BACTERIAL DECAY OF ACQ-TREATED WOOD IN A WATER COOLING-TOWER

Samples of Scots pine treated with an ammoniacal copper quaternary amm onium formulation (ACQ13) to three target retentions and with a commer cial copper chrome arsenic (CCA) preservative to two target retentions were exposed in a water cooling tower for periods of up to 2 yr. The condition of the wood was assessed by microscopy and gravimetric metho ds and compared with untreated control samples. After two years the me an weight loss of untreated samples was 49%, while the mean weight los ses of samples treated with the ACQ13 formulation ranged between 28 an d 34% and 18 and 22% for the CCA-treated wood. Samples treated with th e lowest loading of CCA preservative were decayed by soft rot fungi on ly, while the samples treated with the ACQ13-formation were mostly att acked by tunnelling bacteria.