The vegetation in constructed wetlands (CWs) plays an important role in wastewater treatment. Popularly, the common emergent plants in CWs have been vegetation of natural wetlands. However, there are ornamental flowering plants that have some physiological characteristics similar to the plants of natural wetlands that can stimulate the removal of pollutants in wastewater treatments; such importance in CWs is described here. A literature survey of 87 CWs from 21 countries showed that the four most commonly used flowering ornamental vegetation genera were Canna, Iris, Heliconia and Zantedeschia. In terms of geographical location, Canna spp. is commonly found in Asia, Zantedeschia spp. is frequent in Mexico (a country in North America), Iris is most commonly used in Asia, Europe and North America, and species of the Heliconia genus are commonly used in Asia and parts of the Americas (Mexico, Central and South America). This review also compares the use of ornamental plants versus natural wetland plants and systems without plants for removing pollutants (organic matter, nitrogen, nitrogen and phosphorous compounds). The removal efficiency was similar between flowering ornamental and natural wetland plants. However, pollutant removal was better when using ornamental plants than in unplanted CWs. The use of ornamental flowering plants in CWs is an excellent option, and efforts should be made to increase the adoption of these system types and use them in domiciliary, rural and urban areas.

Modern concrete infrastructure requires structural components with higher mechanical strength and greater durability. A solution is the addition of nanomaterials to cement-based materials, which can enhance their mechanical properties. Some such nanomaterials include nano-silica (nano-SiO2), nano-alumina (nano-Al2O3), nano-ferric oxide (nano-Fe2O3), nano-titanium oxide (nano-TiO2), carbon nanotubes (CNTs), graphene and graphene oxide. These nanomaterials can be added to cement with other reinforcement materials such as steel fibers, glass, rice hull powder and fly ash. Optimal dosages of these materials can improve the compressive, tensile and flexural strength of cement-based materials, as well as their water absorption and workability. The use of these nanomaterials can enhance the performance and life cycle of concrete infrastructures. This review presents recent researches about the main effects on performance of cement-based composites caused by the incorporation of nanomaterials. The nanomaterials could decrease the cement porosity, generating a denser interfacial transition zone. In addition, nanomaterials reinforced cement can allow the construction of high-strength concrete structures with greater durability, which will decrease the maintenance requirements or early replacement. Also, the incorporation of nano-TiO2 and CNTs in cementitious matrices can provide concrete structures with self-cleaning and self-sensing abilities. These advantages could help in the photocatalytic decomposition of pollutants and structural health monitoring of the concrete structures. The nanomaterials have a great potential for applications in smart infrastructure based on high-strength concrete structures.

Abstract:The high costs involved in treating wastewater are problems that developing countries confront, mainly in rural areas. Therefore, Constructed Wetlands (CWs), which are composed of substrate, vegetation, and microorganisms, are an economically and ecologically viable option for wastewater treatment in these places. There is a wide variety of possibilities for substrates and ornamental plants that have not yet been evaluated to be implemented in future CW designs. The goal of this study was to evaluate the process of adaptation and removal of wastewater pollutants in CW microcosms using different terrestrial ornamental plants (Lavandula sp., Spathiphyllum wallisii, and Zantedeschia aethiopica). Those plants were sown in two types of substrate: red volcanic gravel (RVG) and polyethylene terephthalate (PET). CWs with vegetation reduced 5-day biochemical oxygen demand (BOD 5 ) by 68% with RVG substrate and 63% with PET substrate, nitrates 50% in RVG substrate and 35% in PET substrate, phosphates 38% in RVG substrate and 35% in PET substrate, and fecal coliforms 64% in RVG and 59% in PET substrate). In control microcosms without vegetation, reductions were significantly lower than those in the presence of plants, with reduction of BOD 5 by 61% in RVG substrate and 55% in PET substrate, nitrates 26% in RVG substrate and 22% in PET substrate, phosphates 27% in RVG substrate and 25% in PET substrate. Concerning fecal coliforms 62% were removed in RVG substrate and 59% in PET substrate. Regarding the production of flowers, Lavandula sp. did not manage to adapt and died 45 days after sowing and did not produce flowers. Spathiphyllum wallisii produced 12 flowers in RVG and nine flowers in PET, while Zantedeschia aethiopica produced 10 in RVG and 7 in PET. These results showed that the use of substrates made of RVG and PET is a viable alternative to be implemented in CWs. In addition, the reuse of PET is an option that decreases pollution by garbage. The plants Spathiphyllum wallisii and Zantedeschia aethiopica remarkably contribute in the removal of pollutants in wastewater. Additionally, the use of ornamental plants, with commercial interest such as those evaluated, enables an added value to the CW to be given, which can be used for flower production purposes on a larger scale and favor its acceptance within rural communities.

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Constructed wetlands (CWs) are sustainable technologies where the channels are filled with porous material and plants, which collectively remove pollutants, depending on the type of substrate and vegetation. This study evaluated CWs and their functionality by comparing three ornamental plants (Canna indica, Cyperus papyrus, and Hedychium coronarium) as a phytoremediation process of wastewater, in CWs filled with layers of porous stone–tepezil–plastic residues–soil (S-A), or in microcosms with layers of porous stone–tepezil–soil without the presence of plastic (S-B). The findings during 180 days showed that the removals of pollutants (chemical oxygen demand (COD), total solids suspended (TSS), nitrogen as ammonium (N-NH4), as nitrate (N-NO3), and phosphate (P-PO4) were 20%–60% higher in microcosms with plants than in the absence of plants. Statistical differences were not observed when comparing removal effects among S-A and S-B, indicating that plastic residues as filter material in CWs did not affect the pollutant removal, growth, flowering, and shoots of plants. The use of plastic residues as filter may represent a less costly alternative in CW establishments. Dependence on N-NH4 and TSS removal was observed according to plant species. The three species used are suitable for using in CWs as wastewater treatment. In addition, the ornamental plants could generate interest for a commercial option.