Combined ozone and biological treatment of oak wood leachate

In the present study, we investigated the possibility of treating oak wood leachate with a combined ozone and biological treatment. Wood leachate is characterized by high amounts of organic carbon and is reported as being toxic to aquatic organisms. Ozone was used as a pre-treatment before using aerobic degradation. The biological treatment was applied for seven days and evaluated using head-space respirometry. Target pollutant in this investigation was polyphenols in combination with more general parameters, such as chemical oxygen demand (COD), total organic carbon (TOC) and colour. A custom made bubble column reactor was used, 1.5L of wood leachate was exposed to 0-4g/L of ozone, corresponding to a specific ozone dose between 0.7-7g/L O₃/g of initial COD. Oak wood leachate was found to be easily degraded by ozone, with >90% of polyphenols degraded. COD was degraded by 73%, TOC by 61% and colour by 97% by ozone. Furthermore, a positive correlation between biodegradation and ozone pre-treatment was found. This study describes ozonation of polyphenol rich wood leachate combined with biological treatment. Ozone is shown to degrade the polyphenols found in the wood leachate fast. In addition it also enhanced the biodegradability of the wood leachate.