In this study three-dimensional numerical models
were refined to predict reactive processes in disinfection contact
tanks (CTs). The methodology departs from the traditional
performance assessment of contact tanks via hydraulic efficiency
indicators, as it simulates directly transport and decay
of the disinfectant, inactivation of pathogens and accumulation
of by-products. The method is applied to study the effects
of inlet and compartment design on contact tank performance,
with special emphasis on turbulent mixing and minimisation
of internal recirculation and short-circuiting. In contrast to the
conventional approach of maximising the length-to-width ratio,
the proposed design changes are aimed at addressing and
mitigating adverse hydrodynamic structures, which have historically
led to poor hydraulic efficiency in many existing
contact tanks. The results suggest that water treatment facilities
can benefit from in-depth analyses of the flow and kinetic
processes through computational fluid dynamics, resulting in
up to 38 % more efficient pathogen inactivation and 14 % less
disinfection by-product formation.