The effect of different baffles on hydraulic performance of a sediment retention pond

• Porous baffles are superior to solid baffles for increasing the residence time and improving the hydraulic performance.
• Mesh aperture is an important factor for selection of porous baffles.
• The optimum mesh size for porous baffles is dependent on the position and number of the baffles.

Baffles have been utilised in the ponds and wetland to improve the rate of treatment for the polluted water. However, there is limited research in the optimum configuration and type of baffles for sediment retention ponds (SRP). In this study, the effect of porous and submerged solid baffles on the hydraulic performance of a model SRP is assessed. In order to optimise the type and configuration of baffles, several configurations were tested with 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 increasing the retention time and improving the overall hydraulic performance than the solid baffles. The finest mesh with 0.415 mm aperture size and 40% open area had the highest performance for most of the configurations with 3 or less baffles. However, for four and five baffles, the medium-fine mesh with 1 mm aperture size and 42% open area was the best. For three porous baffles, they were more effective when installed in the first half of the pond compared with when installed about the middle point of the pond, regardless of the mesh size. The two porous baffles with same aperture sizes but different open areas had different hydraulic performance which highlights the importance of mesh aperture in addition to the total open area.