Chord of second fiddle: Disinfection processes with higher removal efficiencies of natural and synthetic progesterones in hospital wastewater

Hospital wastewater (HWW) contains plenty of persistent compounds, dangerous substances, and pathogenic microorganisms, such as antibiotics, psychiatric drugs, β-receptor blockers, anesthetics, analgesics, anti-inflammatory drugs, and X-ray contrast agents. Endocrine disrupting chemicals (EDCs) are among the high-risk substances in HWW. Progesterones, as typical representative compounds of steroid hormone EDCs, are capable of entering and accumulating in the human body through the food chain. Due to their incomplete removal, natural and synthetic progesterones can enter surface waters continuously with the discharge of the effluent from HWW treatment stations, which may cause adverse effects on the aquatic environment and organisms. In addition, progesterones can react with albumin and corticosteroid protein in the human body, causing damage to multiple systems, such as the endocrine system, immune system, reproductive system, and nervous system.

Natural and synthetic progesterones and their metabolites were widespread in various water bodies. In a surface water environment, the concentrations of progesterones were usually in the range of nanogram per liter, while in wastewater or livestock farm runoff, the concentrations of progesterones were up to microgram per liter. Two methods are often used to remove the pollutants and pathogenic microorganisms in HWW treatment. The first method combines primary filtration treatment (PFT) with disinfection and the treated effluent is discharged into the urban pipe network and mixed with other urban sewage for further treatment in the MWTP. In the second method, HWW was treated by PFT, secondary biological treatment (SBT), and disinfection in that order, and the effluent can be directly discharged into the receiving water body.

Disinfection is an essential wastewater treatment unit that also exhibits a certain removal effect on trace organic pollutants. Considering the different principles and oxidation capabilities of different disinfectants, the removal efficiency of progesterones in each disinfection process is also different. The disinfectants commonly used in HWW disinfection are chlorine (Cl₂), chlorine dioxide (ClO₂), ozone (O₃), ultraviolet (UV), and UV/chlorine (UV/Cl₂). However, the removal efficiencies of natural and synthetic progesterones in HWW using these disinfection processes have not been reported yet. Moreover, the potential risk of HWW in various disinfection processes has not been evaluated.

In order to investigate their removal efficiencies for progesterones in primary filtration and secondary biological treatment effluents, the researchers from Beijing Forestry University selected five disinfection processes, namely, chlorine (Cl₂), chlorine dioxide (ClO₂), ozone (O₃), ultraviolet (UV)), and UV/chlorine (UV/Cl₂). The removal efficiencies of progesterones by the five disinfection processes were determined by determining the exposure concentrations of natural and synthetic progesterones in HWW, primary filter treated effluent (PFTE) and secondary biological treated effluent (SBTE). This study entitled “Removal efficiencies of natural and synthetic progesterones in hospital wastewater treated by different disinfection processes” is published online in Frontiers of Environmental Science & Engineering in 2022.

In this study, there were 61 natural and synthetic progesterones detected in HWW, with the natural progesterones being the main components with a concentration of 845.51 ng/L and contributing to 75.08% of the total progesterones. The primary filtration treatment presented insignificant removal effects on the progesterones, while the secondary biological treatment significantly reduced the progesterone content by biodegradation. The order of removal efficiencies of total progesterones by different disinfection processes was UV/Cl₂ > Cl₂ > O₃ > ClO₂ > UV. UV/Cl₂ showed the highest removal efficiency against progesterones mainly due to the activation of Cl₂ by ultraviolet (UV) photolysis, which helps open the heterocyclic, aromatic, and phenolic rings, thus accelerating progesterone degradation. In addition, the removal efficiencies of natural progesterones in the five disinfection processes were higher than those of synthetic progesterones (progesterone derivatives, 19-nortestosterone derivatives, and 17α-hydroxyprogesterone derivatives).

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