Effects of compound bioflocculant on coagulation performance and floc properties for dye removal

•CBF was used as coagulation aid with AS and PAC in dye water treatment.•CBF contributed to improving color removal of AS and PAC.•Floc size and floc sedimentation rate were significantly enhanced by CBF.•Floc breakage and recovery factor were improved by CBF. A series of jar tests was conducted to investigate the coagulation performance of using compound bioflocculant (CBF) as a coagulant aid with aluminum sulfate (AS) and polyaluminum chloride (PAC) in synthetic dyeing wastewater treatment. Floc size, growth, breakage, re-growth and sedimentation natural were investigated by PDA2000. The results showed that the corresponding dual-coagulants of AS and PAC enhanced the color removal efficiency, especially at low aluminum dosage. Results also indicated that the floc generated by aluminum salts and CBF had larger size and higher growth rate. In addition, for both AS and PAC the floc recoverability was improved by addition of CBF. The adsorption and bridging effect of CBF performed a positive role in dye wastewater treatment.