Treatment of cork process wastewater by a successive chemical-physical method

In cork processing, the operation of boiling the raw cork generates large volumes of wastewater which are more often than not released directly into the environment untreated. Even when the wastewater is treated, this is usually by retention in evaporation ponds. This procedure, however, causes bad odors and may pollute surface water and groundwater. The present study evaluates a physicochemical method involving Fenton oxidation and coagulation/flocculation for the removal of chemical oxygen demand (COD), total polyphenols (TP), and aromatic compounds (A) from cork manufacturing process wastewater. The experimental variables studied were the dosages of iron salts (from 0.001 to 0.2 mol/L) and hydrogen peroxide (between 0.06 and 1 mol/L). The integrated Fenton-coagulation/flocculation process reduced the COD of the effluent by from 22% to 85%. The removal of total polyphenols ranged from 4% to 98%, and of aromatic compounds from 2% to 97%. A further two experiments were performed modifying the manner in which the reagents were added, splitting the reagent dose (of hydrogen peroxide and ferrous salt) into two and three fractions. Finally, an economic study was made of the chemical costs deriving from the application of this purification system. The cost of a treatment with an H2O2](o)/COD(o) ratio of 1.8 g/g (splitting the reagent dose into three fractions) that yields a COD removal of 73% was estimated to be 11.5 euros/m(3) of wastewater.