PO₄^3– Inhibits Disinfection Byproduct Formation in Corroded Iron Drinking Water Pipes

In the drinking water pipeline, PO43– and iron particles will inevitably coexist, but their effects on water quality are not fully clear. Here, PO43– was shown to inhibit the formation of disinfection byproducts (DBPs) in ductile cast iron pipe (decreases of 8.7%–29.8%). The inhibition effects were proved to be related to particle structure changes induced by PO43–. The PO43– influenced particles had lower roughness, smaller particle size, and a larger amount of negative charge. In the beaker without iron, the concentration of PO43– remained nearly consistent with the initial concentration, oscillating around 1.5 mg/L, whereas the PO43– concentration in the group containing Fe(II) exhibited a notable decline, reaching 1.28 mg/L. Thus, PO43– did not play a direct role in the formation of DBPs, but modulated the physicochemical behavior of water and the characteristics of particles. Therefore, when iron corrosion occurs in drinking water distribution systems (DWDSs), PO43– has the ability to inhibit the formation of DBPs, but other water quality issues should be considered at the same time. This study not only explains how PO43– affects the formation of DBPs in DWDSs, but also provides new thinking on how to control the risk of DBP exposure in DWDSs, which is worthy of further research.