Wastewater reclamation is increasingly important as water scarcity intensifies worldwide. Advanced treatments such as ozonation, UV irradiation, and biological activated carbon filtration are commonly used to remove micropollutants or pathogens that survive conventional treatment. Although these processes can substantially reduce concentrations of original contaminants, oxidation and photochemical reactions may generate transformation products with biological properties that differ from those of their parent compounds. Some byproducts may exhibit cytotoxic, genotoxic, or endocrine-disrupting activity, yet routine chemical monitoring may fail to detect their combined effects. Moreover, individual toxicity tests cannot fully characterize mixtures that simultaneously activate or inhibit different hormone receptors, creating a need for integrated, effect-based assessments across multiple toxicological endpoints.
A study (DOI: 10.48130/een-0026-0014) published in Energy & Environment Nexus on 27 July 2026 by Mei Ma's team, Chinese Academy of Sciences, reveals that although conventional and advanced treatments reduced several estrogen- and thyroid-related effects, UV irradiation and ozonation unexpectedly elevated anti-androgenic activity to potentially hazardous levels.
The researchers evaluated a typical wastewater treatment plant in Tianjin, China, together with two pilot-scale treatment systems. Samples were collected from 11 locations covering the plant inlet, preliminary sedimentation, A2O treatment, secondary sedimentation, UV disinfection, ozonation, coagulation, and biological activated carbon treatment. Organic compounds were isolated from water samples using solid-phase extraction. The extracts were then examined with two-hybrid recombinant yeast assays containing human estrogen receptor alpha, androgen receptor, or thyroid receptor beta, enabling the team to measure both receptor-agonistic and receptor-antagonistic effects. Bioactivity was expressed as equivalent concentrations of reference chemicals, and the researchers derived an effect-based trigger value of 7.97 μg flutamide equivalents per liter for androgen receptor-antagonistic activity. Estrogen receptor-agonistic activity was prominent in untreated and preliminarily treated wastewater but declined progressively and fell below the detection limit after secondary sedimentation. Estrogen receptor-antagonistic activity similarly decreased from 58.4 μg/L in the influent to approximately 7.8–9.2 μg/L after treatment. Thyroid receptor-antagonistic activity dropped from 0.56 mg/L to 0.0085 mg/L through the main plant, while ozonation and ozonation followed by biological activated carbon further controlled this activity in the pilot systems. Coagulation nevertheless produced a slight increase in thyroid receptor antagonism, possibly because residual endocrine-disrupting chemicals competed with other organic matter during removal. The most concerning pattern involved the androgen receptor. No androgen receptor-agonistic activity was detected, but antagonistic activity occurred throughout the treatment train. A2O treatment reduced it markedly from 156.6 to 12.4 μg flutamide equivalents per liter. Subsequent UV irradiation and ozonation, however, increased the activity, pushing treated effluents above the newly established trigger value. Biological activated carbon treatment after ozonation did not fully reverse this increase. The researchers suggest that incompletely mineralized transformation products generated through reactions such as hydroxylation, dealkylation, decarboxylation, or deamination may account for the elevated effects.
Overall, the study shows that treatment performance cannot be judged solely by pollutant removal or by measuring a single biological endpoint. UV irradiation and ozonation remain valuable for pathogen control and contaminant degradation, but their operating conditions and downstream treatments must be optimized to prevent the formation or persistence of hazardous transformation products. Incorporating multi-endpoint, effect-based monitoring into wastewater management could reveal risks missed by conventional chemical analysis and support a better balance between purification efficiency and ecological safety in reclaimed water systems.
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References
DOI
10.48130/een-0026-0014
Original Source URL
https://doi.org/10.48130/een-0026-0014
Funding information
This work was supported by the National Natural Science Foundation of China (52030003), the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB0750400), and the National Key R&D Program of China (2024YFC3214700).
About Energy & Environment Nexus
Energy & Environment Nexus (e-ISSN 3070-0582) is a multidisciplinary journal for communicating advances in the science, technology and engineering of energy, environment and their Nexus.