Surfactant removal was satisfactory in terms of both
removal percentage (up to 85.4%) and effluent concentration
(1.1 0.3 mg/l, always below the limit of 2 mg/l). Despite the
removal of colour was not as high as the one observed for all
the other parameters, effluent colour was always sufficiently
low to allow direct discharge (i.e., colour was not visible after a
20-fold dilution of the sample