Gross Pollutant Traps (GPTs), such as the Ecosol GPT, are primarily designed to remove larger gross pollutants (>3mm) from stormwater at high treatable flow rates (TFR) and can play an integral role reducing pollution in heavily-urbanised catchments that discharge into our waterways.

Treatable Flow Rate

The Treatable Flow Rate (TFR) is the minimum flow that a GPT must treat, without by-pass, to achieve the desired pollutant capture criteria for a particular development style and catchment area. It varies dependent on geography, catchment type and size including pipe size and gradient. Typically, the Ecosol GPT is designed to treat flows between 1-in-3 month and 1-in-1 year Annual Rainfall Intensity (ARI) with greater flows by-passing the unit.

By-pass Capacity and Headloss

The range of Ecosol GPTs has been designed to cater for maximum flow by-pass at minimal headloss. The placement of any structure into a stormwater line will induce headloss. The extent of this headloss is a function of the velocity in the outlet pipe and the k factor adopted. The k factor must be representative of the type of structure and its operation during full-flow conditions as distinct from the TFR.

The Ecosol  GPT has one of the lowest k factors of any GPT currently available. Extensive independent testing has been carried out to confirm the unit’s k factor for a range of pipe and unit sizes based on full flow, worst-case scenarios. These tests show that the k factor can vary between 0.6 and 1.5 depending on the pipe size, configuration, gradient and the relative unit size.

The Ecosol GPT is designed specifically to provide essential primary treatment of stormwater runoff. It is an efficient, cost-effective solution to the ever-increasing problem of gross pollutants present in stormwater. Key to its success is the robust, engineered design and tangential screens housed in a pre-cast concrete pit that provides a significantly greater screening area than that of traditional direct screening trash rack designs. Further its large detention chamber enables gravitational separation to occur at low flow velocities retaining fine particulate matter conveyed in stormwater.

In 1997 and 1998 the Urban Water Resources Centre – University of South Australia (UniSA), was commissioned to undertake a series of tests on the widely-used Ecosol GPT (formerly known as the RSF 4000) to confirm the product’s performance. The tests measured the capture efficiency of the system under varying flow conditions and gradients and also the hydraulic headloss of the system under varying flows and gradients.

In October 1998 after further product development Ecosol commissioned Engtest the Department of Civil and Environmental Engineering at the University of Adelaide to undertake further testing on the system to confirm hydraulic headloss and capture efficiencies.

Concurrently Avocet Consulting was engaged to complete extensive CFD Modelling to determine Pollutant Trapping Performance and fluid hydraulic characteristics under varying flow conditions.

In early 2000 to mid-2001 as part of the company’s continuous product improvement program Ecosol engaged the services of Avocet Consulting to assess the Ecosol GPT‘s hydraulic performance, structural integrity, capture efficiency, treatable flow rates relevant to product sizing and scaling. Additional laboratory testing was also completed to monitor its performance as it filled and also to review the non-blocking, tangential filtration longevity of the system under varying flow conditions and percentage of fill.

Finally in 2013 EngTest Department of Civil and Environmental Engineering – University of Adelaide completed a series of additional product tests to further verify product performance and concurrently reviewed all past laboratory and field testing on the performance of the product to comprehensively determine its performance for current industry applications.

Capture efficiencies have been independently verified by laboratory and field tests confirming that the Ecosol GPT plays an integral part in the treatment train necessary to achieve generally-accepted water quality objectives (WQOs).

Figures quoted are mean collection efficiency statistics based on extensive laboratory and field testing data. It is important to note that the water quality CE values are indicative of potential field CEs given that product is designed primarily as a primary treatment solution providing physical tangential screening and the removal of chemical constituents is largely dependent on the chemical composition of the particles and the bonding of these chemical constituents to the surface of particles.

Further, finer and attached particle filtration performance of the product is also dependent on the body of pollutants forming a media already captured by the filter. Quoted CE values are intended as a general guide, please consult with your Urban Asset Solutions representative for site specific product sizing and modelling.