Management of Ammoniacal Nitrogen in Stormwater Runoff
Davis, Allen P
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Nitrogen in stormwater runoff plays a dominant role in the eutrophication of receiving waters. The challenge in treating nitrogen lies in its diverse speciation and biological cycling. This work aimed to improve removal of influent and mineralized ammonium through the use of sorption media and nitrification in preparation for subsequent denitrification. Two media, clinoptilolite (ZT) and hydrous-aluminosilicate (CA), were characterized in a series of batch and sorption column experiments, which indicated superior performance of ZT because of its higher capacity (206 months life-expectancy) and faster kinetics (60 min). Competition with Ca2+ and K+ resulted in smaller and slower sorption for both media. Removed ammonium in ZT was highly extractable, signifying its potential bioavailability. Sorption columns exhibited high removal during influent NH4+ increases, desorption with influent concentration drops, and lower ammonium removal upon rewetting/saturateting. Nitrification in bio-active sorptive media enhanced removal efficiency, particularly for alternating wet/saturated-dry/unsaturated conditions, with smaller desorption occurring. ZT application in filtration-based stormwater control measures is recommended.