Temperature effects on functionalized filter media for nutrient removal in stormwater treatment

Abstract

Attempts to achieve better removal efficiencies of nutrients in stormwater treatment by using aggregates (e.g., mixes of tire crumbs, sawdust, sand, clay, zeolite, sulfur, or limestone) in filter media, has been a common practice in green infrastructures. These material mixes mainly promote the adsorption/absorption and precipitation of orthophosphate in the physicochemical process step and the transformation of ammonia, nitrite, and nitrate via oxidation and reduction reactions in the microbiological stage. Some processes, however, are known to be active only in a limited temperature range and variations in filtration kinetics of the sorption media are still unknown. This article aims to explore the filtration kinetics of selected filter media mixes for nutrient removal at various temperatures. With the basic understanding gained in material characterization, a laboratory column study was conducted to simulate the conditions in saturated media. A kinetics study of this kind allowed a comparison of a natural soil with soil augmentations in terms of nutrient removal within a range of the initial concentrations and temperatures. The temperatures (28, 23, and 10°C) were selected to reflect the normal temperature variations in subtropical regions. Significant differences of nutrient removal efficiencies associated with these temperatures were statistically confirmed by ANOVA analyses. The temperature correction factor model was finally applied to address the impact on treatment processes due to the seasonal temperature variations. © 2010 American Institute of Chemical Engineers (AIChE).