Effects of a composite phosphate corrosion inhibitor on corrosion behavior and water quality stability in drinking water distribution systems

This study investigated the effectiveness of a composite phosphate corrosion inhibitor in enhancing water quality stability in drinking water distribution systems (DWDSs), guided by practical engineering needs. Through simulated pipelines and community-scale field experiments, the effects of a corrosion inhibitor on the corrosion of galvanized steel pipes and the decay of residual chlorine were explored. Results indicated that after 30 days of operation, a large amount of iron oxides was generated in the galvanized steel pipe layer of the control group, while the galvanized layer of the experimental group remained basically intact. Additionally, the residual chlorine decay rate after corrosion of the pipeline surface reached 0.091 min⁻¹, and the decay rate of DWDSs was reduced by ∼50% after the addition of corrosion inhibitor. Field experiments further demonstrated that following the introduction of the corrosion inhibitor, the mean total chlorine decay dropped from 0.1 to 0.4 mg/L to 0.05–0.2 mg/L, and the Fe release was effectively inhibited. Meanwhile, the average turbidity of the water in the community stabilized below 0.15 NTU after adding the corrosion inhibitor. The chemical stability of water quality was improved, and there was no significant effect on disinfection by-products and biological stability. The use of composite phosphate corrosion inhibitor offers an effective solution to control both corrosion in DWDSs and residual chlorine decay, thereby contributing to the safety management of drinking water.