Table 4.

Advantages and limitations of the biological treatment technologies

Treatment technology	Advantages	Limitations
Aerobic-anaerobic	Increased purification levels, ability to manage high organic loads, generation of limited amounts of sludges that are often quite stable, and production of methane as end-product (Aziz and Abu Amr 2019)	Anaerobic treatment requires time (Samer 2015)
Activated sludge	Inexpensive (Onesios et al. 2009)	Incomplete degradation leading to the creation of toxic degradation by-products Non-effective in the removal of recalcitrant contaminants (Oulton et al. 2010), while biodegradation is affected by structural characteristics and environmental conditions (Rajasulochana and Preethy 2016) Depends on energy (Sharma and Sanghi 2012) Low availability or lack of degraders (Wang and Wang 2016)
Biodegradation	Prime method for the elimination of PPCPs (Wang and Wang 2016)
Constructed wetlands	Low energy requirements Low operational cost (Kaur et al. 2019)	Large area footprint Required operating cost (Kaur et al. 2019)
Membrane bioreactor process	Applicable versus many contaminants (Weiss and Reemtsma 2008)	Inability to remove recalcitrant contaminants (Kaur et al. 2019)