## 2 Pharmaceuticals and Personal Care Products (PPCPs) in the Ecosystems
### Combined Chemical Engineering-Biological Methods
#### 2.3.1 Bioreactors
MBR have been increasingly adopted by industrial and municipal wastewater treatment plants because of their high efficiency to remove emerging organic pollutants, yielding a high quality water effluent, which is especially suitable for reclamation and reuse [293]. MBR systems have demonstrated good performance for the elimination of some emerging organic pollutants that were not effectively removed by activated sludge treatments. The cause could be the concentration of the biological sludge on the membrane surface thus facilitating the degradation of persistent organic compounds and the retention of larger molecules than the corresponding molecular weight cut-off of the membrane [294; 295]. Although MBR processes have been applied for the removal of a wide range of compounds, the effectiveness of elimination can vary greatly from one case to another depending on the nature of the microbial population, the chemical properties of the pollutant and the operation conditions of the process, as in CAS processes. In a pilot scale MBR system, which was equipped with a flat submerged membrane, 23 diverse emerging organic pollutants were evaluated [296]. Five steroid hormones (hydrocortisone, estriol, testosterone, estrone and progesterone) showed high removal degrees (>90%). Similar values were reached by other pharmaceutical products including diuretics, beta-blockers, antibiotics, analgesics and anti-inflammatory drugs such as atenol, bisoprolol, enalapril, tetracycline, ciprofloxacin, trimethoprim, ketoprofen and NPX, with almost complete removal (>99%) of furosemide, paracetamol (acetaminophen), IBU and the stimulant caffeine. However, the removal of other compounds ranged from relatively high (propanolol 84.2%) to very low (DFC 38.8%, hydroxychlorothiazzide 10.2%), or even negligible values (CBZ \(\sim\)0%). The solid retention time (SRT) is the most important operating parameter affecting the removal efficiency of PPCPs in MBR systems. In the case of labile and easily degradable compounds, such as IBU, high removal efficiencies were achieved when SRT was above a critical value of 10 d. For recalcitrant pharmaceutical compounds, for example, CBZ, the removal was low whatever the SRT value [293]. However, for PPCPs with intermediate stability, the removal efficiency can be significantly affected by SRT values. For example, when SRT increase from 8 d to 80 d the removal of ketoprofen and clofibric acid in an MBR increased from \(\sim\)55% to \(\sim\)91% and from \(\sim\)4% to \(\sim\)35%, respectively [297]. The higher degree of PPCPs removal is associated, not only to a higher microbial activity for larger SRT values, but also for the higher microbial diversity reached as SRT increases [293]. Membrane fouling and clogging are two major operational drawbacks with high economic impact on MBR systems [33]. Both aerobic and anaerobic granular sludge have been used to inoculate membrane bioreactors to overcome these limitations. These granular sludge membrane bioreactors (GMBR) allowed for a high biomass loading while nitrogen and organic compounds were effectively removed from wastewaters. The removal of five PPCPs (sulphamethoxazole, norfloxacin, prednisolone, NPX and IBU) from a synthetic wastewater loaded with 50 \(\upmu\)g/L of each drug in a GMBR has been studied under aerobic conditions [39]. The continuous bioreactor was formed by a polyvinylidene hollow fiber membrane module (0.22 \(\upmu\)m pore size) working under a hydraulic retention time (HRT) of 4 h. Prednisolone concentration decreased >98%, while norfloxacin, NPX and sulphamethoxazole reached 87.8, 84 and 79.8%, respectively. In fact, a dynamics in the microbial populations has been observed in aerobic granular sludge membrane bioreactor, where an increase in the presence of bacteria capable of degrading PPCPs is observed throughout the exposure time [39]. These studies show results that exemplify the complex relationships that are established in communities for the complete removal of emerging pollutants.