Performance Optimization of Chemical and Green Coagulants in Tannery Wastewater Treatment: A Response Surface Methodology Approach

Table 1

Range and levels of the independent variables.

Coagulants	Code	Variables	Ranges and levels
			−α	−1	0	+1	+α
Cassava starch		Dosage (g/L)	2.76	4	7	10	11.24
		pH	3.17	4	6	8	8.83
Orange peel powder		Dosage (g/L)	2.76	4	7	10	11.24
		pH	3.17	4	6	8	8.83
Aluminum sulphate		Dosage (g/L)	6.34	8	12	16	17.66
		pH	6.09	6.5	7.5	8.5	8.91