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Increasing volumes of Chromated Copper Arsenate (CCA) treated wood materials are being removed from service, either as a result of reaching the end of their service life or being replaced with non-treated wood materials. These materials, while not regulated as hazardous wastes, have the potential to leach toxic metals into the environment. Incineration and landfilling are not ideal disposal methods as incineration could result in the volatilization of carcinogenic arsenic and chromium, while landfilling requires the waste to be sorted and placed in appropriately lined landfills to prevent contaminant release. Viable disposal methods must be considered to manage the significant waste stream of CCA-treated wood. This study investigates pyrolysis and electrokinetics (EK) as possible remediation techniques for the treatment of CCA-treated wood waste. A unique bench pyrolysis reactor was designed and optimized over three pyrolysis temperatures for retention of CCA metals within the char and bio-oil pyrolysis products. A batch pyrolysis system was constructed to produce large quantities of pyrolysis char for use in EK experiments. Mass balances were performed across both bench and batch pyrolysis systems, with metal distribution trends ascertained. EK experiments were performed on the char generated during batch pyrolysis as well as CCA-treated wood waste to evaluate the efficiency of coupling the two technologies. These EK studies were performed using pH regulation at the cathode and applying constant current. Distribution of the CCA metals post-EK experiment was determined and removal efficiencies were calculated. The mobility of the CCA metals was evaluated during all phases of this investigation using Toxicity Characteristic Leaching Procedure (TCLP), Synthetic Precipitation Leaching Procedure (SPLP), and Deionized Water Leaches to determine the likelihood of metal leaching under different environmental conditions.

The focus of this research is to determine the effects of particle size reduction and chemical pretreatment with strong base oxidizers on the effectiveness of the electrokinetic remediation of wood waste contaminated with chromated copper arsenate. Selection of an oxidative chemical pretreatment solution involved an initial screening between three pre-selected chemicals followed by optimization of oxidative chemical solution strengths and solid to liquid ratios. Samples of each of the three particle sizes were chemically treated with the final oxidative pretreatment and loaded into electrokinetic units where a direct current was applied for approximately fifty days. Similar experiments were performed without subjecting the contaminated wood to oxidative pretreatment to serve as an experimental control. It was identified that oxidative pretreatment of the lowest particle size prior to electrokinetic treatment was able to remove the highest percentages of chromium (75 %), copper (95 %), and arsenic (92 %) from the contaminated wood.

Structures made of chromated copper arsenic (CCA) have been shown to leach arsenic into the surrounding soil. Soil cores were taken adjacent to six CCA decks at 0, 15, 60 and 300 cm from the deck at depths of 0–10, 10–20, and 20–30 cm, and were analyzed for soil arsenic concentrations. Median soil arsenic concentrations ranged from 1.8 μg/g at a depth of 10–20 cm and a distance of 300 cm to 34.5 μg/g at a depth of 0–10 cm and a distance of 30 cm. Soil arsenic concentrations taken at depths of 0–10 and 10–20 cm decreased as distance from the deck increased. Soil arsenic concentrations close to the deck were higher at lower soil depths and at homes with greater deck wipe arsenic concentrations. Age of deck and slope of land had significant effects on the differences in arsenic concentrations between samples taken at different distances when evaluated in models by themselves, but not in models adjusting for deck wipe concentrations. Size of deck and bulk density of soil did not have significant effects on soil arsenic concentrations.

No description available.