• Journal of Korean Society on Water Environment
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• v.28 no.4
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• pp.505-511
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• 2012

While the existing sewage treatment facilities are mainly being operated by biological processes, winter-time efficiency improvement and additional phosphorus treatment equipment using chemicals have been required to follow the effluent criteria of TP (0.2, 0.3 and 0.5 mg/L for the zone of I, II and III respectively) and $BOD_5$ (5.0 mg/L) which is intensified from 2012 in Republic of Korea. We made an investigation into actual condition of biological treatment process and calculated the optimal chemical input amount by jar test of supernatant of secondary sedimentation tank to evaluate the process improvement for the intensified criteria. Ejector BAF system for removing TP, $BOD_5$ of sewage effluent was suggested. The concentration of TP from biological process is 0.3-0.8 mg/L, and the input amount of optimal chemical coagulant was above Al/P ratio of 3(1.9 mg/L as Al) to meet the criteria of TP for secondary treatment effluent. From the results of this experiment, the best Al/P ratio for Ejector BAF system was about Al/P ratio of 1, and LV of BAF process for intensified criteria of $BOD_5$ and TP was below 1.97m/hr.

• Journal of Korean Society of Water and Wastewater
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• v.31 no.2
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• pp.161-168
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• 2017

Microfiltration (MF) and Ultrafiltration (UF) membrane processes capable of producing highly purified water have been extensively applied as a pretreatment process in the wastewater reuse field with the improvement of membrane properties and resistance, development of operating protocols, and improvement of technologies of backwashing and physicochemical cleaning, and improvement of scale and antifoulants. However, despite of the development of membrane production and process technologies, fouling still remains unresolved. This study confirmed that foulants such as polysaccharides, proteins and humic substances existed in final treated effluent (secondary effluent) by fluorescence excitation emission matrix (FEEM) and fourier transform infrared spectroscopy (FTIR) analysis. In addition, when constructing ozone oxidation and coagulation processes as a hybrid process, the removal efficiency was 5.8%, 6.9%, 5.9%, and 28.2% higher than that of the single process using coagulation in turbidity, color, dissolved organic carbon (DOC), and UV254, respectively. The reversible and irreversible resistances in applying the hybrid process consisting of ozone oxidation and coagulation processes were lower than those in applying ozone oxidation and coagulation processes separately in UF membrane process. Therefore, it is considered possible to apply ozonation/coagulation as a pretreatment process for stable wastewater reuse by and then contributing to the reduction of fouling when calculating the optimal conditions for ozone oxidation and coagulation and then to applying them to membrane processes.

• Proceedings of the Korea Society of Environmental Toocicology Conference
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• 2003.10a
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• pp.27-27
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• 2003

Lake Texoma is located on the border of southern Oklahoma and northern Texas. It has 93,000 surface acres, and is a focus of the recreation, and farming industries in the region. There are potential stressors around the Lake Texoma watershed that may cause adverse ecological effects in the lake. System assimilative capacity (SAC) is the ability of abiotic and biotic processes to atteuniate the stressors. SAC Exceeded indicates potential of occuring adverse eco-effects. A number of representative chemical release sites and stressor sources in the surrounding watershed were characterized, and several impact sites having stressors sources, such as being near agriculture, landfills, housing areas, oil production fields and heavy use recreational activity, were selected for surface water, sediment, and groundwater monitoring. A paired reference site, having similar physical characteristics as its impact site, was also chosen based on its proximity to the impact site. Lake water samples were collected at locations identified as marina entrance, gasoline filling station, and boat dock at five marinas selected on Lake Texoma from September 1999 to December 2001. Paired water and sediment samples were also collected. Groundwater samples were collected at about 70 producing monitoring wells. Water quality parameters measured were inorganics (nitrate, nitrite, orthophosphate, ammonia, sulfate, and chloride), dissolved methane, total organic carbon (TOC) (or DOC), volatile organic compounds (VOCs) such as methyl tert-butyl ether (MTBE) and BTEX, and a suite of metals. Biotic communities were evaluated at impact and reference sites. Five basic components were measured; two terrestirial components (plants and bird comminitires) and three aquatic components (benthic inverbrates, litteral-zone fishes, ecosystem attribures). Potential impacts to these comminites were evaluated.

• Journal of Korean Society of Water and Wastewater
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• v.29 no.3
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• pp.337-345
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• 2015

Two step rapid filter system as a pre-treatment for the injected water into aquifer storage and recovery (ASR) in Korea was developed to reduce physical blockage and secure the volume of the injected water. First, single rapid sand filters with three different media sizes (0.4~0.7, 0.7~1.0 and 1.0~1.4 mm) were tested. Only two sizes (0.4~0.7 and 0.7~1.0 mm) satisfied target turbidity, below 1.0 NTU. However, they showed the fast head loss. To prevent the fast head loss and secure the volume of the injected water, a rapid anthracite filter with roughing media size (2.0~3.4 mm) were installed before a single rapid sand filter. As results, both the target turbidity and reduction of head loss were achieved. It was determined that the media size for a rapid sand filter in two step rapid filter system (i.e. a rapid anthracite filter before a rapid sand filter) was 0.7~1.0 mm. In addition, the effects of coagulant doses on the removal of natural organic matter (NOM), which might cause a biological clogging, were preliminarily evaluated, and the values of $UV_{254}$, dissolved organic carbon (DOC) and SUVA were interpreted.

• Journal of Korean Society on Water Environment
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• v.28 no.2
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• pp.255-268
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• 2012

Nonpoint source pollution has become a concern for water quality in the Han River system, especially during the high runoff events during the monsoon season. The patterns in nonpoint source runoff the relationships with land use, rainfall intensity, and stream nutrients concentrations were surveyed in 19 streams in the Han River watershed. The results show that the magnitude of NPS inputs of nutrients and sediment in the Han River watershed are of a serious concern. In the South Han River watershed, event mean concentrations (EMC) for biochemical oxygen demand (BOD), suspended sediment (SS), dissolved organic carbon (DOC), dissolved total phosphorus (DTP), total nitrogen (TN) Nitrate ($NO_3$-N) and total phosphorus (TP) were $1.94mg{\cdot}L^{-1},\;251mg{\cdot}L^{-1},\;2.75mg{\cdot}L^{-1},\;0.076mg{\cdot}L^{-1},\;2.82mg{\cdot}L^{-1},\;2.40mg{\cdot}L^{-1}$ and $0.232mg{\cdot}L^{-1}$, respectively. In the North Han River watershed, EMCs for BOD, SS, DOC, DTP, TN, $NO_3$-N and TP were $1.34mg{\cdot}L^{-1},\;172mg{\cdot}L^{-1},\;2.63mg{\cdot}L^{-1},\;0.032mg{\cdot}L^{-1},\;1.97mg{\cdot}L^{-1},\;1.55mg{\cdot}L^{-1}$ and $0.148mg{\cdot}L^{-1}$, respectively. The specific export coefficients of nutrient and sediments were much higher than those of other reports. Our study also found that the proportion of agricultural field area was significantly correlated with the EMCs for nutrients. Therefore, efforts to reduce NPS loading must focus on agricultural practices in the watershed. The relationships between land use and nutrient and sediment export found in this study can be used to derive estimates of runoff coefficients for agricultural field and as input data for modeling works and to develop total maximum daily load and best management practices in the Han River watershed.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.7
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• pp.492-497
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• 2014

This study investigated removal characteristics of organic matters in pretreatment and reverse osmosis (RO) membrane processes for seawater desalination. Also, the influence of the changes in characteristics of organic matters on the membrane fouling was assessed. The pretreatment processes included dual media filtration (DMF), pressurized membrane filtration (MF), and submerged membrane filtration (SMF). Turbidity, UV absorption at 254 nm, dissolved organic carbon, size exclusion chromatography (SEC), fluorescence excitation emission matrix (FEEM), and transparent exopolymer particles (TEP) in raw and processed waters were analyzed. Ions and minerals were not removed by any pretreatment process tested, but were removed over 99% through the RO membrane process. Hydrophobic organics, which can play major role in organic membrane fouling, were relatively readily removed compared with hydrophilic ones. Membrane based pretreatment such as MF and SMF exhibited better removals of organics than conventional DMF. As the levels of organics in pretreated water decreased, the silt density index (SDI) decreased. MF treated water exhibited the lowest SDI value; this is possibly due to the lowest TEP ($0.1-0.4{\mu}m$) concentrations.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.8 no.1
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• pp.44-57
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• 2003

Seasonal variations of bacterial abundance and production, heterotrophic nanoflagellate (HNF) abundance and HNF ingestion rates on bacteria using FLB together with environmental variables were investigated at intervals of a month in Kyeonggi Bay from December 1991 to November 1998. Bacterial abundance and production ranged from 0.38$\times$10$^{9}$ ~ 3.25$\times$10$^{9}$ cells 1$^{-1}$ (average 1.19$\pm$0.69$\times$10$^{9}$ cells 1$^{-1}$ ) and from 1.51 to 20.4 cells 1$^{-1}$ h$^{-1}$ (average 6.04$\pm$ 1.88$\times$10$^{6}$ cells 1$^{-1}$ h$^{-1}$ ), respectively. Bacterial abundance and production showed no differences at the high tide and low tide, and bacterial abundances were not different with depth, but bacterial production decreased with depth. Seasonal variation of bacterial abundance showed almost similar fluctuation pattern to those of DOC (dissolved organic carbon). HNF abundances ranged from 388 to 4,374 cells ml$^{-1}$ (average 1,344$\pm$130 cells ml$^{-1}$ ), were high in March, April, July and August. HNF abundance showed no difference between the high tide and low tide, and was not different with depth. The ingestion rates of HNF on bacteria were 1.0 to 6.3$\pm$10$^{6}$ bacteria 1$^{-1}$ h$^{-1}$ (average 3.12$\pm$0.55$\times$10$^{6}$ bacteria 1$^{-1}$ h$^{-1}$ ), resulting ingestion rates of HNF removed 19.4 to 141.4 %(average 62.3$\pm$12.0%) of bacterial production. Ingestion rates and grazing pressure of HNF on bacteria showed high correlation with HNF abundance. Although we cannot exactly discussion about seasonal variation of bacteria community in this study area where physical and chemical parameters were very complex, the results indicate that bacterial abundance and production were mainly controlled by resources supply as dissolved organic carbon and chlorophyll-a(bottom-up) except March which bacterial abundance and production uncoupled chlorophyll-a because of low dissolved organic carbon and low temperature, and were controlled by HNF grazing pressure(top-down) in the warm seasons except the winter.

• Proceedings of the Korean Aquaculture Society Conference
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• 2003.10a
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• pp.127-127
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• 2003

Haptophyta(이하 하프토조로 표기)는 그 일부종이 toxin을 가지며, 더욱이 이들 종들이 원인 생물로 발생하는 bloom으로 인한 경제적 피해 발생 등으로 인해 최근 여러 나라에서 활발한 연구가 이루어지고 있다. 남해안 일대의 몇몇 어ㆍ패류 양식장에서 이용하고 있는 식물먹이생물 및 동물먹이생물의 배양수조 내에서 배양을 목적으로 하는 먹이생물 이외의 혼재 생물의 종류를 조사하던 중 Haptophyta의 Prymnesium속 생물이 혼재하고 있는 것을 발견하였으며, 혼재된 Prymnesium은 양식 패류의 인공 종묘 생산 과정에서 사육 치패의 먹이로 이용되는 식물먹이생물 Isochrysis galbana의 증식을 크게 억제하였고, 더욱이 Prymnesium이 혼재된 Isochrysis galbana를 인공 종묘생산 중이던 치패에 투이한 결과 치패 모두가 폐사에 이르는 것을 관찰하였다. 이에 Isochrysis galbana의 배양 수조내에 Prymnesium이 혼입 하였을 경우 Isochrysis galbana의 증식양상을 알아보기 위해, Isochrysis galbana의 세포밀도를 5,440,000cells/ml로 하고 Prymnesium의 세포밀도를 10,000cells/ml로 하여 혼합 배양한 결과 배양개시 1일 후의 각 세포밀도는 Isochrysis galbana가 1,040,000cells/ml로 급격히 저하하였으며, 이와는 달리 Prymnesium은 50,000cells/ml로 증가하였다. 이들 종 각각의 증가 및 감소추세는 계속되어 배양개시 5일 후에는 Isochrysis galbana가 530,000cells/ml로 처음 배양당시 세포수의 90% 이상 감소하였고, Prymnesium은 43,333cells/ml로 4배 이상 증가하였다. 이 실험에서 Isochrysis galana의 세포수가 감소하는 이유는 정확히 알 수는 없으나, 하프토조의 일부 종에서는 광합성을 통한 유기물합성 이외에도 외부로부터의 DOC(dissolved organic carbon)를 직접 배양수로부터 취하거나 또는 영양염 제한 조건에서는 food particle을 섭취하는 경우가 있는 것으로 보고되고 있다. 한편, 이들 Haptopyta가 양식장에서 이용되어지는 해수를 통해 유입되는지를 알아보기 위해 모래여과조를 통과한 해수를 플랑크톤 배양용 배지의 첨가 없이 배양한 결과, Haptophyta의 Prymnesium, Chrysochromulina 및 Phaeocystis 둥의 수 종이 출현하였으며, 일부 종의 경우는 일정기간 지속적으로 배양되어짐을 알 수 있었다.

• Membrane and Water Treatment
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• v.9 no.6
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• pp.473-480
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• 2018

The effect of three iron-based adsorbents pre-depositing on ultrafiltration membrane for humic acid (HA) removal and membrane fouling was investigated. The result showed that pre-depositing adsorbents on membrane could not only reduce membrane fouling but also enhance HA removal. The flux was related to the adsorbent dosage and the optimal dosage for pre-deposition was $35.0g/m^2$. The dissolved organic carbon (DOC) removal of HA was 38.3%, 67.3% and 41.1% respectively when pre-deposited $35.0g/m^2$ $FeO_xH_y$, $MnFe_2O_4$ and $Fe_3O_4$ on membrane. Different adsorption effect of adsorbents on HA contributed to increasing of the flux at different level. Zeta potential of three adsorbents all decreased after adsorbed HA. The adsorption capacity of the three adsorbents was $FeO_xH_y$ > $MnFe_2O_4$ > $Fe_3O_4$. Atomic Force Microscopy (AFM) measurement showed the thickness of pre-deposition layers formed by different adsorbents was different. The scanning electron microscope (SEM) detection showed the morphology and compactness of pre-deposition layers formed by different adsorbents was different.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.4
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• pp.412-418
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• 2007

The purpose of this study was to determine the several factors for affecting chlorine disinfection by-products(DBPs) characteristics by reacting chlorine and organic matters in the aquatic phase. The results of this research yield the following specific conclusions: The concentration of trihalomethanes(THMs) was increased with increasing dissolved organic carbon(DOC), and a trend of THMs formation was parabolic with increasing organic matters. Formations of THMs increased straightly for the first 4 hours and the amounts of producted THMs for the 30 minutes were up to $25\sim43%$ in the entire experiment periods(168 hours). When keeping up the concentration of organic matters at constant and changing that of bromide, the quantity of formed THMs did not show distinguished difference with the reaction times. THMs were gradually increased at $4^{\circ}C$ even though a reaction phase was parabolic formation(PF) phase. However, THMs were increased rapidly in the instantaneous formation(IF) phase and then became slowdown in the PF phase between $20\sim35^{\circ}C$. THMs were gradually increased although entering in the PF phase at pH 5. However, THMswere increased rapidly in the IF phase and then became slowdown in the PF phase at pH 7 and pH 9, and these treads were much more clear at pH 9 than at pH 7.