Phenomenological insights into the occurrence and abatement of disinfection by-products in the novel solar chlor-photo-Fenton process

For the first time, in-depth phenomenological insights were investigated into the formation/degradation of chlorination disinfection by-products (DBPs) during the treatment of actual secondary effluents by the novel solar chlor-photo-Fenton (CPF) process for disinfection and organic microcontaminant removal. To this aim, the influence of solar irradiance and reagents involved in the process (ferric nitrilotriacetate, hydrogen peroxide, and sodium hypochlorite) was assessed at lab scale and further verified in raceway pond reactors operated in continuous flow in terms of DBP degradation, to guarantee the safety reuse of the treated water and thus the implementation on a larger scale. The results were highly encouraging, the concentrations of trihalomethanes (THMs) and haloacetic acids (HAAs) being negligible compared to legislative limits (30 and 60 μg/L; 26- and 3-fold lower for THMs and HAAs, respectively). Solar CPF excels at reducing DBP concentrations, achieving levels of just 6.12 µg/L of THMs and 15.6 µg/L of HAAs, significantly lower than the 27.7 µg/L of THMs and 105 µg/L of HAAs produced by conventional chlorination. These findings proved the capacity of this novel strategy to notably mitigate DBP formation through the synergy of sunlight and HO^•-induced oxidation while allowing simultaneous disinfection and microcontaminant removal.