A 22 Central Composite Design (CCD) was used to study the influence of the wastewater concentration and sodium bicarbonate concentration on the C. vulgaris growth and the removal of wastewater pollutants. The maximum wastewater concentration for the Factorial Run Design was stipulated from the preliminary cultivation tests of the microalgae in the textile waste effluent, using as standard.
Table 1 shows the real and coded values of the variables used in the 22 Central Composite Design (CCD). Distilled water was used for the dilutions of the waste effluent.