Table 2 pH values tested inside different filter layers of the two BTFs
Sampling sites | BTF | Operating time (day) | p-value | ||||||
|---|---|---|---|---|---|---|---|---|---|
12 | 42 | 75 | 108 | 164 | 251 | 273 | |||
Upper | BTF1 | 6.74 | 6.68 | 7.05 | 7.34 | 7.51 | 6.53 | 6.99 | 0.5581 |
BTF2 | 6.71 | 7.66 | 7.03 | 7.43 | 6.90 | 6.99 | 6.93 | ||
Middle | BTF1 | 4.13 | 4.27 | 4.67 | 4.89 | 6.80 | 6.05 | 6.60 | 0.3443 |
BTF2 | 5.14 | 7.07 | 6.01 | 6.51 | 6.05 | 5.86 | 4.94 | ||
Bottom | BTF1 | 1.92 | 2.33 | 2.58 | 2.61 | 3.55 | 3.48 | 3.47 | 0.0004 |
BTF2 | 4.07 | 5.5 | 4.14 | 5.01 | 5.80 | 5.22 | 4.26 | ||