Effects of the interaction between Microcystis aeruginosa and nitrobenzene on coagulation-sedimentation performance

It is rarely reported that the interaction between xenobiotics and algae may cause potential water quality risks and affect the drinking water treatment process. In the present study, a bench-scale jar test was performed to investigate the effects of the interaction between nitrobenzene (NB) and Microcystis aeruginosa on the performance of coagulation-sedimentation by comparing differences in turbidity, optical density at 680 nm (OD₆₈₀), trihalomethane formation potential (THMFP) and microcystin-LR (MC-LR) in an M. aeruginosa solution with or without NB. The results indicated that the quality of M. aeruginosa-containing water can be improved significantly by coagulation-sedimentation, and all of the removal rates were more than 80%. The presence of NB did not affect the performance of coagulation-sedimentation directly. However, the interaction between NB and M. aeruginosa did change the characteristics of the raw water and affect the performance of coagulation-sedimentation. At a non-lethal concentration, NB did not inhibit the growth of M. aeruginosa but weakened the zeta potential of M. aeruginosa, which enhanced the removal of turbidity. The products of NB degradation by M. aeruginosa cause an increased THMFP in extracellular organic matters, which cannot be removed by coagulation-sedimentation efficiently, increasing the risk of disinfection by-products formation in the following disinfection unit.