Optimization of Ozonation Process for the Reduction of Excess Sludge Production from Activated Sludge Process of Sago Industry Wastewater Using Central Composite Design

Table 4

Adequacy of the model resulted for VSS and COD reduction.

	Source	Sum of; squares	DF	Mean; square	𝐹value	𝑃-value; Prob>𝐹	Source	SD	𝑅^2	Adjusted; 𝑅^2	Predicted; 𝑅^2	PRESS
	Sequential model sum of square						Model summary statistics
VSS reduction %	Mean	1.083E + 005	1	1.083E + 005
	Linear	6471.83	3	2157.28	46.82	<0.0001	Linear	6.79	0.8977	0.8786	0.8184	1309.45
	2FI	75.90	3	25.30	0.50	0.6904	2FI	7.13	0.9083	0.8659	0.7773	1605.12
	Quadratic	436.69	3	145.56	6.48	0.0103	Quadratic	4.74	0.9689	0.9408	0.7656	1689.90
	Cubic	172.73	4	43.18	5.00	0.0407	Cubic	2.94	0.9928	0.9772	−0.5167	10933.58
	Residual	51.83	6	8.64
	Total	1.155E + 005	20	5777.21
COD reduction %	Mean	1.143E + 005	1	1.143E + 005	0.44	0.7255
	Linear	160.84	3	53.61			Linear	11.00	0.0767	−0.0964	−0.4815	3106.68
	2FI	416.17	3	138.72	1.19	0.3531	2FI	10.81	0.2752	−0.0594	−1.4699	5179.18
	Quadratic	1276.36	3	425.45	17.47	0.0003	Quadratic	4.94	0.8838	0.7793	0.0979	1891.75
	Cubic	158.29	4	39.57	2.78	0.1266	Cubic	3.77	0.9593	0.8712	−7.8953	18652.95
	Residual	85.27	6	14.21
	Total	1.164E + 005	20	5820.21