Improvement of effluent quality and cost saving at a 750,000pe WRRF using an extensively validated CFD model

Besides trial-and-error approaches, conventional flowsheet modelling (such as tanks-in-series (TIS)) is widely used to optimize the performance of Water Resource Recovery Facilities (WRRFs). However, this modelling approach lacks the ability to consider design parameters such as propellers and aerator configurations. Trial-and-error based optimisation of such parameters is in many cases highly risky or even impossible. By appropriate use of computational fluid dynamics (CFD), one can accurately and efficiently evaluate different design changes prior to actual implementation, while severely extending system understanding. The current study shows the practical application of CFD for full-scale bioreactor optimization in terms of performance (lower effluent nitrate) and cost. The CFD model was unprecedentedly validated using a construction crane for dissolved oxygen profiling. Also flow velocities were measured. Different new propeller settings and aerator configurations were tested. Unwanted oxygen near the inlet of the anoxic zone could be reduced up to 20%. One of the promising scenarios was implemented in practice and the impact on effluent quality is currently being evaluated. The operational change will have a potential operational cost saving of minimum 500,000 EUR/y.