Any chemical or biological contaminant introduced into clean water results in a lower water quality that may adversely affect human health or the environment. Emerging contaminants (ECs) generally refers to chemicals, biological agents and materials, that may pose a potential or real threat to human health or the environment, but which are not generally regulated at present or are expected to undergo changes in regulations.  Ozone (O3) is one of the strongest known oxidants with oxidation potential 2.07 V. It is widely performed for water and wastewater treatment. Mechanism of ozonation is similar to other disinfectants for water and wastewater treatment, which is based on the instability of O3 in water [1]. The extra oxygen radical in an ozone molecule quickly binds to each component that comes in contact with ozone molecules [2]. The unique feature of ozone is its decomposition into hydroxyl radicals (�OH) which are the strongest oxidants in water. Ozone is a very selective oxidant, whereas hydroxyl radicals are non-selective and react fast with wide range of organic compound. Therefore, compounds persistent to molecular ozone are destructed by indirect reaction with the radical species that are formed when ozone decomposes in water. All the chemicals and reagents (high purity analytical or higher grade) were purchased from Sigma Aldrich. The setup comprises of ozone generator, bubble column, degassing unit, and destruct unit. The ozone generator (OZAT CFS-1 2G) was provided by Ozonia Ltd. The samples were taken at regular intervals and were prepared using solid phase extraction (SPE) (Oasis HLB carttriges, Waters) and analyzed using UPLC/MS/MS (Waters). The ozonation and chemically-assisted ozonation of several groups of ECs and endocrine disrupting compounds (EDCs) (bisphenol A, 1,4-dioxane) was investigated. The efficiency of the treatment varied from one compound to another, which allowed making a conclusion about the applicability of these treatment methods to the certain group of compounds. The initial concentrations of all chemicals under study were initial concentrations of 100 �g/L. Pharmaceuticals were sufficiently removed (up to 100%) by direct ozone reaction during ozonation, whereas 1,4-dioxane degradation mostly occurred in hydroxyl radical reaction during peroxone treatment. All steroids were removed in approximately 1 min. No removal was achieved in ozone-based processes for the removal of N,N-Diethyl-meta-toluamide (DEET). The difference in reactivity can be attributed to the structures of ECs. Special study on the reactivity of seven estrogens and five progestins was accomplished by computational methods. However, the slight difference in reactivity between estrogens and progestins attributed to the presence of phenolic moiety in estrogens was found. The electronic structure of these compounds has been studied and several most important parameters were identified. As a result, qualitative structure activity relationship (QSAR) models for these two groups of steroids were developed. Emerging contaminants demonstrate different reactivity towards molecular ozone and hydroxyl radical. The selective treatability is attributed to the chemical nature of the compounds and can be interpreted via detailed structure analysis.1. Bablon, G. 1991. �Practical Application of Ozone: Principles and Case Studies.� Ozone in Water Treatment Application and Engineering. AWWARF2. Von Gunten, U. 2003 Ozonation of drinking water: Part I. Oxidation kinetics and product formation. Water research 37(7), 1443�1467.

Computational methods in the interpretation of reactivity of emerging contaminants by ozone-based technologies: Combined DFT QSAR approach

244th National Meeting (2012)

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