# Efficiency Assessment of Fenton-Based Pre-Treatment of Medical Wastewater Using Fe, Cu, and Mn Catalysts—Impact on the Aquatic Environment

## TL;DR

This study compares the effectiveness of Fenton oxidation using Fe, Cu, and Mn catalysts in treating hospital wastewater and finds that while Fe is most effective at removing contaminants, it increases toxicity.

## Contribution

The study introduces a combined targeted and untargeted analytical approach to assess Fenton treatment efficiency and ecotoxicological impact.

## Key findings

- FeSO4 achieved the highest COD reduction (89%) and contaminant removal (70% peak area reduction).
- CuSO4 and MnSO4 showed lower removal efficiency for certain pharmaceuticals like fluoroquinolones.
- Post-treatment toxicity increased significantly, with 98% growth inhibition in Allivibrio fischeri.

## Abstract

This study evaluated the efficiency and ecotoxicological impact of the Fenton oxidation process with different metal-based catalysts (FeSO4, CuSO4, MnSO4) in removing pharmaceuticals and organic contaminants from real hospital wastewater. All catalytic systems achieved high oxidation, with COD reduction reaching 81–89% after 4 h. Two complementary approaches were applied: targeted LC-MS/MS quantification of a model mixture of antibiotics and pharmaceuticals, and untargeted GC-MS/MS screening method for assessing the overall organic contaminant profile. Toxicity was assessed using Microtox®. Targeted analysis showed complete or near-complete degradation of β-lactams, tetracyclines and most sulfonamides, with slightly lower removal for sulfamethoxazole in FeSO4 system (96%). Fluoroquinolones and selected pharmaceuticals, such as caffeine and propranolol were more resistant, particularly with CuSO4 and MnSO4 catalysts. The untargeted GC-MS/MS screening revealed the highest overall reduction in chromatographic peak areas for FeSO4 (70%), followed by MnSO4 (39%) and CuSO4 (36%). GC-MS/MS profiling confirmed that the Fe-catalyzed process was the most effective in reducing the total chromatographic peak area (70%). However, ecotoxicological assays revealed a significant increase in toxicity post-treatment, with growth inhibition of Allivibrio fischeri reaching 98%. This suggests that high oxidation does not directly correlate with biological safety, likely due to the presence of unconsumed reagents or the formation of transformation products with higher acute toxicity. These findings emphasize the necessity of integrating bioassays into treatment evaluation protocols to assess the true environmental risk of treated effluents.