The process of kilning timber produces condensates which although low in volume, contain high concentrations of organic compounds. If this wastewater is to be discharged to land or waterways, a significant proportion of these components need to be removed. If further removal of organics can be achieved, then the resulting water has considerable value for reuse in on-site kilning and wood treatment processes.
The fixed film Submerged Aerated Filter (SAF) technology was selected as preferred for a trial for its ability to treat kiln condensates, and meet the needs of wood processors in being simple to operate, robust, and low cost. The trial was carried out at Rosvall Sawmill with the aim of gathering “typical” influent and effluent data, evaluating potential organic removal rates, and determining maximum loading capacities. Additionally, risks associated with the solids generation, nutrient deficiency, inhibition, and the fate of CCA (copper, chrome and arsenic) treatment metals were investigated.
A pilot plant was installed, commissioned, and then operated for a series of trials over a period of 4 months. The SAF was found to achieve high levels of treatment effectiveness, removing up to 90% of the BOD5 load, and 77% of the COD load.