designed specifically to remove pharmaceuticals and other organic micropollutants.
Even though data on removal efficiency is widely available, the small sample size on
kinetic parameters, namely, areal removal rates [64, 91, 110], might be hindering the
design of dedicated CWs for pharmaceuticals removal. In addition, we cannot forget
the role that CWs play on the challenges and opportunities in wastewater reuse
[111]. Ultimately further research is needed to optimize the removal of the most
“critical” compounds. The scientists are working on the “critical” compounds, those
that current knowledge indicates that are less effectively removed by CWs, like
antibiotics and some analgesics and anti-inflammatories. Practitioners and water
utilities are waiting for legislation that will dictate which “critical” compounds
they need to meet on their emission targets.
As for other technologies, research on CWs needs to be coupled with the risk
assessment of residual pharmaceuticals and transformation products to the aquatic
environment. There is a clear knowledge gap with respect to the dynamics of
pharmaceutical transformation products in CWs, also in the application of suspectscreening and non-target screening methodologies based on high-resolution mass
spectrometry [112] to support the characterization of pharmaceuticals removal
in CWs.
5 Conclusions
Constructed wetlands, by its main designs SF, HSSF and VF, but also hybrid
systems and most recently aerated systems have demonstrated a good capacity to
remove different pharmaceuticals from wastewater and treated wastewater. Various
processes are involved in pharmaceuticals removal: photodegradation in SF and
sorption, plant uptake and several transformation processes within the plant and
microbial degradation in all different CW designs. Biodegradation is pointed as
proposed the major removal process, but the true extent of plant-driven processes has
not yet been properly quantified.
Processes are not only controlled by CW design, but also limited by pharmaceuticals’ chemical properties. Photodegradation can be explored by using SF wetlands.
Though, removal is limited to sensitive compounds and its implementation may
encounter regulatory limitations (e.g. prohibition of open wastewater). Sorption
occurs in all systems, depending on compound, type of substrate and build-up of
particles and organic matter in the system. Plants can uptake and translocate pharmaceuticals; against earlier expectations of phytoaccumulation, it is now clear that
both the plant and the endophytic bacteria can biotransform pharmaceuticals. Biodegradation, namely, by the concerted synergy of plants and microorganisms, has
proven a key process. There is, though, limited process understanding at the microbial community level, as well as the biochemical degradation pathways. More efforts
are needed in the application of multi-omics (metagenomics, metatranscriptomics,
proteomics, metabolomics) as well as in the characterization of transformation
products to CW studies. Aerobic biodegradation tends to be more efficient than
Constructed Wetlands and Phytoremediation as a Tool for Pharmaceutical Removal
407
Even though data on removal efficiency is widely available, the small sample size on
kinetic parameters, namely, areal removal rates [64, 91, 110], might be hindering the
design of dedicated CWs for pharmaceuticals removal. In addition, we cannot forget
the role that CWs play on the challenges and opportunities in wastewater reuse
[111]. Ultimately further research is needed to optimize the removal of the most
“critical” compounds. The scientists are working on the “critical” compounds, those
that current knowledge indicates that are less effectively removed by CWs, like
antibiotics and some analgesics and anti-inflammatories. Practitioners and water
utilities are waiting for legislation that will dictate which “critical” compounds
they need to meet on their emission targets.
As for other technologies, research on CWs needs to be coupled with the risk
assessment of residual pharmaceuticals and transformation products to the aquatic
environment. There is a clear knowledge gap with respect to the dynamics of
pharmaceutical transformation products in CWs, also in the application of suspectscreening and non-target screening methodologies based on high-resolution mass
spectrometry [112] to support the characterization of pharmaceuticals removal
in CWs.
5 Conclusions
Constructed wetlands, by its main designs SF, HSSF and VF, but also hybrid
systems and most recently aerated systems have demonstrated a good capacity to
remove different pharmaceuticals from wastewater and treated wastewater. Various
processes are involved in pharmaceuticals removal: photodegradation in SF and
sorption, plant uptake and several transformation processes within the plant and
microbial degradation in all different CW designs. Biodegradation is pointed as
proposed the major removal process, but the true extent of plant-driven processes has
not yet been properly quantified.
Processes are not only controlled by CW design, but also limited by pharmaceuticals’ chemical properties. Photodegradation can be explored by using SF wetlands.
Though, removal is limited to sensitive compounds and its implementation may
encounter regulatory limitations (e.g. prohibition of open wastewater). Sorption
occurs in all systems, depending on compound, type of substrate and build-up of
particles and organic matter in the system. Plants can uptake and translocate pharmaceuticals; against earlier expectations of phytoaccumulation, it is now clear that
both the plant and the endophytic bacteria can biotransform pharmaceuticals. Biodegradation, namely, by the concerted synergy of plants and microorganisms, has
proven a key process. There is, though, limited process understanding at the microbial community level, as well as the biochemical degradation pathways. More efforts
are needed in the application of multi-omics (metagenomics, metatranscriptomics,
proteomics, metabolomics) as well as in the characterization of transformation
products to CW studies. Aerobic biodegradation tends to be more efficient than
Constructed Wetlands and Phytoremediation as a Tool for Pharmaceutical Removal
407