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Stormwater Management

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file icon Characteristics of urban run-off derived sediments captured by stormwater interceptorshot! 03/16/2007
Authors
M.G. Faram, K.O. Iwugo and R.Y.G. Andoh
Abstract
Sediment entrained in urban run-off is acknowledged as being an important carrier of pollutants. The paper reports on the physical and chemical characteristics of sediments captured by six installations of a proprietary interceptor device. The sites, located in the United Kingdom and the Republic of Ireland, were selected to represent a range of urban contexts. Particle D50 values were found to range from 7 to 112 mm, corresponding with ranges reported for stormwater ponds. Heavy metal and hydrocarbon concentrations were also found to vary, with the highest corresponding to the most established and heavily trafficked sites. Further to confirming the ability of the interceptor to remove contaminated sediments, useful insights are provided into the interrelation between sediment characteristics and site conditions. Keywords Heavy metals; hydrodynamic vortex separators; polycyclic aromatic hydrocarbons (PAHs); stormwater sediment; urban run-off.
file icon EVOLVING METHODS FOR THE CALIBRATION OF FLOW CONTROLS FOR STORMWATER AND WASTEWATER MANAGEMENThot! 09/26/2006
Authors
LeCornu, J.P. and Faram, M.G.
Abstract
The ability to accurately and reliably control flows in drainage and sewerage systems is critical for the effective operation of such systems. The use of inaccurate or unreliable flow controls can lead to adverse effects including flooding. Conventional methods for the calibration of flow controls are time consuming and can suffer from poor repeatability.
This paper describes work carried out with the aim of developing new, improved methods, to both enhance accuracy and improve repeatability, while also reducing test times. In order to achieve the objectives, a PROFIBUS based instrumentation and control system was fitted to existing hydraulic test facilities, operated by Hydro International. The new methods, applied to the calibration of vortex flow controls and orifice plates, show potential to reduce test times by a factor of more than ten, while also increasing the accuracy and repeatability of results.
file icon An Evaluation Of Upflow Filtration For The Treatment Of Diffuse Pollution At Critical Source Areashot! 09/26/2006
Authors
Lisa Glennon, Marcus Mumford, Uday Khambhammettu, Robert Pitt
Abstract
Runoff from urban drainage areas is a major source of diffuse pollution containing high concentrations of pollutants such as phosphorus and silts (sediments in the 3.9 to 62.5 μm range). Urban drainage areas such as parking lots, vehicle fueling and maintenance stations, and public works storage areas have been dubbed critical source areas due to the observation that runoff from these areas may contain high pollutant loadings of varying diffuse pollutant classifications, including trash and other debris, coarse and fine sediment, hydrocarbons, toxic trace metals, nutrients such as phosphorus and nitrogen, pathogens, and/or other toxicants (Bannerman, et al. 1993; Pitt, et al. 1995; Claytor and Scheuler 1996). One approach to stormwater treatment is to treat urban runoff at end-of-pipe, once runoff from critical source areas has mixed with runoff from less polluted areas. An alternative approach is to use small-footprint treatment devices upstream at critical source areas before the runoff mixes with larger volumes of less polluted runoff. Treatment devices installed at critical source areas need to incorporate several treatment processes, such as sedimentation, screening, and filtration, to target the different classifications of pollutants and respond to the inherent variability of runoff quality from different types of critical source areas (Pitt, et al. 1999). An upflow filter device equipped with a pre-settling sump and a coarse screening system has undergone a full-scale field evaluation at a site near the City Hall in Tuscaloosa, Alabama as part of a Small Business Innovative Research (SBIR) project funded by the United States Environmental Protection Agency (US EPA). This paper presents results of ongoing comprehensive characterization and performance evaluation of the upflow filtration unit tested under controlled laboratory conditions at Hydro International's hydraulics facility in Portland, ME, and compares the results to the field data collected by the University of Alabama (Pitt, et al. 2005; Khambhammeettu 2006).

Upflow filtration is shown to be capable of significant removal of suspended solids down to the 0.45 - 3 μm range. It is also shown that upflow filtration is a high-rate filtration method with a relatively high filtration rate per unit surface area of the filtration media. Field and lab data that evaluate the filtration rate and pollutant removal capabilities of the upflow filtration unit are currently being independently verified under the protocols of the US EPA Environmental Technology Verification Program.

file icon Innovative 'Hard Engineered' Approaches To Urban Stormwater Managementhot! 09/26/2006
Authors
Faram, M.G. and Kane, A.S.
Abstract
In recent years, with the rising profile of 'sustainability' in the planning equation, various environmentally-conscious, and often, novel approaches to stormwater management have emerged. These approaches, which have included 'hard engineered' and 'soft engineered' techniques, have become increasingly applied, providing options to cover a range of types of situation.

As with any new set of methods or approaches, a major challenge has been to break down the barriers and address the concerns held, in particular, by those who might ultimately become responsible for their operation. This is an ongoing process. The paper discusses the application of innovative 'hard engineered' stormwater management techniques, and their suitability for use either in conjunction with, or in isolation from alternative 'soft engineered' structures.

It is found that these techniques, far from being 'new and unknown' have been extensively applied, and have also been the subject of numerous verification studies, demonstrating their effectiveness and fitness for application.

file icon PROTOCOL FOR ASSESSING SEDIMENT RETENTION IN STORMWATER TREATMENT CHAMBERShot! 07/26/2006
Authors
Kwabena Osei, Robert Andoh and Lisa Glennon
Abstract
In approving stormwater BMPs, regulators usually review sediment removal data as the basis for their decisions. One factor that is usually overlooked is the ability of a treatment device to retain captured material in the event of high flow rates. Lately, some agencies are requiring vendors to indicate washout prevention of their stormwater treatment systems. However, no standard protocol exists that measures how much of previously captured pollutant is resuspended and carried downstream of the treatment device during high flows.

This paper discusses an effective test protocol for evaluating the sediment retention efficiency of proprietary stormwater treatment systems. The sump of a full-scale treatment device is filled with a known mass of sediment or sediment tracer. The unit is run at steady-state for a specified duration that exceeds several multiples of its effective detention time. Repeated tests are undertaken at different flow rates and the amount of material retained in the device for each flow rate is determined. The sediment retention efficiency is then calculated based on a comparison between mass of material retained in the sump after running flows through the unit and the original mass of material deposited in the sump.

Test data using this protocol for different device configurations are discussed and this highlights the importance of chamber geometry and hydrodynamic regime on the sediment retention efficacy of stormwater treatment devices.

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