Combination of Fenton oxidation and sequencing batch membrane bioreactor for treatment of dry-spun acrylic fiber wastewater

Dry-spun acrylic fiber (DAF) is typically synthesized by the polymerization of acrylonitrile (AN) monomers under high-temperature conditions. DAF manufacturing factories produce DAF polymerization and AN manufacturing wastewaters that are complex, toxic and bio-refractory. In this study, a bench-scale combined Fenton-sequencing batch membrane bioreactor (SBMBR) process was developed for DAF wastewater treatment. Fenton oxidation was used for the pretreatment of DAF polymerization wastewater, with which the COD removal efficiency exceeded 47.0 % under the optimum conditions of H2O2 90.0 mM, Fe2+ 20.0 mM, pH value 3.0, and reaction time 120 min. The pretreatment increased the BOD5/COD ratio of DAF polymerization wastewater from 0.35 to 0.69 and observably decreased the toxicity (assessed with the Vibrio fisheri bacteria light loss) from 92.0 to 32.0 %. As for the biological treatment, the mixture liquor of Fenton effluent and AN manufacturing wastewater was fed to a bench-scale SBMBR system. Under the designed operation conditions, the average COD, NH4+-N and TN removal efficiencies reached 82.5, 98.4 and 74.6 %, respectively. The final effluent of SBMBR could steadily meet the National Discharge Standard of China of Grade I (GB8978-1996). The polyvinylidene fluoride flat-plate membranes used in this study showed excellent anti-fouling performance throughout the operation period.