Effect of the diffuser plate design on the solid removal efficiency of a commercial pressurised sand filter

Abstract

Proper diffuser plate design can significantly improve flow distribution during filtration in a pressurised sand filter, thus, as hypothesis, this improvement in flow distribution may increase solid removal efficiency. Based on this perspective, this study aims to evaluate the influence of the diffuser plate design on the solid removal efficiency by combining different filtering layer heights and filtration rates, during filtration in a commercial pressurised sand filter. The experiment was performed in a hydraulic bench built as an open-circuit water circulator using water from a stream. Two diffuser plate designs (manufactured model and proposed model) were evaluated, assessing two filtering layer heights (0.225 and 0.45 m) and two filtration rates (20 and 75 m h⁻¹). The proposed diffuser plate model did not show better results regarding solids removal, indicating that a better flow distribution over the filter surface bed did not increase the solids removal capacity. Additionally, it was observed that using the highest filtering layer height and lower filtration rate leads to the highest solids removal efficiency. There is a need to improve the methodology to achieve a more reliable estimate of solid removal efficiency of sand media filters during the filtering process. The temporal variability of the filtered effluent compromised the evaluation quality.