Author(s)

H. K. Saberi & H. Nikraz

Abstract

Rapid development of the big cities and suburbs around the world in the last century has created a situation in which the main focus of urban rainwater runoff is the disposal of the stormwater as quickly and efficiently as possible to the disposal site, without considering the water quality at outfall. This has contributed to the decline of water quality of the rivers, lakes and other receiving bodies. Whilst some progress has been made towards the reduction in pollution at the source, it is the non-point sources of pollution entering the water runoff system at various points and from different sources that is the most difficult to monitor and manage. One of the basic and at the same time major concepts in recent years is to capture and treat as much of the pollutant as possible which is discharged to the drainage system at source or possibly close to the source as the first step. One of the most popular and economical approaches is the use of an off-line stormwater pollutant trap (SPT). Recent developments in stormwater quality management have seen the introduction of SPTs, which are generally the most up-to-date devices designed to capture and store gross pollutants and some micro-pollutants, for subsequent removal and disposal. In this experiment a scale model of a Versa Trap series, a gross pollutant trap that utilises an upstream diversion weir pit to divert the Design Treatment Flow (DTF) into a cylindrical treatment chamber which houses a stainless steel basket, is considered. Treated flow passing through the basket screen is returned via the exit chamber to the diversion pit downstream of the weir, re-entering the drainage system. Peak flows in excess of the DTF bypass the diversion pit over the weir into the pipeline downstream. A mathematical relationship between the flow rate and head loss across the basket can be established for the device, which allows the designer to specify a suitable weir height in the diversion pit and to clarify the allowable range for removing and cleaning the basket at its optimum maintenance situation. Keywords: runoff, stormwater, receiving bodies, off line, pollutant trap, gross pollutant, treatment chamber, diversion pit, weir, head loss.

Keywords

runoff, stormwater, receiving bodies, off line, pollutant trap, gross pollutant, treatment chamber, diversion pit, weir, head loss.