Trihalomethane precursor model for Lake Youngs, Washington

A mathematical model is developed to estimate trihalomethane formation potential (THMFP) in Lake Youngs, Wash. The model simulates both seasonal trends and spatial variations. The model kinetic framework includes total organic carbon (TOC), THMFP, chlorophyll a, zooplankton, Secchi disk depth, dissolved oxygen, dissolved TDP, and total phosphorus (TP). Calculated THMFP concentrations are dependent on external watershed TOC loading, algal cell densities, and TOC associated with extracellular products. Model performance is evaluated by comparison of calculated results with measured data from Lake Youngs. Analyses illustrate how THMFP concentrations in the raw water supply change as a function of watershed TP and TOC loading. A general assessment considers the role of watershed land-use control, reservoir management, alternative treatment technologies, and the operation of the water supply distribution system in complying with finished drinking water standards for THM.