Using waste foundry sands as reactive media in permeable reactive barriers.

摘要

Permeable reactive barriers (PRBs) are in-situ barriers constructed in a subsurface to treat contaminated groundwater using various reactive media. The common reactive medium used in PRB is zero-valent iron, which has been widely used to treat chlorinated solvents (i.e., PCE, TCE). A disadvantage of iron media is high cost. In this study, waste foundry sands were tested to determine the feasibility of their use as a low cost reactive medium.; Batch and column tests were conducted with common groundwater contaminants (i.e., TCE, chlorinated herbicides, and zinc) to determine transport parameters and reactivity of the foundry sands. Batch and column leach tests were also conducted to determine whether foundry sands can be used in PRB media without adversely affecting groundwater quality.; The reactivities of foundry sands for common groundwater contaminants are comparable to or slightly higher than those for Peerless iron, a common medium used in PRBs. In addition, the TOC and clay in foundry sands can significantly retard the movement of target contaminants, which may result in lower effluent concentrations of contaminants due to biodegradation.; Leaching characteristics of the foundry sands and two reference materials were tested using water leach tests and column leach tests. Similar concentrations were obtained from the foundry sands and reference materials. Thus, using foundry sands in PRBs is unlikely to pose a greater risk to groundwater quality than conventional construction materials.; Basic properties of foundry sands (i.e., TOC, clay content, total or zero-valent iron content) are found to be useful to predict partition coefficients and rate constants for compounds tested in this study and also leaching characteristics can be predicted using those properties of foundry sands.