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

Table 4

Central composite design matrix for coagulation experiments with aluminum sulphate coagulants.

Run order	Independent variables		Responses
	Alum dosage (X1) (g/L)	pH, X2	COD removal, (%)	TSS removal, (%)	SVI, (mL/g)
1	16	8.5	36.91	71.07	35.09
2	17.66	7.5	32.30	69.52	27.97
3	12	6.09	39.22	76.03	29.26
4	12	7.5	32.34	73.89	30.23
5	12	7.5	30.18	72.78	29.84
6	12	7.5	31.97	73.01	30.39
7	12	7.5	32.22	72.94	30.03
8	16	6.5	33.47	71.59	27.41
9	12	7.5	30.29	73.78	29.95
10	6.34	7.5	20.81	73.32	35.95
11	12	8.91	34.10	74.05	45.46
12	8	6.5	30.92	75.53	31.05
13	8	8.5	21.97	73.12	45.04