Research was undertaken to characterize raw wastewater, effluent and sludge, and assessed wastewater treatment systems in Ontario's food industry, that discharge wastewater directly to surface water or land. Samples from 48 sampling points in 12 plants were collected seasonally for a whole year and were analyzed for up to 234 parameters. About 45,000 data points were obtained. Two Access databases were built for the data management. Systematic statistical methodologies were developed for the data analysis, including box plot, dot diagram, Levene's test, and one-way ANOVA. Based on intensive data analysis, a comprehensive characterization of raw wastewater, effluent and sludge is presented. The results and corresponding explanations provide a basis for best management practices in Ontario's food processing sector. For example, the leakage of milk and milk products is the main reason for the high levels of pollutants such as TKN in dairy wastewater. Potential measures for the improvement of wastewater treatment systems of certain plants are provided. A good example is that increasing aeration could reduce the concentration of ammonia in the effluent from some plants.