Flow pattern and hydraulic performance of the REDAC Gross Pollutant Trap

This paper discusses the flow pattern and hydraulic performance of a Gross Pollutant Trap (GPT), designed and patented by River Engineering and Drainage Research Centre (REDAC) at Universiti Sains Malaysia. Stormwater problems have become more severe due to the increase in urbanization. The increase in the amount of impervious surface in urban areas produces more stormwater runoff, that is carried to the receiving bodies of water. The higher runoff volume also carries more pollutants (gross pollutants, sediments, and nutrients) from the contributing catchment area. Coarse sediments transported by stormwater runoff have negative effects on the receiving body of water and the aquatic environment by covering up aquatic habitats and clogging waterways. One of the challenges in designing a GPT for urban stormwater drainage is providing effective trapping without hindering the hydraulic function of the channel, thus, avoiding overspill or flooding. The current study presents a GPT design to meet these specific requirements of trapping efficiency and hydraulic function. The current GPT overcame the common problem of overspilling of gross pollutants in GPT by the introduction of additional overspill compartments that can handle excessive runoff and improve pollutant trapping in higher flow conditions. In laboratory testing, the prototype GPT was capable of achieving good trapping efficiency (over 80% for gross pollutants and over 60% for coarse sediments) without causing any overspill.