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USE OF PRETREATMENT ZONES AND ZERO-VALENT IRON FOR THE REMEDIATION OF CHLOROALKENES IN AN OXIC AQUIFER
Citation:
Kenneke, J F. AND S C. McCutcheon. USE OF PRETREATMENT ZONES AND ZERO-VALENT IRON FOR THE REMEDIATION OF CHLOROALKENES IN AN OXIC AQUIFER. ENVIRONMENTAL SCIENCE & TECHNOLOGY 37(12):2829-2835, (2003).
Impact/Purpose:
Elucidate and model the underlying processes (physical, chemical, enzymatic, biological, and geochemical) that describe the species-specific transformation and transport of organic contaminants and nutrients in environmental and biological systems. Develop and integrate chemical behavior parameterization models (e.g., SPARC), chemical-process models, and ecosystem-characterization models into reactive-transport models.
Description:
Pre-treatment zones (PTZs) composed of sand, 10% zero-valent iron [Fe(0)]/sand, and 10% pyrite (FeS2)/sand were examined for their ability to prolong Fe(0) reactivity in aboveground column reactors and a subsurface permeable reactive barrier (PRB). The test site had an acidic, oxic aquifer contaminated with tetrachloroethylene (PCE) and trichloroethylene (TCE). The 10% FeS2 and 10% Fe(0) PTZs removed dissolved oxygen and affected the pH and Eh in the PTZ. None of the PTZs had any effect on pH or Eh in the 100% Fe(0) zone. Nitrate and sulfate were removed more quickly in the Fe(0) zones preceded by either the 10% Fe(0) PTZ or 10% FeS2. PCE first-order degradation rate constants (kobs) decreased significantly (>80%) with increasing column pore volumes regardless of the PTZ material used. kobs finally leveled off after approximately one year of operation. The column results predict that the PRB will experience a breakthrough of PCE in 3-5 years and illustrates the importance of incorporating temporal variations in degradation rate constants when designing PRBs.