Sediment Retention by Alternative Filtration Media Configurations in Stormwater Treatment
2008
Singhal, Naresh | Elefsiniotis, Takis | Weeraratne, Navin | Johnson, A (Anthea)
Urban stormwater can be treated by infiltration at the source using systems like permeable paving. A critical component of such a system is the filtration media. Laboratory experiments were conducted using columns and boxes to evaluate the sediment retention efficiencies of different filtration media--crushed Greywacke, Greywacke mixed with 10% sand, and layered Greywacke and sand-Greywacke mix. Sediments of 0.001-6 mm were applied at concentrations of 460-4,200 mg/l along with water at flow rates of 100-900 ml/min. All columns showed between 96 and 91% sediment retention efficiency for single dry sediment applications, with lowered sediment retentions at higher flow rates. Decreasing the sediment loading, applying particles of <38 μm size, and suspending the particles in inflow as opposed to directly applying sediments to the column surface gave lower sediment retention efficiencies of 55 to 89%. Sediment retention primarily occurred in the top 20 mm of all columns and the 50th percentile value of retained sediments was 100-300 μm. The box tests showed little effect of flow and sediment loading on particle retention, with the tests showing an average retention of 93%. Similar to the column tests, the box tests showed lower sediment retention (84 to 88%) for <38 μm sediments and greater retention (approximately 95%) for larger sediments.
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