Table 3.

Central composite rotational design (CCRD), 2³ with six axial points and four central points was used to analyse the flocculant-coagulant action of chitosan (CS). The same CCRD was used to assess the action of microbiological and standard chitosan in distilled water or tap water. Coded (CD) and uncoded (UCD) values are given in the Table.

Factors	CD (UCD) –α	CD (UCD)	CD (UCD)	CD (UCD)	CD (UCD) +α
[CS]	−1.68 (32 mg/mL)	−1 (100 mg/mL)	0 (200 mg/mL)	1 (300 mg/mL)	1.68 (368 mg/mL)
[dye]	−1.68 (20 mg/mL)	−1 (37 mg/mL)	0 (62.5 mg/mL)	1 (88 mg/mL)	1.68 (105 mg/mL)
pH	−1.68 (1.6)	−1 (3.0)	0 (5.0)	1 (7.0)	1.68 (8.3)

Factors = Independent variables.