Interface Change and Toxicity Risks of Loose Deposits Induced by Boiling Considering Discoloration

Abstract

Boiling is commonly used as a point-of-use household water treatment. This study evaluated the effect of boiling on the water quality with particles originated from loose deposits in drinking water distribution systems. Results showed that during the boiling process, turbidity did not have obvious change before 60 ℃, but abruptly increased after 90 ℃, and finally reached about 220 NTU after boiling (100 ℃) under particle concentration of 100 mg/L with slight initial discoloration. The particles had smaller size, more particle counts and lower agglomeration after boiling. Boiling induced an increase of dissolved organic matter (DOM) in water, and particles contributed DOM significantly. In addition, the particles had increased specific surface area (from 106.8 to 123.4 cm2/g) and roughness after boiling. More importantly, the particles exhibited higher cytotoxicity after boiling for human gastric mucosal cells, and a good negative linear relationship was found between turbidity and cell viability. Interestingly, the increase of intracellular reactive oxygen species was observed in the cells with particles added . Furthermore, particles promoted the formation of DBPs with more aromatic structure which had higher toxicity. This study provided new insights into the effects of boiling on the loose deposits from drinking water distribution system.

Keywords: loose deposits, boiling, DBPs, dispersion, toxicity.