• 상하수도학회지
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• 제26권3호
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• pp.471-478
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• 2012

Where an activated sludge system needs to be converted to biological nutrient removal(BNR) system, the secondary clarifier must handle higher MLSS from bioreactor since nitrification in BNR system that requires higher SRTs than activated sludge system. Either increase the clarifier size or modification of clarifier physical structure is required to cope with MLSS surge. One of recommended structural modification is the insertion of Lamellar within clarifier. In this study, two clarifiers - one has Lamellar structure inserted and the other does not - were used to compare the effect of Lamellar in solid/liquid separation. Same MLSS was fed to both clarifiers and concentrations of MLSS were varied. With all MLSS concentrations, attachment of MLSS on Lamellar was observed and it was found that detached MLSS caused the higher effluent SS concentrations than that of non-Lamellar clarifier effluent. From these results, Lamellar should not be inserted in clarifier to handle MLSS from BNR processes and the recommendation must be withdrawn.

• 상하수도학회지
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• 제22권1호
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• pp.141-148
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• 2008

This study was conducted to evaluate the effect of PAC(Powder Activated Carbon) retention time on stable operation of high concentration powered activated carbon(HCPAC-MBR) in the treatment of secondary domestic wastewater. The pilot scale HCPAC-MBR system was operated at two different SRTs, 25 days and 100 days. The main drawback of HCPAC-MBR system was the rapid increase of trans-membrane pressure. The increase rate of trans-membrane pressure was proportional to SRT value at constant flux. This result seemed to be caused by reduced amount of EPS adsorbed on the PAC in the reactor by decreasing the SRT of the PAC. The particle size of the PAC was also influenced by SRT. The PAC size was decreased as SRT was increased. The change of particle size could be one reason for the change of trans-membrane pressure. The pore volume in the cake-layer formed on the membrane surface became to be increased by reducing SRT, because the cake-layer was highly composed of the PAC. Therefore, increased pore volume might play a role to reduce the trans-membrane pressure. The removal rate of E260 and TOC was also inversely proportional to SRT value.

• 한국환경과학회지
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• 제6권5호
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• pp.521-529
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• 1997

In the study, we Investigated the behavior and removal efficiency of organics, nitrogen. phosphorus with operating conditions in SBRs. Substrate used was synthetic wastewater in which the ratio of $COD_{cr}$. : N : P was 100 : 12 : 2. The cycling the in SBRs was adjusted at 6 hours and 8 hours, and then certainly Included anaerobic and aerobic conditions. Also, for each cycling time. we performed 2 series of experiment simultaneously which was set up 10 days and 20 days as SRT. The removal efficiency of $COD_{cr}$. was over 97% in all operating conditions. In the 6 hours cycling time, the removal efficiency of $PO_4^{3-}-P$ reached almost 100% in steady state. And then we could observe a typical phonemena of phosphorus release and uptake, and the removal efficiency of N was 67%, Residual N source was almost TKN and most of the rest remained as $NO_2-N$. Also the difference in both SRTs was not observed practically. In the 8 hours cycling time, dissolution of sludge appeared. and, $PO_4^{3-}-P was not nearly removed but nitrogen was removed up to 75%, And the residual nitrogen was accumulated as $NO_2^--N$.

• KSBB Journal
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• 제18권4호
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• pp.272-276
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• 2003

혐기성 미생물에 저해가 되는 물질을 포함하는 고농도 폐수의 효모에 의한 처리에 관하여 연구하였다. 폐수는 furfural 부산물이 배출되는 식품가공 공정의 배출폐수를 대상으로 실험하였다. 본 연구에서는 호기성 효모의 일종인 Candida utilis가 실험에 적용되었다. 회분 실험을 통하여 본 폐수는 혐기성 미생물에 저해 영향을 주는 것으로 밝혀졌다. 본 공정의 최적 온도는 25에서 45$^{\circ}C$이었으며 효모의 성장에 적당한 pH는 4에서 8사이임을 알 수 있었다. 연속실험 결과, 체류시간 1일 이상에서 COD가 90% 이상 제거되었다. 그러나 유출수 중의 유기물 농도는 여전히 다소 높은 것으로 조사되었다. 따라서 동력학적으로 해석하여 추정한 결과 남은 유기물은 대부분은 용존 미생물 생성물 (SMP, Soluble Microbial Product)에서 기인하는 것으로 판단되었다.

• Current Optics and Photonics
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• 제1권5호
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• pp.529-537
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• 2017

We explored how changes in blood vessel compliance affected the systolic rise time (SRT) of the maximum blood pressure (BP) peak wave and the diastolic fall time (DFT) of the minimal BP peak wave, compared to photoplethysmograpic (PPG) parameters, using a two-compartment, second-order, arterial Windkessel model. We employed earlier two-compartment Windkessel models and the components thereof to construct equivalent blood vessel circuits, and reproduced BP waveforms using PSpice technology. The SRT and DFT values were obtained via circuit simulation, considering variations in compliance (the dominant influence on blood vessel parameters attributable to BP changes). And then performed regression analysis to identify how compliance affected the SRT and DFT. We compared the SRTs and DFTs of BP waves to the PPG values by reference to BP changes in each subject. We confirmed that the time-shift propensities of BP waves and the PPG data were highly consistent. However, the time shifts differed significantly among subjects. These simulation and experimental results allowed us to construct an initial trend curve of individual BP peak time (measured via wrist PPG evaluations at three arm positions) that facilitated accurate individual BP estimations.

• Membrane and Water Treatment
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• 제10권2호
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• pp.179-189
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• 2019

This study aimed to investigate the effect of temperature and solid retention time (SRT) on membrane fouling in a membrane bioreactors (MBRs). For this purpose, a lab-scale submerged MBR system was used. This system operated at two SRTs of 15 and 5 days, three various temperatures (20, 25 and $30^{\circ}C$) and hydraulic retention time (HRT) of 8 h. The results indicated that decreased the cake layer resistance and increased particles size of foulant due to increasing temperature and SRT. Fourier transform infrared (FTIR) analysis show that the cake layer formed on the membrane surface, contained high levels of proteins and especially polysaccharides in extracellular polymeric substances (EPS) but absorbance intensity of EPS functional groups decreased with temperature and SRT. EEM analysis showed that the peak on the range of Ex/Em=220-240/350-400 in SRT of 15 and temperature of $30^{\circ}C$ indicates the presence of fulvic acid in the cake. In addition, as the temperature rise from 20 to $30^{\circ}C$, concentration of soluble microbial products (SMP) increased and COD removal reached 89%. Furthermore, the rate of membrane fouling was found to increase with decreasing temperature and SRT.

• 대한환경공학회지
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• 제29권3호
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• pp.283-288
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• 2007

연속회분식반응조(SBR) 공정에서 슬러지 체류시간(SRT)에 따른 중금속의 독성도 변화를 측정하였다. 중금속은 구리(Cu), 카드뮴(Cd) 및 아연(Zn)을 사용하였고, SRT는 $2\sim30$일로 변화시켰으며, 독성도는 INT-dehydrogenase 활성도의 변화로 측정하였다. 중금속의 농도가 증가함에 따라 독성도가 증가하였으며, Cu가 Zn 및 Cd 보다 독성도가 높았다. SRT를 변화시켰을 때 $IC_{50}$ 값이 Cu의 경우 $0.37\sim1.96$ mg/L의 범위를 나타내었으며, Cd의 경우는 $15.4\sim16.9$ mg/L를 나타내었다. 또한 Zn의 경우는 $9.70\sim23.4$ mg/L의 범위를 나타내었다. Cu와 Zn의 경우, SRT가 증가함에 따라 독성이 감소하였으며, 이는 긴 SRT에서 세포외 중합체의 농도가 증가하기 때문인 것으로 판단된다. 따라서 중금속을 포함한 산업폐수를 처리하는 SBR 공정에서 SRT를 길게 운영하는 것이 바람직할 것으로 판단된다.

• 한국환경보건학회지
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• 제37권1호
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• pp.64-72
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• 2011

This study was performed to assess the removal efficiency on nitrogen, phosphorus and organic carbon in wastewater by spatial separation and internal recycling in a modified oxidation ditch process (modified OD). The performances of the modified OD were evaluated via laboratory-scale experiments. The process was operated at hydraulic retention times of 6-48 hours and solid retention times of 17-38 days. We found that organic carbon removal efficiency increased after the modified OD operation period. T-N removal efficiency remained stable; average T-N concentration of effluent was 8.02 mg/l after modified OD operation. In contrast, T-P concentration of effluent was over 1 mg/l. Nitrogen and phosphorus removal efficiency of modified OD at HRT 12 hr were 83.1% and 74.1%, respectively. Also, maximum efficiency was found at SRTs from 20 to 30 days. T-N removal efficiency was 83.1% at a C/N ratio from 3.0 to 3.5. However, T-N removal efficiency decreased at C/N ratios over 3.5. Also, T-P removal efficiency increased with HRT at C/P ratios in the same condition. Maximum efficiency was 74.1% at a C/P ratio from 25 to 28. T-N removal efficiency was 79.2% and T-P removal efficiency was 65.3% after M4 mode operation (added to the internal recycle line connected to the anoxic reactor). The modified OD with spatial separation and internal recycling developed in this study is, therefore, believed to be an improvement for solving problems in the nutrient removal technologies.

• 상하수도학회지
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• 제19권6호
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• pp.791-799
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• 2005

The phased isolation intra-clarifier ditch system used in this study is a simplified novel process enhancing simultaneous removal of biological nitrogen and phosphorus in municipal wastewater in terms of elimination of additional pre-anaerobic reactor, external clarifier, recycle of sludge, and nitrified effluent recirculation by employing intrachannel clarifier. Laboratory-scale phased isolation ditch system was used to assess the treatability on municipal wastewater. When the system was operated at the HRTs of 6~12hours, SRTs of 9~31days, and cycle times of 2~8hours, the system showed removals of BOD, TN, and TP as high as 88~97%, 70~84%, and 65~90%, respectively. The rainfall in Korea is generally concentrated in summer because of site-specific characteristics. Especially, the wet season has set in on June to August. In combined sewers, seasonal variations are primarily a function of the amount of stormwater that enters the system. In order to investigate the effect of hydraulic shock loading on system performance, the laboratory-scale system was operated at an HRT of 6hours (two times of influent flowrate) during two cycles (8hours). The system performance slightly decreased by increasing of influent flowrate and decreasing of system HRT. Nitrification efficiency and TN removal were slightly decreased by increasing of influent flowrate (decreasing of system HRT), whereas, the denitrification was not affected by hydraulic shock loading. However, the higher system performance could be achieved again after four cycles. Thus, the phased isolation technology for enhanced biological nutrient removal in medium- and small-scale wastewater treatment plants suffering fluctuation of influent quality and flowrate.

• 멤브레인
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• 제22권6호
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• pp.489-501
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• 2012

두 개의 간헐반응조, 막분리조, 탈기조로 구성된 생물학적 MBR고도처리 공정에 동일한 유입수량과 수질의 하수가 유입되는 경우 운전 온도 및 SRT (Sludge Retention Time)변화에 따른 질소제거 특성을 컴퓨터 시뮬레이션을 통해 파악하였다. SRT가 25일이고 운전온도가 $25^{\circ}C$인 경우 간헐반응조를 간헐폭기 시키는 경우에 운전온도 $13^{\circ}C$의 59%에서 31%로 질소제거효율이 급격히 떨어지는데, 이는 운전온도 $13^{\circ}C$에 비해서 간헐반응조의 RBO (Readily Biodegradable Organic) 농도가 낮아져서 발생한 현상으로 파악되었다. 운전온도 $25^{\circ}C$에서 SRT를 12.6일로 운전하는 경우 간헐반응조 RBO농도는 증가하고 질소제거 효율은 회복되었다. 간헐반응조를 갖는 MBR시스템에서 SRT와 운전온도가 간헐반응조 RBO농도에 미치는 영향은 좀더 깊게 연구되어야 한다.