Comparison of Metals Leaching from CCA- and ACQ-Treated Wood in Simulated Construction and Demolition Debris Landfills.

Dubey, B., Spalvins, E., Townsend, T. , Solo-Gabriele, H.

Journal Of Environmental Engineering
doi: 10.1061/(ASCE)EE.1943-7870.0000051

Abstract : Pressure-treated wood is often disposed of in landfills in the United States, very frequently in construction and demolition (C&D) debris landfills. C&D debris landfills in many states are not equipped with liner systems to protect groundwater.With the voluntary withdrawal of chromated copper arsenate (CCA) treated wood for most residential applications in January 2004, copper-based wood preservatives, including alkaline copper quaternary (ACQ), are more widely used. To evaluate the impact of metal losses from ACQtreated wood disposed in C&D debris landfills and compare to those of CCA-treated wood under similar conditions, leachates from three simulated C&D debris landfills (lysimeters) were collected and analyzed for over a period of one year. The wood component in one lysimeter (the control lysimeter) contained pallet wood; the second lysimeter contained CCA-treated wood, and the third contained ACQ-treated wood. Each lysimeter was buried in an active landfill for temperature control. Several batch leaching tests [including the standardized toxicity characteristic leaching procedure (TCLP) and the synthetic precipitation leaching procedure (SPLP)] were also conducted for comparison purposes. Although the two lysimeters containing treated wood had elevated copper concentrations within the waste matrix, the concentration in the leachate samples from these lysimeters was below detection for Cu (< 4 ug/L) throughout the duration of the experiment, likely a result of precipitation as copper sulfide mineral in the reducing conditions of the simulated C&D landfills. As expected, the lysimeter containing CCA-treated wood showed elevated concentrations of arsenic and chromium, with maximum concentrations of 1.16 mg/L and 0.2 mg/L respectively. Greater amounts of boron (B) leached from ACQ-treated wood than CCA-treated wood or pallet wood debris. The results suggest that copper leaching will not be a major concern upon the disposal of ACQ-treated wood in C&D debris landfills. Arsenic leaching from CCA-treated wood remains a concern for unlined C&D debris landfills . 

Keywords : Landfills, Wood preservatives, Copper, Arsenic, Chromium, Metals, chemical.