Figs. 2. Chemical Oxygen Demand (graph a) and Biochemical Oxygen Demand (7) (graph b) yields according to
the time. c= Effluent treated by S. = Effluent treated by PS. ¡= Effluent treated by P. The points are means
of Chemical Oxygen Demand and Biochemical Oxygen Demand (7) yields. Vertical bars indicate standard
deviation (±) (n=5). For the sake of clarity, only the halves of the interval bars have been represented. Different
letters, for the same date, over points indicate significant differences according to Tukey test at p