Table 2 Average (±SD) effluent concentration, mass loading rate and percentage removal of pollutants in a series-connected two-stage HSSFCW system at different HRTs

1 day HRT

113.3 ± 5.82

376.2 ± 31.86

63.6 ± 11.27

34.2 ± 7.93

25.3 ± 5.3

26.4 ± 0.78

64.5 ± 5.2

11.5 ± 1.31

5 ± 0.91

3.8 ± 0.87

2 days HRT

70.7 ± 16.81

155.9 ± 20.77

37.3 ± 7.67

23 ± 5.89

12.4 ± 4.01

10.2 ± 2.11

24.9 ± 2.97

4.3 ± 0.75

2.1 ± 0.45

1.3 ± 0.34

3 days HRT

31.1 ± 9.57

63.8 ± 11.3

19.9 ± 3.6

15.1 ± 3.99

7.8 ± 3.39

5.2 ± 1.07

15.5 ± 1.91

2.1 ± 0.37

1.3 ± 0.47

0.8 ± 0.32

4 days HRT

15.7 ± 4.85

37.8 ± 9.97

10.1 ± 1.82

9.1 ± 3.66

3.81 ± 1.58

2.9 ± 0.42

11.6 ± 0.94

1.4 ± 0.19

0.9 ± 0.17

0.5 ± 0.15

5 days HRT

11 ± 3.79

29.7 ± 7

7.6 ± 1.75

6.1 ± 2.46

3.83 ± 1.25

2.1 ± 0.37

7.3 ± 0.83

0.8 ± 0.16

0.6 ± 0.12

0.4 ± 0.09

p value

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

<0.05

Operation

Percentage removal efficiency (%)

TSS

COD

TN

TP

PO₄–P

1 day HRT

47.8 ± 1.52

29.2 ± 2.11

32.9 ± 3.08

16.8 ± 1.91

18.4 ± 5.44

2 days HRT

57.8 ± 1.65

61.9 ± 4.26

46.9 ± 4.94

34.8 ± 3.39

41.5 ± 5.44

3 days HRT

75.8 ± 4.75

83.3 ± 1.55

61.1 ± 3.88

51.6 ± 3.13

59.8 ± 3.49

4 days HRT

83.5 ± 2.89^a

90.1 ± 2.64^a

77.5 ± 2.56^a

68.9 ± 5.9^a

77.5 ± 2.84^a

5 days HRT

87.2 ± 2.54^a

90.1 ± 2.25^a

77.7 ± 1.71^a

75.4 ± 6.14^a

76.8 ± 4.97^a

p value

<0.05

<0.05

<0.05

<0.05

<0.05