• 상하수도학회지
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• 제12권1호
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• pp.81-87
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• 1998

The possibility of collision of two particles slowly settling one after another in water can be described using the collision efficiency factor in differential sedimentation (${\alpha}_{DS}$). ${\alpha}_{DS}$ was found to be a function of several parameters particle size, particle size ratio, Hamaker constant, density of liquid and particle, gravity acceleration. Previous researches were limited to the case when there is no electric repulsion assuming that the suspension is destabilized. In this paper, ${\alpha}_{DS}$ is calculated for the stabilized condition. The relative trajectory of two particles are calculated including hydrodynamics, attraction and repulsion forces. Ionic strength and surface potential significantly affect the collision possibility of two settling particles. Depending on the surface potential and ionic strength, ${\alpha}_{DS}$ value is divided into three regions; stable, unstable and transition zone. ${\alpha}_{DS}$ increases as the ionic strength increases, and as the surface charge decreases. This result can be used to model both destabilized and stabilized suspension incorporating the collision efficiency factors of the other coagulant mechanisms such as fluid shear and Browian motion.

• 상하수도학회지
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• 제18권4호
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• pp.427-436
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• 2004

Sedimentation is one of the most common and important units in conventional water treatment plants. Structure such as various baffle walls and inclined plate settler may be obstacles to the horizontal flow when it is poorly designed. Therefore, the effects of these structures on characteristics of hydraulic flow must be evaluated to improve the settling efficiency of the floc. The hydraulic characteristic of the four sedimentations at the three real WTPs (water treatment plants), which have different structural properties respectively inside the settling basin, were investigated by tracer (fluoride) test. The inclined plate settler installed inside settling basin caused a undesirable impact on horizontal flow and produced dead zone. Intermediate baffle and solid baffle wall under the inclined plate settler at GE plant help to minimize the formation of density currents and flow short circuiting. However, installing perforated baffle under the inclined plate settler at other plants could not induce even distribution of flow. NaF used as a tracer was recovered more than 90% at investigated all basin. Morill index ($t_{90}/t_{10}$), Modal index ($t_p/T-HRT$) and short-circuiting index ($[M-HRT-t_p/M-HRT$) were determined from tracer test results performed at three WTPs. Those indices ranged 2.99~3.45, 0.44~0.72 and 0.23~0.47, respectively.

• 한국산학기술학회논문지
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• 제15권5호
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• pp.3336-3344
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• 2014

본 연구의 목적은 소규모 응집침전모듈의 개발 및 lab-scale 테스트를 통한 실증이다. 최근 하수처리율이 높아짐에 따라 비점오염원 관리에 대한 관심이 높아지고 있어 소규모 처리장치 개발의 필요성이 증대되고 있다. 본 연구의 응집침전모듈은 응집공정 이후 외부 영역에서 선회류를 통한 플럭(floc)의 추가 성장 및 미세 플럭 수의 감소, 내부 침전 영역에서 수직 수평류 복합침전방식을 통한 침전효율 증대로 효과적인 고액분리가 가능토록 하였다. 응집침전모듈은 수직 수평류 복합침전 방식을 통해 재래식침전조에 비해 같은 체적에서 침전면적 및 표면부하율을 4.4배 증가시킬 수 있었다. 본 연구에서 외부 및 내부 침전 영역에서의 선회류 형성 유지와 내부 침전영역에서의 균등한 유량분배를 본 공정의 중요한 설계인자로 선정하였고, 이의 도출을 위해 유체유동해석 모델인 FLUENT를 이용하였다. 선회류 유동경향 모사를 통해 유입속도, 외부조의 규격, 하부콘호퍼 깊이 등을 결정하였고 속도분포 및 유량분배 해석을 통해 유출공 직경과 개수, 유출홀 직경 등 내부 침전영역의 세부 규격을 도출하였다. $60{\ell}/hr$규모의 파일럿 테스트 결과 20분의 체류시간 동안(표면부하율은 $37.3m^3/m^2$일)탁도 300~800 NTU의 폐수를 고분자응집제 주입 없이 10 NTU 이하로 처리할 수 있었으며, 유체유동해석 모델을 활용한 설계인자 도출의 가능성을 확인하였다.

• 한국물환경학회지
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• 제21권4호
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• pp.398-402
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• 2005

The enzyme Xeronine was investigated as a microbial activating substance in biological wastewater treatment processes. Xeronine as bio-stimulant was injected in the anaerobic sludge and the activated sludge treating wastewater in order to examine the effect of hidden benefits. Bio-stimulant did not show significant improvement of anaerobic treatablity. In the aerobic system, higher bio-stimulant dose condition resulted in slightly more removal of nitrogen and phosphorus. Floc aggregation and zone settling velocity as solid-liquid separation factors in activated sludge systems was enhanced by bio-stimulant. Effects of bio-stimulants injection on improvement of water quality and microbial activity did not clear in terms of normal operation conditions.

• 한국해안·해양공학회논문집
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• 제24권4호
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• pp.287-294
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• 2012

연안 해역은 해안구조물 건설과 간척 등의 연안 개발로 인해 해안의 퇴적환경이 크게 변화하고 있으며, 이로 인하여 많은 환경변화가 발생하였다. 특히 점착성 퇴적물은 오염물질을 흡착하고 이동하여 환경적으로 큰 변화를 야기한다. 목포해역은 최근에 많은 해안구조물의 건설로 인해 낙조우세가 점점 심해지는 등의 환경변화가 발생하고 있는 지역이다. 이 지역의 점착성 퇴적물을 채취하여 수리실험하고 얻은 침식률 및 침식한계전단응력의 퇴적물 이동모의 활용가능성에 대해 검토하였다. 부유사 농도에 대한 모의 결과는 관측자료와 일치하는 양호한 결과를 보였다. 따라서 수리실험을 통해 결정된 침식률을 사용하는 것이 수치모의에서 정확성을 개선하는 데 기여함을 확인할 수 있었다. 모의과정에서 침식률, 침식한계응력, 침강속도, 활성층 두께 등의 민감도를 분석하였다.

• Journal of the korean society of oceanography
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• 제35권1호
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• pp.16-33
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• 2000

In order to measure the vertical fluxes of particles and reactive radionuclides such as thorium and polonium isotopes, Dunbar-type sediment traps were freely deployed at the Ulleung Basin and in warm and cold water masses around the polar front of the East Sea. We estimated the ratios of the catched (F) to the predicted $^234$Th fluxes (P) using natural tracers pair $^234$Th-$^238$U. The F/P ratios are decreased with increasing water depth. Whereas the concentrations of suspended particles are homogeneous in water column, the mass fluxes are also decreased with increasing water depth like the F/P ratios. These facts indicate that organic matters of settling particles are destructed within the euphotic layer due to decomposition. Whereas regenerations of sinking particles are negligible in the cold water mass, about 80% of them are regenerated in the warm water mass during falling of large particles. These downward mass fluxes are closely correlated with their primary productions in euphotic zone. The activities of $^234$Th, $^228$Th and $^210$Po in the sinking material were increased with water depth. Because $^234$Th steadily produced in the water column are cumulatively adsorbed on the surface of sinking particles, vertical $^234$Th fluxes were observed to increase with water depth. Therefore, these sinking particles play important roles in transporting the particle reactive elements like thorium from surface to the deep sea. The scavenging processes including adsorption and settling reactions generate radio-disequilibrium between daughter and parent nuclides in water column. The activity ratios of $^234$Th/$^238$U and $^228$Th/$^228$Ra were observed to be < 1.0 in the surface water and approached to be equilibrium below the thermocline. The extent of the deficiency of daughter nuclides compared to the parents nuclide was highly correlated with the vertical particle flux. Because most of the $^210$Po in the surface water are scavenged on a labile phase and are recycled at sub-surface depths (< 200 m), the $^210$Po are always observed to be excess activities compared to $^226$Ra in surface water.

• 환경위생공학
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• 제12권3호
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• pp.9-17
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• 1997

This research aims to remove nitrogen in the piggery wastewater by combined process with upflow anaerobic sludge blanket (UASB) and biofilm process. For the effective denitrification. anaerobic and anoxic reactors were connected to a reactor. The effluent of aerobix reactor was recycled equally with influent in the upper filter of anaerobic reactor for denitrification and outlet of UBF reactor was connected to the settling tank with $1.5{\;}{\ell}$ capacity and the settling sludge was repeatedly recycled to UASB zone. The organic loading rate of total reactor was operated from 0.4 to $3.1kgCOD/m^{3}/d$ and it was observed that the removal rate of TCOD was 80 to 95 percentage. Ammonia nitrogen was removed over 90 percentage in the less volumetric loading rate than $0.1{\;}kgN/m^{3}/d$. But because of non-limitation of organic materials, it was reduced to 70 percentage in the more volumetric loading rate than $0.6{\;}kgN/m^{3}/d$. But denitrification rate was observed 100 percentage in the all of loading rate. This is caused by the maintenance of optimum temperature, sufficient carbon source, and competition of electron acceptors. The results of COD mass balance at the $1.21{\;}kgCOD/m^{3}/d$ was observed with the 71.7% percentage of influent COD. It was revealed that the most part of organic materials was removed in the aerobic and the anaerobic reactor because 38.4 percentage was conversed into $CH_{4}$ gas and 11 percentage was removed in the aerobic reactor with cell synthesis and metabolism. Besides, 5.7% organics was used to denitrification reaction and 3.7% organics related to sulfate reduction.

• 상하수도학회지
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• 제35권4호
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• pp.277-284
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• 2021

The ballasted flocculation effects of the mill scale and magnetite on activated sludge were investigated. Both ballasted flocculants (BF) could remarkably improve the sludge settleability in terms of zone settling velocity (ZSV) and sludge volume index (SVI). With the BF dosage of 0.2 to 2.0 g-BF/g-SS, the magnetite particles showed better efficiency on improving settling behavior of activated sludge than the mill scale due to higher surface area and hydrophobic property. The efficiency of SVI₃₀ with magnetite injection was 2.5 to 11.3% higher than mill scale injection and that of the ZSV appreciated from 23.7% to 44.4% for magnetite injection. Averaged floc size of the BF sludge with magnetite dosage (0.5 g-BF/g-SS) was 2.3 times higher than that of the control sludge. Dewaterability of the sludge was also greatly improved by addition of the BF. The specific resistance to filtration (SRF) was reduced exponentially with increasing the dosage of BF. However, the BF's particle size effect on the SRF looks to be marginal. Consequently, for improving the dewaterability, the BF played a physical role to remove the pore water of the biological flocs by intrusive attachment and a chemical role to induce aggregation of the flocs by charge neutralization.

• 한국지형학회지
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• 제18권3호
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• pp.37-51
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• 2011

이 연구는 조석우세하구역인 모산만 하구역의 "에너지혼합구간"에 형성되어 있는 간석지의 퇴적물 분석을 통해 하구역의 지형변화와 퇴적환경변화를 고찰하였다. 모산만 하구역의 간석지 퇴적층은 대부분 홀로세 전기와 홀로세 후기로 나누어 퇴적되어 있으며, 홀로세 중기에 형성된 것으로 보이는 부정합이 관찰되었다. 이러한 부정합의 존재는 홀로세 중기에 있었던 해수면의 급격한 변화와 관련이 있을 것으로 판단된다. 연구지역의 퇴적공간은 크게 3개 그룹으로 구분되었으며, 각각의 그룹을 "간헐적 조수통로퇴적구역"(A1, B1, D3), "창조류지배퇴적구역"(A3, B3, C1, C3) 그리고 "하천퇴적물유입구역"(A2, B2)으로 명명하였다. 이와 같이 퇴적공간이 구분되는 것은 조수통로의 측방이동 제한, 창조류의 회절 현상과 퇴적지연현상에 의한 퇴적작용, 특정 구역에서의 하방침식의 강화와 같은 프로세스들로 설명될 수 있으며, 이 프로세스들은 연구지역과 같은 서해안의 리아형 조석우세하구역의 지형형성 과정의 주요 요인임을 확인하였다. 이 연구는 향후 서해안 하구역의 지형변화에 대한 논의의 방향을 제시하였다는데 의의가 있고, 나아가 서해안의 "육지-해양 상호작용" 모형을 만들어가는 기초적인 자료로 활용될 것이다.

• Journal of Radiation Protection and Research
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• 제32권3호
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• pp.117-122
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• 2007

지속적인 하수 발생량의 증가와 시설 부지비용의 상승효과로 인해 하수처리시설 중 가장 많은 면적을 차지하고 있는 침전조의 효율향상이 중요한 문제로 부각되고 있다. 본 연구에서는 선행연구로 수행한 최종 침전조 구조의 최적화를 위한 CFD(computational fluid dynamics) 모델링 결과를 실험적으로 검증하기 위해, 방사성추적자를 이용하여 정류벽 설치 유무에 따른 침전조 유동분포 변화를 측정하였다. 실제 하수처리장 침전조 설계제원을 바탕으로 수리학적 상사(1/21)를 고려하여 침전조 모형장치를 제작($L{\times}W{\times}H:2.6{\times}0.4{\times}0.2m$)하였으며, 방사성추적자로 Tc-99m 약 $30{\sim}40\;mCi$를 사용하였다. 실험결과, 최종 침전조 내부에 정류벽을 설치함으로써 바닥으로의 강한 밀도류와 출구 방향으로의 슬러지 휩쓸림 현상이 감소되었으며, 슬러지의 침전영역(settling zone)이 증가됨을 방사성추적자를 이용하여 성공적으로 가시화하여 확인하였다. 또한 정류벽 설치로 인하여 단락류가 전체 유출수에서 차지하는 부분이 48 %에서 32 %로 현저히 감소하고, 이의 슬러지 평균체재시간 또한 940 sec에서 810 sec로 감소되는 유동특성을 정량적으로 분석할 수 있었다 이는 선행연구로 실시한 CFD 모델을 이용 침전조 최적설계 조건도출 연구와 일치하는 결과로서, 방사성추적자 기술이 신규로 침전조를 설계할 때나 기존 시설의 성능개선을 위한 구조변경 후 이의 검증을 위해 중요한 자료로 활용될 수 있음을 확인하였다.