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.
Non-point pollutants from surface runoff during rainfall exert adverse effects on urban river water quality management. In particular, the first flush effect during the initial phase of rainfall can deliver significant amounts of pollutant loads to surface waters with extremely high concentrations. In this study, a sustainable first flush effect management system was developed by using settling and filtration that require no additional power or chemicals. A pilot scale experiment has shown that the removal of total suspended solid (TSS), total nitrogen (TN) and total phosphorus (TP) are in ranges of 84 -95%, 31 -46%, and 42 -86%, respectively. An Integrated Stormwater Runoff Management System (ISTORMS) was also developed to efficiently manage the developed system by linking weather forecast, flow rate and water quality modeling of surface runoff and automatic monitoring systems in fields and in the system. This study can provide effective solutions for the management of urban river in terms of both quantity and quality.
An integrated management system was developed for the efficient operation of a storm water treatment unit to assist in the management of urban river water quality and flow. The SWMM hydrological model was calibrated and then used to predict the hydrograph and concentration graphs of surface runoff from a storm events based on weather forecasts. These results are used to decide how to operate the first flush treatment unit in the field by comparing water quality in the unit with that in runoff. This water quality monitoring system will also be used to reflect real-time field conditions, which will be used to improve the efficiency of the treatment system. The first flush treatment unit can be installed underground to use for storage of storm water. The system was tested against field data collected in a sub-basin of the Gwanpyung-cheon stream in Daejeon, Republic of Korea. Continuous monitoring results indicated that the first 4 hours of surface runoff exhibit higher concentrations than normal levels in the study site, and these levels can be used to determine the necessary volume for efficient treatment. When settling in the treatment system over 24 hours, the average removal efficiencies for TSS, TP and TN were 87.4%, 57.3%, and 43.6%, respectively.
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