Ozonation of Yarn dyed Wastewater in a Continous Stirred Tank Reactor : Kinetic Study and Performance Optimisation

Abstract

This paper describes the ozonation process in yarn dyed wastewater using continuous stirred tank reactor with the objective to study the kinetic of COD degradation at various volumetric flow rate (30, 50, 70 ml/min) and ozone concentration (2.70 %, 4.25%, 5.86 % mol/mol). The wastewater which was collected from a yarn dying process located in Surabaya area was pretreated by electrocoagulation prior to ozonation process. The electrocoagulation process was carried out to reduce the color intensity and total suspended solid. The pretreated wastewater was then processed using ozonation for 2.5 hours. The result showed that at various concentration of ozone, maximum COD removal was 90.78% which was achieved at 5.86 %mol/mol of Ozon and volumetric flow rate 50 ml/min. It was found that the degradation process followed the pseudo-first order kinetic model. The obtained pseudo-first order rate constants for volumetric rate of 50 mil/min were 0.0307 min-1, 0.0419 min-1 and 0.053 min-1 for ozon concentration of 2.70 %, 4.25%, 5.86 % mol/mol respectively. The residence time were 41 minutes, 31 minutes and 23 minutes for ozone concentration of 2.70 %, 4.25%, 5.86 % mol/mol respectively. These findings offers an alternative treatment for wastewater containing dyes.