Experience has shown that corrosion and biofouling control are important factors in operating a "clean" open evaporative cooling water system. Treated sewage water as make-up to the cooling tower requires novel approaches to control corrosion and biofouling besides meeting environmental regulations. An intensive field study was conducted to evaluate the effectiveness of a non-chromate treatment program. On-line cleaning of the exchangers occurred prior to instituting the new chemical treatment program. Low carbon steel corrosion rates with minimal deposition was achieved. Microbiological fouling was controlled with chlorination and non-oxidizing biocide program. Field tests are presented that compares the efficacy of these proprietary treatments to control corrosion and inhibit scale and biofouling. Analytical results are presented that provide a comprehensive evaluation program of a new non-chromate chemical treatment program.