Reduction in TDS

Increasing TDS after lime and alum addition

Hi i am working for a project in ETP. Our effluent contains a TDS of 3000 ppm while after equalisation - that is after addition of lime and alum - our TDS increases to 4500 ppm giving our outlet TDS to be 5000 ppm. In this project we haven't installed any tertiary process. It consists of simple equalisation tank, primary clarifier, surface aeration , secondary clarifier followed by sand filter and carbon filter. after addiiton of lime our ph is 11.5 and after addition of alum we maintain a ph of 10.5. Please suggest me some solution for this problem.