Mass Loading and Mass Load Design of Stormwater Filtration Systems

Filtration of stormwater runoff is becoming an increasingly popular method to treat stormwater in order to meet water quality goals set by various agencies throughout the United States. In a broad sense, filtration refers to an array of technologies including sand filters, media filters, bio-filtration, bio-infiltration, and surface and subsurface infiltration. Though highly effective technologies, the downside of these technologies can be clogging by waterborne sediments. Despite the wide spread practice of applying these technologies there are few studies relating to how they will react to loading of solids associated with stormwater runoff. Solids loading onto the surface or within the matrix of a filter will have a substantial impact on the life and performance of a system. This paper presents a general overview of sediment loading characteristics on and within filter beds, and presents a case study of laboratory based loading of filter media. This paper also outlines how mass loading governs the operation and maintenance of a filtration technology and provides design guidelines that have been utilized for sizing on a mass load basis rather than a flow basis.