Leachability and phosphate removal potential of tire derived aggregates in underground stormwater chambers

Applications of tire derived aggregate (TDA) in underground runoff storage and infiltration basins have been proposed because TDA provides high porosity at a relatively low cost compared to gravel and a functional use of a waste product. The primary objective of this study was to investigate the impact of temporary storage of runoff in TDA on the leaching of fifteen metals and sorption of phosphate present in synthetic stormwater. Furthermore, the study analyzed the impact of chloride concentration on leaching and sorption potential of TDA based stormwater treatment systems. The analysis of stormwater effluents from different reactors reveals that in the reactors with TDA, the phosphate concentration was substantially reduced over time, while there was no significant change in the phosphate concentration in the reactors without TDA. The TDA, however, leached zinc, copper and iron into the synthetic stormwater. Even though the rate of leaching decreased with more flushes, the concentrations of iron and zinc after 72 h were still generally above the fresh water chronic criteria for aquatic biota. Thus, it may be necessary to place metal-adsorbing material in with the TDA to adsorb the leached metals. This combination of treatments could provide a stormwater storage system that adsorbs dissolved phosphate and captures particulate phosphorous via settling, without releasing toxic metals.