• Nuclear Engineering and Technology
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• v.55 no.3
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• pp.989-998
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• 2023

Under nuclear reactor severe accidents, the resuspension of radioactive aerosol may occur in the containment due to the disturbing airflow generated by hydrogen combustion, hydrogen explosion and containment depressurization resulting in the increase of radioactive source term in the containment. In this paper, for containment conditions, by considering the contact between particle and rough deposition surface, the distribution of the distance between two contact points of particle and deposition surface, rolling and lifting separation mechanism, resuspension model based on random contact with rough surface (RRCR) is established. Subsequently, the detailed torque and force analysis is carried out, which indicates that particles are more easily resuspended by rolling under low disturbing airflow velocity. The simulation result is compared with the experimental result and the prediction of different simulation methods, the RRCR model shows equivalent and better predictive ability, which can be applicable for simulation of aerosol resuspension in containment during severe accident.

• Journal of Korean Society of Water and Wastewater
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• v.24 no.2
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• pp.165-172
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• 2010

Treated sewage could enable growth by providing key nutrients or seeding the sediments with enterococci strains that can grow in the environment. This study is to test the hypothesis that the flux of bacteria into the water column is rate-limited by the transfer of bacteria across the sediment/water interface. Two conceptual models are derived for the transfer of bacteria to the water column from the sediment/water interface: convective diffusion of isolated bacteria and resuspension of particle-associated bacteria. The model predictions are directly tested together with field measurements of bacteria and sediment in an effluent-dominated stream where high concentrations of enterococci in this stream originate primarily from growth of the bacteria in stream sediments. The results reveal that high concentrations of enterococci in this stream are transported primarily by resuspension of particle-associated bacteria accumulated at the sediment/water interface, either in the form of bacterial aggregates or in the form of inorganic particles.

• Journal of Korean Society on Water Environment
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• v.37 no.1
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• pp.1-9
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• 2021

The depletion of dissolved oxygen (DO) in urban streams has a profound effect on the aquatic ecosystem; however, the change in DO by resuspension of sediments and the cause have not been sufficiently investigated. In this study, the physicochemical properties (particle size, and the content of organic and heavy metals) of the sediments of an urban stream (Anyang Stream) and the characteristics of water quality changes (DO, dissolved organic carbon (DOC), dissolved nitrogen (DN), sediment oxygen demand (SOD), and adenosine triphosphate (ATP)) by sediment resuspension were investigated. The sediment content of fine particles (< 0.2 mm) increased from 36.7% to 52.7% from the upstream to the downstream, and the contents of heavy metals and organic matter of the sediment were also higher towards the downstream. The depletion of DO by resuspension was observed in the sediment at the downstream sites (P8, P9), where the fine particle content was high, and biological SOD (BSOD) was more than 88% compared to the total SOD. The increase in BSOD coincided with the increase in ATP. It was also confirmed that the depletion of DO could increase the amount of heavy metals (such as Fe, Mn, and Pb) released from the sediment. Based on the above results, it can be concluded that resuspension of sediments induces rapid water quality changes and may cause accidents, such as fish mortality, during rainfall, and such a water quality effect can be more pronounced in sediments with a high content of fine particles and organic matter and high biological activity.

• Journal of Korean Society of Water and Wastewater
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• v.29 no.3
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• pp.371-380
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• 2015

Particulate matters in a water distribution system are main causes of turbidity and discoloration of tap water. They could be removed by conventional or uni-directional flushing in a water distribution system. The behaviors and required flow velocity of particles are not well known for their flushing. A model water main and hydrant were made from transparent acrylic pipe of 30mm and 16mm in diameter, respectively. We analyzed the effect of flushing velocity, particle density, and particle diameter. We found that the existence of break-though velocities at which particles begin to be removed, and which are affected by their physical properties. The removal efficiencies seemed to be influenced by resuspension capabilities related to their upward movement from the bottom. Heavy particles like scale were hard to remove through upflow hydrant because the falling velocity, calculated using Stokes' law, was higher. Particle removal efficiencies of upward hydrant and downward drain showed minor differences. Additionally, the length between hydrant and control valve affected flushing efficiency because the particulate matters were trapped in this space by inertia and recirculating flow.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.7
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• pp.469-475
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• 2014

The study investigated the physicochemical characteristics and the ecological risk of the Northport sediment in B city and the releasing properties of heavy metals into seawater during the resuspension also studied. The major components of the sediment are fine silt and clay which contains high organic matter and AVS (Acid volatile sulfide) and the ecological risk of the heavy metals in sediment also very high. The release rate of heavy metals into seawater was in order of Pb>>Cu>Cr>>Zn>Cd during the resuspension in a batch experiment, and the heavy metal release mainly attributed to the oxidation of metal sulfides. Heavy metals which came from easily oxidisable metal sulfides rapidly contaminated seawater within about 1.0 h of the sediment resuspension. The sulfide oxidation during the resuspension increased the residual fraction of heavy metals in the sediment, decreased the organic bound fraction, and changed the other fractions of heavy metals in the sediment. The release of heavy metals from the sediment during resuspension was affected by the resuspension time, the oxidation rate of metal sulfides and resuspended concentration of the sediment particle.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.3
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• pp.221-229
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• 1992

A series of experiments on the resuspension of deposited fine-grained sediments were carried out in a recirculating straight flume to investigate the influence of the sediment type, water content and bed shear stress (${\tau}_b$) on the resuspension characteristics of the sediments. The sediments were sampled from Youngkwang coast and Youngdo coast which are located in the western sea and southeastern sea of Korea, respectively. Critical bed shear stress (${\tau}_c$) for resuspension was deduced for each experimental series. For the same sediment, critical bed shear stress for resuspension decreased but suspension mass or rate increased with increasing water content. The resuspension of deposited fine-grained sediments depended strongly on the water content, and the sediment type characterizing the inter-particle bond strength. It has been found that critical bed shear stress for resuspension in the unidirection flow is about 4 times higher than that in the combined wave-current flow, In case of lower bed shear stress, after an initially high suspension, suspension mass approaches a constant value due to the bed hardening with increasing time, but in case of higher bed shear stress, suspension mass increased successively due to the bed softening with time. Initial suspension rate, $E={\alpha}_3({\tau}_b/{\tau}_c-1)^{\beta}$ (where ${\alpha}_3$ and ${\beta}$=empirical constants), was estimated for each experimental series, ${\alpha}_3$ and ${\beta}$ values for the same sediment increased with water content.

• Journal of Korean Society of Water and Wastewater
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• v.18 no.1
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• pp.5-14
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• 2004

A feasibility of using Particle Entrainment Simulator (PES) to evaluate model variables describing sediment entrainment in a river system was investigated. PES in a laboratory was utilized to simulate the sediment resuspension phenomenon in the river and the subsequent relationship between shear rate and sediment entrainment was developed. The total suspended solids (TSS) data from PES was incorporated into statistical models in an effort to describe behaviors of net particle movement in the river. PES was found to be adequate for simulating particle entrainment phenomenon in a river system. Statistical analysis was used to assess propriety of PES data for predictive purposes. The results showed good relationships between PES results and system variables, such as average stream velocity and net particle movement.

• Progress in Superconductivity and Cryogenics
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• v.22 no.2
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• pp.7-11
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• 2020

When rivers and lakes are contaminated with numerous contaminants, usually the contaminants are finally deposited on the sediments of the waterbody. Many clean up technologies have been developed for the contaminated sediments. Among several technologies dredging is one of the best methods because dredging removes all the contaminated sediments from the water and the contaminated sediments can be completely treated with physical and chemical methods. However the most worried phenomenon is suspension of fine particles during the dredging process. The suspended particle can release contaminants into water and resulted in spread of the contaminants and the increase of risk due to the resuspension of the precipitated contaminants such as heavy metals and toxic organic compounds. Therefore the success of the dredging process depends on the prevention of resuspension of fine particles. Advanced dredging processes employ pumping the sediment with water onto a ship and release the turbid water pumped with sediment into waterbody after collection of sediment solids. Before release of the turbid water into lake or river, just a few minutes allowed to precipitate the suspended particle due to the limited area on a dredging ship. However the fine particle cannot be removed by the gravitational settling over a few minutes. Environmental technology such as coagulation and precipitation could be applied for the settling of fine particles. However, the process needs coagulants and big settling tanks. For the quick settling of the fine particles suspended during dredging process magnetic separation has been tested in current study. Magnetic force increased the settling velocity and the increased settling process can reduce the volume of settling tank usually located in a ship for dredging. The magnetic assisted settling also decreased the heavy metal release through the turbid water by precipitating highly contaminated particles with magnetic force.

• Environmental Engineering Research
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• v.17 no.3
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• pp.167-174
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• 2012

In situ particle size spectra are obtained from two sequent cruises in order to evaluate the physical consequences of suspended particulate matters caused by episodic storm runoff from the Santa Ana River watershed, an urbanized coastal watershed. Suspended particles from various sources including surface runoff, near-bed resuspension, and phytoplankton are identified in empirical orthogonal function (EOF) analysis and an entropy-based parameterization (Shannon entropy). The first EOF mode is associated with high turbidity and fine particles as indicated by the elevated beam attenuation near the Santa Ana River and Newport Bay outlets, and the second EOF mode explains the suspended sediment dispersal and particle coarsening at the near-surface plume. Chlorophyll particles are also distinguished by negative magnitudes of the first EOF mode, which is supported by the relationship between fluorescence and beam attenuation. The integrated observation between the first EOF mode and the Shannon entropy index accentuates the characteristics of two different structures and/or sources of sediment particles; the near-surface plumes are originated from runoff water outflow, while the near-bottom particles are resuspended due to increased wave heights or mobilizing bottom turbidity currents. In a coastal pollution context, these methods may offer useful means of characterizing particle-associated pollutants for purposes of source tracking and environmental interpretation.

• Journal of Ocean Engineering and Technology
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• v.24 no.1
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• pp.99-105
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• 2010

The concentration and size analysis of in-situ suspended particulate material were measured using an optical instrument, LISST-100, in the bottom layer at the three inlets of the Seomjin River Estuary, mouth of Gwangyang bay, and Gwangyang bay-side of the Namhae Bridge. In the Seomjin river estuary and mouth of Gwangyang bay-side of the Namhae Bridge, the in-situ mean grain size of the suspended material changed from a uni-modal distribution with a dominant peak at a coarse fraction to a bi-modal distribution with a secondary peak at the finer particles. Seomjin River. The interactions between suspended particulate concentration and beam attenuation coefficient of suspended particulate matters depended on the supply of finer and coarser particles in the mouth of Gwangyang Bay and Seomjin River. So, interactions reflected difference of the concentration, mean size and sorting of suspended particulate matters. The difference of interaction showed dynamic behaviors to the resuspension and deflocculation processes increased river discharge. This showed that it may be possible to use the interactions between the suspended particle concentration and beam attenuation coefficient to monitor the temporal and spatial distributions of in-situ particles.