Assessing the Effectiveness of Proprietary Stormwater Treatment Devices
Proprietary underground devices are often used as stormwater treatment in dense urban areas due to tight space constraints. Most of these devices remove sediment and other debris from stormwater runoff prior to discharge into lakes, rivers, and streams via the physical separation process of sedimentation. Unfortunately, little is known about the performance of these devices in the field. Evaluation of performance using monitoring studies is problematic because: (i) natural storm events are unpredictable and not reproducible and (ii) it is difficult to obtain representative samples of suspended sediment at both the influent and effluent of the device with automatic samplers. These limitations were overcome in this research by employing a field testing approach.
For the testing, a controlled synthetic storm event containing sediment of a fixed size distribution and concentration is fed to a pre-cleaned device. The captured sediment is then removed, sieved, weighed, and the fraction of sediment captured is recorded. The objectives of this research were to: (i) investigate the feasibility and practicality of such a testing approach and (ii) evaluate the effects of sediment size and fluid flow rate on the performance of four devices from different manufacturers. The results of this work are then used to provide a revised sizing criterion that will improve the selection and sizing of these devices and their overall performance. The resulting approach, refined through field experiments, will be incorporated into a stormwater best management practice assessment document that will be used by consultants, local governments, and state agencies to assist in selecting, designing, and evaluating stormwater treatment technologies for public infrastructure improvement projects.
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