The use of chloride dioxide in the technology of drinking water treatment at the Dnipro river water pipe-line in Kiev
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Hygienic assessment of dangerous chlorites in drinking water treated with chlorine dioxide and the risk of its consumption to the health of the population
Today, chlorine dioxide has begun to be more widely implemented in water treatment technologies on river running water systems of Ukraine. Chlorine dioxide is used in traditional water treatment technology for both primary and secondary water treatment on the Dnipro running water system in Kyiv. Objective – to analyze the results of the content of dangerous chlorites in tap drinking water of certain districts of the city of Kyiv, and calculate and assess non-carcinogenic risk of this drinking water for human health. It was shown that in the drinking water from the running water networks of Svyatoshynskyi, Shevchenkivskyi, Obolonskyi and Podilskyi districts of the city, into which it enters after treatment with chlorine dioxide from the Dnipro running water system, the levels of chlorites were the lowest in winter and spring. In summer, the concentrations of chlorites in the water from the studied networks were the highest and averaged from 0.32 to 0.45 mg/dm3. In autumn, chlorites in the water from these systems were at the level of 0.22-0.28 mg/dm3. In spring (May) and especially in summer, the levels of chlorites in drinking water, according to average data, exceeded the national hygienic standard (0.2 mg/dm3) by 1.5-2 times, but they were never higher than the chlorite standard (0.7 mg/dm3) recommended by WHO. Our analysis of sanitary-chemical and microbiological indicators in drinking water showed that the water is characterized by high quality and safety during the entire period of observation. The risk assessment of the development of non-carcinogenic effects for the oral route of intake of chlorites with drinking water from the specified water networks based on average annual data showed the value of the danger coefficient (HQ) at the level of 0.24-0.38, that is, it was lower than 1.0. The danger coefficient for chlorite content in drinking water was also determined at the level of 0.2 mg/dm3 and 0.7 mg/dm3. According to this indicator, the lifetime use of drinking water with a chlorite content of 0.2 mg/dm3 and even 0.7 mg/dm3 does not pose a threat to human health, since the danger coefficient is within 1.0, which is a permissible (acceptable) risk by degree of danger. Thus, the use of chlorine dioxide in traditional water treatment technology ensures high quality and safety of drinking water in terms of microbiological and sanitary-chemical indicators. There is a periodic (mainly in summer) excess of chlorite content in drinking water in relation to the national standard (0.2 mg/dm3), but its level was never higher than the standard recommended by WHO (0.7 mg/dm3). It has been shown that the existing levels of chlorites in drinking water and its use with such a toxic load do not pose a threat to human health.
Hygienic assessment of dangerous chlorites in drinking water treated with chlorine dioxide and the risk of its consumption to the health of the population
Today, chlorine dioxide has begun to be more widely implemented in water treatment technologies on river running water systems of Ukraine. Chlorine dioxide is used in traditional water treatment technology for both primary and secondary water treatment on the Dnipro running water system in Kyiv. Objective – to analyze the results of the content of dangerous chlorites in tap drinking water of certain districts of the city of Kyiv, and calculate and assess non-carcinogenic risk of this drinking water for human health. It was shown that in the drinking water from the running water networks of Svyatoshynskyi, Shevchenkivskyi, Obolonskyi and Podilskyi districts of the city, into which it enters after treatment with chlorine dioxide from the Dnipro running water system, the levels of chlorites were the lowest in winter and spring. In summer, the concentrations of chlorites in the water from the studied networks were the highest and averaged from 0.32 to 0.45 mg/dm3. In autumn, chlorites in the water from these systems were at the level of 0.22-0.28 mg/dm3. In spring (May) and especially in summer, the levels of chlorites in drinking water, according to average data, exceeded the national hygienic standard (0.2 mg/dm3) by 1.5-2 times, but they were never higher than the chlorite standard (0.7 mg/dm3) recommended by WHO. Our analysis of sanitary-chemical and microbiological indicators in drinking water showed that the water is characterized by high quality and safety during the entire period of observation. The risk assessment of the development of non-carcinogenic effects for the oral route of intake of chlorites with drinking water from the specified water networks based on average annual data showed the value of the danger coefficient (HQ) at the level of 0.24-0.38, that is, it was lower than 1.0. The danger coefficient for chlorite content in drinking water was also determined at the level of 0.2 mg/dm3 and 0.7 mg/dm3. According to this indicator, the lifetime use of drinking water with a chlorite content of 0.2 mg/dm3 and even 0.7 mg/dm3 does not pose a threat to human health, since the danger coefficient is within 1.0, which is a permissible (acceptable) risk by degree of danger. Thus, the use of chlorine dioxide in traditional water treatment technology ensures high quality and safety of drinking water in terms of microbiological and sanitary-chemical indicators. There is a periodic (mainly in summer) excess of chlorite content in drinking water in relation to the national standard (0.2 mg/dm3), but its level was never higher than the standard recommended by WHO (0.7 mg/dm3). It has been shown that the existing levels of chlorites in drinking water and its use with such a toxic load do not pose a threat to human health.
Hazardous chlorites in drinking water: formation and removal when using chlorine dioxide in water treatment technology
The aim of the work was to study the features of the formation and removal of toxic chlorites at the treatment facilities of the Dnipro water pipeline in Kiev, where chlorine dioxide is used in water treatment technology, and the influence of priority natural and technological factors on these processes. Materials and methods. The studies were carried out in 2021-2022. at the Dnipro waterworks in Kyiv, where chlorine dioxide is used instead of chlorine in water treatment technology. We have analyzed the data of water studies for the content of dioxide and chlorites, carried out at the treatment facilities by the laboratory of the Dnipro water pipeline in order to establish the features of the formation and efficiency of chlorite removal when using the applied water treatment technology. Also, selective studies of chlorine dioxide and chlorites in the water supply were carried out by titrimetric and photometric methods, the results of which coincide with the data obtained on the water supply using the ion chromatography method. Main results. A positive hygienic assessment of the modern new technology for the preparation of drinking water from surface sources using chlorine dioxide instead of chlorine gas is given. It is shown that with high purifying and disinfecting effects of water treatment with chlorine dioxide, its by-products, in particular, toxic chlorites, are constantly formed in it, the levels of which are directly dependent on the doses of chlorine dioxide used, which vary according to the seasons of the year. In general, the primary dose of chlorine dioxide and chlorites in the water after CWR, entering the water supply networks, is reduced by 89.3-92.0% for chlorine dioxide, and by 76.2-85.6% for chlorites. At the same time, the concentration of chlorine dioxide in disinfected water is always within the normal range - at least 0.1 mg / dm3, and chlorites often exceed the national hygienic standard (0.2 mg / dm3), but does not go beyond the standard recommended by WHO (0.7 mg/dm3). The highest concentrations of chlorites are formed in water in summer (on average 0.35 mg/dm3) in accordance with the increased doses of chlorine dioxide during this period (on average 2.51 mg/dm3), and the lowest in winter (on average 0.17 mg/dm3). Conclusions. As a result of the study, it was found that the process of treating natural water with chlorine dioxide is accompanied by the formation of its by-products in water, mainly toxic chlorites, the levels of which depend on the doses of chlorine dioxide used and are the lowest in winter and the highest in summer. After coagulation treatment of the source water with aluminum sulfate and ferric chloride (ratio 10:4-5), settling and filtering the level of chlorites in water (LCW) is intensively reduced, but not always reach the standard values. In summer, the maximum levels of chlorites in water with LCW can be higher than the national hygienic standard (0.2 mg/dm3) and range up to 0.7 mg/dm3, which corresponds to the WHO recommended standard for this substance in drinking water. The issue of revising the national standard for chlorites in water from 0.2 mg/dm3 to 0.7 mg/dm3 after appropriate scientific justification is being raised.
Study of the content of chlorites in chlorine dioxide-treated Dniprovo drinking water and assessment of their danger to the health of water consumers
The purpose of the study: analysis of the content of chlorine dioxide and chlorites in drinking water, which enters the water supply networks of certain districts of Kyiv from the Dnipro water supply, and assessment of the non-carcinogenic risk from its consumption for the health of water consumers. Research materials and methods. An analysis of three-year (2021-2023) studies of the quality of drinking water, including the content of chlorites treated with chlorine dioxide, was performed. Which comes from the Dnipro water pipeline in Kyiv to the distribution networks of Podуlskyi, Svyatoshynskyi and Shevchenkуvskyi districts. Testing of tap water for chlorite content was carried out by the laboratory of «Kyivvodokanal» and the selective water laboratory of the Institute. Determination of chlorites was carried out on an ion chromatograph and titrimetric method according to Yu.Yu. Lurie. The non-carcinogenic health risk from drinking water with different levels of toxic chlorites was calculated according to the Guidelines of the International Agency for Research on Cancer (IARC). Research methods: statistical evaluation of factual and analytical material. The results. Research (2021-2023) has established that the use of chlorine dioxide instead of chlorine in concentrations 1,0-3,0 mg/l on the Dnipro water supply system in Kyiv in the traditional water treatment technology is accompanied by a decrease in the oxidant level and the formation of dangerous chlorites in drinking water, the number of which changes according to the seasons of the year. The content of chlorites in drinking water from the distribution networks of Podуlskуі, Svyatoshynskуі and Shevchenkуvskyі districts is a mirror image of their levels in water from the pure water tank of the Dnipro water supply system, which are subject to seasonal dose-time dependence. In winter, they are 0,17-0,39 mg/l, and in summer – 0,32-0,59 mg/l, which exceeds the national standard (0,2 mg/l), especially in summer from 1,5 up to 2,5-3 times. During the observation period, residual concentrations of chlorine dioxide in drinking water from networks were mostly within the standard (≤0,1 mg/l) or slightly exceeded it in individual samples. According to microbiological and sanitary-chemical indicators, the water met the sanitary requirements for tap water. In connection with the excess of chlorite content in drinking water for different levels from 0,2 mg/l (Ukrainian standard) to 0,7 mg/l (WHO standard), a non-carcinogenic risk to human health was calculated and assessed. It is shown that within these values of chlorites in drinking water, the hazard ratio (HQ) does not exceed 1,0, which characterizes it as permissible (acceptable), which does not pose a threat to human health. Conclusions. It is shown that the use of chlorine dioxide instead of chlorine in water treatment technology ensures the required quality of drinking water in terms of microbiological and sanitary-chemical indicators. But at the same time, dangerous chlorites are formed in it in concentrations ranging from normative to over-normative. A non-carcinogenic risk assessment for water levels of chlorites from 0,2 mg/l to 0,7 mg/l, according to the hazard ratio (HQ), showed that within these limits, chlorites in water do not pose a threat to human health. We raise a question before the Ministry of Health of Ukraine about the feasibility of changing the national standard for chlorites in drinking water from 0,2 mg/l to 0,7 mg/l.
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