Contaminants of emerging concern removal from real wastewater by UV/free chlorine process: A comparison with solar/free chlorine and UV/HO at pilot scale.

The removal of contaminants of emerging concern (CECs) from urban wastewater treatment plants (UWTPs) is really important to minimize the risk for human health and environment. In this study, the homogeneous advanced oxidation process (AOP) UV-C/free chlorine (UV-C/FC) was investigated at pilot scale in the degradation of a mixture of four CECs, in different water matrices and compared to a consolidated AOP, namely UV-C/HO. As matter of fact 90% degradation of CECs was observed after 15 min (Q = 0.33 kJ L) by UV-C/FC (5 mg L of FC) and 30 min (0.67 kJ L) by UV-C/HO (5 mg L of HO) in natural water. However, CECs degradation by UV-C/HO and UV-C/FC was comparable (>82%) in wastewater samples, under the investigated conditions (60 min, 1.33 kJ L). The effect of sunlight/FC process on the target CECs was also investigated (in a compound parabolic collector based reactor). Interestingly, a different behaviour was observed between the two light sources. In particular, a total removal of carbamazepine (CBZ) and imidacloprid (IMD) was observed for UV-C/FC process with 0.27 kJ L and 10 mgL of FC, while, in the sunlight/FC process (same FC dose), CBZ total removal took place quite fast (0.50 kJ L), but 90% removal of IMD was observed only after 60 min (7.09 kJ L). In conclusion, UV-C/FC process can be an interesting solution for tertiary treatment of urban wastewater for the removal of CECs and sunlight/FC is worthy of further investigation to evaluate its possible application in small UWTPs.