matter (NOM) is a primary component of fouling in low-pressure membrane filtration, either solely, or in concert with colloidal particles. Various preventive measures to interfere with NOM fouling have been developed and extensively tested, such as coagulation, oxidation, ion exchange, carbon adsorption, and mineral oxide adsorption. Therefore, this article aims to conduct a literature review covering the topics of low-pressure membrane processes, NOM characteristics and fouling behaviors, and diverse fouling control strategies. In-depth explanations and discussion are made regarding why some treatment options are able to remove NOM from source water, but do not reduce fouling. This review provides insight for hybridized membrane processes with respect to NOM removal and fouling mitigation in water treatment.

• Journal of Ecology and Environment
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• v.35 no.2
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• pp.99-109
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• 2012

Litterfall dynamics in forests are assessed by estimating biomass production and decomposition. However, there have been few studies on how litter dynamics impact the health and management of ecosystems. Here, a new approach to measure and assess ecosystem function is presented based on conventional methods using littertraps, litterbags, and the mass on the forest floor. To assess the status of litter dynamics, the decay rate (k) was estimated from a litterbag experiment, and removal rates ($k_i$) were determined from mass balance on the forest floor at 21 sites on three mountains in South Korea. The $k_3$ (organic mass ratio of $O_i$ and $O_e+O_a$ + A horizons in November) values in an equilibrium state in South Korea were within the range of $k{\pm}0.174$ when considering the annual variation of litterfall production. This study also suggests that sampling sites for these types of studies should be in the middle, not at the ends, of steady slopes on the forest floor.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.09a
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• pp.231-234
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• 2004

The experiments on some organic materials used in SAPS are carried out for the better sulfate reduction efficiency and the longer lifetime. Organic materials include spent mushroom compost, sewage sludge, oak chip compost and the combination of there. Reactors with mushroom compost, sewage sludge, the mixture of mushroom compost and sewage sludge, and the mixture of mushroom compost and oak chip compost maintained pH higher than 6.0. Reactors with mushroom compost, the mixture of mushroom compost and sewage sludge, and the mixture of mushroom compost and oak chip compost maintained reduction condition. Reactors with sewage sludge, oak chip compost and the mixture of sewage and oak chip compost produced COD less than 2,000ppm. Reactors with sewage and the mixture of mushroom compost, sewage sludge, oak chip compost showed about 60% of sulfate removal ratios.

• Journal of environmental and Sanitary engineering
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• v.17 no.3
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• pp.89-98
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• 2002

The changes of conventional clarification process and an increase in treatment cost are required to meet increasingly stringent regulations related to the treated water quality. Although many enhanced coagulations have introduced to improve organic matter removal, the results to remove color, nitrogen and phosphorus as well as organic material have not been very efficient yet. The removal of waste matters such as SS, organic matter, color and turbidity contained in dyeing wastewater was carried out by using the combination of calcium hydroxide and magnesium sulfate. The flocculation was investigated as a function of coagulant dose, pH, mixing time, settling time and coagulant addition modes such as the sequential addition of the two coagulants and the simultaneous addition of them. The flocculation by the combination of calcium hydroxide and magnesium sulfate was compared with that by aluminum sulfate. The mechanism of flocculation was investigated as well. About 84% of color in dyeing watewater was removed by flocculation with combination of calcium hydroxide and magnesium sulfate.