Table 3 Significance of quadratic model coefficient of for the three responses.
Responses (RE, %) | Independent variables | Coefficient estimate | Degrees of freedom | Standard error | Prob > F |
|---|---|---|---|---|---|
COD | x 3 | 6.92 | 1 | 0.94 | <0.0001 a |
x 1 × 2 | −4.75 | 1 | 1.63 | 0.0112 a | |
x 1 × 3 | −4.25 | 1 | 1.63 | 0.0108 a | |
\({x}_{1}^{2}\) | −6.47 | 1 | 1.28 | <0.0001 a | |
x 2 2 | −16.22 | 1 | 1.28 | <0.0001 a | |
ammonia | x 3 | 6.00 | 1 | 0.81 | <0.0001 a |
x 1 × 2 | −5.00 | 1 | 1.40 | 0.0045 a | |
\({x}_{1}^{2}\) | −8.07 | 1 | 1.10 | <0.0001 a | |
\({x}_{2}^{2}\) | −16.57 | 1 | 1.10 | <0.0001 a | |
TP | x 3 | 5.08 | 1 | 0.90 | <0.0001 a |
x 1 × 2 | −3.50 | 1 | 1.57 | 0.0023 a | |
x 1 × 4 | 5.25 | 1 | 1.57 | 0.0204 a | |
\({x}_{1}^{2}\) | −12.50 | 1 | 1.23 | <0.0001 a | |
\({x}_{2}^{2}\) | −14.50 | 1 | 1.23 | <0.0001 a |
