Multi-stage ozonation and biological treatment for the removal of azo dye industrial effluent

Abstract

The presence of dyes in various industrial effluents is a major problem due to their adverse effect to many forms of life. Wastewater containing dyes presents a serious environmental problem due to its high toxicity which contributes to water pollution. Dyes are known to have strong colour, high chemical oxygen demand (COD) and low biodegradability. This research focused on treatment of dye industrial effluent by single-stage and multi-stage ozonation and biological treatment process. It was done as to evaluate the performance of ozonation and biological treatment process for colour or concentration and COD removal of Reactive Red 120 dye sample. In the single-stage ozonation and biological treatment, one (1) liter of dye sample was ozonated for 15 minutes and then was biodegraded with 1 % river water for 4 days. In the multi-stage ozonation and biological treatment, the sample was ozonated for 5 minutes and biodegraded by the same method as in single-stage treatment. However, the process of ozonation and biodegradation were repeated until the third stage. The results obtained showed that single-stage ozonation and biological treatment removed 39.51 % of COD while multi-stage treatment removed 76.54 % of COD. Both single-stage and multi-stage ozonation and biological treatment process gave excellent results of 99.90 % colour removal.