Biological treatment of real textile wastewater containing sulphate, salinity, and surfactant through an anaerobic–aerobic system

Abstract

Real textile wastewater containing high salinity (up to 12.6 g·kg−1) and surfactant (up to 5.9 mg·L−1 of linear alkylbenzene sulfonate – LAS) was submitted to biological treatment for colour (up to 652 mg Pt-Co·L−1) and sulphate (up to 1,568.6 mg SO4−2·L−1) removal. The influence of ethanol and molasses supplementation was firstly evaluated in anaerobic batch reactors for the removal of dyes and sulphate. Subsequently, aiming to remove aromatic amines (dye degradation by-products), an anaerobic–aerobic continuous system supplemented with molasses was applied. Supplementation had no influence on colour removal (maximum efficiencies around 70%), while it improved sulphate reduction (23% without supplementation against 87% with supplementation), and conferred robustness to the reactors, which recovered quickly after higher salinity impact. The aerobic reactor removed aromatic amines when the level of surfactants was lower than 1.0 mg LAS·L−1, but the performance of the system was hindered when the concentration was increased to 5.9 mg LAS·L−1. Findings suggest that the supplementation of an easily biodegradable organic matter might be a strategy to overcome wastewater fluctuation in composition. HIGHLIGHTS The characteristics of real textile wastewater vary with the industrial process type and may contain interferences that harm biological treatment.; Interferences are related to high levels of salinity and surfactants.; Good treatment efficiency of colourful wastewater was obtained by applying an anaerobic–aerobic system and electron source supplementation.; To overcome interferences we propose strategies for industrial practices.;

Keywords

• anaerobic co-digestion
• azo dyes
• cod/sulphate ratio
• external carbon source
• interferences
• las