The Safe Drinking Water Act (SDWA) Amendments of 1986 and the proposed
Disinfectants/Disinfection Byproducts Rule (D/DBPR) impose somewhat conflicting
disinfection regulations whereby the finished water level of disinfection must be
increased while the disinfectant and disinfection byproduct residuals must be
lowered. The aim of this research project was to evaluate a method for maximizing
the hydraulic efficiency of contactors in order to reduce required disinfectant
concentrations and subsequently, the disinfection byproduct
formation can be controlled and/or minimized. Effective design of new basins and
retrofitting of existing basins play an important role in disinfection regulation
compliance. The hydraulic performance of a contactor can be influenced by
internal baffling and inlet and outlet location. To understand the effects of the
basin configuration on hydraulics and disinfection, empirical data obtained from
tracer tests performed on full scale or pilot scale basins are usually analyzed.
An attractive alternative to these expensive experimental tracer testing methods,
is the use of computational fluid dynamics (CFD) modeling to simulate tracer
studies. In addition to determining concentration profiles as obtained from
tracer tests, CFD modeling offers insight on the internal flow patterns including
velocity, energy, and pressure. The goals of this research project were to
evaluate the ability of simulated tracer tests to reproduce data from tracer
experiments, and to analyze the influence of baffling arrangements and inlet and
outlet positions on the performance of the contactor. Various configurations of
disinfection contactors were modeled using a commercially available finite
element CFD software package called FIDAP(R). The hydraulics and concentration
distribution were used to determine optimal basin designs. Tracer studies were
simulated using the CFD software and ultimately compared to empirical data to
validate this approach. Includes 22 references, tables, figures.