Table 5: Variance analysis of the polynomial model of first order for the dairy wastewater treatment by photocatalyst treatment.

Coefficient SE coefficient T P Constant 8.852 8.558 1.02 0.382 Reaction time 3.765 2.850 1.32 0.278 Thickness of ZnO 1.835 2.850 0.64 0.565 pH −4.600 2.850 −1.61 0.205 Effluent concentration −0.260 2.850 −0.09 0.933

S = 4.03031, = 61.4%, (adjusted) = 10.0%.