Volume No. 2 Issue No.: 4B Page No.: 691-701 April-June 2008

 

INVESTIGATION INTO THE RELATIONSHIP BETWEEN HEAD LOSS AND FLOW RATE IN A ROCLA VERSA TRAP (VTA) STORMWATER POLLUTANT TRAP (SPT) AND THE HYDRAULIC CHARACTERISTICS OF A WEIR IN A DIVERSION WEIR PIT

 

H.K. Saberi, H. Nikraz and Will Hepburn

Department of Civil Engineering, School of Engineering,
Curtin University of Technology, Perth (AUSTRALIA)

 

Received on : Novemeber 13, 2007

 

ABSTRACT

 

The main focus of urban rainwater runoff disposal systems has traditionally been to provide structurally sound drainage systems with the capacity to carry runoff water from surfaces such as rooftops, paved streets, highways, parking lots, lawns, and paved and gravelled roads as quickly and efficiently as possible to the disposal site, without regard, necessarily, for water quality at the outfall. This has contributed to the decline in the water quality of rivers and lakes and other receiving bodies. Whilst some progress has been made towards the reduction in pollution at source, it is the non-point sources of pollution entering water runoff systems at various points and from different sources that is the most difficult to monitor and manage.
Recent developments in stormwater quality management have seen the introduction of stormwater pollutant traps (SPT), which are generally end-of line devices designed to capture and store gross pollutants and some micro-pollutants, for subsequent removal and disposal.
The Rocla VersaTrap (VT) range of pollutant traps have been designed to separate gross pollutants and sediments from stormwater by utilising vortex flow. This vortex flow is generated by introduction of the influent water tangentially into a cylindrical chamber, where it descends and exits through a cylindrical stainless steel screen to the exit chamber, and back into the drainage system.
The VersaTrap Series A SPT is an offline stormwater pollutant trap which utilises an upstream diversion weir pit to divert the Design Treatment Flow (DTF) into the treatment chamber. Treated flow is returned to the diversion pit downstream of the weir, where it re-enters the drainage system. Peak flows in excess of the DTF bypass the SPT over the weir into the pipeline downstream.
It has been demonstrated that the aggregate of all flows of 3 month Average Recurrence Interval and less represent the vast majority (up to 97.5%) of the total flow generated by a stormwater drainage catchment. It is therefore considered that treatment of all flows up to that generated by a 3 month ARI event will ensure the capture of the vast majority of pollutants1. There is some conjecture as to the veracity of the

 

Keywords : Offline stormwater pollutant trap, Diversion weir pit, Simulating weir height, Optimum maintenance regime, Best Management Practices (BMPs).

 

 

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