Remediation of Out-of-Service CCA-Treated Utility Poles Using Ozone and Peroxyacetic Acid

Chromated copper arsenate (CCA) has been one of the most widely used since the 1933's as a wood preservative to protect wood against decay and insects for exterior applications such as decks, housing, utility poles, play equipment and fences. Although its major use for consumer lumber products was replaced with chromium- and arsenic-free preservatives in the USA, Canada and European Countries by the end of 2003, large volumes of CCA-treated wood has been still coming out-of-service each year. Therefore, at present, the potential diffusion of heavy metals from CCA-treated wood waste after disposal has become an important problem. The aim of this study was to investigate the ozone and peroxyacetic acid as potential alternatives and their effectiveness in terms of removal of Cu, Cr and As from CCA treated wood sawdust. Extraction experiments were designed to determine optimum extraction conditions using aqueous peroxyacetic acid which was prepared by mixing 50-50% (v/v) of 30% H2O2 and 100% acetic acid. Experiments were carried out in 50 mL screw-capped test tubes at room temperature, 3 different concentrations (100%, 50% and 25%), and for 5 reaction time intervals (0.5 h, I h, 2 h, 6 h, and 24 h). For each series, two replicate samples were evaluated using 3 g wood sawdust and a mass ratio of liquid extractant to solid wood of 10-1. An additional series of extractions were done using ozone. CCA-treated wood sawdust samples were exposed to ozone at room temperature for 2 reaction time intervals (15 and 30 min) using Enaly 20K-4U (20g/hr) Ozone Generator. The results showed that both peroxyacetic acid and ozone were very effective to remove Cu, Cr and As from CCA-treated sawdust. It was found that about 96% Cu, 98% Cr and 98% As were extracted when wood sawdust samples were remediated with 25% of peroxyacetic acid while 96% Cu, 94% Cr and 92% As when wood samples were remediated with ozone. The results showed that concentrations of peroxyacetic acid did not affect the remediation efficiency while reaction time intervals significantly enhance the remediation efficiency up to 6 hours.