• 대한환경공학회지
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• 제22권7호
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• pp.1263-1271
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• 2000

Alum을 이용한 응집 과정에서 탁도 및 유기물 제거와 응집 floc의 특성을 파악하였다. 본 실험에서 구한 탁도 제거영역을 Amitharajah의 연구결과와 비교했을 때 sweep floc 및 charge neutralization의 제거영역이 낮은 pH 영역으로 이동하였는데 그 원인은 원수에 포함된 유기물 농도가 다른데서 찾을 수 있다. 대체적으로 탁도 및 유기물($UV_{254}$와 TOC)의 제거영역은 비슷하였으나 탁도 제거에 비해 낮은 pH에서 유기물 제거의 효과가 높았다. Floc의 특성은 AIA, SALLS 방법을 이용하여 volume diameter과 fractal dimension을 측정하였다. AIA 방법에 비해 SALLS 방법의 측정이 용이하고 신뢰성도 높았다. SALLS 방법을 이용하여 floc을 측정한 결과 sweep floc 영역의 floc이 charge neutralization 영역의 floc 보다 fractal dimension과 평균 직경이 크게 측정되었으며, 오염물질의 제거율이 높을수록 floc의 fractal dimension과 평균 직경도 크게 나타났다.

• 한국물환경학회지
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• 제16권4호
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• pp.459-468
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• 2000

This study is to investigate the floc structure and removal of turbidity and organic matter by PACI coagulation. The turbidity removal by PACI coagulation was obtained at larger pH range than alum coagulation. And the removal of organic matter was obtained at smaller pH range than that of turbidity. The organic matter was removed by the adsorption of $Al(OH)_3$ precipitates. Floc structure was characterized by measuring fractal dimension and volume diameter using AIA and SALLS. Fractal dimension measured by AIA did not show the different characteristics of floc produced in sweep floe and charge neutralization region. Using SALLS, floes in sweep floc region were found to be larger size and fractal dimension than flocs in charge neutralization region. As pollutant removal increased. larger fractal dimension and size of floc were measured. SALLS method was found to be more useful method to characterize flocs in coagulation than AIA method.

• 상하수도학회지
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• 제18권2호
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• pp.235-241
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• 2004

The dissolved air flotation (DAF) process has been widely used for removing suspended solids with low density in water. It has been known as measuring the size of microbubbles precisely which move upward rapidly in contact zone is difficult. In this study particle counter monitoring (PCM) method is used to measure the rising microbubble after injection from a nozzle. Size and distribution curve of microbubbles are evaluated at different conditions such as pressure drop at intermediate valve, length of pipeline between saturation tank and nozzle and low pressure. And the efficiency is also checked when it collides with different size floc. The experimental results show the following fact. As the final pressure drop occurred closer to a nozzle, the bubble size became smaller. And small bubble collides with large floc as well as small one because of its physical characteristic. However large bubble collides well with large floc rather than small one since hydrodynamic flow in streamline interferes to collide between two. With performing computational process by mathematical model we have analyzed and verified the size effect between bubble and floc. Collision efficiency is the highest when P/B ratio shows in the range of 0.75 < P/B ratio ($R_{particle/Rbubble}$) < 2.0.

• Korean Chemical Engineering Research
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• 제60권1호
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• pp.125-131
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• 2022

The microstructure of highly aggregated colloidal dispersions was investigated by probing the rheological behavior of magnetic suspensions. The dynamic moduli as functions of frequency and strain amplitude are shown to closely resemble that of colloidal gels indicating the formation of network structure. The two types of characteristic critical strain amplitudes, γ_c and γ_y, were characterized in terms of the changing microstructure. The amplitude of γ_c indicates the transition from linear to nonlinear viscoelasticity and depends only on particle volume fraction not magnetic interactions. The study of scaling behavior suggests that it is related to the breakage of interfloc, i.e., floc-floc structure. However, yielding strain, γ_y, was found to be independent of particle volume fraction as well as magnetic interaction. It relates to extensive deformation resulting in yielding behavior. The scaling of elastic constant, G_e, implies that this yielding behavior and hence γ_y is due to the breakage of long-range interfloc interactions. Also, the deformation of flocs due to increase strain was indicated from the investigation of the fractal nature.

• Korean Chemical Engineering Research
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• 제44권2호
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• pp.207-215
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• 2006

본 연구의 목적은 응집공정에서 생성되는 플럭의 성상을 가시화하여 PACC의 응집 특성을 고찰하였다. 인공 원수내탁질 입자의 제타전위는 pH 8~9에서 영으로 수렴하였고 이 영역에서 TDS와 전기전도도가 최소값을 나타내 주었다. 급속 및 완속 교반의 최적 혼화강도가 관측되었으며, 특히 탁도의 제거에 있어서는 급속교반의 속도경사가 가장 낮은 $95.1sec^{-1}$에서 최대의 제거율을 나타내었다. 급속교반 후에는 $3{\sim}5{\mu}m$의 작은 입자가 급격히 생성되었으며 교반강도가 클수록 더 많은 수의 입자가 생성되었다. 완속교반이 진행될수록 $3{\sim}5{\mu}m$의 작은 입자의 수는 급격히 감소하였고 $7{\sim}21{\mu}m$의 중간 크기의 입자는 증가하는 경향을 나타내주었다. $23{\mu}m$ 보다 큰 입자의 경우는 급속교반의 속도경사가 $95.1sec^{-1}$에서 가장 많은 수가 생성되었고, $3{\sim}5{\mu}m$의 작은 입자의 경우에는 급속교반의 속도경사가 $760.7sec^{-1}$에서 가장 많이 생성되었다.

• 상하수도학회지
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• 제18권5호
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• pp.689-695
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• 2004

Electrocoagulation has been suggested as a promising alternative to conventional coagulation. The process is characterized by reduced sludge production, no requirement for chemical use, and ease of operation. However, this coagulation has scarcely been studied in water purifying process. This study was performed several batch experiments to compare turbidity removal between electrocoagulation and chemical coagulation. In addition, characteristics of floe were evaluated with zeta potential and particle size distributions. Electrocoagulation showed a relatively higher removal of turbidity (approximately 5%) with the same aluminum amount than conventional chemical coagulation. In addition, turbidity removal by electrocoagulation was less sensitive to pH and was greater for more extensive pH range than chemical coagulation. The results of zeta potential and floc size distributions illustrated that electrocoagulation provided the preferable conditions for coagulation such as zeta potential close to zero millivolt and increased portions of particles in the range of 40 and $100{\mu}m$.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2000년도 춘계학술발표대회
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• pp.386-389
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• 2000

Polysaccharides are very effective adsorbents for heavy metals. In this study, the adsorption characteristics of various polysaccharides for heavy metal adsorption were investigated. Tested polysaccharides were homogeneous polysaccharides such as curdlan, chitin, starch, cellulose, Avicel, and Solka floc and heterogeneous polysaccharides such as zooglan, locust bean gum, ghatti gum, pectin, and xylan. Lead(II) adsoption characteristic on these polysaccharides followed Freundlich isotherm and the isotherm parameters were calculated. For adsorption of lead(ll), Avicel, starch, and zooglan were found to be good adsorbents.

• 한국습지학회지
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• 제14권4호
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• pp.629-635
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• 2012

본 연구는 부영양화 호소의 개선을 위하여 분말활성탄 공정을 적용하고 호소수 내의 용존 유기물과 인의 제거특성을 파악하고자 수행되었다. 용존 유기물의 제거특성은 부유물질의 제거특성과 다르며 응집제 주입량과 pH에 영향을 받음을 확인하였다. 용존 유기물은 분말활성탄에 의해 흡착으로 제거되며 응집과정에서 용존 유기물의 제거효율을 증가시킬 수 있었다. 응집침전공정의 인 제거 과정과 같은 화학침전과정에서 형성되는 용존성 착화합물과 콜로이드성 물질은 인의 제거효율을 저하시키는 요인이다. 분말활성탄의 주입으로 콜로이드성 물질과 용존성 착화합물을 흡착함으로써 인의 제거효율을 증가시킬 수 있었다. 또한 분말활성탄은 응집과정의 floc의 밀도를 증가시켜 침전속도를 높이고 고액분리 효율을 높일 수 있었다.

• 한국물환경학회지
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• 제21권1호
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• pp.40-45
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• 2005

Sedimentation is one of the most common and important units in conventional water treatment plant. 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 two sedimentations at Y water treatment plant (YWTP), which have different deflector baffles inside the settling basin, were investigated by tracer (fluoride) test. The inclined plate settler installed inside settling basin caused an undesirable impact on horizontal flow and produced dead zone. Solid baffle wall under the plate settler could help to minimize the formation of density currents and flow short circuiting. NaF used as a tracer was recovered more than 90% at investigated all basins. 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 YWTP. Those indices ranged 2.95~3.02, 0.40~0.53 and 0.32~0.46, respectively.

• 한국물환경학회지
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• 제25권6호
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• pp.935-942
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• 2009

During period of the rainy season of spring tide Aug. 2005, the suspended sediment transport rate from Seomjin River increased ten times as high as neap tide of low river discharge. During ebb tide of high terrestrial input, the grain size of suspended particles of both surface and bottom layer of the water column, showed a uni-modal distribution with a dominant peak at coarse fraction, which suggests a characteristic development of floc-sized particles of low mean effective density. On the contrary, the particles supplied toward upstream of Seomjin river from Gwangyang Bay during flood tide showed a bi-modal distribution with a secondary peak at finer fraction, possibly due to the resuspension and the deflocculation associated with the increased shear velocity at near bottom. Break-up of large flocs is also suggested by the increased mean effective density. However, settling velocity was lower during flood tide because of smaller grain size. Thus, net deposition of suspended sediment is expected at within Gwangyang Bay instead of upstream of Seomjin River, even though suspended sediment transport rate at near bottom water was three times higher than that at surface water during flood tide.