However, for Cv, all the parameters fit the Portuguese legisla-tion, except for P, although 77% of removal was achieved. An expla-nation for this fact can be related to the high initial level of P in the urban wastewater used for this trial, which was quite high when compared to the other ones. The high value was probably due to an unexpected discharge of pollutants and/or to the seasonality of Figueira da Foz region, where the treatment plant is located.