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.