Demonstration-scale urban wastewater reclamation using concentrated solar radiation

This study explores the potential of solar disinfection (SODIS) enhanced by solar concentration technology for urban wastewater reclamation at demonstration scale, with application to crop irrigation, highlighting a novel approach to integrating renewable energy into wastewater treatment while reducing operational costs and environmental impact. A pioneering demonstration plant, based on a 36-m 2 Fresnel solar collector, was set up at an urban wastewater treatment plant (WWTP) in Almería (Spain) to evaluate the inactivation of Escherichia coli ( E. coli ) and total coliforms under continuous-flow operation. Preliminary laboratory experiments were conducted to study E. coli inactivation at different operating temperatures and UV-A irradiances using actual secondary effluent. The demonstration plant was designed, constructed, and automated following these results. Its operation was assessed at outlet temperatures of 40, 50, 60, and 70 °C for two configurations: one involving a preheating/aftercooling stage based on heat recovery through a tube-and-shell heat exchanger, and the other without it. Log reduction values (LRVs) of 2.0 ± 0.1 and 5.6 ± 0.1 in E. coli concentration were achieved using the enhanced system configuration (Fresnel + heat exchanger) at 50 °C (200 L h −1 ) and 60 °C (150 L h −1 ), respectively. Furthermore, the addition of 20 ppm of H₂O₂ as a chemical enhancement for disinfection (solar/H 2 O 2 ) was studied at an outlet temperature of 50 °C, resulting in LRV increases of up to 1.6 in E. coli concentration. • A 36-m 2 Fresnel solar collector was evaluated for urban wastewater reclamation. • Classical cascade control strategy was implemented for the outlet temperature. • The plant baseline design was upgraded by implementing an energy recovery stage. • Reclaimed water qualities Class D (200 L h −1 ) and Class A (150 L h −1 ) were achieved. • H 2 O 2 dosing was proposed as a complementary strategy for low-radiation intervals.