Integrating anaerobic and photochemical processes: UV –vis‐driven post‐treatment for micropollutant abatement and toxicity control in UASB secondary effluent

Abstract BACKGROUND Upflow anaerobic sludge blanket (UASB) reactors are widely used in low‐ and middle‐income countries, but secondary effluents may still contain organic micropollutants and residual toxicity. This study evaluated UV–Vis photolysis and UV/H 2 O 2 as post‐treatment options for UASB secondary effluent (SE), integrating micropollutant removal and toxicity responses. Photodegradation experiments were conducted in a 125 W UV–Vis photochemical reactor (200–800 nm; 254 nm at 12.1 W m −2 ), with accumulated UV‐C doses ranging from 0.23 to 0.69 kJ L −1 . Treatment performance was assessed through the removal of atrazine (ATZ), rifampicin (RIF), and 17α‐ethynylestradiol (EE2), acute toxicity to Daphnia magna , and phytotoxicity to Lactuca sativa seeds. RESULTS UV/H 2 O 2 promoted rapid removal of the target micropollutants, while UV–Vis photolysis reached similar final removals under the tested conditions. UASB treatment reduced the organic load and eliminated acute toxicity to Daphnia magna , whereas toxicity responses after UV‐based treatment varied depending on the matrix and process. Phytotoxicity assays showed no inhibition of germination, although root elongation responses varied with accumulated UV‐C energy. CONCLUSIONS Overall, UV‐based post‐treatment improved micropollutant abatement in UASB matrices, but transformation products, chronic effects, disinfection performance, and real‐effluent operation should be assessed before inferring reuse safety or full‐scale applicability. © 2026 The Author(s). Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).