Anaerobic Treatment of Real Dye Wastewater Using a Modified Internal Circulation Reactor

Abstract

Proper treatment of dye wastewater containing significant concentrations of organic matter is imperative for the abatement of water pollution. Unfortunately, most studies on the treatment of dye wastewater employ synthetic wastewaters that hardly match the characteristics of real wastewater. In the present study, real wastewater generated from the manufacturing of Solvent Black 46 (SB46) dye was treated in an internal circulation reactor, modified with a bed of sponge cubes. The reactor was operated in different phases to investigate the impact of parameters such as feed chemical oxygen demand (COD), organic loading rate (OLR), and hydraulic retention time (HRT) on COD removal and methane generation. At a feed COD concentration of 10,000 mg/L and an OLR of up to 3 Kg COD/m3/day, 82% COD was removed with methane generation ranging from 0.28 to 0.31 L/g-COD removed. COD removal and methane generation increased with an increase in upflow velocity. The rate of substrate (COD) removal correlated well with the organic loading rate using the modified Stover–Kincannon model with a correlation factor (R2) of 0.9974. LC-MS analysis of treated wastewater revealed that one of the constituents of SB46, namely Metanil yellow, was decomposed by azo bond cleavage, producing corresponding aromatic amines. Overall, this study provides evidence of the successful anaerobic treatment of real industrial wastewater and its potential contribution to achieving UN Sustainable Development Goals 6 (Clean Water and Sanitation) and 7 (Affordable and Clean Energy). Importantly, the process parameters developed in this study have been utilized by the industry to install two full-scale anaerobic reactors to treat SB46 wastewater which has led them to double the SB46 production while conforming to the prescribed environmental discharge norms.