overview of the first laboratorial and pilot tests accounting in total for less than five
published works. Already by that time, both White, Belmont [43] and Schröder,
Navarro-Aviñó [44] considered wetlands (both natural and CWs) promising to
remove pharmaceutical compounds from wastewater.
Early in 2010s, a couple of review papers started to include some mentions to
natural and water treatment wetlands for the removal of emerging pollutants,
including pharmaceuticals [25, 45–47]. However, the second overview of the topic
on a review paper dedicated to CWs was performed by Haarstad and Bavor [48]
within a vast revision of organic and metallic pollutants. By then, not more than nine
publications were available. As publication rate kept increasing, the three first larger
review works specifically focused on pharmaceuticals, and CWs were published in
2014 [27, 49, 50]. By then, around 40 publications were available and a careful
systematization of the data was produced. These works, for the first time, compared
CWs design as well as different levels of treatment (primary to tertiary) being still a
reference in the field.
Li et al. [49] focused on the application of CWs for secondary wastewater
treatment and as a wastewater polishing treatment. Removal efficiencies published
started to point to the inherent variability associated with (1) compound: some
compounds are easily removed, typically because they are easily biodegraded,
while others tend to be recalcitrant (poor biodegradability); and (2) CW design:
different removal mechanisms can be promoted/inhibited due to specific configurations (e.g. aerobic, anaerobic, photodegradation). However, the studies were few,
and the majority limited to lab-scale studies. Therefore, the authors carefully phrased
a “consensus towards the potential of CWs for pharmaceuticals removal” [49]. This
review paper also provided a simple overview of design parameters and description
of substrate, plants and microbes role on removal, as well as of the research gaps at
the time. Complementarily, Zhang et al. [50], from the same research group,
provided a smaller overview on removal efficiency and placed more emphasis on
removal mechanisms (photodegradation, sorption, plant uptake and
phytodegradation and microbial degradation), design and operational parameters
(bed depth, vegetation, hydraulic retention time), as well as attempted to establish
correlations with compound physicochemical properties, namely, the octanol water
partition coefficient [50]. More details in Sect. 3.
Verlicchi and Zambello [27] had a broader scope, so besides the secondary and
tertiary treatment, also covered CWs used for primary treatment. In addition, they
limited their review to pilot and full-scale systems (operated outdoors in “real
environmental conditions”) treating urban wastewater. The paper also includes a
large discussion section on removal mechanisms, modelling and design parameters.
The potential of CWs to remove a wide spectrum of pharmaceuticals was described
and linked to the coexistence of anoxic-aerobic-anaerobic microenvironments within
surface flow, as well as subsurface flow systems that favour the different mechanisms involved in their removal. More specifically, SF and HSSF CWs used as
primary treatment revealed removals above 40% for 14 compounds (acetaminophen,
atenolol, caffeine, diclofenac, diphenhydramine, ibuprofen, ketoprofen, metoprolol,
naproxen, salicylic acid, sulfamethoxazole, sulfapyridine, triclocarban and
Constructed Wetlands and Phytoremediation as a Tool for Pharmaceutical Removal
389
published works. Already by that time, both White, Belmont [43] and Schröder,
Navarro-Aviñó [44] considered wetlands (both natural and CWs) promising to
remove pharmaceutical compounds from wastewater.
Early in 2010s, a couple of review papers started to include some mentions to
natural and water treatment wetlands for the removal of emerging pollutants,
including pharmaceuticals [25, 45–47]. However, the second overview of the topic
on a review paper dedicated to CWs was performed by Haarstad and Bavor [48]
within a vast revision of organic and metallic pollutants. By then, not more than nine
publications were available. As publication rate kept increasing, the three first larger
review works specifically focused on pharmaceuticals, and CWs were published in
2014 [27, 49, 50]. By then, around 40 publications were available and a careful
systematization of the data was produced. These works, for the first time, compared
CWs design as well as different levels of treatment (primary to tertiary) being still a
reference in the field.
Li et al. [49] focused on the application of CWs for secondary wastewater
treatment and as a wastewater polishing treatment. Removal efficiencies published
started to point to the inherent variability associated with (1) compound: some
compounds are easily removed, typically because they are easily biodegraded,
while others tend to be recalcitrant (poor biodegradability); and (2) CW design:
different removal mechanisms can be promoted/inhibited due to specific configurations (e.g. aerobic, anaerobic, photodegradation). However, the studies were few,
and the majority limited to lab-scale studies. Therefore, the authors carefully phrased
a “consensus towards the potential of CWs for pharmaceuticals removal” [49]. This
review paper also provided a simple overview of design parameters and description
of substrate, plants and microbes role on removal, as well as of the research gaps at
the time. Complementarily, Zhang et al. [50], from the same research group,
provided a smaller overview on removal efficiency and placed more emphasis on
removal mechanisms (photodegradation, sorption, plant uptake and
phytodegradation and microbial degradation), design and operational parameters
(bed depth, vegetation, hydraulic retention time), as well as attempted to establish
correlations with compound physicochemical properties, namely, the octanol water
partition coefficient [50]. More details in Sect. 3.
Verlicchi and Zambello [27] had a broader scope, so besides the secondary and
tertiary treatment, also covered CWs used for primary treatment. In addition, they
limited their review to pilot and full-scale systems (operated outdoors in “real
environmental conditions”) treating urban wastewater. The paper also includes a
large discussion section on removal mechanisms, modelling and design parameters.
The potential of CWs to remove a wide spectrum of pharmaceuticals was described
and linked to the coexistence of anoxic-aerobic-anaerobic microenvironments within
surface flow, as well as subsurface flow systems that favour the different mechanisms involved in their removal. More specifically, SF and HSSF CWs used as
primary treatment revealed removals above 40% for 14 compounds (acetaminophen,
atenolol, caffeine, diclofenac, diphenhydramine, ibuprofen, ketoprofen, metoprolol,
naproxen, salicylic acid, sulfamethoxazole, sulfapyridine, triclocarban and
Constructed Wetlands and Phytoremediation as a Tool for Pharmaceutical Removal
389