Optimisation of Baffles for Sediment Retention Ponds

Effective treatment of the polluted stormwater runoff from earthworks sites is a major concern for water authorities. Sediment retention ponds provide a quiescent place for settling the suspended particles in runoff. However, improper design of ponds can lead to significantly low treatment efficiency. As a retrofit practice, baffles have been utilised to improve the rate of settling of the suspended particles. Yet there is limited information in the design guides about the optimum configuration and type of baffles. This study investigates the effect of porous and submerged solid baffles on the hydraulic performance and trap efficiency of a model sediment retention pond. Several configurations were tested using four different metal meshes (with different aperture size and open area) as porous baffles, and acrylic sheets as solid baffles. The porous baffles were more effective in improving the overall hydraulic performance than the solid baffles. For 4 and 5 baffles, the medium-fine mesh with 1 mm aperture size and 42% open area was the best. The two porous baffles with same aperture sizes but different open areas had different hydraulic performance which highlights the importance of aperture size in addition to the total open area. The trap efficiency for the tested configurations was consistent with the result of hydraulic performance analysis. The present paper is continuation of the work presented at the Water New Zealand’s 2014 Stormwater Conference.