• Journal of the Korean GEO-environmental Society
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• v.23 no.9
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• pp.33-40
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• 2022

Sedimentation and pH neutralization has been investigated as preteatment of acid contaminate water. The settling and neutralizing process derive more effective degradation efficiency as the pre-treatment process before the removal process of adsorption, volatile, biodegradation, or oxidation. Settling velocity, uniformity coefficient, coefficient of curvature, and grain size index can define in the sedimentation process for characteristics of the soil. The stainless steel sieve has been used to separate each particle size of the dry soil by assembling in order of 4, 10, 20, 40, 80, 100, and 200 mesh sizes. The soil from Gamcheon Port in Busan drops upper side of the sieve and shakes back and forth to separate each different size of the particle. The 1L of Imhoff cone and 200 mL of the mass cylinder were used as settling tanks to calculate settling velocity. Stokes' equation was used to figure out the average density of dry soil with a value from settling velocity. In the results, the average particle density and lowest settling velocity were 1.93 g/cm³ and 0.11 cm/s, respectively. These values can detect the range of settling points of sediment to prevent chemical accidents. In pH neutralization, the initial pH of 2, 3, 4, and 5 of nitric acid and sulfuric acid are used as an acid solution; 0.1, 0.01, and 0.001 M of sodium hydroxide and calcium hydroxide are used as a base solution. The main goal of this experiment is to figure out the volume percentage of the acid solution becomes pH 7. The concentration of 0.001 M of base solution exceeds all the conditions, 0.01 M exceeds partially, and 0.1 M does not exceed 5 v/v% except pH 2. Calcium hydroxide present less volume than sodium hydroxide at pH neutralization both sulfuric and nitric acid.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.3
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• pp.140-148
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• 2017

The effectiveness of the first flush treatment system using settling process was evaluated to reduce urban nonpoint source pollutant loads to surface water during storm events. A pilot scale system was constructed and tested in the field and surface runoff samples were collected automatically according to pre-defined conditions. Nine rainfall events were tested and average removal efficiencies of TSS (Total Suspended Solid), TP (Total Phosphorus) and TN (Total Nitrogen) were evaluated as 87.4%, 75.3%, and 43.6%, respectively. Concentration and removal efficiency of pollutants were found to be affected by an amount of rainfall and rainfall intensities of the respective events. This seemed to be caused by the greater particulate fractions of first flushed samples than the samples collected in later time periods during the same rainfall events. The study showed that it is possible to remove a significant portion of the nonpoint source pollutant loads in initial rainfall runoff by using a simple settling process for TSS and TP without requiring additional power or chemicals.

• Journal of Animal Environmental Science
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• v.8 no.3
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• pp.145-152
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• 2002

This experiment was conducted to investigate the efficiency and compatibility of the coagulation and settling processes of leachates from the compost of two swine farms. And results obtained are as follows : 1 In the farm A where $COD_{Cr}$, $COD_{Mn}$ and $BOD_5$ of original leachate were 4,400, 2,950 and 87mg/l, respectively, the rate of coagulation and settling process was more efficient in the leachate treated with the conjugate of Alum and cation polymer than that of Alum and anion polymer. The concentrations of BOD$_{5}$, T-N and T-P of the effluent after treatment with the conjugate of Alum and cation polymer under the optimum condition were 19, 257.5 and 0.4mg/l, respectively which are under the governmental regulation level. 2. In the farm B where $COD_{Cr}$, $COD_{Mn}$ and $BOD_5$ of original leachate were 4,720, 3,040 and 95mg/l, respectively, the conjugate of $FeCl_3$, 1,500mg/l and cation polymer 10mg/l ($FeCl_3$+FO4240) was most effective coagulation and settling agent compared with the others. The concentrations of BOD$_{5}$, T-N and T-P of the effluent after treatment with $FeCl_3$+FO4240 were 15.3, 829.4 and 2.8mg/l, respectively. And the concentration of T-N was higher than the governmental regulation level, presumably because of too high concentration of NH$_4$$^{+}$-N in the leachate.

• Journal of Korean Society on Water Environment
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• v.26 no.1
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• pp.44-51
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• 2010

A lab-scale apparatus for turbid water transport control was tested and examined. The channel had a dimension of $100cm{\times}30cm{\times}15cm$ (length${\times}$hight${\times}$width). And the turbidity water was prepared using two types of particles, bentonite and loess. The channel equipped with filamentous mat was operated under various shock load conditions. In the control channel, instantly, turbid water mixed with the clean water inside the channel and turbidity prevails the entire channel. While in the mat-equipped channel, it increases only at the bottom. Overall, the filamentous mat gave capture efficiency of 70~90% compared with the control group. The capture efficiency of turbid particles decreased with increased input turbidity flux. The result of experimental run on how turbid particles are separated in the mat channel shows that settling, filtration and attachment are the main processes. Meanwhile, turbidity was diffused from the channel bottom due to turbidity gradient before and after mat zone. The particle size before mat zone was lightly coarser than that after mat zone.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.1134-1138
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• 2008

Electret filter media are used in general ventilation filters, disposable respirators, vehicle cabin filters, vacuum cleaners and room air cleaners. There are basic mechanisms of interception, inertial impaction, diffusion, gravitational settling, electrostatic attraction by which an aerosol particle can be deposited onto a fiber in a filter. The ability of fine particle removal strongly depends on the electrostatic forces between particles and polarized fibers. Thus, the stability of the fiber polarization is a major factor in the reliability of electret filters. In this study, electrical properties and filtration performance of electrospun filter media are quantitatively investigated. Electrical properties of electrospun filters have been studied on surface charge potential and surface charge density. Also the filtration performance of the electret filters are evaluated on collection efficiency. Electrospun filters show same collection efficiency with low pressure drop compare to commercialized HEPA filters. Surface charge potential and surface charge density of electrospun filters are increased with increasing applied voltage. Also collection efficiency of electrospun filters is increased with increasing surface charge potential and surface charge density.

• Journal of Korean Society of Water and Wastewater
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• v.20 no.6
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• pp.875-883
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• 2006

The carbon and nitrogen removal process using PVA-gel (Polyvinyl Alcohol) immobilized microorganisms was studied. The process has been operated under diverse process conditions for 12 months. The process consists of denitrification with internal recycle of 300%, nitrification, aerobic digestion reactors and settling tank. Nitrificatoin and nitrogen removal efficiency according to gel packing ratio and temperature were studied. Yield for Heterotrophs ($Y_H$), decay coefficient for Heterotrophs($b_H$) in aerobic digestion reactor were determined to seize sludge reduction mechanism and compared with typical data of activated sludge process. Then SRT in aerobic digestion reactor was determined on an experimental basis and sludge reduction efficiency was calculated. The process was implemented successfully with sludge reduction efficiency of 92.0~98.5% on a basis of biomass.

• Korean Chemical Engineering Research
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• v.55 no.2
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• pp.201-213
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• 2017

Water is removed from crude oil containing water by using oil separator. This study aims to develop a three-dimensional (3D) Eulerian computational fluid dynamics (CFD) model to predict the separation efficiency of air-water-oil separator. In the incompressible, isothermal and unsteady-state CFD model, air is defined as continuous phase, and water and oil are given as dispersed phase. The momentum equation includes the drag force, lift force and resistance force of porous media. The standard k-${\varepsilon}$ model is used for turbulence flow. The exit pressures of water and oil play an important role in determining the liquid level of the oil separator. The exit pressures were identified to be 6.3 kPa and 5.1 kPa for water and oil, respectively, to keep a liquid level of 25 cm at a normal operating condition. The time evolution of volume fractions of air, water and oil was investigated. The settling velocities of water and oil along the longitudinal separator distance were analyzed, when the oil separator reached a steady-state. The oil separation efficiency obtained from the CFD model was 99.85%, which agreed well with experimental data. The relatively simple CFD model can be used for the modification of oil separator structure and finding optimal operating conditions.

• Journal of Korean Society of Water and Wastewater
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• v.29 no.2
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• pp.233-241
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• 2015

Polytetrafluoroethylene (PTFE) membrane has high resistance to chlorine, which is a great advantages in chemical cleaning to recover water flux during membrane processes in drinking water systems. A humic kaolin water with approximately 4 mg/L of DOC and 10 NTU of turbidity was prepared as a feed water. Coagulation pretreatment with or without settling was applied. The coagulation with settling showed the greatest water production. The reduced flux was effectively recovered by NaOCl cleaning, i.e., 21% recovery by 50 mg/L of NaOCl cleaning and 49% recovery by 500 mg/L NaOCl cleaning. The images of SEM and AFM analyses were corresponded to the water flux variation. However, when the floc was accumulated on the membrane surfaces, the efficiency of NaOCl cleaning was substantially limited. In addition, dynamic contact angle became greater after cleaning, which indicates changes in characteristics of fouling layer such as surface hydrophobicity. Proper cleaning technologies during enhanced backwash using NaOCl would expand application of PTFE membranes in drinking water systems.

• Journal of the Korea Organic Resources Recycling Association
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• v.22 no.2
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• pp.50-56
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• 2014

Conventional coagulation-gravity settling processes in heavy metal removal have a problem in coagulant cost and instability of the settling efficiency. The authors investigated the effects of pH and slow mixing conditions on heavy metal hydroxide precipitation and the particle size distribution of the precipitate for a precipitation-membrane separation process. The optimum pH values for the hydroxide precipitation ranged from 9 to 10. The addition of $FeCl_3$ did not enhance the heavy metal removal. 20 min of slow mixing at 70 rpm showed the maximum heavy metal removal to meet the water quality criteria for effluent discharge. More than 99.9% of the heavy metal precipitate particles were bigger than $2{\mu}m$.

• Journal of Korean Society of Water and Wastewater
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• v.20 no.6
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• pp.911-918
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• 2006

This study was conducted to evaluate the effect of the launder type on settling performance and hydrodynamic behavior within the two certain full-scale sedimentation basins (each flow rate/one basin; $10,000m^3/d$); one is the transverse typed launder(existing basin) and the other is building the finger type launder in combination with the longitudinal baffle. Comparative experimental investigations have been carried out through residual turbidity and particle concentration measurements in each effluent from two basins with the transverse and the finger type launders, respectively. From the experimental results, we could observe that turbidity removal rate in the finger type launder basin (modified basin) is about 30% higher than that in the transverse type launder basin (existing basin). Also, from the measurement of total particle concentration in each effluent, the removal efficiency was improved about 27% within modified basin compared to the existing basin. In order to explain the comparative experimental results and investigate the hydridynamic behavior within each basin in more detail, we conducted computational fluid dynamics (CFD) simulation and verified simulation results with acoustic Doppler velocimetry (ADV) technique. From the CFD simulation, it was investigated that extreme upward flow occurs underneath of the transverse launder. On the other hand, in the case of modified basin, the upward flow, which occurred in the beneath of launder, was much less than that in the existing basins.