There was no need to add the number of experiments since the detention time adopted for the sedimentation lagoon
was two days and the changes of algae density was insignificant(itwasmainly changedby season). The effluent samples in these experiments had a TSS concentrations of 30 to 400 mg/L and chlorophyll a concentrations of 100 to 1600 mg m-3 determined respectively by gravimetric and spectrophotometric methods [according to the Standard Methods, procedure No. 10200.H for chlorophyll a determination]. Aluminum concentration was also measured by a colorimetric method (spectrophotometer model DR2500 from the Hach Co.) and pH was determined by a lab pH-meter (from the Hach Co).