## 3 Results  
Removal of a Mixture of Alkylphenol Compounds and Nutrients from Contaminated Water by CWs Microcosms  
Plants of all systems showed vitality (by visual inspection) and even new plant shoots appeared along the 8 weeks of experiment. Alkylphenol compounds removals by CWs were assessed in each one-week cycle along the eight weeks period. In the water of Ribeira de Joane (influent of CWs) and in CWs effluents, the NP and OP concentrations were always below the limit of detection (0.25 \(\upmu\)g\(\cdot\)L\({}^{-1}\) for OP and 0.33 \(\upmu\)g\(\cdot\)L\({}^{-1}\) for NP), even when the stream water was doped with a mixture of NP and OP, indicating a significant removal (always \(>\)99%) of both alkylphenol compounds in CWs. In the plant root bed substrate, collected at the beginning (T0) and end (T8) of the experiment, no NP was detected (LOD of 0.12 \(\upmu\)g\(\cdot\)g\({}^{-1}\)), indicating that the compound was totally removed from the system. Regarding OP, the compound was detected in both T0 e T8 plant root bed substrate in both control and doped systems, all values being statistically identical (\(p>0.05\)) (ca. 0.45 \(\upmu\)g\(\cdot\)g\({}^{-1}\)). The compound was also detected in the sediment of estuary of Rio Lima collected to prepare the plant root bed substrate (0.53 \(\pm\) 0.03 \(\upmu\)g\(\cdot\)g\({}^{-1}\)), being probably this the source of the compound. Results indicate that only OP added to CW systems by doping the CW influent was removed/degraded. To evaluate a possible effect of the mixture of alkylphenol compounds on the CWs performance, organic matter (through COD) and nutrients (NH\({}_{4}\)\({}^{+}\), NO\({}_{2}\)\({}^{-}\), NO\({}_{3}\)\({}^{-}\) and PO\({}_{4}\)\({}^{3-}\) ions) removals were determined. COD of Ribeira de Joane water varied between 15 and 83 mg\(\cdot\)L\({}^{-1}\) along the experimental period (Table 1). COD removal values also varied significantly ranging from non-removal to 73.0% in control systems (not doped water) and from non-removal to 83% in systems with water doped with both NP and OP. A high variability among CWs replicates was observed. In the first weeks there was no removal of organic matter or that removal was very low, probably due to an adaptation of the systems, adaptation that was longer for the doped systems. In fact, in the latter there was a tendency for removals to increase over time (after week 5 an increase from 53% to 83% was observed, although differences were not statistically significant (\(p>0.05\)), whereas in control systems, after the adaption period (first two weeks), removals were mostly constant, being statistically identical (\(p>0.05\)). Therefore, NP and OP showed some impact in COD removal efficiency in the initial period. Along the eight weeks of the experiment, NH4\({}^{+}\) ion concentrations in CWs influent varied between 34 and 163 \(\upmu\)M (Table S1). Removal of NH4\({}^{+}\) ions was always higher than 85%, with the exception of week 6, with no significant differences (\(p>0.05\)) between control and doped systems (Figure 1). CWs influent concentration of NO2\({}^{-}\) ion varied between 6.3 and 53 \(\upmu\)mol\(\cdot\)L\({}^{-1}\) (Table S1). Removal percentages of NO2\({}^{-}\) ions were always higher than 96%, with no significant differences (\(p>0.05\)) between control and doped systems (Figure 1). The concentration of NO3\({}^{-}\) ion varied between 211 and 655 \(\upmu\)mol\(\cdot\)L\({}^{-1}\) in CWs influent (Table S1). The removal percentage of NO3\({}^{-}\) ions was always higher  
The concentration of PO4\({}^{3-}\) ions in CWs influent varied between 2.0 and 20 umol\(\cdot\)L\({}^{-1}\) (Table S1). PO4\({}^{3-}\) ions removal showed a significant variation in removal percentages (removals between 0 and 95%) (Figure 1). The presence of NP and OP did not interfere with PO4\({}^{3-}\) ions removal, with removal percentages being statically identical (\(p>0.05\)) between control and doped systems, except in weeks 5 and 7 with slightly lower removals in control systems.