Characterising bioreactor mixing with residence time distribution (RTD) tests

This paper presents a technique for configuring wastewater process simulations so that the hydraulic characteristics are similar to the real plant. Residence time distribution (RTD) tests are performed on two biological nutrient removal pilot plants. The RTD tests proved valuable for evaluating mixing effectiveness, volume utilisation and for determining an appropriate hydraulic topology for the dynamic models of the pilot plants. As a result of this work, simulation execution times became much faster due to a significant reduction in the number of effective stirred tanks required in the model. The work also identified short circuiting and dead zones in the pilot plants.