In this study, calcium lactate is proposed as a coagulant-flocculant. The operational conditions for efficient removal of suspended solids from water were optimized by use of a central-incomplete 33 design, to evaluate the effect of the calcium lactate dose (between 2 and 10 g l(-1)), pH (between 5 and 7) and initial sediment concentration (between 4 and 16 g l(-1)) on reducing water turbidity. It was found that within the ranges tested, the greatest reductions of turbidity were achieved with a moderate concentration of calcium lactate at pH 5. After 2 h treatment with calcium lactate the turbidity of water was reduced to 77-88% of that in the untreated control. Moreover 6 g l(-1) and 2 g l(-1) of calcium lactate reduced the water turbidity from 300 NTU to 2.5 and 5.5 NTU respectively after 18 h of treatment at pH 5. For short treatment times, the most important independent variable was the concentration of sediment, whereas for longer treatment times, pH was the most important variable. (C) 2011 Elsevier B.V. All rights reserved.