Table 2 The CCD experimental conditions and corresponding AN removal rates.

From: Optimization pilot scale study on ammonia nitrogen removal by bio filter

Run

Type

Uncoded Level

AN removal rate (%)

C/N

X1

pH

X2

HL (d−1)

X3

1

Star

15

7

0.5

65.30

2

Star

25

7

0.5

59.45

3

Star

15

8

0.5

80.35

4

Star

25

8

0.5

69.21

5

Star

15

7

1.5

57.35

6

Star

25

7

1.5

58.58

7

Star

15

8

1.5

76.89

8

Star

25

8

1.5

76.08

9

Axial

11.59

7.5

1

73.15

10

Axial

28.41

7.5

1

56.84

11

Axial

20

6.66

1

51.35

12

Axial

20

8.34

1

82.15

13

Axial

20

7.5

0.16

69.97

14

Axial

20

7.5

1.84

77.33

15

Center

20

7.5

1

87.05

16

Center

20

7.5

1

89.83

17

Center

20

7.5

1

89.50

18

Center

20

7.5

1

92.09

19

Center

20

7.5

1

88.28

20

Center

20

7.5

1

88.78

  1. AN ammonia nitrogen.