How to Use a Color Reducer for a Waste Water Plant?

Hi there all, I have a problem in my WWTP plant. The color is very high, as well as COD. I heard that color reducer agent can remove color from water and I would like to know in which stage do I have to use the color reducer - in primary treatment or in tertiary treatment? In which ppm do I have to use it?  Currently, the chemical dosage is:  Lime 1000 ppm Alum 1200 ppm and poly 1 ppm  Color reducer ??? ppm  Kindly share you experience guys.    Thanks/Regrads, Abdul Gaffar - Senior Chemist.