Treatment of Simulated Textile Dyeing Wastewaters Using Avanced Oxidation Processes-A Bench-Scale Study

摘要

Reactive dyes are extensively used in textile dyeing industry nowadays due to their superior performance, but they are environmentally hazardous, refractory in nature and difficult to treat effectively by the existing conventional methods. In the present work, decolourisation and degradation of simulated textile dyeing wastewater were experimented using ozonation, photo-assisted ozonation (UV/O_3), photocatalysis (UV/TiO_2) and photocatalytic-ozonation (UV/TiO_2/O_3) process. The experiments were carried out in a reactor of 15 L capacity. All the wastewaters were highly coloured with Chemical Oxygen Demand (COD) ranging from 200 to 480 mg/L and Total Organic Carbon (TOC) from 55 to 120 mg/L. The low biodegradability ratio (＜1) indicated the recalcitrant nature of the dyes used. The study revealed that UV/TiO_2 without ozonewas slow with only 40% colour removal and 33% COD removal while ozonation and UV/O_3 processes removed 99% colour and 62-80% COD after 30 minutes of treatment. The highest efficiency was achieved in coupled UV/O_3/TiO_2 process with colour and COD removal of 99% and 88% respectively at 100 mg/L TiO_2 concentration, 8.85 g/h ozone dose and alkaline pH. It was also observed that the maximum oxidation and biodegradability improvement occurred in coupled photocatalytic-ozonation process. The reaction kinetics followed pseudo-first order and the rate of reaction is faster in the coupled advanced oxidation process (AOP) than the other.