Sustainable Treatment of Municipal Secondary Effluent from UASB Systems by Solar Photo-Fenton: CECs Removal and Toxicity Control

Upflow Anaerobic Sludge Blanket (UASB) systems are vastly implemented for municipal wastewater treatment in developing tropical countries. Despite that, efforts related to the removal of contaminants of emerging concern (CECs) from municipal secondary effluents (MSE) via post-treatment by solar photo-Fenton are mainly conducted with MSE from Conventional Activated Sludge (CAS). Hence, it is critical to investigate the efficiency of solar photo-Fenton to treat MSE from UASB systems. This is the first study to evaluate the performance of solar photo-Fenton and dark Fenton conducted with intermittent additions of Fe2+ and at circumneutral pH for the removal of CEC from UASB followed by Trickling Filter (UASB+TF) and UASB effluent. Acute and chronic ecotoxicity to Aliivibrio fischeri and Raphidocelis subcapitata, respectively, and phytotoxicity to Lactuca sativa were also evaluated for both matrixes. Solar photo-Fenton removed 83% of ΣCECs from UASB+TF effluent and resulted in non-toxic samples. Solar photo-Fenton performed in MSE from UASB system alone showed 65% ΣCECs removal and reduced chronic effect to R. subcapitata (growth inhibition) from 11% to 26%. In addition, no acute toxicity was verified for A. fischeri nor L. sativa. This work shows the feasibility of applying solar photo-Fenton at circumneutral pH to improve the quality of MSE resulting from UASB systems prior to wastewater discharge or reuse in agriculture.