ZVI horizontal permeable reactive barriers for the treatment of chlorinated solvents vapors

The intrusion of vapors from the subsurface to overlying buildings is one of the major concerns for human health of residents at sites contaminated by chlorinated solvents. Due to their massive use in industry, chlorinated compounds such as Tetrachloroethylene (PCE) or Trichloroethylene (TCE) are widely present in urban settings. Besides, because of the low biodegradability of these compounds that makes natural attenuation in most cases not significant, even relatively low contamination by chlorinated solvents in the subsurface can pose potential long-term risks for human health, especially related to the vapour intrusion pathway or more in general to inhalation of vapors. Over recent years, a vapor mitigation system was proposed, that involves the use of solid potassium permanganate to create a horizontal permeable reactive barrier (HPRB) aimed at treating upward volatile organic compounds (VOCs). One of the possible drawbacks related to the use of soluble oxidants such potassium permanganate, is the progressive dissolution and leaching of the reactive material by infiltrating water that can lead to a depletion of the barrier and consequently to possible subsidence issues (Verginelli et al., 2017). This issue can be overcome using a less soluble reactive material. For instance, the use of zero-valent iron as a fillermaterial of HPRBs can represent an attractive alternative from both the leaching behavior and reactivity point of view. In this work , we report the results of some experimental tests aimed at assessing the feasibility of using granular iron to treat TCE vapors as filling material of HPRB. In particular, the reduction of TCE in gas phase by different types of zero-valent iron was examined in anaerobic batch systems performed at room temperature. Concentrations of TCE and byproducts were determined at discrete time intervals by analysis of the headspace vapors (Zingaretti et al., 2019). (author)