Water Treatment by Phytoremediation and Filtering Through Agricultural Residues

Phytoremediation can be defined as the use of plants to extract, immobilize, contain and/or degrade contaminants from soil, water or air. It can be applied for the removal and/or the immobilization of inorganic and organic pollutants with several mechanisms, namely extraction, stabilization, degradation and volatilization. It can be applied to the treatment of natural waters, municipal wastewaters, sewage waters, spillage areas and other polluted sites, such as acid mine drainage waters. The choice of the plants most suitable for a phytoremediation process depends on the pollutants to be removed and the features of the polluted site; when possible, native species should be selected. Most plants used in phytoremediation are hyperaccumulators, i.e. they have the ability to absorb high levels of contaminants. The most common aquatic species are water jacinth, water ferns, duckweeds and water lettuce. Several applications for the sorption of potentially toxic elements, radionuclides, organic solvents, explosives and other contaminants are reported. The disposal of plants after phytoremediation is an important step, to avoid the diffusion of pollutants into the environment or their entering into the food chain. An alternative form of phytoremediation is the use of non-living biomass as a biosorbent. Many agricultural residues, like coconut husk, rice husk and fruits can be used for pollutant retention. Such residues often undergo pretreatment steps to improve their sorption capabilities. Other non-agricultural materials, such as seafood waste, industrial by-products and clays, can be used to filter waters and wastewaters.