V. Zaitsev ¹, N. Rublevskaya ¹, V. Rublevsky ²

¹ State Institution “Dnipropetrovsk Medical Academy of the Ministry of Health of Ukraine”, Dnipro, Ukraine

² Oles Honchar Dnipro National University, Dnipro, Ukraine

ABSTRACT. More than 80 % of the population of Ukraine is provided with drinking water by means of surface water intakes, for the disinfection of water, as a rule, liquefied chlorine is used. When this method of disinfection is applied due to the interaction of organic substances with chlorine, chlororganic compounds (COC) are formed, among which trigalomethanes prevail, and among the latter, 60–90 % of the content is chloroform. Since January 2015, the hygienic norm of chloroform in tap water has been in effect in Ukraine and the obligatory program of daily monitoring of the chloroform content during the chlorination of water has been justified. Therefore, it became necessary to search for chloroform chlorine form in chlorinated water that is labor-consuming and economically accessible for water pipes. The chloroform content depends on the value of the integral index of organic water contamination — permanganate oxidation. The higher the value of permanganate oxidability in drinking chlorinated water, the more reliable (p <0.05) the higher the chloroform content in it. The method of indirect determination of the chloroform level in chlorinated water using the permanganate oxidation level is simple, reliable and operative in comparison with the prototype in the absence of the possibility of determining the chemical composition of water, the ability to determine the level of chloroform at any point in the water distribution network, reduces the cost of research and, accordingly, water for the population.

Key Words: drinking tap water, organochlorine compounds, chloroform, permanganate oxidibility.

Introduction. More than 4/5 of the population of Ukraine is provided with drinking water at the expense of surface water intakes, where organochlorine compounds are used in 85 % for the decontamination of water. Upon chlorination of surface water intakes (primarily rivers) due to the chemical interaction of organic substances with hypochloride ion, numerous organochlorine compounds (OHCs) are formed, among which the prevailing part is chloroform. According to the State Sanitary Regulations and Rules 2.2.4.171-10 “Hygienic requirements for drinking water intended for human consumption” on water pipes where chlorination of water is carried out, the concentration of chloroform should be systematically determined in the drinking water, which requires modern, reliable methods for the determination of chloroform in chlorinated drinking water.

The most common method of determining the level of chloroform in drinking chlorinated tap water [1] is based on the chemical analysis of water samples by gas chromatography using modern high-precision gas chromatograph. A water sample is placed in a thermally insulated hermetically sealed space and the gas phase is analysed by gas chromatography using an electronic capture detector.

The disadvantage of the method is the necessity of using a special device — gas chromatograph and other equipment that is absent in the vast majority of production laboratories of water treatment plants and therefore economically inaccessible and labour-intensive for most of the water pipelines in Ukraine, which prevents it from being widely used for the purpose of assessing and predicting the safety of drinking water for chloroform content.

Objective. Increase the reliability and efficiency of the method for determining the level of chloroform in drinking chlorinated tap water and propose a method for determining chloroform by regression analysis of selected drinking water quality parameters related to the content of chloroform in drinking water.

Object and methods. As the “basic” or experimental objects, drinking chlorinated tap water of the Municipal Enterprise “Vodovid of Aulsk” and Municipal Enterprise “Dniprovodokanal” (Region of Dnipropetrovsk) were selected. The processing of the data was performed using the Statistica v6.1 software package (Statsoft Inc., USA), license number AJAR909E415822FA.

Results and discussion. According to our previous studies, systematic excess levels of chloroform in the drinking chlorinated driver, which is fed to the population of Dnipro and Kamianske [2], have been detected. There are no devices for determining chloroform in the water on the specified water pipelines, therefore, monthly samples are delivered to the appropriate laboratory structures of the Ministry of Health of Ukraine. The test results are obtained with significant delay and after payment of the tests. There is a need for obtaining more rapid test results on the content of chloroform in drinking water. We have analysed the protocols of measurements of the content of chloroform in drinking water, as well as parameters of the level of colouration and oxidizability in the water of the water source (Dnipro river) and drinking water at the output to the distribution network. Based on the results of the regression analysis, a two-factor model for indirect determination of chloroform level in chlorinated drinking water was proposed:

Y= І+C • а + PО • b + Year • с,

where: Y – chloroform content in drinking chlorinated tap water, μg/dm³;

C – colouration in the water of the water source, deg;

PO – permanganate oxidizability of the water source, mg/dm³;

Year – annual trend (last two digits of the current year);

I, a, b, c are the regression factors, in particular, I = 78.17 μg/dm³; a = 0.706 μg/dm³/deg; b = 4.04 μg/dm³/•μg/dm³; c = 2.311 μg/dm³.

The presence of organochlorine compounds in drinking water, primarily chloroform, is associated with the presence of natural organic compounds — humic and fulvic acids. The latter determines the level of colouration and, to a large extent, its permanganate oxidizability. Therefore, the content of chloroform directly depends on colouration and permanganate oxidizability — an integral parameter of organic pollution of water. A correlation-regression analysis of the array of actual parameters of organic pollution of water from the river Dnipro at the water intake of ME “Vodovid of Aulsk” (colouration, permanganate oxidizability) and chloroform content in chlorinated drinking water. Using special equipment over time for 2002–2015 (total number of observations 158), a direct correlation between the concentration of chloroform in drinking water and such parameters as colouration and oxidizability has been established. In addition, a tendency for an annual increase in the level of colouration and permanganate oxidizability of water, indicating the presence of other unrecognised factors or the annual trend in changes in these parameters has been established. The advantage of the proposed utility model is the economic availability and accuracy of the determination of chloroform in chlorinated drinking water without conducting additional chemical tests, which allows it to be widely used in water pipelines to evaluate and predict the safety of drinking water.

The results of the conducted studies suggest tatting the higher is the value of permanganate oxidizability and colouration in the water source of household water supply, the significantly higher (p < 0.05) is chloroform content in drinking chlorinated tap water. The level of significance of the regression factors according to the Student’s test is p < 0.001. Model validity was estimated by Fisher’s (F) test: F = 22.09, p < 0.001.

Method of determining the content of chloroform in drinking chlorinated tap water is performed as follows. Initially, the levels of colouration and permanganate oxidizability in the water of the source of drinking water supply are determined instrumentally. According to GOST 3351-74. “Drinking water. Methods for determining taste, odour and turbidity”, colouration is determined by the photometric method by comparing the water colour with the standard scale. According to GOST 23268.12-91. “Mineral drinking, medicinal, medicinal-table and natural table waters. Method for determining permanganate oxidizability”, oxidizability is determined by titrimetry. The obtained values are applied in the formula Y = I + C • a + PO • b + Year • c, where: Y – chloroform content in drinking chlorinated tap water, μg/dm³; C – colouration in the water of the water source, deg; PO – permanganate oxidizability of water of water source, mg/dm3; Year – time (annual) trend (last two digits of the current year); I, a, b, c are the regression factors. Factors I = 78.17 μg/dm³ characterizes the constant value of chloroform content in drinking water; factors a = 0,706 μg/dm³/deg and b = –4,04 μg/dm³ / • mg/dm³ indicate the number of units by which the chloroform content changes (μg/dm³) with the corresponding change in the water colouration of the water source by 1 deg. and water oxidizability index by 1 mg/dm³. Factor c = 2.311 μg/dm³, multiplied by the last two digits of the year of calculation, shows changes in the content of chloroform under the exposure to other unrecognised factors.

The obtained result is a predicted concentration of chloroform in drinking water.

Example 1. Colouration and permanganate oxidizability in the water of the river Dnipro at the water intake of the ME “Vodovid of Aulsk” in October 2012 was 42.1 degrees and 10 mg/dm³, respectively. According to the calculation of the proposed method, the concentration of chloroform in drinking chlorinated water should be 95.22 μg/dm³. During chromatographic determination, in the same sample of drinking water, the concentration of chloroform was 97 μg/dm³, which matches with its predicted concentration with an accuracy of –1.8 %, which indicates the reliability of the new method compared to the prototype in the absence of the ability to determine the chloroform content by the chromatographic method, which greatly simplifies and reduces the cost of appropriate tests.

Example 2. Colouration and permanganate oxidizability in the water of the river Dnipro at the water intake of the ME “Vodovid of Aulsk” in April 2015 was 36.3 degrees and 11.3 mg/dm³, respectively. According to the calculation, the concentration of chloroform in drinking chlorinated water should be 92.81 μg/dm³. During chromatographic determination in the same sample of drinking water, the concentration of chloroform was 96.9 μg/dm³, which matches with its predicted concentration with an accuracy of 4.2 %. This indicates the validity of the new method compared to the prototype in the absence of the ability to determine the content of chloroform by the chromatographic method, which greatly simplifies and reduces the cost of appropriate tests.

Conclusion

1. The content of chloroform depends on the integral index of organic pollution of water — permanganate oxidizability.
2. The higher the value of permanganate oxidizability in drinking chlorinated water is, the significantly higher is the content of chloroform (p < 0.05).
3. The method of indirect determination of chloroform in chlorinated drinking water using the level of permanganate oxidizability is simple, reliable and effective compared to the prototype in the absence of the ability to determine the chemical composition of water, the ability to determine the level of chloroform at any point of the water distribution network, which reduces the cost of tests and respectively, drinking water for the population.

Prospects for further studies. In the future, it is planned to develop technical and technological measures to reduce the level of OHCs in drinking chlorinated water consumed by the urban population.

REFERENCES

1. Gas chromatographic determination of trihalomethanes (chloroform) in water: method. reference number 0052-98 (No. 2, 01.02.1999). ‒ K.: Ministry of Health of Ukraine, 1999. – 9 p.

2. Zaitsev V. V. Hygienic assessment of the content of organochlorine compounds in drinking water of a group water supply from a surface water intake / V. V. Zaitsev, N. I. Rublevska, N. O. Kurbatova // Collected papers of staff members of the National Academy of Post-Graduate Education named after P. L. Shupyk. – Edition No. 24 (3). – K., 2015. – P. 441–447.

3. Prokopov V.O. Organochlorine compounds in drinking water: factors and conditions of their formation / B.O. Prokopov, G.V. Chichkovska, V.O. Zorina // Environment and health. – 2004. – No. 2 (29). – P. 70–73.

Надійшла до редакції 11.06.2018 р.