Effects of heating temperature and water age on the formation of disinfection by-products in drinking water

Abstract

Tap water is often heated to different temperatures for various household uses (e.g., cleaning, washing, showering, bathing, and preparing hot drinks). Typical water ages (i.e., residence time in the distribution system) range from hours to days prior to household water uses. The concentrations of twenty-one disinfection by-products (DBPs) were investigated in heated drinking water (i.e., heating temperatures of 40, 65 or 90 °C, with a heating duration of 1 h) at varying water ages (i.e., 2, 8, 24 and 48 h). DBP concentrations in heated drinking water were found to increase, remain largely constant, decrease or show a mixed changing pattern (i.e., decrease following an initial increase) with increasing water age, depending on the heating temperature. A shorter water age resulted in larger increases in DBP concentrations during the heating process due to more chlorine residuals and organic precursors available for DBP formation. A kinetic model was proposed to illustrate DBP concentrations in heated drinking water, incorporating the effects of both heating temperature and water age. The relatively low discrepancies (i.e., within or near ±20%) between modeled and experimentally measured DBP concentrations suggest the potential of the model to predict DBP concentrations in household heated drinking water across the distribution system.