ibuprofen and iohexol revealed that the adsorption capacity of these materials was
low (at the level of μg g
À1 ) compared to well-known sorbents such activated carbon
(at the level of mg g
À1 ). Columns packed with the six materials showed an increase
of 2–58% in pharmaceutical removal over 66 days and attributed to microbial
degradation. Furthermore, community-level physiological profiling analysis indicated that materials shaped the microbial community metabolic function not only in
the interstitial water but also in the biofilm. Although the adsorption capacity of the
common materials was low, they may be a driver to improve the removal of OMPs
by altering microbial community function in CWs [87].
Overall, the role of adsorption in the removal of pharmaceuticals has been
considered fairly moderate [57].
3.4 Plant Uptake, Translocation, Phytodegradation
and Microbial Degradation Within the Plant
Phytoremediation is a technology relying on plants, and their associated rhizosphere
microorganisms to remove, transform or contain toxic chemicals located in soils,
sediments, groundwater, surface water and even the atmosphere [77]. The main
mechanisms that constitute phytoremediation include phytostabilization,
phytoextraction, phytoaccumulation, phytovolatilization, phytotranspiration,
phytodegradation/transformation, endophytic degradation and rhizosphere remediation [60, 88]; these can occur simultaneously and to varying degrees.
Phytostabilization is used to minimize migration of contaminants in soils, mainly
associated with the precipitation and immobilization of heavy metals.
Phytoextraction and phytoaccumulation exploit the ability of plants to remove
contaminants from soil or water into harvestable plant biomass. Plants uptake
pollutants through their roots (phytoextraction), which can be translocated to the
aboveground parts, such as stems, leaves or even fruits where it can be accumulated
(phytoaccumulation) or further transformed/degraded (phytodegradation/transformation, endophytic degradation). Phytotranspiration and phytovolatilization aim to
exploit plants’ capacity of “pumping” high volumes of water and converting a
contaminant into a volatile form, thereby removing the latter from the soil or water
into the atmosphere [77].
Interestingly, studies on the uptake of pharmaceuticals by plants used in
phytoremediation started much later than on crop plants and where driven by the
interest to understand the potential phytotoxic effects [26]. Thus, considering the
concentration levels that pharmaceuticals normally present in the environment,
either in wastewaters or reclaimed water, it is not expected that phytotoxic effects
will occur in phytoremediation systems, including CWs.
Since then, research on plant uptake and processes, in spite of its developments, is
still not so well understood, as for example sorption. Part of the reason has been the
need to perform hydroponic studies to better understand plant-driven processes. Four
Constructed Wetlands and Phytoremediation as a Tool for Pharmaceutical Removal
401
low (at the level of μg g
À1 ) compared to well-known sorbents such activated carbon
(at the level of mg g
À1 ). Columns packed with the six materials showed an increase
of 2–58% in pharmaceutical removal over 66 days and attributed to microbial
degradation. Furthermore, community-level physiological profiling analysis indicated that materials shaped the microbial community metabolic function not only in
the interstitial water but also in the biofilm. Although the adsorption capacity of the
common materials was low, they may be a driver to improve the removal of OMPs
by altering microbial community function in CWs [87].
Overall, the role of adsorption in the removal of pharmaceuticals has been
considered fairly moderate [57].
3.4 Plant Uptake, Translocation, Phytodegradation
and Microbial Degradation Within the Plant
Phytoremediation is a technology relying on plants, and their associated rhizosphere
microorganisms to remove, transform or contain toxic chemicals located in soils,
sediments, groundwater, surface water and even the atmosphere [77]. The main
mechanisms that constitute phytoremediation include phytostabilization,
phytoextraction, phytoaccumulation, phytovolatilization, phytotranspiration,
phytodegradation/transformation, endophytic degradation and rhizosphere remediation [60, 88]; these can occur simultaneously and to varying degrees.
Phytostabilization is used to minimize migration of contaminants in soils, mainly
associated with the precipitation and immobilization of heavy metals.
Phytoextraction and phytoaccumulation exploit the ability of plants to remove
contaminants from soil or water into harvestable plant biomass. Plants uptake
pollutants through their roots (phytoextraction), which can be translocated to the
aboveground parts, such as stems, leaves or even fruits where it can be accumulated
(phytoaccumulation) or further transformed/degraded (phytodegradation/transformation, endophytic degradation). Phytotranspiration and phytovolatilization aim to
exploit plants’ capacity of “pumping” high volumes of water and converting a
contaminant into a volatile form, thereby removing the latter from the soil or water
into the atmosphere [77].
Interestingly, studies on the uptake of pharmaceuticals by plants used in
phytoremediation started much later than on crop plants and where driven by the
interest to understand the potential phytotoxic effects [26]. Thus, considering the
concentration levels that pharmaceuticals normally present in the environment,
either in wastewaters or reclaimed water, it is not expected that phytotoxic effects
will occur in phytoremediation systems, including CWs.
Since then, research on plant uptake and processes, in spite of its developments, is
still not so well understood, as for example sorption. Part of the reason has been the
need to perform hydroponic studies to better understand plant-driven processes. Four
Constructed Wetlands and Phytoremediation as a Tool for Pharmaceutical Removal
401