Substrate layers (cm)

Bacterial density (10⁶ CFU/g)

Aerobic bacteria

Anaerobic bacteria

Total bacteria

Planted bed

Unplanted bed

Planted bed

Unplanted bed

Planted bed

Unplanted bed

0 - 10

9.6^a

1.9^a

0.1^a

0.2^a

9.7^a

2.0^a

10 - 20

7.4^b

1.2^d

0.3^b

0.4^b

7.7^b

1.6^b

20 - 30

5.1^c

1.0^c

0.4^c

0.5^c

5.5^c

1.5^c

30 - 40

3.7^d

0.7^d

0.5^d

0.7^d

4.2^d

1.4^c

40 - 50

3.0^e

0.4^e

0.7^e

0.9^e

3.7^e

1.3^c

50 - 60

1.4^f

0.1^f

0.7^f

1.0^f

2.1^f

1.1^c