Electrodialytic remediation of CCA-treated waste wood in a 2 m3 pilot plant

Waste wood that has been treated with chromated-copper-arsenate (CCA) poses a potential environmental problem due to the content of copper, chromium and arsenic. A pilot plant for electrodialytic remediation of up to 2 m3 wood has been designed and tested and the results are presented here. Several process parameters were investigated, and it was found that the use of collecting units and soaking of the wood prior to the electrodialytic process had a positive influence on the remediation process. There was a tendency towards higher removal of CCA from wood chips <2 cm, compared to larger wood size fractions. The best remediation efficiency was obtained in an experiment with an electrode distance of 60 cm, and 100 kg wood chips. In this experiment 87% copper, 81% chromium and >95% arsenic were removed. One other experiment was also analysed for arsenic. In this experiment the distance between the working electrodes was 1.5 m and here 95% As was removed. The results showed that arsenic may be the easiest removable of the copper, chromium and arsenic investigated here. This is very encouraging since arsenic is the CCA components of most environmental concern.