Hydraulics of Intermittent Sand Filters Loaded with Single-Cell Oxidation Pond Effluent

A study of the hydraulic characteristics and suspended solids removal efficiency of eight pilot-scale intermittent sand filters loaded with single-cell oxidation pond effluent was performed. Sand particle sizes utilized varied from 0.17 to 0.79 mm effective size, and hydraulic loading rates varied from 187 to 561 ${\rm l}/{\rm m}^{2}\cdot {\rm d}$. The filters were loaded for two separate loading periods of 113 and 125 days. Suspended solids concentrations in the filter influent averaged 132 and 168 mg/l, respectively, for the two loading periods. Results indicated that suspended solids removal efficiencies on the order of 30 to 70% can be expected in practice. The clogging process was shown to be related to sand size, hydraulic loading rate, weather conditions, and suspended solids loadings. Presently available methods for estimating filter run lengths were shown to be inadequate for design.