and operation strategy, the different designs SF, HSSF, VF, aerated or hybrid
designs can behave very differently not only hydraulically but also in terms of
pollutant removal, due to different removal/transformation processes.
The research on CWs for pharmaceuticals phytoremediation has been mostly
focused in wastewater, the major source of pharmaceuticals to the environment.
Combined sewer overflows (CSOs) can also be a relevant source of pharmaceuticals
and CWs can be an effective technology to treat CSOs, including to control
pharmaceuticals emission [37], but literature is scarce for this specific application.
Agricultural run-off is also of importance when manure or sludge is applied to land,
and pharmaceutical compounds might leach from the soil. However, the use of CWs
to control agricultural run-off has been mostly studied for pesticides [38–40] and not
for pharmaceuticals. Therefore, lessons learned from wastewater treatment systems
are the most valid when considering CWs to treat CSO and agricultural run-off for
pharmaceutical compounds.
When treating wastewater, CWs can be used alone as a decentralized solution,
either as single-house application or for small housing agglomerates, or as centralized solution employed in rural areas or urban areas up to around 1,000 persons
equivalent (PE). Typically, a sedimentation tank is used for primary treatment, while
the CW ensures the secondary treatment. When hybrid systems are used, sometimes
tertiary treatment is also achieved [29]. In basic wastewater treatment terms, primary
treatment ensures removal of solid material; secondary treatment deals with the
removal of dissolved and suspended organic material, as well as potentially the
nutrients (nitrogen and phosphorus); and tertiary treatment are the polishing methods
used following a traditional wastewater treatment plant (WWTP) [41]. The exception to the common CWs configuration is the so-called French system that consists
of a hybrid design containing multiple beds and operated to perform both primary
and secondary treatment using planted beds [42]. However, CWs can also be used as
part of larger classical WWTPs (conventional activated sludge), in this case usually
as a polishing step (tertiary treatment). It is therefore important to study CWs
performance for pharmaceuticals treatment, not only by CW type but also wastewater strength (e.g. secondary vs tertiary treatment). As for classical pollutants, design
and operational factors (area, depth, hydraulic loading rate, organic loading rate and
hydraulic retention time) and physicochemical parameters (dissolved oxygen, temperature and pH) are critical for the performance of the systems. The geographical
and environmental inherent variability, for instance plants used (that should be
native) or temperature (that is linked with microbial activity and evapotranspiration)
makes systematization and comparison of systems a complex task.
2.2 Historical Developments
A good starting point to understand the potential of CWs to control pharmaceutical
contamination from wastewater is to study the relevant review papers on the topic
(Table 1). The first mini-review work by White, Belmont [43] provided an earlier
382
P. N. Carvalho
designs can behave very differently not only hydraulically but also in terms of
pollutant removal, due to different removal/transformation processes.
The research on CWs for pharmaceuticals phytoremediation has been mostly
focused in wastewater, the major source of pharmaceuticals to the environment.
Combined sewer overflows (CSOs) can also be a relevant source of pharmaceuticals
and CWs can be an effective technology to treat CSOs, including to control
pharmaceuticals emission [37], but literature is scarce for this specific application.
Agricultural run-off is also of importance when manure or sludge is applied to land,
and pharmaceutical compounds might leach from the soil. However, the use of CWs
to control agricultural run-off has been mostly studied for pesticides [38–40] and not
for pharmaceuticals. Therefore, lessons learned from wastewater treatment systems
are the most valid when considering CWs to treat CSO and agricultural run-off for
pharmaceutical compounds.
When treating wastewater, CWs can be used alone as a decentralized solution,
either as single-house application or for small housing agglomerates, or as centralized solution employed in rural areas or urban areas up to around 1,000 persons
equivalent (PE). Typically, a sedimentation tank is used for primary treatment, while
the CW ensures the secondary treatment. When hybrid systems are used, sometimes
tertiary treatment is also achieved [29]. In basic wastewater treatment terms, primary
treatment ensures removal of solid material; secondary treatment deals with the
removal of dissolved and suspended organic material, as well as potentially the
nutrients (nitrogen and phosphorus); and tertiary treatment are the polishing methods
used following a traditional wastewater treatment plant (WWTP) [41]. The exception to the common CWs configuration is the so-called French system that consists
of a hybrid design containing multiple beds and operated to perform both primary
and secondary treatment using planted beds [42]. However, CWs can also be used as
part of larger classical WWTPs (conventional activated sludge), in this case usually
as a polishing step (tertiary treatment). It is therefore important to study CWs
performance for pharmaceuticals treatment, not only by CW type but also wastewater strength (e.g. secondary vs tertiary treatment). As for classical pollutants, design
and operational factors (area, depth, hydraulic loading rate, organic loading rate and
hydraulic retention time) and physicochemical parameters (dissolved oxygen, temperature and pH) are critical for the performance of the systems. The geographical
and environmental inherent variability, for instance plants used (that should be
native) or temperature (that is linked with microbial activity and evapotranspiration)
makes systematization and comparison of systems a complex task.
2.2 Historical Developments
A good starting point to understand the potential of CWs to control pharmaceutical
contamination from wastewater is to study the relevant review papers on the topic
(Table 1). The first mini-review work by White, Belmont [43] provided an earlier
382
P. N. Carvalho