Treatment of a clinical analysis laboratory wastewater from a hospital by photo-Fenton process at four radiation settings and toxicity response.

Abstract

The photo-Fenton process was performed with four radiation settings to treat clinical analysis laboratory wastewater (CALWW) from a hospital, with the aim of evaluating its treatability and acute toxicity response in Daphnia magna and Lactuca sativa. The experiments were performed in a borosilicate bench-scale conventional reactor for 320 min. The light radiation was suspended 13 cm from the CALWW surface for mild radiation or immersed into the matrix for intense radiation. All photo-Fenton experimental conditions were set at pH 3.0, 15 mg L-1 of Fe2+, and initial H2O2 of 300 mg L-1. The initial Fe2+ concentration was converted to Fe3+ ion in the first 15 min of photooxidation for all processes. Furthermore, the intense radiation processes regenerated Fe2+ faster than other systems. Neither mild UVA-Vis nor mild UVC-Vis radiation significantly treated the organic matter or phenols. However, mild UVC-Vis resulted in a higher biodegradability transformation rate (biochemical oxygen demand/chemical oxygen demand 0.51), indicating that it could treat more recalcitrant organic matter than mild UVA-Vis. Intense radiation proved to be more efficient, with a chemical oxygen demand removal rate of 95% for intense UVA-Vis and 99% for intense UVC-Vis treatments. All treatments reduced acute toxicity in D. magna. Moreover, photo-Fenton treatment by intense UVA-Vis decreased toxicity ~98%, compared to mild and intense UVC-Vis, ~75%. Both of the mild radiation treatments inhibited the germination of L. sativa seeds. The intense UVA-Vis photo-Fenton treatment was the only setting that removed phytotoxicity, resulting in a non-significant effect, and the intense UVC-Vis treatment inhibited the seed growth.