## 2 Pharmaceuticals and Personal Care Products (PPCPs) in the Ecosystems
### Combined Chemical Engineering-Biological Methods
#### 2.3.2 Constructed Wetlands  
Constructed wetlands (CWs) are ecoremedial engineered systems that are designed to utilize the natural functions of wetland vegetation, sediments, and their associated microbial assemblages for wastewater, greywater or storm water treatment within a more controlled environment [58]. The use of CWs arises from the desire to mimic the ability of natural wetlands to survive and re-establish the functional relationships after out/in disturbances. Nevertheless, on the scale of the impact on planet Earth, anthropic perturbations are the most important detrimental elements [307], so that successful design, the integration of components and the improvement in efficiency are fundamental. These systems have revealed as excellent solutions for the elimination of emerging contaminants and antibiotic resistance genes [308]. Overall, the effectiveness of these full-scale systems is equal to and even higher than the conventional wastewater treatment plant (WWTP) but at low cost [309; 310]. Some of the removal processes that take place in these systems are: phytoremediation, sediment sorption (adsorption, absorption), microbial degradation (anoxic, anaerobic, and aerobic) located on sediment or associated to plants [311; 312], and photodegradation [299]. The integration of microalgae-based biotechnologies (such as open algal ponds) and constructed wetlands could increase the efficiency of PPCPs removal systems (Figure 6), since microalgae can accumulate and degrade pollutants, produce oxygen through photosynthesis (a limiting factor in the degradation processes of CW), and the algal debris can be used as the organic substrate for microorganisms ([238], Figure 6). In algal ponds,  
Figure 6: Towards the CSCM reactivation, serial system. **A**. Anaerobic bioreactor-pond. Removal of Aerobic microorganisms and PPCPs [229; 236]. **B**. Algal canal-contracted wetland. Removal of anaerobic bacteria, PPCPS and PPCPs residue removal [223]. **C**. Mixed treatment (constructed wetland). Remove of nutrients and contaminants. Reuse of zero waste [306]. photodegradation processes are dominant and removal by biosorption is usually low, except for very hydrophobic pollutants [106]. The association in series of both systems, together with anaerobic bioreactors, favors the elimination of pathogenic microorganisms [313] in addition to the degradation of PPCPs (Figure 6). Technical details on the types of wetlands developed, as well as the physical-chemical and biological parameters limiting factors, can be consulted in different reviews [58; 299; 306; 314; 315]. The CW success on PPCPs removal depends on multiple factors, such as the type of CW (subsurface flow, horizontal or vertical subsurface flow, etc. ), the plant model used and its remediation functions (absorption, degradation, mineralization, volatilization, etc.) and radicular penetration [316], the interaction with the microorganisms present in the CW and the biome that is associated with the plant [316], the chemical nature of each compound [310], the background nutrients and bacterial community evolution in the sediments [125], as well as, abiotic factors such as temperatures, pH, season of the year, aeration systems, etc. [316; 317; 318; 319]. These factors can be balanced to stabilize the system. For example, cold-resistant bacteria can compensate for the negative effects of low temperatures [320]. Among them, the selection of the plant is a determining factor. The roots provide surface area for attached microorganisms, and root growth maintains the hydraulic properties of the substrate. Vegetal species present in the CW determine the composition of the microbial community on the roots and the rhizosphere [290]. The vegetation cover protects the surface from erosion and shading prevents unwanted algae growth [321]. Plants are the main factor that regulates the amount of nutrients in aquatic systems, buffering saprophytic processes and reducing eutrophication [322].