• 한국농공학회지
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• 제45권1호
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• pp.63-73
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• 2003

The settling of the dredged soil may vary with mineral composition, grain size distribution, initial water content and salt concentration of suspension of the site. A series of settling column test was performed to investigate the behaviour of solid suspension material from dredging and reclamation. Settling mode was divided into four types from the observation of interface and settling curves of clay minerals and marine clay samples, and the relationship charts of salt concentration and the initial water content were established to use in the dredging operation with any salt concentration. The critical initial water content which was defined as a threshold of zone settling and the consolidation settling was varied with salt concentration of water and was proportional to the plasticity of soil in sea water.

• 대한전기학회논문지:시스템및제어부문D
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• 제50권2호
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• pp.65-71
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• 2001

The step response of the Manabe standard form[2] has little overshoot and show almost same waveforms regardless of the order of the characteristic polynomials. In some situations it is difficult to control the rise time and settling time simultaneously of the step response of the Manabe standard form To control its rise time and settling time efficiently, We develop the Manabe standard form: We try to find out the SRFS(Slow Rise time & Fast Setting time) form which has the slower rise time and faster settling time than those fo the Manabe standard form. We also consider the other three forms: FRSS(Fast Rise time & Slow Settling time), SRFS(Slow Rise time & Fast Settling time) and SRSS(Slow Rise time & Slow Settling time) forms. In this paper, by using the evolutionary strategy, we obtain all the coefficient of the four forms we mention above. Finally, we design a controller for a given plant so that the overall system has the performance that the rise time is faster, the settling time is faster than those of the Manabe standard form.

• 한국해양환경ㆍ에너지학회지
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• 제5권1호
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• pp.3-10
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• 2002

미세점착성 퇴적물 침강속도의 정량적 산정은 퇴적학적 측면에서뿐만 아니라 환경공학적 측면에서도 매우 중요한 과제이다. 미세점착성 퇴적물의 침강특성은 입자간의 충돌과 입자간의 점착으로 인하여 발생하는 응집에 의해 크게 영향을 받는다. 한편, 미세점착성 퇴적물의 응집강도는 광물질 구성, 입경분포, 유기물 함량 등으로 묘사되는 퇴적물의 물리ㆍ화학적 기본 특성에 따라 크게 변화하고, 이러한 물리ㆍ화학적 기본특성은 또한 지역적으로 변화하므로, 한 특정지역에서의 점착성 퇴적물의 침강특성은 현장관측이나 실내실험을 통하여 관측되어야만 한다. 본 연구에서는 최근 수행된 새만금 및 군산해역 점착성 퇴적물의 침강속도 관측 결과를 이용하여, 기존의 침강속도 경험식을 검토하고, 새로운 침강속도 곡선식이 개발된다. 새로 개발된 침강속도 곡선식은 기존의 복잡한 곡선식에 비해 단순하며, 측정치로부터의 계수산정이 편리하고, 또한 측정치의 변화 경향을 더욱 잘 나타낸다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 춘계 학술발표회 초청강연 및 논문집
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• pp.1061-1064
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• 2008

A completion of settling process takes a lot of time for dredged materials of high moisture content, such as contaminated sludge, in landfill site. In general, additives (e.g. flocculants) are used for reducing settling time of such colloidal material, which results in the increase of sludge volume, and hence much space is required in landfill site. This study is to suggest alternative method in order to enhance the settling process of cohesive clayey soils. A number of gravitational sedimentation tests as well as electrokinetic experiments were conducted to investigate the variation of initial moisture content on the settling behaviour of clay slurry. Surface settlement, electric current and local voltage gradient were monitored during the experiment, and moisture content and soil pH were measured after the experiment. From the results, the application of electrokinetics was found to be effective in volume reduction (i.e. increase of settling velocity and decrease of final moisture content) by comparison with gravitational settling process.

• 상하수도학회지
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• 제22권6호
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• pp.627-632
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• 2008

It is necessary to investigate methods for improvement by diagnosing sludge settling characteristics on inflow of slurry to thickener. The results of the settling tests are correlated to determine zone settling velocities at the various sludge solids concentrations. Conditioning of WTP residuals is generally done by either chemical or physical treatment. The settling test was conducted with 1m columns dosing polymer to WTP residuals at various solids concentration. The estimated results for dosing to WTP residuals for a sludge of 2,100 ~ 16,012 mg/L solids concentration were the zone settling velocities of 48.38 ~ 6.8 m/day, supernatant solid concentration of 3.2 ~ 19 mg/L and solid flux of $101.6{\sim}317.61kg/m^3{\cdot}day$. The values for non-polymer treatment were the zone settling velocities of 28.37 ~ 0.12 m/day, supernatent solid concentration of 8.5 ~ 108 mg/L and solid flux of $59.58{\sim}1.92kg/m^2{\cdot}day$. The limiting solid flux value by Yoshioka methods was $4.0kg\;TS/m^3{\cdot}day$ for Non-polymer and $228.0kg\;TS/m^3{\cdot}day$ for dosing polymer. These results are to indicate a possibility of improvement on the thickening characteristics and the quality of supernatant as increasing the settling velocities by dosing polymer to WTP residuals.

• 상하수도학회지
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• 제20권6호
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• pp.857-865
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• 2006

The submerged barrier, employed in a reactor, divided a reactor into sludge settling zone and mixing zone according to flow type. In spite of mixing in the mixing zone, the lower part of sludge settling zone than the top of barrier was in a steady flow due to the barrier, which prevented the turbulent flow, produced from the mixing zone, from being diffused into the sludge settling zone. Therefore, the sludges in the mixing zone flowed backward over the barrier into the upper part of the sludge settling zone by turbulent flow and settled down in the sludge settling zone by the force of gravity. When barrier/water level ratio was 0.5, most sludges almost did not settle down in tile sludge settling zone because the sludges were directly affected by the turbulent flow, generated from mixer in the mixing zone. At 0.63 of barrier/water level ratio, sludge in the middle part of sludge settling zone rocked from side to side weakly. And sludge in the lower part became piled up on the bottom over this ratio. After 10minutes of sludge settling, the lower part of sludge settling zone was over 5000mg/L of sludge concentration although intial sludge concentration was 2300mg/L. By using the submerged barrier and the flow types, it could transfer sludge from this to that.

• 한국수자원학회논문집
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• 제35권5호
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• pp.475-484
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• 2002

새만금 미세점착성 퇴적물의 침강특성을 퇴적물 자체의 물리ㆍ화학적 기본특성과 연계 해석하기 위하여, 퇴적물의 입경분포, 광물질 구성 및 유기물 함량 조사로 구성되는 새만금 퇴적물에 대한 물리ㆍ화학적 특성 조사가 수행되었다. 새만금 퇴적물의 물리ㆍ화학적 특성에 대한 분석 결과, 새만금 퇴적물은 평균입경(52$\mu\textrm{m}$)이 비교적 크고 유기물 함량(2%)이 매우 작으며, 점착력이 비교적 자은 석영이 주된 광물질 구성성분으로 점착력에 의한 침강효과 보다는 중력에 의한 침강효과가 더 큰 퇴적물인 것으로 밝혀졌다. 따라서 이러한 효과로 인하여, 새만금 퇴적물은 응집효과가 침강속도를 증가시키는 응집침강 영역에서 비교적 작은 침강속도를 가지며, 응집효과가 침강속도를 감소시키는 간섭침강 영역에서는 비교적 큰 침강속도를 갖는 것으로 나타났다.

• 상하수도학회지
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• 제20권1호
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• pp.147-155
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• 2006

For the further study of the solids flux theory, several researchers have proposed models to predict sludge settling velocity for each different concentration by using sludge indexes, SVI, SSVI and $SSVI_{3.5}$. It is difficult to apply the above models to predict sludge-water interface height in a batch column because sludge settling velocity changes while sludge settle down. While sludge settle down in a batch column, sludge concentration becomes high. The sludge concentration change is one of the most critical causes of the change of sludge settling velocity. Also, sludge concentration change causes of sludge index to change. SVI is more sensitive than SSVI or $SSVI_{3.5}$ to the change of sludge concentration. Each sludge has physical characteristics of its own which makes the settling velocity for each sludge different. The purpose of this study is to establish the correction factors that are able to compensate the errors derived from each different sludge settling characteristic by using sludge indexes, therefore the correction factors are applicable to the model for the change of sludge-water interface height.

• 상하수도학회지
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• 제28권5호
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• pp.609-614
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• 2014

Researcher of this study improved conventional circle secondary settling basin, through the way such as extend of inlet pipe length, introduction of device for inducting uniforming of flow, keeping of height of sludge interface. Also, we compared conventional circle settling basin to improved circle settling basin the water treatment efficiency. Result of research, when SVI is average 117, improvement rate of SS and BOD were 51.0%, 37.0% approximately compared to conventional settling basin. And when SVI is average 178, improvement rate of SS and BOD were 22.7%, 36.0% approximately. Also when SVI is average 196, improvement rate of SS and BOD were 24.7%, 30.3% approximately. When it's winter, improvement rate of SS, BOD, COD, TN and TP were 20.6%, 17.9%, 13.9%, 13.5%, 12.4% approximately. Therefore, we can be the judge, this improved settling basin can be used as the final settling basin in the waste water treatment plant.

• 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).