Polytech Nice-Sophia - UNS-UCA

Polytech Nice-Sophia, Polytech'Lab
Parc de Sophia Antipolis
930 Route des Colles
06410 Biot
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Thèse soutenue le 28 novembre 2014

Bonjin Koo
Directeur Thèse I-CiTy Philippe Gourbesville

study on the filtration efficiency of micro-particle pollutants from non-point source - Focused on road runoff and CSOs


The impermeable area and the peak discharge volume have been consistently increasing due to widening of city development and renewal. Thus, distortion of water cycle has been serious problem compared to the past. When it comes to NPS pollution, lack of information on the load and characteristics of pollutants led to the insufficient reduction measures. The purpose of this study is to investigate the effectiveness of filters to control micro particles from non-point sources, especially from road runoff and Combined Sewer Overflows (CSOs). The study first examined the particle size and characteristics of NPS pollutants, and then analyzed the head loss, treatment efficiency and changes in particle size distribution before and after the treatment using device type facilities. The four most commonly used filters - Expanded Polypropylene (EPP), Expanded polystyrene (EPS), and Perlite as floatability filtering materials, and Zeolite as non-floatability - were compared. The upward-type filtering equipment was manufactured for the lab experiment, and CFD modeling was conducted to identify optimized design parameters. The results showed that the ratio of micro particles (<100 µm), to which the filtering process can be applied, was highest in samples from the road runoff, followed by one from the bridge, and from the parking lot. The results using road runoff displayed that EPP was most efficient with ratio of 89% to treat SS and COD. The removal rate of EPP for Zn and Cu was also high over 80%, which is 7 ~ 40% higher than those of other filters tested. The continuous filtering period calculated was again longest for EPP to reach 163 days. The calculated filtering period for CSOs was apparently shorter than that for road runoff, due to the hydraulic loading and SS quantity. The filters compared were not efficient to removeTN and TP in CSOs. The results from the numerical analysis for the particles over 100 µm, to which the gravity sedimentation can be applied, showed that sedimentation efficiency can be improved by controlling the inflow velocity through the utilization of the bent pipe or baffle wall. The operation and management can be also easier by placing appropriate facilities such as manhole at the sedimentation point This study suggested the best filtration material to treat NPS pollutants tested by road runoff and CSOs samples. The experimental results shown in this study and following discussions may act as base information for proper design and operating parameters of the filtering facilities to control NPS pollutants.