Design of a Gross Pollutant Trap (GPT) for Drainage Systems in Malaysia

Abstract Gross Pollutant Trap (GPT) is a mechanical device that is installed prior to the river outfall to capture gross pollutants such as debris and coarse sediments from stormwater. Gross pollutants are defined as solid debris with the dimension of 5 mm or above. By eliminating gross pollutants from entering rivers, the water treatment process can be carried out more effectively leading to improved water quality. However, despite its benefits, GPT use in Malaysia is limited due to challenges in its maintenance and high installation costs. The purpose of this study is to design and evaluate a GPT for use under Malaysian weather conditions, able to capture general wastes and suitable to be placed according to infrastructure conditions. The efficiency of waste removal, stormwater flow, and ease of maintenance were considered. Evaluations were carried out using a scaled model. The trapping efficiency of solid debris and also of coarse sediments were conducted on the model. In the solid debris experiment, scaled down debris was used for testing based on the scale ratio of the full prototype to the scale model. It was found that the GPT had an average debris trapping efficiency of 86.6%. In addition, the GPT showed an efficiency of 74.5% for trapping coarse sediments. These results indicated that the purpose designed GPT can be used to trap gross pollutants efficiently from stormwater with a similar performance expected for a full-scale prototype. Its efficiency was considered high based on previous studies. This study was able to demonstrate that a purpose designed GPT to suit local conditions could safeguard the environment through preventing gross pollutants from entering rivers which reduces pollution and potential for flash floods.