Effect of substrate, redox mediator and aeration on biogranulation treatment of textile wastewater

Abstract

Wastewater discharged by dye manufacturing and textile industries has become a major environmental concern. The treatment of textile wastewater is important and has been an issue due to the toxicity of the wastewater and aesthetic impact on water sources. One of the alternatives in treating textile wastewater is by using biological treatment via biological granulation method. Biogranulation treatment strategy based on anaerobic reduction of the azo dyes, followed by aerobic transformation of the formed aromatic amines, holds promise. The biogranulation process of textile dyeing wastewater and its performance in terms of COD and color removal can be influenced by many factors. Among them, substrate (electron donor), redox mediator and aeration time were identified as factors that may give effect on the rate of COD removal and dye degradation process. This research is aimed at optimising these factors. Research was conducted in a batch test with the hydraulic retention time of 24 hours. Glucose, sodium acetate and methanol were used as the different substrates with concentrations of 1000, 2000 and 3000 ppm. Glucose with concentration of 3000 ppm was the preferred among the substrate tested with COD removal of 65.2 % and color removal of 84%. Riboflavin was used as the redox mediator with concentrations of 1 , 2 and 3 µM and concentration of 2 µM was preferred among the other concentrations with COD removal of 50.8 % and color removal of 87.9 %. Three anaerobic-aerobic reaction time models were tested, namely, 23:1, 21:3 and 7:17. Among them, model 7:17 had the highest COD removal of 93.4 % and model 21:3 has the highest color removal of 90.9 %. The effect of three factors mentioned was verified through an analysis of variance (ANOVA).