This study aims to establish a connection between the trihalogenomethanes content in drinking water of an infiltration intake and parameters characterizing water quality (turbidity, chromaticity, oxidizability), chlorine doses, and water consumption. Trihalomethanes include chloroform, bromodichloromethane, dibromochloromethane, and bromoform. It is known that trihalomethanes can harm public health. These compounds have a toxic polymorphism and can cause long-term effects, including carcinogenesis. It is shown that a satisfactory description of the trihalogenomethanes content can be obtained by modeling the annual cycle, taking into account the displacement of parameters (2-3 months), relative to the trihalogenomethanes content. Equations considering the displacement of water quality indicators have a high determination coefficient (0.95-0.97). The use of the same displacement for the time series of true values allows us to obtain equations with a sufficiently high determination coefficient, which indicates the possibility of their use for the predictive assessment of the trihalomethanes content in drinking water.

The main drawback of drinking water chlorination involves the formation of quite hazardous disinfection by-products (DBPs), represented mainly by halogenated species. Based on the authors’ monitoring data since 2002, the prevalence of chlorine over bromine in the composition of volatile DBPs was shown for the drinking water in Ufa (Russia). However, the situation was completely reversed in the case of semi-volatile DBPs. The principal goal of the present study involved rationalization of the results of the long-term monitoring. Gas chromatography–mass spectrometry (GC-MS) was used for the qualitative and quantitative analysis of volatile DBPs. Identification of semi-volatile compounds was carried out with GC-MS, while gas chromatography with an atomic emission detector (GC-AED) was used for their quantification. A significant contribution of oxygen to the composition of semi-volatile compounds proves the decisive role of the dissolved organic matter oxidative destructive processes. Statistical analysis revealed notable linear correlations for trihalomethane and haloacetic acid formation vs. chlorine dose. On the contrary, halogenated semi-volatile products do not demonstrate any correlations with the water quality parameters or chlorine dose. Principal component analysis (PCA) placed them into separate groups. The results allow for proposing that formation of the organohalogenated species involved the fast penetration of bromine into the humic matter molecules and, further, their oxidative destruction by active chlorine.

There has been analyzed the nature of the distribution of the oxidability of water. It is revealed that the nature of the distribution of indicator values during the year depends largely on the seasonal factor, and therefore the analysis of the distribution of oxidability is proposed to be studied separately for each month. A variation series is constructed and empirical distribution functions of oxidability distribution is derived. It is established that the law of water oxidability distribution differs from the normal and lognormal distributions, but it is described with sufficient accuracy by the gamma distribution or by a cubic polynomial function (being the simplest). The hypothesis about the distribution law is confirmed by the Kolmogorov–Smirnov test. The water oxidability distribution function allows to determine the probability of exceeding the specified values of the indicator and quantitatively assess the risks of exceeding them, which can become the basis for developing solutions for managing water quality and increasing the efficiency of the water treatment process.

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The distribution of turbidity values in given sample is analyzed. The results demonstrated that the nature of the distribution of turbidity values during the year largely depends on the seasonal factor, hence the analysis of the distribution of turbidity is performed separately for each month. Order statistic (variation series) is computed and an empirical distribution function of turbidity values is derived. It is concluded, that the distribution of turbidity in given water sample differs from normal, log-normal and gamma distributions. However, it can be described with sufficient accuracy by a cubic polynomial function. The turbidity distribution hypothesis is tested by the Kolmogorov–Smirnov test. The water turbidity distribution function predicts the probability of exceeding the specified values of turbidity and enables numerical assessment of its likelihood.