Performance of a novel HABR–CFASR system for the biological treatment of mixed printing and dyeing wastewater (MPDW)

Mixed printing and dyeing wastewater (MPDW) is characterized by a low-strength chemical oxygen demand (COD; average of around 1,000 mg/L), a high fraction of recalcitrant components, a low COD/ ratio (approximately 1.0), and a high pH (about 8–10 without adjustment). In this study, a biological system that combined a hybrid anaerobic baffled reactor (HABR) and a cross flow aerobic sludge reactor (CFASR) was successfully used to treat MPDW that was discharged from an industrial zone. The HABR–CFASR system was fed with real MPDW. In the start-up stage, the system had low organic loading rates of 0.66 and 0.45 kg COD/(m3·d) for the HABR and CFASR, respectively. These increased to 2.03 and 1.00 kgCOD/(m3·d), respectively, in the steady stage. The pH of the HABR influent was reduced by adding H2SO4 at a decreased dosage over the course of the experiment. Most of the final effluent from the combined treatment process was stable below 100 mg-COD/L and 20 mg-BOD/L after 12 h-HRT in the HABR followed by 20 h in the CFASR. The sulfate removal rate reached 17.59%, and the COD/ ratio varied slightly around 1.0, regardless of the Ns (sulfate loading rate), which varied between 1.5 and 2.5 kg/(m3·d). A GC/MS analysis demonstrated that the amount and types of organic compounds declined significantly after the HABR treatment.