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.

According to results of the estimation of drinking water on the index of the chemical harmlessness of five water intake structures of the city of Ufa, the drinking water of a superficial water intake on total and population cancerogenic risks was shown to be more harmful in comparison with water from infiltration water intakes. At the same time, drinking water from an infiltration water intake with ultra-violet disinfecting has smallest values of cancerogenic and non-cancerogenic risks. Trigalogenmetans and dichloroacetic acid (water disinfection chlorine by-products)| make the main contribution to the value of the total cancerogenic risk of the studied drinking waters, trigalogenmetans and di(2-ethylhexyl)phthalate make the contribution to the value of noncancerogenic risk. Polycyclic Aromatic Hydrocarbons fail to have a significant impact on the value of total cancerogenic risk of drinking water of the city in view of their presence at low concentration. Work is carried out according to R 2.1.10.1920-04 and MR 2.1.4.0032-11.

No abstract

Introduction. To conduct a total assessment of carcinogenic, non-carcinogenic, and organoleptic risks to public health and cover both normalized and non-normalized pollutants of potable water, based on the results of long-term monitoring studies, it is possible using an integral indicator of chemical harmlessness of water. Material and methods. Authors studied potable water of water intakes of surface and infiltration types from potable water reservoirs and remote zones of Ufa water distribution networks. Impurities were determined by chromatography, inductively coupled plasma mass spectrometry, photometric, nephelometric, and titrimetric methods. Results. The main effect on the amount of carcinogenic risk in potable water of the surface water intake are chloroform, bromodichlethane, dichloroacetic acid, in the infiltration water intake - in addition to these compounds zinc, lead and chromium are in addition influenced. Organic compounds (phthalates, benz(a)pyrene, volatile aromatic compounds, etc.) have no effect on this type of risk due to the presence in water in low background concentrations. The identified number of individual carcinogenic risks for bromodichloroacetic acid and dichloroacetic acid according to the WHO classification corresponds to the second range. As the surface type water intake is removed from the potable water reservoir, the total carcinogenic risk of water decreases by 13-30%, and the infiltration type increases by 41-84%. Values of noncancerogenic and organoleptic risks are constant for potable water of different water intakes and correspond to recommended limit values. The excess of the maximum permissible concentrations (SanPin 1.2.3685-21) of individual substances in the potable water of the city has not been detected for the whole period of observation. In terms of the integral indicator of chemical harmlessness, the most favorable is the po-table water of the infiltration water intake, in the technology of which is mainly used the UV for decontamination of water. Conclusion. Using a risk assessment methodology complements the traditional approach to assessing water quality under modern hygiene standards. It becomes possible to evaluate the effect of pollutants of various classes on water quality when they are present together.

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.