Water quality evaluation of tire derived aggregate

The primary objective of this study is to investigate the rate that potential water quality contaminants leach from tire-derived aggregate (TDA) as a function of time. A laboratory and field experiment is conducted to provide insight into both controlled and field settings. The laboratory portion of this study also provides a basis for evaluating the effect that alternating periods of wet and dry weather have on the potential water quality impacts of the leachate as compared to the worst-case operating condition, when TDA is constantly submerged (i.e., when placed below the permanent groundwater table). The field experiment is used to determine if the leachate constituents identified in the laboratory experiment are observed when TDA is used as a stormwater filtration media. This portion of the study also determines if a TDA fill followed by a soil layer provides removal of urban stormwater runoff constituents. The laboratory experiment suggests that, of the 83 tested constituents, benzene, methyl isobutyl ketone (MIBK), cadmium, zinc, iron, manganese, total phosphate, and total suspended solids (TSS) are leached from TDA and dissolved oxygen (DO) is altered by TDA. For the eight constituents suspected to leach from TDA, a decrease in release over time was observed, with release rates for the majority of these constituents reaching values below their respective detection limits by the end of the experiment. Of these constituents with Maximum Contaminant Levels (MCLs), only iron and manganese exceeded their respective Secondary MCLs, and these standards are an aesthetic rather than a human health concern. The rate at which metals leach from TDA is the highest when continuously submerged. A higher loss in iron, manganese, and zinc was observed for TDA that was always wet compared to TDA that experienced short (1 to 7 days) cycles of wet and dry. At the end of the 15 month experiment, manganese, zinc, and iron cumulative mass losses (per kg of tire) were 1.7, 1.6, and 2.6 times greater under the always wet operating condition compared to the average of the other operating conditions. There was not a difference in the loss rates that could be attributed to the different wet and dry cycles investigated. The results of the field experiment suggest that a TDA-soil system provides removal of the following constituents from urban stormwater runoff: acetone, cadmium, chemical oxygen demand, iron, lead, manganese, methyl isobutyl ketone (MIBK), oil and grease, phosphate, and zinc. In addition, the constituents suspected to leach from TDA are removed by a TDA-soil system. The results of this study have demonstrated that the use of TDA as a fill material in civil engineering applications is a responsible method of recycling automotive scrap tires. TDA fills that are seasonally or always saturated are very unlikely to compromise the quality of the receiving water. The number of potentially harmful compounds leaching from the TDA is limited, and the rate of leaching is sufficiently low that the concentrations of these compounds in the surrounding waters do not pose any environmental degradation. In addition, sufficient dilution and soil adsorption effects further reduce impacts compounds might have on receiving waters. Sufficient dilution and soil adsorption processes further reduce the potential impacts that these compounds might have on any receiving water