• Title/Summary/Keyword: Sand bed

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A comparative study of granular activated carbon and sand as water filtration media with estimation of model parameters

  • Chatterjee, Jaideep;A, Shajahan;Pratap, Shailendra;Gupta, Santosh Kumar
    • Advances in environmental research
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    • v.6 no.1
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    • pp.35-51
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    • 2017
  • The use of Granular Activated Carbon (GAC) and naturally occurring silica (Sand) as filtration media in water and waste water treatment systems is very common. While GAC offers the additional functionality of being an "adsorptive" filter for dissolved organics it is also more expensive. In this paper we present an experimental evaluation of the performance of a bed of GAC for colloid removal and compare the same with that from an equivalent bed of Sand. The experiments are performed in an "intermittent" manner over extended time, to "simulate" performance over the life of the filter bed. The experiments were continued till a significant drop in water flow rate through the bed was observed. A novel "deposition" and "detachment" rate based transient mathematical model is developed. It is observed that the data from the experiments can be explained by the above model, for different aqueous phase electrolyte concentrations. The model "parameters", namely the "deposition" and "detachment" rates are evaluated for the 2 filter media studied. The model suggests that the significantly better performance of GAC in colloid filtration is probably due to significantly lower detachment of colloids from the same. While the "deposition" rates are higher for GAC, the "detachment" rates are significantly lower, which makes GAC more effective than sand for colloid removal by over an order of magnitude.

Removal characteristics of NOMs in a slow sand filter at different media depth and operation time (완속여과공정에서 운전시간 및 여층깊이에 따른 자연유기물질(NOM) 제거 특성)

  • Park, Noh-Back;Park, Sang-Min;Seo, Tae-Kyeong;Jun, Hang-Bae
    • Journal of Korean Society of Water and Wastewater
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    • v.22 no.4
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    • pp.467-473
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    • 2008
  • Natural organic matter (NOM) removal by physico-chemical adsorption and biological oxidation was investigated in five slow sand filters with different media depths. Non-purgeable dissolved organic carbon(NPDOC) and $UV_{254}$ absorbance were measured to evaluate the characteristics of NOM removal at different filter depths. Removal efficiency of NOM was in the range of 10-40% throughout the operation time. At start-up of the filters packed with clean sand media, NOM was probably removed by physico-chemical adsorption on the surface of sand through the overall layer of filter bed. However, when Schumutzdecke layer was built up after 30 days operation, the major portion of NPDOC was removed by biological oxidation and/or bio-sorption in lower depth above 50 mm. NOM removal rate in the upper 50 mm filter bed was $0.82hr^{-1}$. It was about 20 times of the rate($0.04hr^{-1}$) in the deeper filter bed. Small portion of NPDOC could be removed in the deeper filter bed by both bio-sorption and biodegradation. SEM analysis and VSS measurement clearly showed the growth of biofilm in the deeper filter bed below 500 mm, which possibly played an important role in the NOM removal by biological activity besides the physco-chemical adsorption mechanism

Behavior of sand columns reinforced by vertical geotextile encasement and horizontal geotextile layers

  • Shamsi, Mohammad;Ghanbari, Ali;Nazariafshar, Javad
    • Geomechanics and Engineering
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    • v.19 no.4
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    • pp.329-342
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    • 2019
  • In this paper, the effect of a group of sand columns in the loose soil bed using triaxial tests was studied. To investigate the effect of geotextile reinforcement type on the bearing capacity of these sand columns, Vertical encased sand columns (VESCs) and horizontally reinforced sand columns (HRSCs) were used. Number of sixteen independent triaxial tests and finite element simulation were performed on specimens with a diameter of 100 mm and a height of 200 mm. Specimens were reinforced by either a single sand column or three sand columns with the same area replacement ratio (16%) to evaluate the Influence of the column arrangement. Effect the number of sand columns, the length of vertical encasement and the number of horizontal reinforcing layers were investigated, in terms of bearing capacity improvement and economy. The results indicated that the ultimate bearing capacity of the samples with three ordinary sand columns (OSCs) is eventually about 11% more than samples with an OSC. Also, comparison of the column reinforcing modes showed that four horizontal layers of geotextile achieved similar performance to a vertical encasement geotextile at the 50% of the column height, from the viewpoint of strength improvement, while from the viewpoint of economy, the geotextile needed for encasing the single column is around 2.5 times of the geotextile required for four layers.

A Study on the Optimal Design in the Indirect Aerated Fluidized Bed (간접 포기식 유동상의 이상적 설계에 관한 연구)

  • 안송엽;김환홍;권희태
    • Journal of Environmental Science International
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    • v.8 no.1
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    • pp.95-100
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    • 1999
  • Process intensification without any increase in bed requires the exploitation of fluid mechanical phenomena as the basis for elegant solutions to the process engineering problems which result from the need to retain and control the immobilized biomass, and for biomass recovery. The fluidized bed biological reactor provides a solution to these needs. The wastewater treatment characteristics of the fluidized bed was filled with sand media. Indirect aeration were studied experimentally. The researcher was filled with sand particle size(0.60~0.42mm) in three reactors with different section area(A)/height(H), in the state BOD loading 4.5kg-$BOD_5/m^3$ㆍd, and under the fixed state of hydraulic retention time for around 32 minutes.

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An Experimental Study on the characteristics of Flow and Bed Topography with Changing Bed Material in a Curved Channel (만곡수로에서 하상재료 변화에 따른 흐름과 하상변동 특성에 관한 실험적 연구)

  • Jeong, Jae-Uk;Yun, Se-Ui
    • Journal of Korea Water Resources Association
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    • v.31 no.3
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    • pp.291-301
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    • 1998
  • The objective of this study is to analyze the characteristics of flow and bed topography with changing bed material in a 180-degree, with constant-radius curved experimental channel. Sand($D_{50}$ = 0.56 mm, s = 2.65) and anthracite($D_{50}$ = 0.26 mm, s = 1.54) were selected as bed materials. The maximum scour depth was found to be about two times for the mean flow depth at the outer bank of bend angle $30^{\circ}~60^{\circ}$, and in case of anthracite, it was found upper part of bend angle $5^{\circ}~15^{\circ}$ than that of sand. Regardless of bed materials the path of maximum streamwise velocity is skewed inwards in the upper part of the bend, the maximum velocity shifts outwards, and it lagged downward as bed roughness increases. The maximum skewed angle of flow grows faster in the smooth bottom than in the rough one, and its value also increases. The secondary flow in anthracite bottom was measured larger than that of sand one, and two cells of secondary flow was found in this experiment.

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EFFECTS OF RIVER DISCHARGE ON GROWTH OF PERIPHYTON IN SAND RIVER

  • Toda Yuji;Tsujimoto Tetsuro;Fujimori Noriomi
    • Water Engineering Research
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    • v.6 no.3
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    • pp.113-122
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    • 2005
  • Periphyton is known to be one of major primary producers for river ecosystem. While the growth of periphyton usually observed on the stone surface in gravel river, the large growth of periphyton is sometimes seen even in sand river with relatively small river discharge. In the present study, field observations and numerical simulations were performed to investigate the growth of periphyton in sand river. In the field observation, the growth of periphyton on fixed sand bed was measured weekly. The results of the field observations show that the large growth of periphyton occurs in sand river until the bed material sands have not moved. An integrated numerical simulation model is presented to describe the growth of periphyton at observed river reach, and a series of numerical simulations were performed to study the effect of river discharge on growth of periphyton in the sand river. The results of the numerical simulations show that the net primary production of periphyton decreases with the river discharge. These results suggest that the reduction of river discharge at ordinary water stage strongly affects the primary productivity of periphyton even in sand river.

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Characteristics of Fish Community Structure before the Dam Operation in the Naeseong Stream, Korea (내성천에서 영주댐 운영전 어류 군집구조의 특성)

  • Won, Jong-Seo;Kim, Seog Hyun;Cho, Kang-Hyun
    • Ecology and Resilient Infrastructure
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    • v.4 no.1
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    • pp.34-43
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    • 2017
  • The Naeseong Stream as a tributary of Nakdong River has conserved the unique structure and function of a typical sand-bed stream ecosystem. However, it is expected to change the stream bed environments and then the fish fauna in the downstream of the dam after the operation of the Yeongju Dam from 2016. We collected fishes and investigated their habitat environments from 2014 to 2016 in the downstream of the Yeongju Dam under construction in order to monitor changes in habitat environment, fauna and community structure of fishes in the Naeseong Stream. The size of the bed materials increased immediately downstream of the Yeongju Dam under construction. Before the operation of the Yeongju Dam, Zacco platypus was dominated and Opsarichthys uncirostris amurensis, Coreoleuciscus splendidus, Hemibarbus longirostris and Pseudogobio esocinus were sub-dominated according to the different sampling sites. Hemibarbus labeo, H. longirostris, Pseudogobio esocinus, Gobiobotia nakdongensis, Cobitis hankugensis and Leiocassis ussuriensis were found as a psammophilous fish specific to sand stream in the Naeseong Stream. At the downstream of the dam, the fish community was classified into a group of gravel-bed fishes such as Microphysogobio yaluensis, Coreoleuciscus splendidus and Coreoperca herzi and a group of sand-bed fishes such as Hemibarbus labeo, Cobitis hankugensis and Gobiobotia nakdongensis. These fish communities gradually tended to change from sand-bed fish community to gravel-bed fish community during the construction of the Yeongju Dam. Therefore, it is necessary to collect the baseline data for the stream ecosystem conservation in the sandy stream by continuously monitoring changes in the environment and fish in the downstream of the Youngju Dam.

Effect of Bed Height on Ginseng Growth and Soil Physical Properties (인삼포 두둑높이가 인삼의 생육 및 토양물리성에 미치는 영향)

  • 이일호;박찬수
    • Journal of Ginseng Research
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    • v.15 no.3
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    • pp.197-199
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    • 1991
  • Growth of ginseng and physical properties of soil were compared with bed height in experimental plots of sand loam for four year and clay loam soil for three year old ginseng plants, respectively. Field survey was also carried out to compare yield and soil physical properties with bed height in the same fold of six years old ginseng fields. High yield of ginseng root was observed at high bed both in the experimental plots and field survey as well. The rate of rusty root was significantly reduced at high bed. Soil porosity increased but soil hardness decreased at high bed.

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The Pressure Drop and Heat Transfer Characteristics of a Direct Contact 4-Stage Fluidized Bed Heat Exchanger (직접 접촉식 4단 유동층 열교환기의 압력손실 및 열전달 특성)

  • 임동렬;박상일;전광민
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.16 no.2
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    • pp.325-335
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    • 1992
  • In this work, direct contact 4-stage fluidized bed heat exchanger is experimentally studied to develop a new type of heat exchanger which recovers the energy contained in the high temperature waste gas exhausted from the industrial furnaces. A sand is used as a heat transfer medium in this experiment. To determine the optimum operating condition, 11 different perforated plates which have a different free area ratio with different hole diameter are used in the experiment. From the room temperature experiment, the pressure drop which is caused by fluidized bed formation is observed. The high temperature experiment is carried out to seek the optimum operating condition of high heat efficiency at low heat exchanger operation cost. The results of experiment are as following. The pressure drop in the high temperature condition can be predicted from the results of the room temperature experiment. And Nusselt number becomes smaller due to the increased interference between sand particles as Reynolds number increases when the dilute phase fluidized beds are formed in nigh temperature condition. But heat transfer amount through the total sand surface area become larger due to the large resident amount of sand. Considering the heat transfer amount and the heat exchanger operation cost, perforated plates which have either a 30% or 35% of free area ratio with 15mm of hole diameter are best fitted for our goal of this work. The values of .phi. which is a dimensionless number representing the absorption heat amount per unit sand rate are in the range from 0.4 to 0.5, when Reynolds number of waste gas ranges from 25-30 with these perforated plates.

A Study on the Process Selection for Two-stage and Dual Media Filtration System for Improving Filtration Performance (여과 성능향상을 위한 이단이층 복합여과시스템의 공정선정 연구)

  • Song, Si Bum;Jo, Min;Nam, Sang Ho;Woo, Dal Sik
    • Journal of Korean Society of Water and Wastewater
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    • v.21 no.2
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    • pp.203-214
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    • 2007
  • This study aimed at researching the process selection for two-stage and dual media filtration system, as a technology substituting the existing sand filter without expanding the site when retrofitting an old filter bed or designing a new one. In order to select the process for optimum complex filtration system, three running conditions have been tested. Test results demonstrated that Run 3 in which the 1st stage was filled with anthracite and coarse sand, and the 2nd stage was filled up with activated carbon and fine sand reduced the head loss and the load of turbidity substances. Also, Run 3 showed better performance in removing TOC, particle counts, THMFP and HAAFP, compared to other two conditions. 99 % of Cryptosporidium was removed. Bisphenol-A was rarely removed from the 1st stage of coarse sand and 2nd stage of fine sand, but 99 % of it was removed from the 2nd stage of activated carbon. In conclusion, when it is required to retrofit an old rapid filter bed or design a new one for the purpose of improving filtration performance, the following two-stage and dual media filtration system is suggested: the 1st stage of filter bed needs to be filled up with coarse sand to remove turbidity as the pretreatment for extending duration of filtering, the top part of 2nd stage needs to be filled up with granular activated caron to remove dissolved organic matters and others as the main process, and finally the bottom part of 2nd stage needs to be filled up with fine sand as the finishing process.