The Application of a Surface Response Methodology in the Solar/UV-Induced Degradation of Dairy Wastewater Using Immobilized ZnO as a Semiconductor

Table 1

Variables and levels based on the Surface response methodology (15 runs with replication) for the dairy wastewater photocatalytic process.

Control variables	Level −1	Level 0	Level 1
pH	6.0	8.0	10.0
ZnO coating thickness (μm)	0	50	100