Treatment of cork processing industrial effluent with an innovative system of Constructed Wetland and Ozonation

During a three stages biomass adaptation process to cork boiling wastewater (CBW) treatment the performance of two constructed wetland (CWL) systems, with horizontal subsurface flow configuration filled with LECA, one used for control and other planted with Phragmites australis, were compared. Dilutions of the CBW with 500, 600 and 750 mg of Chemical Oxygen Demand (COD) with the pH set to 6.5-7.5 were sequentially used. The others features of the feed solution were the intense dark colour, the total phenols (TPh) concentration ranging from 36 to 62 mg/L and low biodegradability. Both bioreactors presented close removals of COD (44.7 to 56.6%), TPh (40 to 65%) during an extended period of 4 months. Until now the contribution of plants for depuration was limited to the removal of total phosphorus (TP), which varies between 22 and 33% at the planted CWL and only ranged from 2 to 9% in the control. After stage 1 (500 mg/L of COD) the major drawback was the decolourization, that for same samples was close to null or negative. To increase decolourization ozonation was integrated as post-treatment. However, the amount of ozone used was limited to 18.9±2.3 mg to keep the cost low. Beside the mean yield limited to 27% it was possible to achieve over 85% of colour removal and increase the biodegradability from 390 to 955%, which are relevant contributions for the pollution emissions reduction and consequently may contribute to sustainable use of water.