Table 3.
Relative and absolute removal of nitrate–N, total phosphorus (TP) and total suspended solids (TSS) based on raw data and the meta-analysis for free water surface constructed wetlands (FWS), denitrifying bioreactors (DBR), controlled drainage (CD) and saturated (SBZ) and integrated buffer zones (IBZ). Kam is the number of study sites included when calculating the arithmetic mean, and Kmeta is the number of study sites included in the meta-analysis
| Drainage mitigation measure | Kam% | Kmeta | Removal Mean ± SD (%) | Removal Meanmeta ± SD (%) | Kam | Removal Mean ± SD (g m−2 year−1) |
|---|---|---|---|---|---|---|
| Nitrate–N | ||||||
| FWS | 18 | 14 | 40 ± 17 | 41 ± 21 | 21 | 60 ± 69 |
| DBR | 19 | 12 | 44 ± 21 | 40 ± 27 | 2 | 594 ± 481 |
| CD | 20 | 19 | 48 ± 18 | 50 ± 20 | 6 | 1 ± 1 |
| SBZ | 6 | 68 ± 39 | 13 | 23 ± 18 | ||
| SBZa | 6 | 37 ± 25 | ||||
| IBZ | 2 | 26 ± 4 | 19 | 140 ± 50 | ||
| TP | ||||||
| FWS | 16 | 15 | 18 ± 46 | 33 ± 28 | 8 | 0.68 ± 4.19 |
| CD | 7 | 7 | 29 ± 26 | 34 ± 32 | 2 | 0.03 ± 0.03 |
| DBR | 3 | -50 ± 136 | 3 | − 5.79 ± 20.96 | ||
| IBZ | 2 | 48 ± 6 | 20 | 2.44 ± 0.76 | ||
| SS | ||||||
| FWS | 6 | 41 ± 16 | 6 | 1555 ± 936 |
aIncludes the water and nitrate–N bypassing the SBZ