Authors

Dr D A Phipps, Dr R M Alkhaddar, Mr James Dodd, Dr M G Faram, Professor R Y G Andoh and Miss Cathryn Roberts

Abstract

Hydrodynamic Vortex Separators (HDVS) are used for removing solids from stormwater before discharge into watercourses and for Combined Sewer Overflow (CSO) and wastewater treatment. Their internal geometry generates flow patterns which promote solids separation and deposition in a hopper at the base. This study examines re-entrainment of captured solids at a range of flow rates, for four separator configurations. Dye-tracer experiments for one configuration have shown that the hopper region is a slow mixing zone (SMZ), with the rate of mixing and interchange with the main body of flow depending on overall flow rate. With the hopper part filled, dye tests showed minimal mixing of interstitially held water; supporting the view that removal of solids will occur only from the top of the bed. The onset and extent of reentrainment occurring when the hopper was full of sediment was found to depend on the configuration, with a general increase in its occurrence with increasing flows. The study highlights the importance of providing isolated zones for sediment collection and adequate shielding of the collected sediment.

Authors

Darrell A. Egarr, Michael G. Faram, Timothy O’Doherty, David A. Phipps, Nicholas Syred

Abstract

A Hydrodynamic Vortex Separator (HDVS) has been modelled using Computational Fluid Dynamics (CFD) in order to predict the residence time of the fluid at the overflow and underflow outlets. A technique which was developed for use in Heating, Ventilation and Air Conditioning (HVAC) was used. The results have been compared to those determined experimentally. It is shown that in using CFD, it is possible to predict the mean residence time of the fluid and to study the response to a pulse injection of tracer. It is also shown that it is possible to apply these techniques to predict the mean survival rate of bacteria in a combined separation and disinfection process.

Authors

D. Egarr, M.G. Faram, T. O’Doherty, D. Phipps and N. Syred

Abstract

A Hydrodynamic Vortex Separator (HDVS) has been modelled using Computational Fluid Dynamics (CFD) in order to predict the residence time of the fluid at the overflow and underflow outlets. A technique which was developed for use in Heating, Ventilation and Air Conditioning (HVAC) was used to determine the residence time and the results have been compared with those determined experimentally. It is shown that in using CFD, it is possible to predict the mean residence time of the fluid and to study the response to a pulse injection of tracer. It is also shown that it is possible to apply these techniques to predict the mean survival rate of bacteria in a combined separation and disinfection process.

Authors

R.Y.G. Andoh, A.J. Stephenson and P. Collins

Abstract

The need for a more holistic approach in the development of solutions to wet-weather induced problems in urban drainage systems is advocated. A review of current approaches to resolving problems of premature overflows and flooding is presented outlining a case example of the successful application of non-conventional approaches, techniques and devices that assist in the better management and control of wet-weather flow sources. This involves the seeking of solutions within the upstream portions of drainage systems by intercepting, containing, controlling and treating excess wet-weather flows before they cause hydraulic and water quality problems in downstream areas (sections of the drainage system). These approaches have been found to be more cost-effective than conventional solutions and involve the implementation of distributed/decentralised schemes which in turn offer improved opportunities for wider community and other stakeholder involvement leading to the realisation of amenity and other non-structural benefits.

Authors

D.S. Jarman, M.G. Faram, G. Tabor

Abstract

The current climate of interest in water-environmental issues has lead to increased use of advanced computer-based simulation techniques in the evaluation and improvement of water management systems. This paper reviews the usage history of computational fluid dynamics (CFD) techniques by a supplier of technologies for urban water management, leading to the development of insights and guidance on the adoption of such tools, presented in the context of a number of practical case studies. The paper finds that CFD methods offer genuine opportunities and can yield direct tangible benefits. However, this is reliant on organ isations having a realistic understanding of what such approaches can offer, their limitations, and also having an appreciation of the long-term commitment that is required to achieve maximum value.