Removal of Reactive Black W-2N from synthetic wastewater by an integrated membrane coagulation reactor

• Decolorization could be achieved by an integrated membrane coagulation reactor.
• Membrane fouling experienced three phases as reflected by trans-membrane pressure.
• Fractal dimension value of flocs increased with the increasing coagulant dose.
• Ferrate addition increased mean size and porosity of floc particles formed.
• Ferrate could reduce trans-membrane pressure increment rate and membrane fouling.

Herein, a new integrated membrane coagulation reactor (IMCR) was developed to effectively treat synthetic wastewater containing Reactive Black W-2N. The optimal operation conditions were determined as follows: influent pH 5.5, polyferric sulfate (PFS) dose 1.2 mmol/L, and hydraulic retention time 3 h, under which a nearly complete decolorization was achieved and chemical oxygen demand removal reached 92%. Membrane fouling experienced three phases as reflected by different increment rates of the trans-membrane pressure. A high PFS dose aggravated the membrane fouling. The fractal dimension value of flocs increased with the increasing coagulant dose. In comparison to the control experiment, ferrate addition significantly increased the mean size and porosity of the floc particles formed. Because ferrate addition could reduce the trans-membrane pressure increment rate, the steady-state performance of the IMCR process was improved.