Reduction of COD and TOC concentration in pharmaceutical wastewater using Fe2+ catalyzed ozone: Full-scale case study

Abstract

This work was carried out to improve the performance of an ozonation system used for wastewater treatment in a pharmaceutical industry. In order to improve the mineralization of organic matter, ferrous sulfate was applied as a catalyst to the reaction system. After this, the pH of the water was adjusted to 8.5–10, so that the process is carried out under alkaline conditions. Finally, O3 was injected through a Venturi tube in order to improve the mass exchange between gas and water. Preliminary operating data indicate that the treatment system achieves chemical oxygen demand (COD) removals of less than 10%. The tests were conducted at full scale and the water quality variables were analyzed at different reaction times. It was determined that for an ozone dose equal to 10 g/h and 10 mg/L Fe2+ and an initial water pH equal to 9, 4.5 hours were required to achieve a reduction of 30.73% COD and 36.85% total organic carbon (TOC). The results obtained with an initial pH higher than 9.5 indicate that the effectiveness of the process is reduced, a fact that may be caused by the rapid formation of insoluble Fe(OH)3, which decreases the availability of the catalyst for the formation of OH* radicals in the water.