The effects of activated carbon originated Ballasted Flocculant (BF) on the settleability of activated sludge and the recovery of BF by Hydro-cyclone (HC) were analyzed experimentally. Two kinds of BF (M-I: 125-250 μm, M-II: 250-425 μm in dia.) and three kinds of activated sludges with different SS concentration (2,300-7,100 mg/L) were applied for this study. With the dosage variation of BF from 0.14 to 1.3 g-BF/g-SS, we could obtain 24-31% improvement in SV30 (Sludge Volume after 30min sedimentation) for the lowest SS concentration sludge (2,300 mg/L). Whereas the SV30 improvement was much higher as 44-48% for the highest SS concentration sludge (7,100 mg/L). The settling characteristics of the sludge with BF followed Vesilind model the best among three models (Vesilind, Takacs and Cho model). HC could effectively separate BF with the separation efficiency of 70-90% and over 95% separation efficiency could be obtained when the HC was applied twice.

Although microalgae are considered as a promising feedstock for biofuels, cost-efficient harvesting of microalgae needs to be significantly improved. In this study, the use of electro coagulation as a more rapid flocculation method for harvesting a freshwater (Scenedesmus dimorphus) microalgae species was evaluated. The results showed that, electro coagulation was shown to be more efficient using an aluminum anode than using an iron anode. And optimum conditions of electro coagulation for harvesting Scenedesmus dimorphus were found. The optimum stirring speed was 100 rpm and optimum pH was 5. Furthermore, the current density which the fastest and highest recovery efficiency is achieved at 30 A/m2, while the highest energy efficiency was achieved at 10 A/m2. A the rapid and high recovery efficiency indicate that electro coagulation is a particularly attractive technology for harvesting microalgae.

A coagulation-flocculation (CF) process using aluminum sulfate as a coagulant was employed to treat highly suspended solids in tunnel wastewater. Response surface methodology (RSM) based on a Box-Behnken design was applied to evaluate the effects of three factors (coagulant dosage, pH and temperature) on total suspended solids (TSS) removal efficiency as well as to identify optimal values of those factors to maximize removal of TSS. Optimal conditions of coagulant dosage and pH for maximum TSS removal changed depending on the temperature (4 ~ 24°C). As temperature increased, the amount of coagulant dosage and pH level decreased for maximum TSS removal efficiency during the CF process. Proper adjustment of optimal pH and coagulant dosage to accommodate temperature fluctuations can improve TSS removal performance of the CF process.

The glucomannan content of Aloe vera gel was measured by a novel method using a bentonite suspension that floc-culates upon mixing with gels prepared by hand filleting of aloe leaf. An optimum flocculation condition was deter-mined to be Aloe vera gel diluted in the range of 2 to 5-fold and then a bentonite suspension 1% (w/v) mixed withthe gel sample in the ratio of 8:2 (v/v) to provide a mixture volume of 10mL with the length to diameter ratio of5. Under the conditions of these experiments, a rapid settling (<3 min) of more than 90% of the bentonite wasachieved only when the aloe gel sample was properly diluted. The glucomannan concentrations in various dilutedsamples with the highest settling rates were identified in the range of 195.7±21.4mg/L; thus, the results indicate thatthe glucomannan content may be determined from the dilution rate of the aloe gel sample that exhibits the highestsettling rate. This study provides a simple, rapid, and cost-effective assay for the estimation of the glucomannanlevel in raw Aloe vera gel.

This paper presents a Computational Fluid Dynamics(CFD) based simulation and experimental tracer test of flow pattern and turbulent energy dissipation inside a serpentine flocculation basin with continuous operation. Research focused on the evaluation of a specific flow pattern on the hydraulic behavior on the flocculation basin. From the results of CFD simulation and actual tracer test, both results were in good accordance with each other. Also, each Morill index were calculated as 1.5 from CFD simulation and 1.7 from actual tracer test, respectively. Especially, turbulence energy was dissipated relatively higher in the vicinity of inlet to the flocculation basin than other region. The differences between the CFD simulation and actual tracer test were 1.4 min in T50, and 1.3 min in Tp, respectively.

The mean velocity gradient, G, has been used as a principal design and operation parameter for flocculation unit. This paper questions that significance. The physical and qualitative meaning of collision efficiency factors of each transport mechanism (Brownian motion, fluid shear, and differential sedimentation) are reviewed. The overall collision frequency function is calculated by summing up the collision frequency function of each mechanism. In the collision of two particles of different size, a diagram showing the dominant region in which each mechanism is important is developed and the meaning of the diagram is discussed. The primary ramification of this curvilinear, heterodisperse approach is that G is found to be not nearly so important. Previous experimental work in which the role of G has been examined is reviewed in light of this finding.

We investigated the effects of leaching concentration (0.1 ~ 1.0 M) and time (1 ~ 120 min) on the phosphorus recovery from ash and dried sewage sludge produced by titanium tetrachloride (TiCl4) flocculation by acidic (H2SO4 and HCl) or alkaline (KOH and NaOH) leaching. The extraction efficiencies of dried sludge were 2.7 ~ 12.6% for H2SO4, 2.5 ~ 10.5% for HCl, 3.6 ~ 9.6% for KOH, and 7.1 ~ 9.9% for NaOH with 1 M, and the maximum efficiency was obtained within 45 min. The maximum %P extracted of sludge ash was 83.1 for H2SO4, 80.2 for HCl, 51.2 for KOH, and 51.2 for NaOH with 1 M, obtained within 45 min. The rate constants (min−1) for the leaching of P from sludge ash were found to be 1.199 for H2SO4, 1.026 for HCl, 0.264 for KOH, and 0.622 for NaOH. The P leaching increased with the increase in leaching concentration, and the maximum leaching for ash was obtained within 0.3 M, regardless of acidic or alkaline leaching. The overall results indicate that the ash of TiCl4 flocculated sewage sludge can be treated with H2SO4 to efficiently recover P.

생체고분자물질은 수자원환경에서 점토, 미생물, 바이오매스 등 부유입자들을 응집시키고, 침전, 퇴적시키는 역할을 한다. 본 연구는 다양한 수질화학 조건이 생체고분자물질에 의한 부유입자 응집에 미치는 영향을 파악하고자, 수질화학 조건을 제어하여 응집실험을 수행하였다. 각 응집실험은 이온강도, 2가 양이온 농도, 휴믹물질 분율이 제어된 실험조건에서 Kaolinite 현탄액에 생체고분자물질인 Xanthan Gum을 주입하여 수행하였다. 수체가 가지는 응집능은 응집체 크기 및 잔류 고형물 농도를 측정을 통하여 평가하였다. 본 연구에서, 이온강도 증가는 점토입자 및 생체고분자물질 간 정전기적 반발력을 감소시키고 생체고분자물질이 점토 입자 간 가교를 형성하여 응집을 증대시킨 것으로 파악되었다. 이온강도가 0.001에서 0.1 M NaCl로 증대될 경우, 응집을 증진시켜 응집체 크기는 약 3배 이상 증 대되고 부유고형물농도는 약 2.5배 이상 저감되었다. 또한, 2가 양이온이 수체에 존재하는 경우, 점토입자-생체고분자물질 혹은 생체고분자물질 상호 간 가교를 형성하여, 즉 점토-Ca2+-고분자 또는 고분자-Ca2+-고분자 가교를 형성하여, 생체고분자물질에 의한 부유입자 응집을 증대시켰다. 수체에 Ca2+가 낮은 농도라도 존재 할 경우, 응집을 크게 증진시켜 부유고형물농도가 원주입농도에 비하여 20배 이상 저감되는 것으로 나타났다. 하지만, 휴믹물질이 존재하는 경우, 점토입자 표면에 흡착되어 점토입자의 정전기적 반발력을 증대시켜 생체고분자물질의 흡착을 방해하고 응집을 감소시켰다. 수체에 휴믹물질이 존재할 경우, 응집을 저감시켜 부유고형물농도는 저감되지 않고 원 주입농도와 유사하게 나타났다. 본 연구의 결과는 수자원환경에서 부유입자 및 퇴적물 거동을 이해하고 수질 및 퇴적물에 대한 최적 관리 방안을 도출하기 위한 기초 자료로 활용될 수 있으리라 기대된다.

이군집 응집현상은 수자원환경에서 점착성 유사가 결합-해체의 과정을 통해 응집핵-응집체의 이군집 입자크기분포(Biomodal Floc Size Distribution)를 형성하는 일련의 과정을 의미한다. 본 연구는 저난류 및 고난류 두 가지 조건에서 수행한 응집-침전관 실험결과를 바탕으로 이군집 응집모형(TCPBE: Two Class Population Balance Equation)의 적용성을 단일군집 응집모형(SCPBE: Single Class Population Balance Equation) 및 다군집 응집모형(MCPBE: Multi Class Population Balance Equation)과 비교·평가하였다. 기존 SCPBE에 비하여, TCPBE는 응집핵-응집체의 상호작용 및 침강속도차에 따른 응집 기작을 모의할 수 있었다. 또한, 3개의 연립미분방정식을 가진 TCPBE는 30개 미분방정식을 가진 다군집 응집모형(MCPBE: Multi Class Population Balance Equation)과 대등한 모의 결과를 나타내었다. 따라서 TCPBE는 이군집 응집현상을 모의 할 수 있는 가장 단순한 모델로 검증되었고, 향후 수자원환경이나 수처리 공정에 다양하게 적용할 수 있으리라 판단된다.

The effects of pH (5, 7 and 9) and ionic strength of different salts on the flocculation characteristics of humic acid by inorganic (alum, polyaluminum chloride (PAC) with degree of neutralization, r=(OH/Al) of 1.7) and organic (cationic polyelectrolyte) coagulants, have been examined using a simple continuous optical technique, coupled with measurements of zeta potential. The results are compared mainly by the mechanisms of its destabilization and subsequent removal. The destabilization and subsequent removal of humic acid by PAC and cationic polyelectrolyte occur by a simple charge neutralization, regardless of pH of the solution. However, the mechanism of those by alum is greatly dependent on pH and coagulant dosage, i.e., both mechanisms of charge neutralization at lower dosages and sweep flocculation at higher dosages at pH 5, by sweep flocculation mechanism at pH 7, and little flocculation because of electrostatic repulsion between negatively charged humic acid and aluminum species at pH 9. The ionic strength also affects those greatly, mainly based on the charge of salts, and so is more evident for the salts of highly charged cationic species, such as CaCl2 and MgCl2. However, it is found that the salts have no effect on those at the optimum dosage for alum acting by the mechanism of sweep flocculation at pH 7, regardless of their charge.

본 연구에서는 포항시 양덕정수장에 tracer test를 이용한 pilot plant를 설치하여 기존 플록형성지에 대한 문제점을 도출하였다. 또한 플록형성지 각단 유출부의 단면을 여러 가지 형태로 변경시키면서 수리학적 평가를 실시하였고, 그 결과 플록형성지의 각단 유출부에 대한 최적 개량단면을 제시하였고, plant에 적용하여 현재 운전중에 있다. 또한 입자의 크기별 개수를 측정할 수 있는 particle counter를 이용하여 플록형성지 개량후의 효

The study of flocculation kinetics is of fundamental interest in the field of water treatment, because rational study of the factors affecting the coagulation process should be based on the rate of particle growth. The effect of sulfate on flocculation kinetics were examined using ferric nitrate as a coagulant to coagulate kaolin clay in water under several experimental conditions. Both the particle size distribution data obtained from the AIA and the on-line measurement of turbidity fluctuation by the PDA were used to measure flocculation kinetics. Results show that sulfate ion added to the kaolin suspension played an important role in the flocculation process, not only improving flocculation kinetics at more acidic pH levels but also changing surface charge of particles. The kinetics of flocculation were improved mainly by the enhanced rate and extent of Fe(Ⅲ) precipitation attributed to the addition of sulfate, and thereby, better interparticle collision frequency, but little by the charge reductions resulting from the sulfate addition. The increase in sulfate concentration beyond 3×10 exp (-4)M (up to 2×10 exp (-3)M) did not induce further improvement in flocculation kinetics, although the higher concentrations of sulfate ion substantially increased the negative ZP value of particles.

Flocculation kinetics using ferric nitrate as a coagulant to coagulate kaolin clay in water was examined as a tool to investigate the effect of low temperature under tightly controlled treatment conditions. Both the particle size distribution data obtained from Automatic Image Analysis (AIA) system and the on-line measurement of the degree of turbidity fluctuation in a flowing suspension by Photometric Dispersion Analyzer (PDA) were used to measure flocculation kinetics. Results show that cold water temperature had a pronounced detrimental effect on flocculation kinetics. For improving flocculation kinetics at low water temperature, maintaining constant pOH to adjust water chemistry for temperature changes was found to be partially effective only in the more acidic pH range studied.