Investigation on the Factors Affecting Corrosion of Tertiary-Treated Municipal Wastewater

Abstract

Tertiary treatment of municipal wastewater is necessary to reduce its scaling potential for using as makeup water of circulating cooling systems. In this study the corrosivity and the factors affecting corrosion of municipal wastewater tertiary-treated by nanofiltration membrane process were assessed by weight-loss method. The results show that concentration of salt ions such as Ca2+, Mg2+, Cl- and SO42- has a significant effect on corrosivity to carbon steel. Certain quantity of calcium and magnesium ions could inhibit the corrosion of carbon steel, however, chlorine and sulfate ions could accelerate the corrosion of carbon steel. The corrosion inhibition effect of three inhibitors (PC-604, RP-101 and poly epoxy succinate (PESA)) in tertiary-treated municipal wastewater on the carbon steel was evaluated. PC-604 had the best corrosion inhibitor effect and the lowest dosage. This research has guiding significance for using tertiary-treated municipal wastewater as makeup water of circulating cooling systems.