• 상하수도학회지
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• 제35권2호
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• pp.153-162
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• 2021

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 ㎛, M-II: 250-425 ㎛ 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.

• Environmental Engineering Research
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• 제25권3호
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• pp.400-408
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• 2020

Hydrodynamic study of Activated Sludge Process (ASP) is important to optimize the reactor performance and detect anomalies in the system. Residence time distribution (RTD) study has been performed using LiCl as tracer on a pilot scale aeration tank (AT) and ASP, treating the pulp and paper mill effluent. The hydraulic performance and treatment efficiency of the AT and ASP at different operating parameters like residence time, recycle rate was investigated. Flow anomalies were identified and based on the experimental data empirical models was suggested to interpret the hydrodynamics of the reactors using compartment modelling technique. The analysis of the RTD curves and the compartment models indicated increase in back-mixing ratio as the mean hydraulic retention time (MHRT) of the tank was increased. Bypassing stream was observed at lower MHRT. The fraction of dead zone in the tank increased by approximate 20-25% with increase in recycle rate. The fraction of the stagnant zone was found well below 5% for all performed experiments, which was under experimental error. The substrate removal of 91% for Chemical oxygen demand and 96% for Biochemical oxygen demand were observed for the ASP working at a hydraulic mean residence time 39 h MRT with a 20% recycling of activated sludge.

• 멤브레인
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• 제24권3호
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• pp.249-257
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• 2014

본 실험은 실험실적 규모의 침지식 평막형 분리막이 장착된 활성슬러지 생물반응기에 인공폐수를 사용하여 수행하였다. 분리막 운전은 MLSS 5,000 mg/L 활성슬러지 용액을 일정 유량으로 계속 투과시키는 방식과 주기적으로 10분여과/2분휴지 방식으로 구분하여 실시하였다. 산기량은 0.25 L/min로 일정하게 유지한 상태에서 투과유속을 10에서 $25L/m^2{\cdot}hr$까지 증가시키면서 막간차압을 측정하였다. 또한 분리막 오염 상태를 판단하기 위하여 완전막힘, 표준막힘, 중간막힘, 비압축성 케이크 및 선형압축성 케이크 오염 모델을 실험값에 적용하였다. 10분운전/2분휴지 운전방식에서는 매 주기마다 펄스형태로 막간차압이 변화하므로 최고점 및 최저점 연결선으로 구분하여 막오염 모델을 적용하였다. 활성슬러지 케이크 막오염은 이상의 5가지 오염 모델 중 선형압축성 케이크 오염 모델이 모든 투과실험 결과와 가장 잘 일치하였다.

• 한국물환경학회지
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• 제25권6호
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• pp.964-971
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• 2009

In this paper, activated sludge settling was characterized based on field trip and zone settling tests. Plants used for this study include 5 conventional activated sludge processes and 3 A2O type treatment processes. The treatment capacities are in the range from 12,000 to $250,000m^3$/day. Total number of zone settling tests were 188 set and SVI values representing settling characteristics were from 100 to 300 mL/g. It was found out that zone settling velocity of these examined plant sludges can be approximated by mean values calculated by Keinath and Daigger/Roper models. Based on these three models, solid flux analysis were carried out in order to compare design criteria ($3.96{\sim}6.04kg/m^2-hr$) recommended by Korea Sewage Facility Design Guideline with two models used in USA. The results show that design criteria are only applicable for normal condition in settling characteristics (below SVI 100 mL/g). Solid flux analysis of surveyed plants indicates that most of the plants are operated underload conditions except several plants experiencing poor sludge settling problem. Most of the plants are operated under high sludge blanket depths (SBD).

• 한국환경과학회지
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• 제14권9호
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• pp.881-888
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• 2005

The biosorption of dye, Rhodamine B(Rh-B), onto waste activated sludge was investigated. The biosorption capacity and contact time were shown as a simulation of dye adsorption equilibrium and kinetics models. We observed that biosorption of Rh-B occurred rapidly less than 4 hr. These experimental data could be better fitted by a pseudo-second-order rate equation than a pseudo-first-order rate equation. The equilibrium dependence between biosorption capacity and initial concentration of Rh-B was estimated and it was found that the equilibrium data of biosorption were fitted by four kinds of model such as Langmuir, Freundlich, Redlich-Peterson, and Koble-Corrigan model. The average percentage errors, $\varepsilon(\%)$, observed between experimental and predicted values by above each model were $21.19\%,\;9.97\%,\;10.10\%\;and\;11.76\%$, respectively, indicating that Freundlich and Redlich-Peterson model could be fitted more accrately than other models.

• 대한환경공학회지
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• 제30권2호
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• pp.199-206
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• 2008

동시 질산화 탈질은 낮은 DO 농도로 유지되는 동일한 반응조에서 질산화 반응과 탈질 반응이 동시에 발생함을 의미한다. 동시 질산화 탈질 반응을 모사할 수 있는 몇몇 수학적 모델들이 개발되었지만, 모델 구조가 복잡하거나 모델을 적용하기 위한 다양한 제반 지식을 얻어야만 정확한 결과를 얻을 수 있어 범용적인 모델 적용에 한계점이 있는 단점이 있었다. 이와 같은 문제를 해결하기 위해, 동시 질산화 탈질 반응이 반응기 내 DO 농도의 부분적 부재로 발생한다는 가정 하에, 만약 활성슬러지모델을 사용하여 동시 질산화 탈질 반응의 거동을 해석할 수 있다면, 모델의 구조가 다른 개발된 모델들보다 복잡하지 않고, 다양한 운전 조건에서 모델이 활용될 수 있을 것으로 판단하였다. 하지만 기존의 활성슬러지 모델로는 호기 조건에서 발생하는 탈질 반응을 표현하기 어려운 점이 있기 때문에, 본 연구에서는 활성슬러지 모델을 수정함으로써 동시 질산화 탈질 반응을 해석하고자 하였다. 활성슬러지 모델 No.1(ASM1)이 선택이 되어 탈질 반응식이 수정되었으며, 수정된 ASM1의 시뮬레이션 결과는 측정값의 거동을 잘 모사하였다. 이를 통해 수정된 ASM1은 실험 결과에 기반하여 구한 ${\eta}_g$의 값과 호기 조건에서의 탈질 반응을 모사하기 위해 수정된 Monod 식의 영향으로 모델의 구조가 본 연구의 실험 결과에서 확인된 동시 질산화 탈질 반응을 해석할 수 있도록 구성되었다고 사료된다.

• 전기학회논문지
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• 제67권11호
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• pp.1477-1485
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• 2018

There are two major issues for activated sludge process in sewage treatment plant. One is how to make sewage be more clean and the other is the energy saving in sewage treatment process. The major monitoring sewage qualities are chemical oxygen demand, phosphorus, nitrogen, suspended solid in effluent. These are transmitted to the national TMS(Telemetry Monitoring System) at every hour. If these exceed the environmental standard, the environmental charges imposed. So, these water qualities are to be controlled below the environmental standard in operation of sewage treatment plant. And recently, the energy saving is also important in process operation. Over 50% energy is consumed in blowers and motors for injection oxygen into aeration tank. So, with the water qualities to be controlled below the environmental standard, the energy saving also is to be accomplished for efficient plant management. Almost researches are aimed to control water quality without considering energy saving. AI techniques have been used for control water quality. AI modeling simulator provided the optimal control inputs(blower speed, waste sludge, return sludge) for control water quality. Blower speed is the main control input for activated sludge process. To make sewage be more clean, the excessive blower speed is supplied, but water quality is not better than the previous. In results, non necessary energy is consumed. In this paper we propose a new method that the energy saving also is to be accomplished with the water qualities to be controlled below the environmental standard for efficient plant management. Water qualities in only aeration tank are used the inputs of fuzzy models. Outputs of these models are chemical oxygen demand, phosphorus, nitrogen, suspended solid in effluent and have the environmental standards. In test, we found this method could save 10% energy than the previous methods.

• 상하수도학회지
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• 제26권6호
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• pp.889-896
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• 2012

In this study, simulation results of nitrogen and phosphorus removals and microbial activities for an $A_2O$ process in wastewater treatment plant are presented by using Activated Sludge Models (ASMs). Simulations were performed using pre-calibrated model and layout implemented in GPS-X simulation software. The models were used to investigate variations of SRT, water temperature, DO and C/N ratio effect on nutrients removal and microbial activity. According to the simulated results, the successful nitrification required SRT higher than 10.3 days, whereas increase of $NO_3$-N loading in the anaerobic reactor caused phosphorus release by PAOs; the effluent $NH_4$-N showed rapid change between $12^{\circ}C$(21.7 mg/L) and $13^{\circ}C$(3.2 mg/L); the effluent phosphorus was increased up to 1.9 mg/L at water temperature of $25^{\circ}C$; the DO increase was positive for heterotrophs and autotrophs growths but negative for PAOs growth; the PAOs showed low activity when C/N ratio was lower than 2.5. The experimental results indicated that the calibrated models can assure the prediction quality of the ASMs and can be used to optimize the $A_2O$ process.

• Korean Chemical Engineering Research
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• 제60권1호
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• pp.80-85
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• 2022

In wastewater treatment processes huge quantities of sludge are produced continuously each year. This work investigated the reuse of two types of sludge as biosorbents of a toxic dye. The potential of granular and filamentous fungus dried sludge for the elimination of eosin from aqueous solution was studied in batch system. The effect of initial concentration and temperature was examined. Maximum uptake was observed at 100 mg l^-1 and 30 ℃. The maximum removal rate was 92% for the granular sludge and 90% for the filamentous one. Equilibrium was attained after 30 min for the studied dye concentrations. The equilibrium uptake increased with the initial eosin concentration. The Freundlich and Langmuir adsorption models were also investigated. The reuse of disposed sludge as adsorbent could be a solution for the valorization of such dangerous waste to resolve two environmental problems at the same time.

• 한국환경과학회지
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• 제4권5호
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• pp.509-516
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• 1995

The treatment performances of anaerobic-aerobic activated sludge process were investigated under various operation conditions. The treatment system proposed in this study gave a relatively stable performance against hourly change of the flow rate and showed a satisfactory removal of nitrogen and phosphorus compounds under experimental conditions. The recycle ratio of mixed liquor from aerobic to anaerobic region and peak coefficient primarily controlled the extent of nitrogen removal. The recycle ratio had the optimum values which were determined by the microbial activities of nitrification and denitrification. The behavior of the treatment unit could be simulated by using the kinetic equations and reactor models which considered the treatment units as complete mixing tanks.