• Korean Journal of Ecology and Environment
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• v.33 no.1 s.89
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• pp.23-30
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• 2000

n situ sediment oxygen demand (SOD), which takes place with the uptake of dissolved oxygen for biological metabolism and chemical oxidation in sediments, ranged from 1.57 to $12.55\;mg\;O_2\;m^{-2}\;h^{-1}$ in onshore of Lake Paldang from April to November 1999. SOD was influenced by the amount of organics and oxygen diffusion. Comparing the oxygen demands partitioning between overlying water and sediment during initial phase, SOD accounted for $63.8{\sim}94%$ of total oxygen demand in Lake Paldang. The chemical SOD and nitrogenous oxygen demand ranged $1.2{\sim}18.3%$ and $8.3{\sim}51.7%$ of total SOD, respectively. This result indicated that SOD in Lake Paldang occurred mainly by aerobic respiration and nitrification. Although the flow velocity could increase SOD within a certain limit, the effect of sediment depth on SOD was dependent on physicochemical properties of the sediment. This study showed that SOD can represent a significant portion of the total oxygen up-take in Lake Paldang. Therefore, the assessment of SOD might be necessary for the control of water quality.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.2
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• pp.177-183
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• 2005

The effluent quality is directly affected by the separation of biological solids in a final clarifier because the majority of discharged $BOD_5$ and SS are virtually dependent on the results of biological solids in the sedimentation tank effluent. If a final clarifier is effectively designed and operated, the desired goal of clarification for wastewater can be achieved together with the cost reduction in the treatment of wastewater. To this end flow characteristics and the removal efficiency of SS are numerically investigated especially by the change of the inlet position and the installation of baffle to improve the performance of a rectangular final clarifier. The 2-D computer program developed in a rectangular coordinates has been successfully validated against experimental residence time distribution(RTD) curves obtained by tracing radio-isotope. The lowering of the inlet position weakens the density current and induces the settling of SS in the front zone of a clarifier. Thus the decreased traveling distance of the sludge increases the removal efficiency of SS in the effluent. The inlet baffle installed in the front region of clarifier prevents the short circuiting flow and induces to flow into the dense underflow, which eventually improves the effluent quality. In the case of lower inlet position, however, installation of baffle results in degradation of effluent quality. Consequently it is strongly recommended that in-depth numerical study be performed in advance for optimizing a clarifier design and retrofitting to improve effluent quality in a final clarifier.

• Proceedings of the Korean Society of Environment and Ecology Conference
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• 2003.10a
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• pp.105-126
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• 2003

In Korea most of annual rainfall is concentrated in several episodic heavy rains during the season of summer monsoon and typhoon. Because of uneven rainfall distribution many dams have been constructed in order to secure water supply in dry seasons. The Han River system has the most dams among Korean rivers, and the river is a series of dams now. Reservoirs need different strategy of water quality control from river water. Autochthonous organic matter and phosphorus should be the major target to be controlled in lakes. In this Paper some problems are discussed that makes efforts of water quality improvement ineffective in lakes of Korea, even after the substantial investment to wastewater treatment facilities.1) Phosphorus is the key factor controlling eutrophication of lakes and the reduction ofphosphors should be the major target of water treatment. However, water quality management strategy in Korea is still stream-oriented, and focused on BOD removal from sewage. Phosphorus removal efficiency remains as low as 10-30%, because biological treatment is adopted for both secondary treatment and advanced treatment. The standard for TP concentration of the sewage treatment plant effluent is 6 mgP/l in most of regions, and 2 mg/l in enforced region near metropolitan water intake point. TP in the effluents of sewage treatment plants are usually 1-2 mg/1, and most of plants meet the effluent regulation without a further phosphorus removal process. The generous TP standard for effluents discourages further efforts to improve phosphorus removal efficiency of sewage treatment. Considering that TP standard for the effluent is below 0.1 mg/l in some countries, it should be amended to below 0.1 mg/l in Korea, especially in the watershed of large lakes.2) Urban runoff and combined sewer overflow are not treated, even though their total loading into lakes can be comparable to municipal sewage discharges on dry days. Chemical coagulation and rapid settling might be the solution to urban runoff in regard of intermittent operation on only rainy days.3) Aggregated precipitation in Korea that is concentrated on several episodic heavyrains per year causes a large amount of nonpoint source pollution loading into lakes. It makes the treatment of nonpoint source discharge by methods of other countries of even rain pattern, such as retention pond or artificial wetland, impractical in Korea.4) The application rate of fertilizers in Korea is ten times as high as the average ofOECD countries. The total manure discharge from animal farming is thought to be over the capacity of soil treatment in Korea. Even though large portion of manure is composted for organic fertilizer, a lot of nutrients and organic matter emanates from organic compost. The reduction of application rate and discharge rate of phosphorus from agricultural fields should be encouraged by incentives and regulations.5) There is a lot of vegetable fields with high slopes in the upstream region of the HanRiver. Soil erosion is severe due to high slopes, and fertilizer is discharged in the form of adsorbed phosphorus on clay surface. The reduction of soil erosion in the upland area should be the major preventive policy for eutrophication. Uplands of high slope must be recovered to forest, and eroded gullies should be reformed into grass-buffered natural streams which are wider and resistant to bank erosion.

• Journal of Environmental Health Sciences
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• v.36 no.3
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• pp.229-235
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• 2010

Efforts to evaluate water pollution using indicator microorganisms have been underway for decades, and driven by research on water purity control applications, water quality criteria are growing more and more strict. Furthermore, recent reports indicate that high concentrations of antibiotics are not absorbed, and are present in excrement from animals and humans dosed with unnecessarily high levels of antibiotics. This has emerged as very important issue from the standpoint of being an ecological and health hazard. In this study, water pollution was analyzed through physicochemical and microbiological means, and antibiotic resistance in indicator microorganisms was assessed. In physicochemical analysis, biochemical oxygen demand (BOD)$_5$ and chemical oxygen demand (COD)$_{Mn}$ evaluation showed that pollution by organisms was highest at the G1 location with a high human population, and the DP location which has many livestock-containing households. The indicator organism levels at the G1 location were: Total Coliforms (1205 colony forming units (CFU)/100 ml), Fecal Coliforms (270 CFU/100 ml), Escherichia coli (253 CFU/100 ml) and Fecal Streptococci (210 CFU/100 ml), while for the DP location levels were: Total Coliforms (1480 CFU/100 ml), Fecal Coliforms (438 CFU/100 ml), E. coli (560 CFU/100 ml), and Fecal Streptococci (348 CFU/100 ml). Levels of fecal indicator microorganisms such as Fecal Coliforms, E. coli and Fecal Streptococci were high at all locations in the fall (the period after the rainy season), and the yearly distribution was similar between these organisms. If the number of livestock-containing households was high, almost all strains of E. coli (as distinct from the other indicator organisms) showed resistance to antibiotics, with the degree of resistance varying between areas. E. coli strains from the OY area in particular, which has a high population density, showed strong resistance to AM10 and Va30. While strong antibiotic resistance was observed overall at the DP and OY locations, no resistance was observed at the EB location.

• Journal of Korean Society on Water Environment
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• v.29 no.6
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• pp.847-851
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• 2013

This study describes the results of an investigation conducted in order to characterize the quantity and quality of individual gray water streams. The highest pollutants concentrations were found in gray water originating from kitchen and laundry with $BOD_5$ concentrations in the order of several hundreds $mgl^{-1}$. In contrast to this, bathroom was regarded as a major contributor of Escherichia coli. Laundry gray water has higher pH, sodium, sulfate, anionic surfactants. Individual gray water types had different contribution to the overall daily discharge and relative pollutants loads. Kitchen, although accounting for only 13% of the total volume, was identified as a major source of microorganisms with Total coliforms, Escherichia coli, Fecal streptococcus taking up 82%, 74% and 54% of their relative daily load, respectively. The laundry gray water, although being responsible for 36% of the total daily discharge, was established as a significant contributor of sodium, sulfate, anionic surfactants and TOC (70%, 72%, 84% and 52%, respectively). But the laundry gray water was a minor source of microorganisms. Bathroom was found to be a major gray water producer, making up 51% of the flow, but constituted less than 50% of the relative daily load in most cases.

• Korean Journal of Environmental Biology
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• v.38 no.4
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• pp.678-690
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• 2020

In this study, the histological changes of Zacco platypus exposed to discharge from a Wastewater Treatment Plant (WTP), which is a point source, for a long time (2 to 3 years) were compared to the same species at a reference site (Ref.). Overall, tissues displayed various lesions in samples obtained at the point where discharge water from the point source was mixed. In the skin tissue, mucus cells from the epithelial layer expanded to the multilayered epithelium, indicating the immune system was activated. Epithelial cell detachment and proliferation were most prominent in the gills, which may have adversely affected circulation and respiration. Our data suggest immune system collapse was due to stimulation by aquatic substances. Both the fish phase analysis and the water quality analysis demonstrated depreciated conditions at the point source as compared to the reference stream, supporting the histological health evaluation results. These data together suggest a histological approach can also be used to assess water quality, and to an even higher degree when combined with other existing methods. Given the presented evaluation, improvement in the water quality of water discharged from WTP's is required.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.468-468
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• 2023

최근 급격한 기후변화에 의한 이상가뭄 발생 등을 대비하기 위한 비상용수 또는 대체 수자원으로서의 지하수 개발수요가 증가함에 따라 기저유량 확보 및 수질개선 방안을 수립하는 것은 지속가능한 수자원 이용 관리 측면에 있어서 매우 중요하다. 국내 지하수 사용에 따른 하천유량의 변동에 관한 연구는 활발히 진행되었으나, 실질적으로 적용가능한 지하수 저감 방안 및 지하 수질개선방안에 대한 연구는 미비한 실정이다. 이에 본 연구에서는 바이오차를 이용하여 시험포를 설계 및 시공하였으며, 실내 인공강우 실험을 통해 지하 침투수 확보 능력 및 수질개선 효과를 평가하였다. 대조구는 폭 1 m × 길이 1 m × 깊이 0.60 m로 시공하였으며, 바이오차 시험포는 폭 1 m × 길이 1 m, 시험포 상단과 하단 각 0.10 m씩 대조구와 동일한 흙으로 채웠으며, 그 사이 0.40 m만큼은 바이오차를 채워서 시공하였다. 시험의 정밀도를 높이기 위해 동일한 조건으로 대조구와 바이오차 시험포 각 2개씩, 총 4개의 시험포를 시공하여 실내 인공강우 실험을 진행하였으며, 시험포에서 발생한 직접유출수와 기저유출수를 이용하여 바이오차의 지하 침투량 확보 및 수질개선효과를 분석하였다. 시험포 완공 후 총 2번의 실내인공강우 실험 결과 대조구에서 발생한 직접유출량은 총 0.214 m³, 바이오차 시험포에서는 총 0.194 m³로 대조구 대비 총 직접유출량 저감효과는 9.4%로 나타났다. 기저유출의 경우 바이오차 시험포(0.036 m³)에서 대조구(0.003 m³) 대비 약13배 많은 양의 기저유출수가 발생한 것으로 나타났다. 각 시험포에서 발생한 유출수의 오염부하를 산정해 대조구 시험포 대비 바이오차 시험포에서 발생한 직접유출수의 오염부하 저감효과를 분석한 결과 BOD₅ 항목과 COD_Mn 항목, 그리고 TOC 항목의 경우 26.3%과 22.0%, 그리고 27.6%로 저감 된 것으로 나타났으나, SS 항목과 T-N 항목, 그리고 T-P 항목의 경우 저감효과가 없는 것으로 나타났다. 이와 같이 바이오차는 지하 침투수 확보 능력은 효과적인 것으로 나타났으나, 직접유출수의 수질개선 효과는 미비한 것으로 나타났다. 그러나 바이오차의 지하 침투량 및 수질개선 효과는 바이오차 생산 시 사용된 열분해 방식, 사용된 바이오차의 양 등에 따라 편차가 클것으로 판단되며, 바이오차의 생산 방법, 토양 흡착 기간, 바이오차의 양 등 다양한 조건에서의 모니터링을 통해 정량화 되어야 할 것으로 판단된다.

• Journal of Marine Bioscience and Biotechnology
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• v.16 no.1
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• pp.63-86
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• 2024

This study analyzed the distribution, diversity, and density variation of algal clusters in a freshwater reservoir from an oceanic island and a traditional inland water system to gain insights on future marine freshwater resource management. In the Paldang water system (Han River), despite the upstream Paldang Dam and the downstream Jamsil underwater reservoir being in the same meteorological zone, their algae density patterns varied inversely. The distinct algal cluster structure (diversity/dominance) of Paldang was altered in the downstream reservoir, suggesting that physical devices aid algae management in traditional water systems. In contrast, 24 out of 35 genera (63.2%) identified in the Jeolgol Reservoir (Baeknyeong Island) were unique, lacking regulatory mechanisms, and existing in a complex ecotone. The desmid Chlorophyceae Cosmarium, adapted to higher photosynthetic stress and low temperatures, dominated in January (38.04%) and August (86.45%) during the periods of extreme photosynthetic stress. Jeolgol's annual algal cluster structure (H' 2.097; D 0.259; S' 35) demonstrated higher stability than Paldang (H' 1.125; D 0.448; S' 13) and the Jamsil underwater reservoir (H' 1.078; D 0.469; S' 12), maintaining an H' above 1.5 even during midwinters. No evidence of TN/TP inflow from surrounding soils was observed, even during torrential rainfalls, with phosphorus being the limiting factor for algal growth. TOC, BOD, chlorophyll-a, and turbidity peaked during Cosmarium bloom. Future climate change is expected to cause fluctuations in algal clusters and related water quality factors. The complex transitional nature of the Jeolgol Reservoir, its algal diversity, and the interspecies interactions contribute to the high stability of its algal community.

• Korean Journal of Ecology and Environment
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• v.38 no.3 s.113
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• pp.372-381
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• 2005

This study was conducted to test the efficiency of water quality improvement using the dissolved air flotation (DAF) technique in a shallow eutrophic reservoir. The application of DAF was followed by the addition of a chemical coagulant (poly aluminum chloride; PAC). The experiment was conducted in the mesocosm scale (wide ${\times}$ length ${\times}$ depth: 6 m ${\times}$ 6 m ${\times}$ 3 m). Suspended solids (SS) and volatile SS (VSS) concentration decreased by 54 ${\sim}$ 71% and 57 ${\sim}$ 79% of the initial concentrations, respectively. Total phosphorus and Chl- a concentration also decreased by 74 ${\sim}$ 92% and 54 ${\sim}$ 98%, respectively. BOD decreased by>86% while COD decrease ranged 29 ${\sim}$ 63%. Dissolved inorganic P (DIP) and dissolved total P (DTP) concentration decreased by 34 ${\sim}$ 88% and 62 ${\sim}$ 88%, respectively. After DAF application further onto the sediment, DIP-release rates from the sediment decreased by 17% (0.82 ${\to}$ 0.68 mg $m^{-2}$$day^{-1}$ in the oxic condition and 23% (2.27 ${\to}$ 1.76 mg $m^{-2}$$day^{-1}$) in the anoxic condition, compared to the release rate from the untreated sediment. DTP-release rate from both the oxic and anoxic sediments also decreased by 33% (5.62 ${\to}$ 3.78 mg $m^{-2}$$day^{-1}$) and 20% (6.23 ${\to}$ 4.99 mg $m^{-2}$$day^{-1}$), respectively. These results suggest that the DAF application both to the water column and onto the sediment be effective to improve water quality by removing particulate matters in the water column as well as reducing P-release from the sediment.

• Korean Journal of Ecology and Environment
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• v.40 no.2
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• pp.254-263
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• 2007

The objective of this study was to evaluate biological water quality using fish assemblages in Nakdong River watershed. We selected 6 sites along the main axis of the river and evaluated the Index of Biological Integrity (IBI), Qualitative Habitat Evaluation Index (QHEI) and chemical water quality during July 2004${\sim}$March 2006. For the study, we applied the 10 metric IBI model, which was developed for national biological water quality criteria. Nakdong River's IBI value averaged 20.8 (n=14) during the study which means poor biological water quality. Physical habitat health at all sites, based on QHEI model, was measured as 110, indicating fair${\sim}$good condition. The habitat health varied depending on the locations sampled. Habitat health in sites 1 and 6 was judged as good, while the health in sites 3 and 4 was $poor{\sim}fair$. Especially, we found the metric values of $M1{\sim}M5$, M7, M10 were low in sites 3 and 4 compared to other sites. In these sites, thus, habitat restoration of substrate composition, riffles, and bank vegetation may be necessary. In the mean time, chemical water quality, based on BOD, COD, TSS, and nutrients, had no large spatial and temporal variations. Overall data analysis indicated that site 3 was largely impacted by the polluted-tributary, Keumho River and the downstreams showed better water quality due to the dilution of the polluted river water by Nam River and Hwang River.