3. Link CWs usage and developments with the recent trends of nature-based
solution and phytoremediation implementation towards a green transition
2 Constructed Wetlands for Pharmaceuticals Removal
2.1 The Basics of the Ecotechnology
First of all, it is important to clarify that “constructed wetland” is currently a broad
ecotechnology name that encompasses a range of different technical solutions. A
review of CW technology is outside the present scope, thus a good starting point for
learning the basics of these systems would be the most cited text book on the topic by
Kadlec and Wallace [29]. For the present chapter, one needs to take into consideration the three classical designs (based on hydrological characteristics – the water
position and flow direction):
• Surface flow (SF; usually 0.3 m shallow beds with only a small layer of substrate
at the bottom (few cm) for plants to root; water flows horizontally above
substrate; fed continuously; Fig. 1a)
• Horizontal subsurface flow (HSSF; usually 0.5 m depth bed filled with substrate,
sand and/or gravel; water flows horizontally below the surface; fed continuously;
Fig. 1b),
• Vertical flow (VF; usually 1 m depth bed, filled with substrate, sand and/or
gravel; water flows vertically top to bottom; fed by pulses; Fig. 1c).
For a broader overview of the different CWs designs and subdivisions in the
classification, one can refer to Fonder and Headley [30]. For a question of systematization, the present chapter follows the most common grouping used in the
published reviews within the field, the three classical designs: SF, HSSF and VF.
In the recent years, among other alternatives and intensified wetland designs,
aeration at the bottom of the beds has been one of the most well accepted approaches
to increase performance and decrease area requirements [31, 32]. Aeration has been
introduced mostly in HSSF and VF designs and studies exist regarding its performance with respect to pharmaceuticals, further detailed. Other types of intensification (e.g. fill and drain, or usage of specific sorbing media) are not covered in this
chapter.
The three classical designs, SF, HSSF and VF are the ones most exhaustively
used for water treatment, while aerated CWs have been gaining popularity for the
past decade [23, 33]. It is very important as well to mention the hybrid systems,
which combine more than one type of CW to make use of different processes
(e.g. VF + HSSF, for aerobic followed by anaerobic processes [34]). In addition, it
is important to consider that any given design can be employed for different types of
water (e.g. stormwater, wastewater, surface water). Specific designs are preferred for
certain types of water and pollutant loadings (e.g. VF or aerated systems when
nitrification is demanded); more details can be found in traditional CW literature and
design guidelines [29, 35, 36]. The key point is that depending on pollutants loading
380
P. N. Carvalho
solution and phytoremediation implementation towards a green transition
2 Constructed Wetlands for Pharmaceuticals Removal
2.1 The Basics of the Ecotechnology
First of all, it is important to clarify that “constructed wetland” is currently a broad
ecotechnology name that encompasses a range of different technical solutions. A
review of CW technology is outside the present scope, thus a good starting point for
learning the basics of these systems would be the most cited text book on the topic by
Kadlec and Wallace [29]. For the present chapter, one needs to take into consideration the three classical designs (based on hydrological characteristics – the water
position and flow direction):
• Surface flow (SF; usually 0.3 m shallow beds with only a small layer of substrate
at the bottom (few cm) for plants to root; water flows horizontally above
substrate; fed continuously; Fig. 1a)
• Horizontal subsurface flow (HSSF; usually 0.5 m depth bed filled with substrate,
sand and/or gravel; water flows horizontally below the surface; fed continuously;
Fig. 1b),
• Vertical flow (VF; usually 1 m depth bed, filled with substrate, sand and/or
gravel; water flows vertically top to bottom; fed by pulses; Fig. 1c).
For a broader overview of the different CWs designs and subdivisions in the
classification, one can refer to Fonder and Headley [30]. For a question of systematization, the present chapter follows the most common grouping used in the
published reviews within the field, the three classical designs: SF, HSSF and VF.
In the recent years, among other alternatives and intensified wetland designs,
aeration at the bottom of the beds has been one of the most well accepted approaches
to increase performance and decrease area requirements [31, 32]. Aeration has been
introduced mostly in HSSF and VF designs and studies exist regarding its performance with respect to pharmaceuticals, further detailed. Other types of intensification (e.g. fill and drain, or usage of specific sorbing media) are not covered in this
chapter.
The three classical designs, SF, HSSF and VF are the ones most exhaustively
used for water treatment, while aerated CWs have been gaining popularity for the
past decade [23, 33]. It is very important as well to mention the hybrid systems,
which combine more than one type of CW to make use of different processes
(e.g. VF + HSSF, for aerobic followed by anaerobic processes [34]). In addition, it
is important to consider that any given design can be employed for different types of
water (e.g. stormwater, wastewater, surface water). Specific designs are preferred for
certain types of water and pollutant loadings (e.g. VF or aerated systems when
nitrification is demanded); more details can be found in traditional CW literature and
design guidelines [29, 35, 36]. The key point is that depending on pollutants loading
380
P. N. Carvalho