Comprehensive utilization of phosphate in a highly concentrated recirculating cooling water system using secondary-treated municipal wastewater as make-up

AbstractA comprehensive utilization process using phosphate was developed for the reuse of high hardness secondary-treated municipal wastewater to a highly concentrated recirculating cooling water system (RCWS). It showed that the soluble phosphate in the wastewater could be directly reused as a corrosion inhibitor to prevent the RCWS from severe corrosion caused by the contaminants in the wastewater. Based on the synergetic corrosion inhibition of and Zn2+, a chemical program was achieved for recirculating cooling water treatment. It contains 1-hydroxyethylidene-1,1-diphosphonic acid, polyepoxysuccinic acid, zinc sulfate heptahydrate, and a copolymer dispersant of LN-104B. In addition, LN-104B was verified to have excellent inhibition capability to calcium phosphate scale and zinc salts scale in the bench experiments. The pilot-scale experimental results showed that the simulated RCWS operated very well under the condition of high Ca2+ concentration (1,500 mg/L as CaCO3) using the chemical program and au...