• Membrane and Water Treatment
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• v.3 no.2
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• pp.133-140
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• 2012

The overall performance of BNR-MBR, so-called Anoxic-Anaerobic-Aerobic Membrane Bioreactor ($A^3$-MBR), developed for nutrient removal was studied to determine the efficiencies and mechanisms under different solid retention time (SRT). The reactor was fed by synthetic high-rise building wastewater with a COD:N:P ratio of 100:10:2.5. The results showed that TKN, TN and phosphorus removal by the system was higher than 95%, 93% and 80%, respectively. Nitrogen removal in the system was related to the simultaneous nitrification-denitrification (SND) reaction which removed all nitrogen forms in aerobic condition. SND reaction in the system occurred because of the large floc size formation. Phosphorus removal in the system related to the high phosphorus content in bacterial cells and the little effects of nitrate nitrogen on phosphorus release in the anaerobic condition. Therefore, high quality of treated effluent could be achieved with the $A^3$-MBR system for various water reuse purposes.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.249-249
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• 2019

하천에서 하상과의 접촉 없이 부유 상태로 이동하는 유사는 부유사로 정의된다. 부유사의 이동은 유사 입자의 침강 속도와 난류의 섭동 성분에 따라 결정된다. 실제 하천에서 부유사는 단일 크기가 아닌 여러 크기의 유사 입자가 혼재된 상태로 존재하는데, 유사의 이동을 보다 정확히 이해하기 위해서는 침강 속도를 결정하는 유사 입자 크기의 분포에 대한 이해가 요구된다. 진흙과 같은 점착성 유사의 경우에는 모래와 같은 비점착성 유사와는 달리 입도 분포를 구성하는 유사 입자의 크기가 끊임없이 변화한다. 이러한 유사의 특성 변화는 유사 알갱이 표면의 전자기적 점착력으로 인한 응집 현상(Flocculation Process)에서 기인한다. 응집 현상으로 인해 점착성 유사는 물과 유사 입자의 덩어리인 플럭(Floc)을 형성하며, 플럭의 특성은 지속적으로 변화한다. 따라서 점착성 유사의 이동을 이해하기 위해서는 흐름 특성 및 입도 분포뿐만 아니라 플럭의 응집 현상에 관한 이해가 함께 이루어져야함을 알 수 있다. 본 연구에서는 플럭의 응집 현상으로 인한 크기 변화와 입도 분포를 이해하기 위한 모형 개발의 방법론을 제시하고자 한다. 입도 분포 모형의 개발을 위해 추계학적 접근법이 이용되며, 추계학적 접근법을 이용하여 수치 실험을 수행하기 위해 몬테-카를로 방법이 적용되었다. 입도 분포 모형과 유사 이동 모형의 결합을 통해 흐름 내 부유 상태로 이동하는 점착성 유사 입도 분포에 관한 수치 모형 개발이 가능하다.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.181-181
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• 2020

점착성 유사는 유사가 가지는 점착력에 의해 응집현상을 겪으며 그 크기와 밀도가 변화한다. 유사의 크기와 밀도는 침강속도에 직접적인 영향을 주며 침강속도으 변화는 유사의 거동에 매우 중요한 작용을 한다. 따라서 점착성 유사의 크기 특성을 파악하는 것은 매우 중요하다. 이전의 많은 연구는 점착성 유사의 입도분포가 대수정규분포를 따른다고 주장하고 있다. 그러나 그 가정이 합리적인지에 대해 분석한 연구는 많지 않다. 본 연구는 통계학적 방법 중 적합도 검정을 이용하여 실제 점착성 유사가 어떠한 분포를 모사하는지 분석하였다. 사용된 적합도 검정 방법은 Kolmogorov-Sminorv(K-S) 검정이며 적합도 판정의 기준은 유의수준 5%를 기준으로 하였다. 그 결과, 실험실 실험에서 측정된 플럭의 입도분포와 현장 실험에서 측정된 입도분포는 다른 결과를 보였다. 현장 실험의 경우, 분포가 오른쪽으로 왜곡된 지수분포의 형태를 나타냈으며, Gamma 분포가 가장 우수하게 모사하였다. 실험실 실험의 경우 일반적인 양의 왜도를 가지는 분포를 나타냈으며 GEV분포가 점착성 유사의 입도분포를 가장 잘 모사하였다. 대수정규 분포의 경우 일반적으로 이용하는 2-매개변수 대수정규분포일 경우 현장실험과 실험실 실험 모두 적합하지 않았다. 그러나 위치 매개변수를 추가하여 3-매개변수 대수정규분포를 사용하면 점착성 유사의 입도분포를 잘 모사하는 것으로 판단된다. 따라서 점착성 유사의 입도분포를 무조건적으로 대수정규분포로 사용하는 것은 지양해야할 것으로 판단된다.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.11
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• pp.834-846
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• 2011

The objective of this study is to development of IDFIS system, that are consisted of hydrocyclone, rapid flocculation and inclined settler with chitosan coagulant. As the results of Jar test, a chitosan optimum dosage of 40 mg/L for river sediment, and 5 mg/L for tunnelling wastewater sediment, which these conditions leaves of residual turbidity of less than 5 NTU. Because of the effectiveness of chitosan in removing turbidity was independent on pH, the operation of IDFIS system would be simple. The synthesized turbidity was made with clay particles, river sediment, river suspended sediment, and tunnelling wastewater sediment. Results indicate that the mean overall removal efficiency of turbidity, SS, COD and TP were 98%, 99%, 85% and 95%, respectively. Chitosan is very efficient in removing turbidity in the entire turbidity range examined. IDFIS system would have possibility with compact design, because of the increase of floc size favours the floc settling speed and reduces the settling time.

• Clean Technology
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• v.7 no.1
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• pp.35-42
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• 2001

This study was performed to evaluate the effect of zeolite addition on biofloc in aictvated sludge process. Two units were compared each other, in which one was operated as control unit (CU) and the other was managed by adding zeolite into aeration basin to sustain 4,000 mg/l (ZU). It was observed that flocs of both units were enduringly increased in medium size by extending SRT (Solid Retention Time), although their effect size of ZU was smaller than theirs of CU. Zeolite application excessively improved sludge settling property and ZU presented sludge settling velocity of 3.4 to 11 m/h regardless of SRT variation. The sludge volume index (SVI) was in the range of 50 and 108 ml/g. Conversely, the sludge settling velocity of CU seriously depended on SRT increase, and sludge sedimentation was not achieved at a 40 days of SRT due to Sphaerotilus appeared predominantly in reactor.

• Journal of Korean Society of Water and Wastewater
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• v.35 no.4
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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.

• Journal of the Korean Ceramic Society
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• v.40 no.7
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• pp.677-682
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• 2003

The physical properties of sintered body made from 3 kinds of slip, F (Flocculated), M (Moderate), and D (Dispersed) for coal fly ash 70-clay 30 (wt%) were studied in terms of slip states and pore size distribution of sintered bodies. The floc particle size distribution for slip F was wider than slip D and the slip F contained flocs larger than 11 $\mu\textrm{m}$. The pore size distribution of the green body of all slips ranged over 1∼4 $\mu\textrm{m}$. The pores smaller than 1 $\mu\textrm{m}$ almost disappeared during the sintering process, while the larger pore of 2.5∼3 $\mu\textrm{m}$ growed by 1 $\mu\textrm{m}$. The pore distribution for the green body of slip F became a narrow in width and high in height after sintering and the large pore limit in a slip F sintered body was 5.1 $\mu\textrm{m}$ which is smaller than that of other slip. The slip F rather flocculated was favorable over slip D well dispersed, in offering a higher compressive strength. From these results, the mechanical strength of sintered body is dependent on the pore distribution which could be controlled by dispersion state of the slips.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.32 no.6
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• pp.706-712
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• 1999

PSD (particle size distribution) for 2,000 mg/$\ell$ natural loess in seawater showed normal distribution cure at 0 minute settling time, accompanying with very large particle distribution range with its mean particle diameter of 31.6 $\mu$m and coencient of variance of $72.6\%$, With elapsed time it showed that the PSD was rapidly changed from normal distribution cure to abnormal distribution curve, steepened the right-hand side of it and its coefficient of variance was getting increased because of rapid settling of large size particles, Cumulative weight distribution showed that 2,000 mg/$\ell$ natural loess in seawater was almost $100\%$ constituted of particles bigger than 20 $\mu$m in diameter. Ratio of $V_s/(D_{bm})^{1/2}$ for loess particles in seawater was increased with increase of particle size in geometrical progression. Almost all loess particles in seawater had Stokes settling velocity not less than 2,255 times of Brownian diffusion coefficient, There was almost to EDL (about 0.4 nm) around natural loess particles in seawater, Thus, there was always LVDW attractive force between loess particles approaching each other in seawater, and almost no EDL repulsive force. Loess particles were not always in the condition of easy floe formation. Concentration of natural loess in seawater increasing from 400 mg/$\ell$ to 10,000 mg/$\ell$, characteristics of the settling was changed from Type I settling (discrete settling) to Type II settling (flocculation settling). PVD (particle volume distribution) showed that natural loess particles in seawater were largely constituted of two types of particles, such as rapidly settling particles and suspended and dispersed particles for a long time. Amount of the latter was much less than that of the former.

• Microbiology and Biotechnology Letters
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• v.26 no.3
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• pp.257-263
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• 1998

Alcaligenes eutrophus was successfully recovered from high cell density broth by pre-treatment with Fe-based coagulants. An inorganic coagulant, Fe$_2$(SO$_4$)$_3$, and a polymerized coagulant, Ferix-3, were used. Good coagulation was observed in broad pH range of 3 to 13, the floe size was increased with increasing pH of culture broth. The optimum pH of fermentation broth for cell recovery was 10 to 13. The optimum coagulant dosages to recover cells with 95% cell recovery were increased with increasing cell concentration. Optimal coagulant dosage was lower when the polymerized coagulant was used rather than the inorganic coagulant. The coexistence of NH$_4$$\^$+/ was increased coagulant requirement, and the coagulant requirement was 0.066g Fe$_3$$\^$+//g NH$_4$$\^$+/.

• Korean Journal of Microbiology
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• v.47 no.1
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• pp.50-55
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• 2011

A simple and rapid method was developed for monitoring of Gram-positive bacteria in the wastewater treatment system. Culture suspensions of 4 Gram-positive and 4 Gram-negative strains were filtrated and stained with a polyethersulfone membrane filter and Toluidine Blue-O. To establish quantitative color image analysis, the intensity value of RGB (red-green-blue) color of a scanned filter image was analyzed with a photographic program. Red and green color values of Gram-positive bacteria were higher than those of Gram-negative bacteria. This method was applied to the activated sludge mixed with the Gram-positive bacteria. Although evaluation was difficult due to the irregular size and shape of flocs, the population of Gram-positive bacteria in the activated sludge could be monitored with floc dispersion technique. The more amounts of Gram-positive bacteria in the activated sludge led to the increase of red and green color values. This method provides a rapid and quantitative measurement of Gram-positive bacteria within the wastewater treatment systems.