Online colloidal particle monitoring for controlled coagulation pretreatment to lower microfiltration membrane fouling at a potable water reuse facility

•Colloidal particles in membrane feed monitored using a light scattering technology.•Colloidal particle levels in the membrane feed water followed a diurnal pattern.•Correlation developed between colloidal particle level and optimum coagulant dose.•Real time “targeted” coagulant release reduced 80 to 96% membrane fouling.•This technique lowered irreversible fouling with no coagulant leakage in filtrate.