Development and autocalibration of an input-output model of chlorine transport in drinking water distribution systems

Chlorine concentrations within drinking water distribution systems (DWDS) must be maintained between an Environmental Protection Agency enforced minimum and maximum values driven by formation of harmful disinfectant byproducts. The DWDS input-output (I-O) model developed expresses the chlorine concentration at a given pipe junction and time as a weighted average of exponentially decayed values of the concentrations at all adjacent upstream junctions. The upstream junction concentrations are known if they are a chlorine treatment point, or can be calculated in the same manner as the original unknown junction concentration. This is the basis for a recursive procedure with which the I-O model backtracks through the DWDS until all paths from consumption to treatment are found. Since the I-O model finds all paths from treatment to a given measurement, the reaction rate associated with chlorine decay at the pipe wall can be adjusted to improve predicted chlorine concentrations.