Further contributions to nitrogen removal modelling in waste stabilization ponds.

A large database from an experimental maturation pond system in Brazil was used to verify the agreement of field results with values predicted by some of the most widely accepted models to describe ammonium and total nitrogen (TN) removal in facultative and maturation ponds. The same database was used to derive a pH-independent linear model to predict ammonium removal in ponds, which was proved to be, essentially, a function of ammonium surface loading rate. In general, all these models made reasonable predictions of ammonium or TN removal but tended to overestimate low ammonium effluent concentrations while underestimating higher values of field data.