Effects of boiling on iron particles in drinking water

Discoloration events in drinking water distribution systems (DWDSs) caused by iron particles have occurred worldwide, and boiling has been applied in drinking water treatment households globally, but the effects of boiling on iron particles are not clear. Here, the effect of boiling on different kinds of iron particles (including loose deposits from the DWDS and their main components FeOOH, Fe2O3, and Fe3O4) was studied. At 10 mg/L, the turbidity values before/after boiling of Fe2O3, Fe3O4, and FeOOH were 134.00/121.00, 25.07/21.22, and 120.40/114.20 NTU, respectively. All the particles had a lower degree of crystallinity after boiling. After boiling, the number of particles in loose deposits increased and the particle size decreased, while iron oxides were on the contrary. Among the three iron oxides, the existence of Fe3O4 and Fe2O3 had different effects on disinfection by-products (DBPs) formation. The activity of microorganisms was the highest under particle concentration of 0.1 mg/L than other concentrations for all the particles, but the total microbiological risks were still very low after boiling. Thus, the boiling treatment would increase the turbidity and risks of the particles. As the particle concentration under low concentration is hard to be found, this risk is hard to be found.