## 3 Survey Results of the Use of Ornamental Flowering Plants in CWs
### Influence of Plants on Treatment Performance in Constructed Wetlands  
Some studies have provided evidence of the positive effects that vegetation of natural wetlands has on pollutant removal (organic matter, nitrogen and phosphorus compounds) in constructed wetlands when compared to systems without plants [5; 10]. In planted mesocosms with _Phragmites australis_, the efficiency of total nitrogen and total phosphorous removal was 97% and 91%, respectively, while, in systems without plants, the removal efficiency was 53% for total nitrogen and 61% for total phosphorous [121]. A similar situation was observed when studying fluoride ion removal in constructed wetlands, where the pollutant removal in systems without plants was 20% lower than in systems with vegetation [45]. The increase in the removal of pollutants in systems with plants is due to the increased oxygen supply to the rhizosphere through the plants' roots [2; 8]. The use of ornamental plants in constructed wetlands for pollutant removal has been applied in different countries around the globe (Table 1), commonly in tropical and subtropical areas. A comparison of average performance efficiencies of CWs with different OFP showed that the removal percentages were similar across all plant genera for TSS (62-86%; \(n=26\); \(p=0.236\)), COD (41-72%; \(n=49\); \(p=0.211\)), BOD (51-82%; \(n=38\); \(p=0.241\)), TP (49-66%; \(n=44\); \(p=0.111\)), NH\({}_{4}\)-N (62-82%; \(n=24\); \(p=0.301\)), NO\({}_{3}\)-N (63-93%; \(n=34\); \(p=0.214\)) and TN (48-72%; \(n=32\); \(p=0.116\)) (Figure 2). Such values are within the range reported [6] for CWs from China, India, Ireland, Spain and Thailand, as well as for the values reported in a review of wastewater treatment of CWs in developingcountries [122] and CWs in tropical and subtropical regions [123; 124], all using plants typically found in natural wetlands (_Cyperus, Typha_ and _Phragmites_ sp. ), which were 67-92.5% for TSS, 49-81% for COD, 60-91.5% for BOD, 33-90% for NH\({}_{4}\)-N, and 50-77% for TP. In general, the mean TN and TP removal when using ornamental plants in CWs were less than the mean removal of the other pollutants (TSS, CDO, BOD, NH\({}_{4}\)-N or NO\({}_{3}\)-N) (Figure 2). Such removal is influenced not only by the plants, but also by other parameters, such as filter media, or operational parameters, such as hydraulic and influent loading, which are related with the removal of pollutants in CWs and need to be considered in system designs [125]. When comparing the removal efficiency of pollutants in CWs with OFP and CWs without plants (Figure 2), pollutant removal was almost 40% higher for TSS, COD, BOD, NT and N-NO\({}_{3}\) in CWs with plants than in those without. For TP, the removal efficiency was almost 70% higher in CWs using ornamental plants than in those without vegetation. [PERSON] et al. [124] evaluated the use of CWs in Brazil, including systems with ornamental plants, and concluded that warm temperatures, extensive sunlight hours and available land are important characteristics for encouraging plant growth and proliferation. Such features are typical in tropical and subtropical regions, where the option of a CW with ornamental plants can be an excellent choice for the removal of pollutants. In cases where the wetlands are constructed to assist rural communities that involve big areas, the growth of OFP also creates a useful source of commercialization. The flowers could be sold as bouquets, as plants with attached roots for use in gardens, or for crafts made with parts of the plants, providing another strategy for convincing landowners to adopt these systems. The statistics that we report here regarding the removal efficiency of ornamental plants in CWs around the world is evidence that urban areas can also use CW systems as beautiful landscapes in supermarkets, streets, universities, hospitals, in riverine areas or as floating wetlands in rivers, lakes or lagoons.