• Title/Summary/Keyword: Settling characteristics

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Evaluation of Solids Removal Characteristics on Sewage Treatment Plants Using T-P sludge Return into the Primary Settling Tank (총인슬러지의 1차 침전지 반송에 따른 하수처리장 고형물 제거특성 연구)

  • Kim, Jong-Oh;Jung, Dong-Gi;Kwon, Hye-Jeong;Hwang, Joon-Seok
    • Journal of Korean Society of Water Science and Technology
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    • v.26 no.6
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    • pp.73-80
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    • 2018
  • In this study, the solids removal characteristics using T-P sludge generated from PACl coagulation were analyzed by laboratory scale and full scale experiment. As the amounts of T-P sludge injection into the raw sewage influent increased at the rate of 0, 1, 2, 3, 4 %, the suspended solids concentrations after 20 minutes setting test decreased to 210, 137, 91, 64, 43 mg/L, respectively. The filtration time required for dewatering test of the raw sewage influent decreased to 982, 728, 658, 581, 492 sec for 0, 1, 2, 3, 4% of T-P sludge injection, respectively. As the amounts of PACl coagulant into the effluent from final setting tank increased at 0, 10, 20, 30, 40 mg/L, the required filtration times for T-P sludge increased into 12.3, 41.7, 53.7, 67.2, 79.5 sec and the dewaterability of T-P sludge decreased. After T-P sludge returned into the primary settling tank on J-si sewage treatment plants, the effluent concentrations of COD, SS, T-N and T-P from primary settling tank into bioreactor decreased by 35.9, 27.9, 22.2, and 52.6% due to the coagulation effects of the T-P sludge. Finally, it was found that the return of T-P sludge into the primary settling tank could result into the sludge reduction having a lower water content of 3.03% p than in case of the only T-P sludge dehydration.

Characteristics of Farming Settlement for Young Farmers (청년농업인의 영농정착 특성 분석)

  • Lee, So-Young;Lee, Min-Soo;Kim, Jin-Jin
    • Journal of Agricultural Extension & Community Development
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    • v.29 no.2
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    • pp.99-110
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    • 2022
  • This study aims to examine the characteristics of farming settlement in young farmers. In order to analyze the effect of each characteristic on young farmers' intention for settling into farming, an ordered logit model was employed. As for the individual characteristics affecting their intention for settling into farming, age and the highest education level showed a positive effect, while family-run farming had a negative effect, which was found statistically significant. For the financial characteristics, farm income had a statistically significant positive effect. On the other hand, the social and policy characteristics did not show any statistically significant effect.

FLOW CHARACTERISTICS OF A TWO-DIMENSIONAL NEUTRALLY BUOYANT JET IN A MODEL SETTLING TANK

  • Kim, Young-han;Seo, Il-Won;Ahn, Jung-kyu
    • Water Engineering Research
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    • v.2 no.1
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    • pp.21-31
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    • 2001
  • In this study, laboratory experiments were performed to investigate the flow characteristics of a two-dimensional neutrally buoyant jet in the inlet region of a rectangular laboratory settling tank. Velocity measurements were made with a three-component ADV. Two types of baffles were installed in front of two-dimensional slot; a one-sided and a two-sided baffle. The flow fields from a plane jet impinging on these two types of baffles and a plane jet without a baffle showed quite different characteristics. To concentrate on investigating these flow characteristics, the effects of density currents due to temperature difference or the presence of sediments were not studied. Results of the experiments reveal that the use of the two-sided baffle results in the shortest inlet region. Also shown is that, in addition to the types of baffles, the Froude number turns out to be an important factor in the extent of the inlet region.

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Experimental investigation of turbulent effects on settling velocities of inertial particles in open-channel flow (개수로 흐름에서 난류가 관성입자의 침강속도에 미치는 영향에 대한 실험연구)

  • Baek, Seungjun;Park, Yong Sung;Jung, Sung Hyun;Seo, Il Won;Jeong, Won
    • Journal of Korea Water Resources Association
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    • v.55 no.11
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    • pp.955-967
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    • 2022
  • Existing particle tracking models predict vertical displacement of particles based on the terminal settling velocity in the stagnant water. However, experimental results of the present study confirmed that the settling velocity of particles is influenced by the turbulence effects in turbulent flow, consistent with the previous studies. The settling velocity of particles and turbulent characteristics were measured by using PTV and PIV methods, respectively, in order to establish relationship between the particle settling velocity and the ambient turbulence. It was observed that the settling velocity increase rate starts to grow when the particle diameter is of the same order as Kolmogorov length scale. Compared with the previous studies, the present study shows that the graphs of the settling velocity increase rate according to the Stokes number have concave shapes for each particle density. In conclusion, since the settling velocity in the natural flow is faster than in the stagnant water, the existing particle tracking model may estimate a relatively long time for particles to reach the river bed. Therefore, the results of the present study can help improve the performance of particle tracking models.

Development of NH3 Emission Factors using a Dynamic Flux Chamber in a Sewage Treatment Plant (부유형 챔버를 이용한 하수처리장에서의 암모니아 배출 특성 연구)

  • Jeon, Eui-Chan;Sa, Jae-Hwan;Park, Jong-Ho
    • Journal of Environmental Impact Assessment
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    • v.14 no.5
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    • pp.263-273
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    • 2005
  • In this study, the major emission procedures and emission characteristics were identified at the site of sewage treatment plant which is one of the major sources of ammonia. At the same time the emission factors and emission rates were estimated. In order to calculate the emission flux, we used a Dynamic Flux Chamber(DFC), which is found to be a proper sampling devise for area sources such as sewage treatment plant. It was found that the most stable sampling condition was when the stirrer's speed of DFC was 120RPM, and it would be the best time to take a sample 60 minutes later after setting the chamber. The relatively higher flux was shown in Autumn compared to summer and winter. Annual ammonia emission rates procedures were calculated as $906.32{\mu}g/activity-ton$, $1,114.72{\mu}g/activity-ton$ and $437.53{\mu}g/activity-ton$ each at the primary settling basin, aeration basin and the final settling basin, respectively. The ammonia emission rate the highest at in the aeration basin according to this test. This results was due to that the surface of aeration basin or the final settling basin is relatively wider than the primary settling basin.

A Basic Study on the Removal of Iron Ion in Waste Water by the Precipitation Method (침전법에 의한 폐수중의 철이온 제거에 관한 기초 연구)

  • 강동현;김형석;조동성
    • Resources Recycling
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    • v.2 no.2
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    • pp.16-21
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    • 1993
  • This study was carried out to investigate the settling characteristics of Fe(II) and Fe(III) hydroxide precipitates formed by pH adjustment of aqueous solution to remove ferrous and ferric ion in waste water. The results obstained in this study are as fellows : The settling rate was effectively increased with increasing the pH values of aqueous solution regulated by CaO and with increasing the amount of flocculant, on the other hand, application of excess flocculants decreased the settling rate. It is desirable that the concentration of iron ion is kept under $10^{-2}$ mol/ㅣ because the settling rate was decreased with increasing the concentration of iron hydroxide precipitates.

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Effects of a new type of clear overlay retainer on occlusal contacts

  • Kim, Kyoung Yeon;Ahn, Hyo-Won;Kim, Seong-Hun;Nelson, Gerald
    • The korean journal of orthodontics
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    • v.47 no.3
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    • pp.207-212
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    • 2017
  • The popularity of clear overlay retainers (CORs) has increased recently because of their advantages such as better esthetics, cost effectiveness, easy fabrication, and good compliance. However, a deficiency in posterior occlusal settling is a reported limitation of CORs. The aim of this study was to evaluate the posterior occlusal contact changes in a new type of clear orthodontic retainer called Oral-treaper (OTP), which consists of three layers and has stronger mechanical characteristics than do conventional retainers. Three patients who completed fixed orthodontic treatment received OTP as a removable retainer. Cast models were fabricated after the removal of fixed appliances (T1) and after 4 to 11 months of using the retainers (T2). We evaluated all the cast models to compare the post-orthodontic settling pattern during the use of the OTPs. The depth of occlusal contacts was evaluated using color maps. The OTP did not prevent vertical settling in all patients but resulted in an improvement in posterior occlusal contact points.

Application of Particle Size Analysis to Predict the Settleability of CSO Pollutants (입경분포 분석을 활용한 합류식 하수관거 월류수(CSO) 오염물질 침강성 예측)

  • Yoon, Hyun Sik;Lee, Doojin;Park, Young Suk
    • Journal of Korean Society of Water and Wastewater
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    • v.20 no.2
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    • pp.295-302
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    • 2006
  • Over the past decades, a flocculation and/or sedimentation process have been adopted to remove pollutants from CSOs. It has been learned that major factors affecting settlement of pollutants are the particle size distribution, their settling velocities and their specific gravity. It is, therefore, a good idea to analyze the particle size distribution and settleability of CSOs pollutants in order to develop details in designing a process. Discussed in this study are pollutant characteristics of CSOs such as particle size distribution and settleability of pollutants. The power law function is applied and is found to be an effective and reliable index for expressing the particle size distribution of pollutants in CSOs. Based on the regression analysis it is observed that the derived constants of curves representing settling velocity profile are proportional to the initial concentration of particles and to the ${\beta}$-values of power law distributions.

A Low-Voltage High-Performance CMOS Feedforward AGC Circuit for Wideband Wireless Receivers

  • Alegre, Juan Pablo;Calvo, Belen;Celma, Santiago
    • ETRI Journal
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    • v.30 no.5
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    • pp.729-734
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    • 2008
  • Wireless communication systems, such as WLAN or Bluetooth receivers, employ preamble data to estimate the channel characteristics, introducing stringent settling-time constraints. This makes the use of traditional closed-loop feedback automatic gain control (AGC) circuits impractical for these applications. In this paper, a compact feedforward AGC circuit is proposed to obtain a fast-settling response. The AGC has been implemented in a 0.35 ${\mu}m$ standard CMOS technology. Supplied at 1.8 V, it operates with a power consumption of 1.6 mW at frequencies as high as 100 MHz, while its gain ranges from 0 dB to 21 dB in 3 dB steps through a digital word. The settling time of the circuit is below 0.25 ${\mu}s$.

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Evaluation of Hydraulic Characteristics Influenced by Different Deflector Baffles in the Sedimentation Basin with Inclined Plate Settler (경사판 침전지에서 저류벽의 설치위치에 따른 수리학적 특성의 평가)

  • Yu, Myong-Jin;Kim, Hyun-Chul;Ryu, Seong-Ho
    • Journal of Korean Society on Water Environment
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    • v.21 no.1
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    • pp.40-45
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    • 2005
  • Sedimentation is one of the most common and important units in conventional water treatment plant. Structure such as various baffle walls and inclined plate settler may be obstacles to the horizontal flow when it is poorly designed. Therefore, the effects of these structures on characteristics of hydraulic flow must be evaluated to improve the settling efficiency of the floc. The hydraulic characteristic of the two sedimentations at Y water treatment plant (YWTP), which have different deflector baffles inside the settling basin, were investigated by tracer (fluoride) test. The inclined plate settler installed inside settling basin caused an undesirable impact on horizontal flow and produced dead zone. Solid baffle wall under the plate settler could help to minimize the formation of density currents and flow short circuiting. NaF used as a tracer was recovered more than 90% at investigated all basins. Morill index ($t_{90}/t_{10}$), Modal index ($t_p/T-HRT$) and short-circuiting index ($[M-HRT-t_p]/M-HRT$) were determined from tracer test results performed at YWTP. Those indices ranged 2.95~3.02, 0.40~0.53 and 0.32~0.46, respectively.