Generally speaking, the pH (X1)was the most significant vari-able for all the analyzed responses, as this variable presented higher regression coefficients among the others. The pH is nega-tively related to turbidity, color, and viscosity. All samples treated
at pH 6 presented turbidity and color reductions superior to 90%
and viscosity reduction of almost 40%,regardless the chitosan con-centration. Within the analyzed range, the chitosan concentration (X2)showed a negative effect on all the analyzed responses. How-ever, the effect of chitosan concentration is more evident at pH
3. According to Rizzo et al. [23] pH and chitosan concentration,
as well as the initial turbidity of the solution to be treated, are
important variables for coagulation process using chitosan. Slow
agitation speed (X3) did not present significant effect over any of
the analyzed variables. Slow agitation time (X4) did not present
significant effect over color response and presented a positive
effect for turbidity, color, and viscosity responses.In general, the
obtained results showed that the analyzed Jar test parameters are
less important than pH and chitosan concentration for the coagu-lation process. Sánchez-Martín et al. [16] also observed that rapid