• Journal of Microbiology and Biotechnology
• /
• 제7권4호
• /
• pp.282-286
• /
• 1997

The floc strength of Escherichia coli was enhanced by adding water soluble polymer flocculants (BPA-5020 and BPA-5000) to the particulate flocculant (BPA-1000) as indicated by the increase in the shear index. The shear index of the E. coli flocs increased from 0.39 with the particulate flocculant alone to 0.94 with the particulate flocculant in conjunction with the water soluble polymer flocculant. In addition, the sedimentation rate of flocs was higher and the sedimented volume of flocs was smaller when the particulate flocculant was used with the water soluble polymer flocculant. When E. coli was flocculated first with the water soluble flocculant and the particulate flocculant was added later into the E. coli flocs formed, the sedimentation rate of the flocs was greater than that of any other combination. The shear index of the flocs was, however, independent of the sequence of the flocculant addition.

• 공업화학
• /
• 제16권1호
• /
• pp.74-80
• /
• 2005

탁질입자 및 인의 효과적인 제거 특성을 고찰하기 위해서 물리화학적 인자들(pH, 알칼리도, 응집제의 종류)의 체계적인 고찰을 수행하였다. AI(III)과 Fe(III)계 응집제들은 제타전위 값이 거의 영에 수렴하는 pH 7~9 영역에서 높은 탁도 제거율 및 인 제거율을 나타내었다. 응집제의 주입량이 증가함에 따라 탁도는 급격하게 감소하는 경향을 보였으며, 인의 경우에는 금속이온과의 당량적 결합에 기인하여 비례적으로 감소하였다. 고속카메라(Motion Scope 2000, Redlake Co.)를 이용하여 플럭의 생성과정을 가시화하였고 광학현미경을 통해서 플럭의 성상과 형태를 고찰하였다. Fe(III)계 응집제에 의해 생성된 플럭들은 Al(III)계 응집제에 의해 생성된 플럭들에 비해 치밀하였으며 침강성도 뛰어났다.

• 상하수도학회지
• /
• 제25권2호
• /
• pp.231-240
• /
• 2011

The objectives of this research are to investigate coagulation efficiencies of two coagulants l.e., alum and polyaluminum chloride and to understand effects of the coagulants on membrane fouling in microfiltration. The turbidity of supernatant from alum coagulation was increased with increasing doses whereas the turbidity from PACl coagulation was maintained at the low values. The observed injection volume of PACl for the same removal was approximately 30 percent less than alum, which produced a low sludge volume. The settling velocity of PACl flocs was greater than alum flocs. The results corresponded well with floc size measurements. Flux decline from alum coagulation was significant due in part to small sizes of flocs. At the low dose, alum floc had less specific cake resistance than PACl floc. However, as the dosage was increased, the increases in specific cake resistances of alum was substantial. Alum coagulation pretreatment needs careful operation to reduce membrane fouling by flocs. In general, PACl coagulants were more effective than alum coagulants for pretreatment of membrane processes because PACl showed the better performance in coagulation and membrane fouling.

• 한국물환경학회지
• /
• 제22권3호
• /
• pp.468-474
• /
• 2006

In the secondary settling tanks, three different types of settling phenomena occurs; i.e., zone settling for sludge thickening in the bottom part of settling tank, and discrete and flocculent settling for clarification in the upper part. In this paper, morphological parameters of the floc in sludge blanket layers along the length of a long rectangular tank were investigated. The plant used for this study had a serious bulking problem caused by Microthrix parvicella. Floc size decreased as the surface area of settling tank increases, which indicates that in the secondary settling tank where zone settling believed to be predominant, free or flocculent type of settling contributes to floc size distributions. Large floc particles deposit in the front zone of settling tank, but small and loose flocs mostly in the zone near its outlet. On the other hand, filament length contained in one gram of sludge blanket solid increases along the flow direction. Large flocs with less filaments settle faster, but small flocs having more filaments result in poor settling. These results support function of microorganism selection occurring in secondary settling tank. In addition, designing a long rectangluar settling tank with double hoppers might be one of the ways of bulking control, but this idea has to be verified with a further study.

• 한국환경과학회지
• /
• 제17권3호
• /
• pp.275-285
• /
• 2008

The floc formation, breakage and reformation of humic acid by inorganic (alum and PAC) and organic coagulants (cationic polyelectrolytes) at several conditions (pH, ionic strength and floc breakage time) were examined and compared among the coagulants at different conditions using a continuous optical monitoring method, with controlled mixing and stirring conditions. For alum, the shapes of formation, breakage and reformation curves at different pH (5 and 7) were different, but the shapes and the sizes of initial floc and reformed floc were nearly the same in the absence and presence of electrolytes at pH 7. For PAC, similar shapes of the curves were obtained at different pH and ionic strength, but the sizes were different, except for those of reformed flocs at different pH. However, for these coagulants, reformed flocs after floc breakage, occurred irreversibly for all the conditions used in this study. For organic coagulants, the time to attain the initial plateau floc size, the extent of floc strength at high shear rate and reversibility of reformed floes were different, depending floc formation mechanism. Especially, for the cationic polyelectrolyte forming humic flocs by charge neutralization or electrostatic patch effect mechanism, reformed flocs occurred reversibly, regardless of pH and floc breakage time, but occurred irreversibly in the presence of electrolytes.

• 상하수도학회지
• /
• 제21권6호
• /
• pp.717-726
• /
• 2007

Fully-grown flocs in a mixing tank of membrane filtration with dead-end membrane are ruptured while passing through a pump and the ruptured flocs are aggregated again in a Membrane-Feed-Pipe (MFP). To look at more details, this study tries to relate the reaggregation to a parameter of mixing intensity in MFP, i.e., G-value. The G-value is a function of Reynolds number, pipe diameter, friction factor and average velocity in MFP. To deal with polydispersity condition, we develop a representative particle size called in this study EDPD (Effective Diameter for Polydispersity condition in Dead-end filtration). The experimental results show that as the G-value increases, the EDPD decreases and also the cake resistance increases. Through comparison between EDPD and cake resistance, these results show that cake resistances are controlled by reaggregation phenomenon in MFP. The effect of detention time in MFP, however, does not affect the reaggregation of the broken flocs as G-values are increased.

• 산업기술연구
• /
• 제32권A호
• /
• pp.21-27
• /
• 2012

The characteristics of floc formation of the iron(Fe) ions contained in the acid mine drainage was studied for developing the process treating the acid mine drainage. The iron(Fe) ions were formed into flocs by the acid-base reaction with the added $Ca(OH)_2$. The molal ratio of iron(Fe) vs $Ca(OH)_2$ was one of major control variables in treatment; pH change, iron(Fe) ions concentration in treated drainage, DO (dissolved oxygen content). In addition, the air gave much effect on the color of the $iron(Fe)-Ca(OH)_2$ flocs and the attachment to magnet. The attaching to the magnet of the flocs formed in the air was much less than the case without air.

• 대한환경공학회지
• /
• 제28권3호
• /
• pp.337-344
• /
• 2006

응집플록은 그 특성에 따라 분리막 오염에 지대한 영향을 미친다. 기존의 연구결과에서 보면, 자연입자에 의해 형성된 플록함유수는 인공입자에 의한 플록함유수에 비하여 낮은 투과량을 보이는 것으로 나타났다. 따라서 본 연구에서는 응집플록의 특성을 정량적으로 분석하고, 분리막 오염과의 상관성을 알아보고자 하였다. 이를 위해 응집 플록에 대한 image analysis, specific cake resistance 및 cake compressibility 등을 측정하였다. Image 분석은 플록의 fractal dimension을 구하는데 이용되었으며, dimension은 플록의 다공성, 크기나 표면의 거칠기를 표현하는데 유용하게 사용된다. 또한 케익 압축능은 플록이 쌓여 만들어진 막표면층의 특성을 분석하는데 사용되었다. 두 가지의 다른 특성을 가지는 플록으로서 자연입자를 핵으로 하는 응집플록과 카올린 입자를 핵으로 하는 응집플록을 선택하여 실험하였다. 실험결과에 따르면 자연입자와 인공입자에 의해 형성된 플록의 fractal dimension($D_2$) 값은 $1.79{\pm}0.07,\;1.84{\pm}0.06$을 각각 나타내었으며, 이것은 자연입자에 의해 형성된 플록이 인공입자에 의한 것 보다 더 다공성의 느슨한 형태로 존재하고 있다는 것을 나타내는 것이다. 자연입자에 의해 형성된 다공성의 느슨한 플록이 분리막 표면에서 케익층을 형성 할 때에는 상대적으로 쉽게 압축되어 케익비저항이 커지는 것을 확인하였다.

• 한국펄프종이공학회:학술대회논문집
• /
• 한국펄프종이공학회 2005년도 추계학술발표논문집
• /
• pp.45-53
• /
• 2005

A novel method for evaluating the anisotropy of the deterministic features in a stochastic 2D data is introduced. The ability of the wavelet transform for the identification of the abrupt discontinuities could be used to characterize the boundary of the deterministic area in a 2D stochastic data, such as flocs in paper structure. The one-dimensional wavelet transform with a small-scale range in MD and CD could quantify the amount of the edge in both directions, depending on the intensity of each floc. The flocs that are aligned in the MD direction result in a higher value of local wavelet energy in the CD direction. Therefore, the ratio of the total wavelet energy in CD and MD directions can be used as a new anisotropy index. This index is a measure of the floc-orientation and can provide an excellent tool to obtain the orientation distribution and the major oriented angle of flocs. Various simulated images and real stochastic data such as local gloss variation of printed image and formation image, have been tested and the results show this analysis method is very reliable to measure the anisotropy of the deterministic features.

• 상하수도학회지
• /
• 제20권2호
• /
• pp.245-255
• /
• 2006

Dissolved air flotation is a solid-liquid separation system that uses fine bubbles rising from bottom to remove particles in water. In order to enhance the flotation velocity and removal efficiency of flocs in the flotation process, we tried to obtain pretreatment conditions for the optimum DAF process operation by comparing and evaluating features of actual floc formation and flotation velocity etc, according to coagulant types and conditions for flocculation mixing intensity by using PIA, PDA, and FSA. Accordingly, generating big flocs that have low density at low flocculation mixing intensity may reduce treatment efficiency. In addition, generating small flocs at high flocculation mixing intensity makes floc-bubbles smaller, which reduces flotation velocity, In this study, it was found that high flocculation mixing intensity could not remove the remaining micro-particles after flocculation, which had negative effects on treated water quality, Therefore, in order to enhance treatment efficiency in a flotation process, flocculation mixing intensity around $50sec^{-1}$ is effective.