various processes that take place are sorption, complex formation, precipitation, and
metal valence reduction and treat sites contaminated with lead (Pb), copper (Cu),
arsenic (As), chromium (Cr), cadmium (Cd), and zinc (Zn) and mining-affected and
superfund sites.
6.4 Rhizofiltration
Rhizofiltration also called phyto-stimulation is a method for remediation of wastewater, extracted groundwater, and surface water with low contaminant concentrations (Ensley 2000) by use of plants roots (terrestrial and aquatic) for absorption,
concentration, and precipitation of contaminants from polluted aqueous sources. It
may be used to retain for Pb, Ni, Cd, Cu, Zn, and Cr within the roots. It is
advantageous in its ability to undergo either in situ or ex situ process by utilizing
both terrestrial and aquatic plants, and the contaminants do not need to be
translocated to the shoots. Due to the fibrous and much longer root system, the
terrestrial plants are preferred as they also increase root area (Raskin and Ensley
2000).
6.5 Phytovolatilization
This process involves the transformation and transpiration of contaminants from soil
into the atmosphere by the use of plants to take into volatile forms. It is primarily
used for mercuric mercury. It could be transformed into less toxic form or in reverse
may be disadvantageous by being redeposited back into lakes or oceans, and
reproduction of methylmercury occurs by anaerobic bacteria. Members of the
Brassica genus and some microorganisms are particularly good volatilizers of Se
(Terry et al, 1992). Among the aquatic species, rice, rabbit-foot grass, Azolla, and
pickleweed are the best Se volatilizers (Hansen et al. 1998; Lin et al. 2000; PilonSmits et al. 1999; Zayad et al. 2000).
7 Future Perspective and Challenges
Wetlands being the most important biodiversity areas in the world vary widely
because differences in locality and region, vegetation, topography, hydrology, and
human involvement are experiencing a rapid decline. We can meet many future
challenges like food and water security, climate change resilience, human health, and
disaster risk reduction that can be checked by conservation and sustainable use of
wetland. Constructed wetlands are considered an efficient technology for treating
wastewater and removing organic matter, nitrogen, suspended solids, phosphorus,
11 Toxic Metals in Industrial Wastewaters and Phytoremediation Using. . .
277
metal valence reduction and treat sites contaminated with lead (Pb), copper (Cu),
arsenic (As), chromium (Cr), cadmium (Cd), and zinc (Zn) and mining-affected and
superfund sites.
6.4 Rhizofiltration
Rhizofiltration also called phyto-stimulation is a method for remediation of wastewater, extracted groundwater, and surface water with low contaminant concentrations (Ensley 2000) by use of plants roots (terrestrial and aquatic) for absorption,
concentration, and precipitation of contaminants from polluted aqueous sources. It
may be used to retain for Pb, Ni, Cd, Cu, Zn, and Cr within the roots. It is
advantageous in its ability to undergo either in situ or ex situ process by utilizing
both terrestrial and aquatic plants, and the contaminants do not need to be
translocated to the shoots. Due to the fibrous and much longer root system, the
terrestrial plants are preferred as they also increase root area (Raskin and Ensley
2000).
6.5 Phytovolatilization
This process involves the transformation and transpiration of contaminants from soil
into the atmosphere by the use of plants to take into volatile forms. It is primarily
used for mercuric mercury. It could be transformed into less toxic form or in reverse
may be disadvantageous by being redeposited back into lakes or oceans, and
reproduction of methylmercury occurs by anaerobic bacteria. Members of the
Brassica genus and some microorganisms are particularly good volatilizers of Se
(Terry et al, 1992). Among the aquatic species, rice, rabbit-foot grass, Azolla, and
pickleweed are the best Se volatilizers (Hansen et al. 1998; Lin et al. 2000; PilonSmits et al. 1999; Zayad et al. 2000).
7 Future Perspective and Challenges
Wetlands being the most important biodiversity areas in the world vary widely
because differences in locality and region, vegetation, topography, hydrology, and
human involvement are experiencing a rapid decline. We can meet many future
challenges like food and water security, climate change resilience, human health, and
disaster risk reduction that can be checked by conservation and sustainable use of
wetland. Constructed wetlands are considered an efficient technology for treating
wastewater and removing organic matter, nitrogen, suspended solids, phosphorus,
11 Toxic Metals in Industrial Wastewaters and Phytoremediation Using. . .
277