# Nitrate-Polluted Waterbodies Remediation: Global Insights into Treatments for Compliance
## 5 Alternative Strategies  
Other alternative technologies to those already mentioned are available and could be implemented for nitrate removal, depending on the specific situation to be addressed. The solutions that have recently received the most attention are those based on natural processes [43]. Phytoremediation is one of the techniques categorized as a nature-based solution, and involves the use of plants and plant-derived microbes to eliminate pollutants from soil and water. Phytoremediation of water is an ecotechnology, based on the ability of some plants to tolerate, absorb, accumulate, and degrade pollutant compounds. Compared to traditional physical-chemical techniques, phytoremediation has several advantages, among which we can highlight its lower economic cost, its more respectful approach to the ecological processes of the aquatic ecosystem, and the fact that it is a more socially, aesthetically, and environmentally accepted technology. It is therefore not surprising that phytoremediation is increasingly seen as an environmentally friendly alternative  
Figure 10: Nitrate photocatalytic reduction on TiO\({}_{2}\). to physical-chemical technologies. This approach offsets the expensive cost of physico-chemical processes and is an affordable option for economically deprived regions where conventional water treatment plants cannot be financed. Plants, powered by solar energy through photosynthesis, while absorbing nitrates and other pollutants present, also increase dissolved oxygen levels [219]. The phytoremediation process may use several strategies to reduce the pollutant content, such as phytoextraction, phytovoltaisation, phytostabilisation, phytodegradation, rhizodegradation, or rhizofiltration [220]. These strategies to bioremove nitrate from polluted waterbodies are based on the capacity of aquatic plants to absorb nitrate for their growth. With the ultimate aim of restoring the damaged ecosystem, the behaviour of plants such as bamboo, water lilies, cattleail, water lettuce, water hyacinths, arrowhead, poplar, and eucalyptus were investigated [43; 219; 220]. Constructed wetlands (CW) are systems designed to reproduce and optimize the pollutant removal processes in the same way as they occur in natural wetlands and are also an interesting option for the treatment of nitrate-polluted water. CWs are treatment frameworks that use wetland vegetation, soils, and their related microbial gatherings to remediate the contaminated destinations. They are considered a natural, simple, affordable, and green technique for water treatment. The close interplay between growing vegetation, root-associated microbes, and substrate performs a determining influence in the removal of pollutants [43]. CWs offer a preferred alternative for wastewater treatment, but they are also effective for surface water treatment [221]. There are detailed studies on the adaptability of various plant species to CWs under changing water status [222]. Macrophytes such as _Commelia communis_, _Phragmites australis_, _Penniserum purpureum_, _Ipomoaa aquatic_, and _Cyperus alternifolia_, all of them with a high rate of vegetative growth, are among the most commonly used in these wetlands [221; 222]. Nitrate removal through CWs is mainly due to the presence of facultative anaerobic denitifying microorganisms in their rhizosphere as well as their uptake by roots. [20]. CWs are ideal for nitrate removal, since they provide an anaerobic environment and fixed CO\({}_{2}\) as a carbon source for denitifying bacteria. The estimated potential nitrate elimination rates are around 40-50 kg/ha/day [223]. Applications of CW for the denitrification of waterbodies include the rejuvenation of nitrate-contaminated aquifers, treatment of returning irrigation flows in hydrologic systems, groundwater treatment for industrial facilities, and treatment of nitrified wastewater effluents [223].