Characterization of particles from road runoff is very important for the selection of Best Management Practice (BMP) in the stormwater management. In this study, runoff samples during two rainfall events at four sites in Gyunggio-Do were collected and Particle Size Distributions (PSD) in the size range of 2-880 µm were determined. Then number and mass fraction of each size range was obtained from a total of 89 samples. Also, rainfall amount, flow rate, and other pollutants in samples were analyzed. Particles with less than 5 µm accounted for more than 80% of number fraction while their mass fraction was about 12%. Particles larger than 50 µm contributed more than 40% of mass fraction. Partial Event Mean Concentration (PEMC) of particle showed inverse relationship with accumulated rainfall and sharply decreased at the early stage of rainfall, implying that the first flush is major contribution to particle runoff. Other pollution parameters such as turbidity, TSS, BOD, TN, and TP also have similar temporal runoff trend with the PEMC. Particle settling velocities of runoff particles were obtained by column tests and their values were compared with theoretical velocities. Based on the settling velocity distribution, removal efficiency of particles from runoff by sedimentation was evaluated.
Upflow granular media filtration devices are widely used for stormwater runoff treatment. However, the system performance is not well characterized due to the irregular removal of suspended solid (SS) in the pretreatment (sedimentation) chamber and, hence, its irregular input to the media layer. In this regard, the performance of the granular media layer of an upflow filtration system is investigated herein by the use of various models. Due to the significant variation in the SS concentration of the influent and effluent to and from the media layer, the deep bed filtration model, the k-C* model, and the porous media capture model provide limited descriptions of the system performance. By contrast, the performance is well described using the kinetic model, the modified k-C* model using a specific deposit, and the modified porous media capture model using a specific deposit. The parameters of the latter models are shown to be in good correlation with the filtration velocity, SS removal, and specific deposit. The results suggest that modeling using a specific SS deposit can provide an accurate description of the granular media layer performance under a highly variable influent SS concentration.
<p>Oxytetracycline (OTC) is one of the popular antibiotics accumulated in soils and groundwater, posing harmful effects on ecological systems and human health. This work aims to examine the feasibility of OTC degradation using a new catalyst, oxygen-doped graphitic carbon nitride (O-gC<sub>3</sub>N) for in-situ oxidative remediation. The in-situ oxidation system was simulated with column experiments to investigate the performance of PMS activation and OCT removal in saturated porous media. Numerical modeling as HYDRUS 1D was used for analyzing the transport behaviors of OTC in saturated porous media. The results show that OTC transport in saturated porous media is non-equilibrium. O-gC<sub>3</sub>N can efficiently activate PMS to degrade OTC and the increase of PMS and O-gC<sub>3</sub>N can enhance OTC removal. A wide pH range is beneficial for OTC degradation in saturated porous media. EBCT significantly affects OTC degradation and the optimal velocity was 0.4 cm/min. The findings of this work suggest that the O-gC<sub>3</sub>N catalyst can effectively be utilized for the in-situ oxidation of organic pollutants in contaminated sites.</p>
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