The presence of municipal wastewater at the intake of a major drinking water treatment facility located on Lake Ontario was examined using fluorescence data collected during a period of continuous monitoring.In addition,controlled mixing of lake water and wastewater sampled from a local treatment facility were conducted using a bench-scale fluorescence system to quantify observed changes in natural organic matter.Multivariate linear regression was applied to components derived from parallel factors analysis.The resulting mean absolute error for predicted wastewater level was 0.22％(V/V,wastewater/lake water,indicating that wastewater detection at below 1.0％(V/V)was possible.Analyses of sucralose,a wastewater indicator,were conducted for treated wastewater as wel1 as surface water collected at two intake locations on Lake Ontario.Results suggested minimal wastewater contribution at the drinking water intake.A wastewater detection model using a moving baseline was developed and applied to continuous fluorescence data collected at one of the drinking water intakes,which agreed well with sucralose results.Furthermore,the simulated addition of 1.0％(V/V)of wastewater/wastewater was detectable in 89％of samples analyzed,demonstrating the utility of fluorescence-based wastewater monitoring.