Study of Sources of Drinking Water and Processes of Water’s Purification from Pollutants

Abstract

This chapter presents an analysis of the sensory, physical-chemical, and microbiological aspects of water samples from drinking water sources in Azerbaijan. In the investigation, the presence of heavy metals, trace natural radionuclides, and other inorganic components is assessed. Results show that the chemical composition and microbiological parameters of waters transported to Baku, Azerbaijan through the Shollar and Oguz-Gabala pipelines comply with GOST 2874-82, AZS 216-2006, and AZS 282-2007 standards for drinking water, making them suitable for consumption. The study also found that the radioactive radon concentration in the thermal springs of the Istisu sanatorium in the Kalbajar region of Azerbaijan falls below the guideline indicator, rendering the springs safe for medical use under physician supervision. However, the radon levels in cold and thermal springs situated at an altitude of 2385 m above sea level exceed the recommended threshold by 100 times, making them unfit for drinking. The study also investigated the polluted water of the Araz River as well as measured background radiation along its watercourse. Finally, the study determined the optimal parameters for the chemical and radiological purification of water contaminated with harmful emissions and pathogenic microorganisms. This chapter also delves into the mechanisms underlying chemical and radiation-chemical processes involved in purifying polluted water.

1. Introduction

In 2015, we began carrying out sensory, chemical, physical-chemical, and microbiological analyses of water samples taken from polluted sources of water in Azerbaijan to study the degree of pollution of water reservoirs in the country. Determining the amounts of pollutants in water sources and methods for purification of contaminated water is important for preventing pollution of human habitats [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14].

Ensuring a consistent supply of safe drinking water to people worldwide is one of the most pressing challenges of our time. The escalating ecological crisis, exacerbated by human activities, underscores the critical need to safeguard our natural habitats and resources, particularly drinking water sources. It is imperative that we address these challenges promptly and efficiently to ensure the sustainable and economical utilization of these vital resources [13, 14, 15, 16, 17, 18].

The problem of providing drinking water to large cities in Azerbaijan was solved by using the flow of two large intercrossing rivers: Kur and Araz [14, 16]. The provision of drinking water to Baku, a city housing a significant portion of the country’s population, has always been a focal point. However, relying solely on the water flow from the Sabirabad district into the Caspian Sea in the Neftchala region proved insufficient to meet the agricultural and drinking water needs of the country. To tap into alternative underground water sources, the Shollar drinking water pipeline was constructed, spanning from the Khachmaz district to Baku. Though operational since the early twentieth century, this pipeline struggled to keep up with the city’s growing demand. In response, the Oguz-Gabala drinking water pipeline was completed at the beginning of the twenty-first century.

Today, the Jeyranbatan, Shollar, and Oguz-Gabala water pipelines supply drinking water to all areas within the city of Baku. Additionally, modern drinking water treatment facilities meeting contemporary standards, along with the Hovsan aeration station for wastewater treatment, have been established and are operational in the city.

Addressing ecological safety concerns surrounding agricultural products involves studying the accumulation of toxic elements in water, soil, and vegetation. The accumulation of harmful substances in the soil poses a risk of these elements migrating into the human body through water pathways [14, 15, 16].

The pollution of soil and major rivers in the country by anthropogenic emissions contributes to the increase in xenobiotic levels in the environment. This increasing technogenic pressure on natural habitats, coupled with the utilization of natural reserves, has led to critical ecological conditions. Therefore, there is a pressing need to conduct radiological, chemical, and biological analyses to gather objective data about the state of the environment, which allows for predicting trends in the occurrence of environmental crises.

Electron accelerators, as well as radioactive sources such as Co60, have proven effective in diverse applications within radiation-chemical technology, including in the purification and disinfection of water sources contaminated by anthropogenic emissions [1, 4, 5, 16].

Our investigation of pollution levels caused by anthropogenic organic and inorganic emissions (xenobiotics) in one of Azerbaijan’s major rivers yielded valuable insights that offer opportunities for strategizing preventive and regulatory measures, as well as implementing chemical and radiological purification and disinfection processes for water treatment.

2. Methodical part and discussion of results

2.1 Instruments and methods for analysis

For radiometric measurements and analysis of water samples, we used İnSpector 1000 and Radiagem 2000 radiometers, a gamma spectrometer featuring an HPGe detector from Canberra, and the identiFİNDER radionuclide identification device (RID) from Thermo Scientific. Additionally, we conducted atomic absorption using the AA-6800 spectrometer by Shimadzu. We also used Expert-3 L and XRF X-ray fluorescence spectrometers [14, 15, 16, 17, 18, 19, 20, 21].

We carried out microbiological analyses by growing colonies of microorganisms on selective standard nutrient media and microbiological tests from HiMedia in India, Condalab in Spain, and R-Biopharm in Germany [7, 8, 9, 10, 14, 16].

We determined components in solutions using physical-chemical methods, such as liquid chromatography, gas chromatography, and mass spectroscopy (LC-10AVP, GC-2010, GCMS-QP 2010).

We used traditional analytical-chemical and modern research physical-chemical methods to identify and determine the quantity of reactants and organic and inorganic (harmful chemicals, heavy metals, radionuclides) emissions.

We used presterilized dishes for water sampling, which was carried out in accordance with the requirements of GOST 24481-80 and 18968-73, as were transportation and storage of the samples.

Express analyses with microbiological test napkins and sensory assays were carried out in all possible cases.

We conducted the comprehensive sensory, analytical-chemical, physical-chemical, and bacteriological analyses in accordance with the requirements of GOST standards 2761-84, 3351-74, 2874-82, 18164-72, 4151-72, 4011-72, 4245-72, 4386-81, 18963-73, 4595-49, 18826-73, and 18190-72 to determine the conformity of water samples to standards for drinking water (GOST 2874-82, AZS 216-2006, AZS 282-2007) [14, 16].

We used the AlphaGUARD professional radon monitor (Frankfurt, Germany) to determine levels of radioactive radon in the investigated water sources. The radioactive radon gas was carried into the ionization chamber of the measuring device by bubbling 3 liters of atmospheric air from the water sample for 10 minutes [6].

Analytical-chemical and physical-chemical laboratory installations and equipment were used for conducting comprehensive analyses of the water and its minerals.

We measured the energy of ionizing rays or particles using a detector and this measured energy value was then used to identify the specific element or its isotope that emits these rays or particles.

We used LDZH-30FBS and Tengor steam sterilizers to sterilize chemical glassware and glass jars for water sampling.

The GFL-2304 distiller produced double-distilled water for rinsing chemical glassware and for making solutions.

We used TDL-5 M and TD5A-WS centrifuges for centrifugation and sedimentation of solid impurities in water samples in ampoules with different volumes. Membrane filters were used to isolate solid impurities from water samples and for accelerated filtration.

The surfaces and structure of water minerals were comprehensively examined and studied under a scanning electron microscope (SEM, Carl Zeiss) at various magnifications. X-ray spectra and the composition of the content of chemical elements in the studied water minerals were obtained using an additional stand for the SEM equipped with an X-ray tube.

Weighing obtained by evaporation of water samples of mineral masses was carried out on a laboratory electronic balance. Active reactions of aqueous samples were determined by universal indicator tests and pH meters. Evaporation of aqueous samples from laboratory heat-resistant glass beakers was carried out on laboratory tiles.

To determine the types and number of colonies of microorganisms in water samples, we used both express test napkins and nutrient media. Nutrient media were applied in a thin layer on the inner surface of Petri dishes stored in a thermostat for the reproduction of bacterial colonies for 1 day at 37°C and for the reproduction of microscopic fungi colonies for 2 days at 28°C. After this time, the total number of colonies formed was determined by multiplying the total number of cells of colony counter by the number of colonies per cell. A detailed description of the rules for carrying out these procedures is given in the instructions of these test napkins and nutrient media.

Irradiation of water samples was carried out at radiation research facilities (absorbed dose rate 0.0045, 0.18 Gy/s or 2.81 ∙ 10¹³, 1.12 ∙ 10¹⁵ eV/g s) [16, 17, 18, 19, 20, 21, 22].

2.2 Discussion of results

In this study, we determined the mineral content of water taken from reservoirs, rivers, springs, and water pipes. The conducted analyses show that the mineral balance of the water samples varies in the range of 0.3–3.5 g/l. Tables 1 and 2 present the results of the water sample analysis.

Regions	Соmponents, mg/l
	Sulfates	Chlorides	Na; K	Ca/all carbonates/	J	Sr	NO3; NO2	Fe; Mn	Zn	As
Khachmaz/water of spring/	24	22	19; 11	138	0.04	0.6	3; 0.001	0.2; 0.2	0.01	0
Quba/Qudiyal River/	42	35	25; 12	96	0.05	0.4	4; 0	0.2; 0.03	0.1	0.001

Table 1.

Concentrations of the chemical components in samples taken from water sources of the Azerbaijan regions.

Regions	Isotopes, Bq/l
	11Na^22	19K^40	26Fe^60	27Co^57	30Zn^65	38Sr^91	50Sn^113, 50Sn^126	63Eu^152, 63Eu^154	88Ra^226	90Th^228
Khachmaz/water of spring/	0.4	0.12	0.24	0.24	0.05	0.22	0.04; 0.1	0.16; 0.2	0.24	0.03
Quba /Qudiyal River/	0.5	0.16	0.24	0.26	0.05	0.08	0.06; 0.06	0.12; 0.12	0.24	0.02

Table 2.

Activity of radionuclides in water samples taken from the water sources of region of the Azerbaijan.

When contaminated water is exposed to gamma rays and supplemented with small wood chips, water molecules and organic waste break down into active particles and physical and chemical sorption takes place. This entails the adhesion of molecules and active particles onto the surface of the chips, enhancing the purification process. Table 3 shows the mechanism of this process [15, 17, 18, 19, 20, 21, 22].

Table 3.

Comparison of the rates of elementary reactions for radiolysis of oxygen-containing water contaminated with organic substances, oil products (RH, ROH) in volume to which was added the mass of cut wood chips.

The elementary reactions (4), (5), (8), (9), (11), (12), (17), (22), (23), (24), (28), (29), (33), and (34) are the chain termination reactions. Reactions (7), (8), (9), (11), (17), (20), (21), (22), (23), and (24) are reactions for the formation of new products of the process. Reactions (1) and (2) are initiation reactions of the process.

Table 3 clearly shows that the macroradicals formed by ionizing rays on the surface of wood chips (RH, R) are actively involved in fast reactions 10, 11, and 14.

The principal reactions in the radiation-induced conversion of organic waste in water solutions involve the generation of hydroxyl-substituted derivatives and the formation of products resulting from the mutual recombination of organic peroxides, linked by an oxygen bridge. In the presence of small chips, the hydroxyl-substituted and peroxide radicals of organic compounds interact with other hydroxyl-substituted radicals and macro radicals present on the surface of the chips.

The notable increase in the weight of removed organic waste during reservoir irradiation suggests chemical sorption, in addition to physical adsorption, occurring on the surface of wood chips. This dual sorption effect holds promise for enhancing water purification processes aimed at removing oil products and phenol.

After centrifugation, filtration, and evaporation of different samples of drinking water, it was determined that the compositions of the obtained mineral residues are not identical. Table 4 presents the results of the organoleptic, physical-chemical, and microbiological analyses of drinking water samples.

№	Parameters	Requirement of standards (2874-82, АZS216-2006)	Factual data
1	2	3	4	5	6	7	8	9
1.	Transparency, sm	>30*	>30*	>30*
		>10**			>30	>30	>30	>30
2.	Turbidity, °	≤1.5	0	0	0	0	0	0
3.	Sediment	0 or traces	0	0	0	0	0	0
4.	Сolor, °	≤20*	0	0
		≤40**			0	0	0	0
5.	Smell, in points at 20°C	≤2*	0	0
		≤3**			1	0	1	0
6.	Taste and flavors, in points at 20°C	≤2*	0	0
		≤2**			1	0	1	0
7.	Active reaction (pH)	6.0–9.0	6.9	6.8	7.7	7.6	7.6 (7.7)	7.6
8.	Dry residue, mg/l	100–1000*	350	450
		>1000***			950	370	470 (800)	570
9.	Total rigidity, mg-ekv/l	7.0*	2.9	3.7	8.7	3.1	4.1 (7.1)	5.0
10.	Disposable rigidity, mg-ekv /l	<7*	0.8	1.0
		Not standardized**			2.5	1.2	2.3	1.4
11.	Zn, mg/l	5	0.2	0.01	0	0	0	0
12.	Phenol, mg/l	0.001	0	0	0	0	0	0
13.	Sulfide, mg/l	0.05	0	0	0	0	0	0
14.	I, mg/l	0.001–0.05*	0.05	0.04
15.	Residual chlorine, mg/l	0–0.5*	0.01	0.01	0	0	0	0
16.	Chlorides, mg/l	350*	18	20	90	33	78 (90)	80
17.	Nitrates, mg/l	45*	4.5	2.0	7.0	4.5	5 (7)	2
18	Cd, mg/l	0*	0	0	0	0	0	0
19	As, mg/l	0.05*	0	0	0.003	0	0	0
20	Fe, mg/l	0.3*	0.14	0.2
		1**			0.01	0.01	0.01	0.01
21	Pb, mg/l	0.03*	0	0	0	0	0	0
22	Hg, mg/l	0*; 0.001**	0	0	0	0	0	0
23	Nitrites, mg/l	0–0.1*	0	0
		0.1**			0.3	0.05	0.05 (0.07)	0.02
24	Sulfates, mg/l	500*	10	33	155	40	111 (148)	50
25	Ecoli number, in 1 liter	≤3*	1	1
		≤9**			30–40	14–19	22 (35)	15
26	Coli-titr, quantity water in ml wherein found E. coli	>300*	1000	1000
		>100**			30	67	50 (30)	67
27	Pathogens (Salmonella, Yersinia), in 1 liter	0*	0	0	6–10 (Salm.)	0 (Salm.)	1 (3) (Salm.)	1 (Salm.)
28	Vibrio cholerae, in 1 liter	0*	0	0	0	0	0	0

Table 4.

The results of the analysis of water samples taken from the Araz and Kur Rivers before and after their discharge into a single stream (in the Sabirabad region) and from the old and new water supply systems supplying residential areas of Baku with “Shollar” and “Oguz-Gabala” drinking water.

^*

Standard for drinking water [14, 16].

^**

Water for technical use [14, 16].

Note: 4—water taken from the water pipeline, supplying the city of Baku with “Oguz-Gabala” drinking water; 5—water taken from the water pipeline, supplying the city of B aku with “Shollar” drinking water; 6—water taken from Araz River at the crossing of the Beylagan district’s territory; 7—water taken from Kur River at the crossing of the Mingaçevir district; 8—water taken from of Rivers stream on the Suqovushan village after intercrossing Kur and Araz Rivers: sample taken from surface part of stream; (sample taken from bottom part of stream); 9—water taken from of Rivers stream after intercrossing (1 km) of Kur and Araz Rivers.

2.2.1 Shollar drinking water

As shown in Table 4, the total salinity of the Shollar drinking water is 450 mg/l. Of this amount, sulfates account for 23–33 mg/l is sulfates, chlorides account for 20 mg/l, calcium carbonates accounts for 142 mg/l, nitrates account for 2 mg/l, and nitrite compounds amount to practically zero.

The samples of Shollar drinking water are characterized by the same indicator, with the following trace element concentrations: Na 18 mg/l, K 10 mg/l, I 0.04 mg/l, Sr 0.4 mg/l, Fe 0.2 mg/l, Mn 0.1 mg/l, Zn 0.01 mg/l, and As 0 mg/l.

The Shollar drinking water samples exhibited consistent trace amounts of radionuclides, with the following concentrations:

• ₁₁Na²²: 0.30 Bq/l

• ₁₉K⁴⁰: 0.10 Bq/l

• ₂₆Fe⁶⁰: 0.14 Bq/l

• ₂₇Co⁵⁷: 0.12 Bq/l

• ₃₀Zn⁶⁵: 0.05 Bq/l

• ₃₈Sr⁹¹: 0.12 Bq/l

• ₆₃Eu^152,154: 0.12 Bq/l

• ₈₈Ra²²⁶: 0.12 Bq/l

2.2.2 Oguz-Gabala drinking water

As also shown in Table 4, the total salinity of the Oguz-Gabala drinking water is 350 mg/l. Of this amount, sulfates account for 10–24 mg/l, chlorides account for 18–19 mg/l, calcium carbonates account for 76 mg/l, nitrates account for 1.3–4.5 mg/l, and nitrites account for 0–0.01 mg/l.

The samples of Oguz-Gabala drinking water are characterized by the same indicator, with the following trace element concentrations: Na 20 mg/l, K 10 mg/l, I 0.05 mg/l, Sr 0.9 mg/l, Fe 0.14 mg/l, Mn 0.03 mg/l, Zn 0.16 mg/l, and As 0.001 mg/l.

The Oguz-Gabala drinking water samples exhibited consistent trace amounts of radionuclides, with the following concentrations:

• ₁₁Na²²: 1.0 Bq/l

• ₁₉K⁴⁰: 0.15 Bq/l

• ₂₆Fe⁶⁰: 0.48 Bq/l

• ₂₇Co⁵⁷: 0.28 Bq/l

• ₃₀Zn⁶⁵: 0.05 Bq/l

• ₃₈Sr⁹¹: 0.16 Bq/l

• ₆₃Eu^152,154: 0.2 Bq/l (each)

• ₈₈Ra²²⁶: 0.28 Bq/l

2.2.3 Kur River water

Table 4 also shows the total salinity of Kur River water, which is 370 mg/l. Of this amount, sulfates account for 40 mg/l, chlorides account for 33 mg/l, calcium carbonates account for 165 mg/l, nitrates account for 4.5 mg/l, and nitrite compounds account for 0–0.05 mg/l.

The samples of Kur River water are characterized by the same indicator, with the following trace element concentrations: Na 20 mg/l, K 8 mg/l, I 0.02 mg/l, Sr 1.1 mg/l, Fe 0.01 mg/l, Mn 0 mg/l, Zn 0 mg/l, and As 0 mg/l.

The Kur River water samples exhibited consistent trace amounts of radionuclides, with the following concentrations:

• ₁₁Na²² 0.48 Bq/l

• ₁₉K⁴⁰ 0.16 Bq/l

• ₂₆Fe⁶⁰ 0.24 Bq/l

• ₂₇Co⁵⁷ 0.16 Bq/l

• ₃₀Zn⁶⁵ 0.02 Bq/l

• ₃₈Sr⁹¹ 0.08 Bq/l

• ₆₃Eu^152,154 0.15, 0.12 Bq/l

• ₈₈Ra²²⁶ 0.12 Bq/l

2.2.4 Araz River water

As shown in Table 4, the total salinity of the Araz River water is 950 mg/l. Of this amount, sulfates account for 155 mg/l, chlorides account for 55–90 mg/l, calcium carbonates account for 540 mg/l, nitrates account for 7.0 mg/l, and nitrite compounds account for 0.3 mg/l.

The samples of Araz River water are characterized by the same indicator, with the following trace element concentrations: Na 38 mg/l, K 9 mg/l, I 0.02 mg/l, Sr 4 mg/l, Fe 0.01 mg/l, Mn 0.1 mg/l, Zn 0 mg/l, and As 0.003 mg/l.

The samples of Araz River water exhibited consistent trace amounts of radionuclides, with the following concentrations:

• ₁₁Na²² 0.50 Bq/l

• ₁₉K⁴⁰ 0.22 Bq/l

• ₂₆Fe⁶⁰ 0.21 Bq/l

• ₂₇Co⁵⁷ 0.38 Bq/l

• ₃₀Zn⁶⁵ 0.04 Bq/l

• ₃₈Sr⁹¹ 0.2 Bq/l

• ₆₃Eu^152,154 0.2, 0.2 Bq/l

• ₈₈Ra²²⁶ 0.3 Bq/l

The results of the complex organoleptic, physical-chemical, and microbiological analyses show that the waters of the Araz and Kura Rivers, without special treatment, are not potable.

However, the chemical composition and microbiological indicators of the waters transported to Baku through the Shollar and Oguz-Gabala pipelines are in accordance with the requirements of drinking water standards GOST 2874-82, AZS 216-2006, and AZS 282-2007. The pathogenic bacteria Salmonella, Yersinia, and Cholera vibrio are absent in these samples and the amount of the bacteria Escherichia coli in these samples is less than the permissible amount in drinking water; thus, these waters are drinkable.

The concentration of radioactive radon in the thermal springs in the foothills along the Dalidag mountain range of the Kalbajar region of Azerbaijan, as well as in the Lower Istisu thermal spring and in the waters of the thermal springs of the Istisu sanatorium in the Kalbajar region, is below the guideline indicator (60 Bq/l). As such, these waters are suitable for use in medical procedures.

The concentration of radioactive radon in the waters of cold and thermal springs located at an altitude of 2385 m above sea level in the western territories of the region exceeds the directive indicator by 100 times, and thus, these waters are undrinkable.

Table 5 lists concentrations of chemical trace elements determined by analytic-chemical and physical-chemical analyses in soil samples taken from the surrounding Araz River’s landscape in Nakhchivan city, Sadarak and Ordubad regions of the Nakhchivan Autonomous Republic (AR), and the Beylagan district.

№	Trace elements	In the soil of the Sadarak region, mq/kq	In the soil of the Nakhchivan sity, mq/kq	In the soil of the Ordubad region, mq/kq	In the soil of the Beylagan district, mq/kq
1.	Sulfates	1440	148	180	113
2.	Chlorides	260	106	127	111
3.	Na; K	220; 120	207; 109	193; 500	35; 71
4.	CaCO3	6587	707	1408	920
5.	Br	0.2	0.02	0.05	0.02
6.	Sr	18	12	10	8
7.	Ti; Zr	0; 0	0.1; 0.1	0.2; 0.1	0; 0.03
8.	Fe; P	5.7; 0.7	3.4; 0.1	5.5; 0.3	1.7; 0.05
9.	Zn	0.05	0.02	0.05	0.02
10.	As	0.03	0.005	0.005	0.004

Table 5.

Concentrations of trace elements in soil samples taken from the surrounding Araz landscape.

Table 6 lists concentrations of chemical trace elements determined by analytic-chemical and physical-chemical analyses in vegetation samples (trees, leaves, and small branches of bushes, flowers, and grass) taken from the surrounding Araz River’s landscape in Nakhchivan city, Sadarak and Ordubad regions of the Nakhchivan AR, and the Beylagan district.

№	Trace elements	In the soil of the Sadarak region, mq/kq	In the soil of the Nakhchivan sity, mq/kq	In the soil of the Ordubad region, mq/kq	In the soil of the Beylagan district, mq/kq
1.	Sulfates	477	366	380	342
2.	K	6462	5567	9075	5885
3.	Ca	7645	933	1675	1755
4.	Sr	104	97	93	90
5.	Ti; Zr	0.1; 0	0.1; 0.1	0.2; 0.1	0.1; 0.03
6	Fe; P	14; 1.7	8; 0.7	1; 0.9	3; 0.4
7.	Zn	1.1	0.6	1.1	0.6
8.	As	0.007	0	0	0
9.	Mn	18	6.7	15	14

Table 6.

Concentrations of trace elements in vegetation taken from the surrounding Araz River landscape.

The radioactive background and the types of radioactive radiation were detected in the territory of the Nakhchivan AR and the degree of contamination with radionuclides of the Araz River along the territory of the Azerbaijan was determined.

Alpha and beta radiation were not detected from water samples taken from the Araz River.

The measured dose rate from the natural radioactive background (soil) varies in the range of 0.03–0.08 μSv/h (the maximum permissible value is 0.12 μSv/h), and the alpha radiation intensity is within 0–0.11 Bq_eq/sm².

The measured dose rate from the natural radioactive background detected in the surrounding Araz River’s landscape in the territory of the Beylagan and İmishli regions varies in the range of 0.03–0.04 μSv/h and the alpha radiation intensity is 0 Bq_eq/sm².

The activity (radiation intensity) of Na²² and K⁴⁰ isotopes in the water of the Araz River flowing through the territory of the Nakhchivan AR is 0.54 and 0.40 Bq/l, respectively.

The activity of Na²² and K⁴⁰ isotopes in the water of the Araz River flowing through the territory of the Beylagan-İmishli regions is 0.35 and 0.20 Bq/l, respectively.

For comparison, the concentration of the Na²² isotope (radiation intensity) in the samples of drinking water supplied to enterprises and the population in the cities of Nakhchivan and Baku, respectively, is 0.32 Bq/l and 0.28 Bq/l. Similarly, the concentration of the K40 isotope is 0.18 Bq/l and 0.16 Bq/l, respectively.

Additionally, the dose rate of gamma radiation in the natural radioactive background in these cities varies, with intervals of 0.04–0.07 μSv/h for Nakhchivan and 0.01–0.04 μSv/h for Baku. The intensity of alpha radiation also varies, with intervals of 0–0.01 Bq_eq/sm² for Nakhchivan and 0–0.04 Bq_eq/sm² for Baku.

The results of microbiological analyses, as presented in Table 7, indicate that the count of pathogenic microorganisms in each liter of water samples taken from the Araz River at the crossing of the Sadarak region of the Nakhchivan AR exceeds the maximum permissible norm. However, at the intersection of the Ordubad region, there is a significant reduction in the microorganism count in the water of the Araz River. Conversely, in the territory of the Beylagan region, the count of pathogenic microorganisms is observed to increase. This suggests that pollution of the Araz River occurs at the intermediate area situated between Ordubad and Beylagan.

№	Parameters	Requirements of standards (2874-82)	Actual results
1	2	3	4	5	6	7	8
1.	Transparency, sm	>30*	>30*
		>10**	—	>30	>30	>30	>30
2.	Turbidity, °	≤1.5	0	0	0	0	0
3.	Sludge	0 or traces	0	0	0	0	0
4.	Color, °	≤20*	0	0	0	0	0
1	2	3	4	5	6	7	8
5.	Odors, at 20°С, points	≤2*	0	1–2	1–2	1	1
		≤3**
1	2	3	4	5	6	7	8
6.	Tastes, at 20°С points	≤2*	0	2	2	1	1
		≤2**
7.	Activity (pH)	6.0–9.0	6.8	7.1	7.2	7.2	7.7
8.	Dry residue, mg/l	100–1000*	166	1645	1495	595	950
9.	Total hardness, mg-eq/l	7.0*	1.6	15	14	5.4	8.7
10.	Hydrocarbonate hardness, mg-eq/l	<7*	—	—	—	—	—
		Are not standardized**	0.7	7.1	6.7	1.4	2.5
11.	Zinc, mg/l	5	0	0.01	0	0.01	0
12.	Phenol, mg/l	0.001	0	0	0	0	0
13.	Sulfides, mg/l	0.05	0	0	0.01	0	0
14.	Iodine, (bromine), mg/l	0.001–0. standardized**	0.02 (Br)	0.15 (Br)	0.2 (Br)	0.05 (Br)	0.02 (Br)
15.	Residual chlorine, mg/l	0–0.5*	0–0.01	0	0	0	0
16.	Chlorides, mg/l	350*	36	55	238	90	90
17.	Nitrates, mg/l	45*	4.4	12.8	4.4	3.4	4.9
18	Cadmium, mg/l	0*	0	0	0	0	0
19	Silver, mq/l	Are not standardized**	0	0-0.01	0	0	0
20	Strontium, mg/l	7.0*	0.7	9	2.5	2.3	7
21	Arsenic, mg/l	0.05*	0	0.005	0.005	0.005	0.003
22	İron, mg/l	0.3*; 1**	0.2	0.2	1.0	1.0	0.01
23	Lead, mg/l	0.03*	0	0	0	0	0
24	Mercury, mg/l	0*; 0.001**	0	0	0	0	0
25	Nitrites, mg/l	0–0.1*; 0.1**	0.05	0.1	0.2	0.1	0.3
26	Sulfates, mg/l	500	18	318	230	68	155
1	2	3	4	5	6	7	8
27	Na, K, W, mg/l	Are not standardized**	23; 9; 0.03	56; 12; 0.1	54; 18; 0.1	58; 22; 0.05	38; 9; 0
28	E.coli, the number of bacteria in 1 l	≤3*; ≤9**	3; 3	20–26	82–90	20	30–40
29	Coli-titr, amount of water in which 1 bacterium was detected, ml	>300*; >100**	333; 333	50–40	12–10	50	30
30	The amount of Saprophytic microorganisms in 1 ml	100*	0	8	10	6	10
	Аspergillus (in 1 ml)		0	0	1	0	0-1
	Сandida al. (in 1 ml)		0	6-8	8-9	6	6-9
31	Staphylococcus, Strept., (in 1 1);	0	0 (Staur),; 0 (Stepid)	0 (Staur),; 16 (Stepid)	30 (Staur),; 42 (Stepid)	0–1 (Staur),; 7–8 (Stepid)	8 (Staur), 20(Stepid)
32	Pathogenic microorganisms, including Salmonella (in 1 l)	0	0	0–1	10–13	3–6	6–10

Table 7.

The results of organoleptic, analytical-chemical, physico-chemical and microbiological analyzes of water samples taken from the Araz River in the Beylagan district, in the territories of the Sadarak and Ordubad districts of the Nakhchivan AR and drinking water samples, supplied to enterprises and population of the city of Nakhchivan.

*

Standard for drinking water.

**

Spring water and water for technical use.

Notes: 4—water taken from the water pipeline, supplying the city of Nakhchivan and its population with drinking water; 5—water taken from Araz river at the crossing of the Sadarak region of the Nakhchivan Autonomous Republic with the borders of Turkey and Armenia; 6—water taken from Araz river at the territory of the Sadarak region after the Customs Transition Gate; 7—water taken from Araz river at the intersection of the territory of the Ordubad region with the borders of the IİR and Armenia; 8—water taken from Araz river at the crossing of the Beylagan district’s territory.

The results of analytic-chemical, physical-chemical, and microbiological analyses show contamination by organic and inorganic emissions of the Araz River when it reaches the territory of the Sadarak region and its further contamination through parts of the territory of neighboring countries located between the Ordubad region of Nakhchivan AR and Beylagan district.

In addition to the increased number of microorganisms, the concentration of chlorides and other halides, nitrites, sulfides, and alkaline-underground metals in the water of the Araz River in the Sadarak region is also relatively increased up to the permissible limits.

The results of the chemical and physical-chemical analyses presented in Table 7 show that total quantity of inorganic substances in water samples taken from Araz River at the crossing of the Sadarak region of the Nakhchivan AR is three times greater than the maximum permissible limit for drinking water. The total quantity of inorganic compounds decreases along the path of the river to the Ordubad region, naturally diminishing by a factor of 3 due to partial adsorption on silt soils. However, in the Beylagan-Imishli territory, it increases again by 50%. Upon entering the Sadarak region, the concentration of strontium (Sr88) in the river water exceeds the maximum permissible norm by 30%. This concentration naturally decreases along the path of the river to the Ordubad region, due to partial adsorption on the silt soils, reducing by 3–4 times. However, in the Beylagan-Imishli territory, it increases again by 2–3 times.

Moreover, the relative amounts of sulfates and nitrates decline from Sadarak to Ordubad by 4–5 times, but in the Beylagan-Imishli territory, they increase again by 2 times.

Nitrite-containing compounds were detected in the water samples taken from the Araz River, even though the probability of finding nitrite-containing compounds in current waters is generally negligible.

The formation of nitrites from nitrate-containing salts of alkaline earth metals occurs at sufficiently high temperatures (400–500):

$${\text{2KNO}}_3\mathbf{-}\mathbf{-}\mathrm{T},\mathrm{K}\to {\text{2KNO}}_2+{\mathrm{O}}_2$$E1

The disproportionation of nitrogen dioxide/nitrogen (IV) oxide/in alkaline media (reaction (2)) also occurs in water (reaction (3)):

$${\text{2NO}}_2+\text{2NaOH}\to {\text{NaNO}}_3+{\text{NaNO}}_2+{\mathrm{H}}_2\mathrm{O}$$E2

$${\text{2NO}}_2+{\mathrm{H}}_2\mathrm{O}\to {\mathrm{HNO}}_3+{\mathrm{HNO}}_2$$E3

However, the absorption of nitrogen dioxide on the surface of river water and reaction (3) proceed at low rates. Therefore, the observed excessive levels of nitrites cannot be solely explained by reaction (3). As mentioned, pollution of the Araz River by anthropogenic emissions, along with high concentrations of inorganic compounds, including chlorine-containing compounds, in the river water and chlorine-containing salts in the soil of Nakhchivan AR, indicate that the formation of nitrites in the water of the Araz River is accompanied by processes involving the mechanism of nitrite formation in chlorine-containing waters [18]:

$${\mathrm{NO}}_2+\mathrm{ClO}\to {\text{ClNO}}_3$$E4

$${\text{ClNO}}_3+{\mathrm{H}}_2\mathrm{O}\to \text{HOCl}+{\mathrm{HNO}}_3$$E5

$$\text{4Mg}\left(\mathrm{Ca}\right)+10{\mathrm{HNO}}_3/\text{slightly acidic}/\to 4\left(\mathrm{Ca}\right)\mathrm{Mg}{\left({\mathrm{NO}}_3\right)}_2+{\mathrm{N}}_2\mathrm{O}\left(\mathrm{NO}\right)+{\text{5H}}_2\mathrm{O}$$E6

$$\text{3Cu}+{\text{8HNO}}_3/\text{slightly acidic}/\to \text{3Cu}{\left({\mathrm{NO}}_3\right)}_2+{\text{2NO}}_2+{\text{4H}}_2\mathrm{O}$$E7

$${\mathrm{N}}_2\mathrm{O}+\mathrm{NO}\to {\mathrm{N}}_2+{\mathrm{NO}}_2$$E8

$${\mathrm{NO}}_2+{\mathrm{NO}}_2\to {\mathrm{N}}_2{\mathrm{O}}_4$$E9

$${\mathrm{N}}_2{\mathrm{O}}_4+{\mathrm{H}}_2\mathrm{O}\to {\mathrm{HNO}}_2+{\mathrm{HNO}}_3$$E10

$${\text{2HNO}}_2+\mathrm{Mg}{\left({\mathrm{HCO}}_3\right)}_2\to \mathrm{Mg}{\left({\mathrm{NO}}_2\right)}_2+{\text{2H}}_2{\mathrm{CO}}_3$$E11

As evident from the outlined mechanism, molecules of atmospheric nitrogen dioxide (NO₂) and ClNO₃, NO₂, N₂O₄ molecules, formed in reactions (4) and (6)-(9), react with water to produce nitric acid (HNO₃) molecules in a slightly acidic environment. Additionally, the minerals present in water contribute to the formation of nitrogen oxides through slow reactions (6) and (7).

Nitrite acid molecules, resulting from reactions (3) and (10) of nitrogen oxides with water, facilitate the formation of small concentrations of stable nitrite compounds in the water of the Araz River via reaction (11) with hydrocarbons.

The chemical composition and the sensory, physical-chemical, and microbiological characteristics of water samples taken from Araz River in Sadarak and Ordubad districts of the Nakhchivan AR and in the Beylagan-Imishli region do not meet the requirements of the GOST 2874-82, AZS 216-2006, and AZS 282-2007 standards for drinking water.

The results of experiments involving the disinfection of water samples from the Araz River using various concentrations of calcium perchlorate show that treatment with 1 mg of calcium perchlorate (a solution containing 1 mg of calcium perchlorate with 60% active chlorine in 5 ml of distilled water added to 1 liter of river water) resulted in a reduction of approximately 10% in the microorganism count after 1 hour. No residual chlorine was detected in the river water sample.

Increasing the concentration to 2 mg of calcium perchlorate led to a more significant decrease in the microorganism count, approximately by 2–3 times, after 1 hour. Similarly, no residual chlorine was observed in the river water sample.

Sterilization experiments using 5 mg of calcium perchlorate resulted in the complete elimination of microorganisms and the absence of residual chlorine after 1 hour in the river water samples.

Lastly, experiments with 10 mg of calcium perchlorate demonstrated the absence of microorganisms after 1 hour, with residual chlorine concentrations below the maximum permissible value (<0.5 mg/l) for drinking water.

Higher amounts of calcium perchlorate along with the total clearance of all microorganisms in contaminated river water leads to the accumulation of residual chlorine in quantities greater than the maximum permissible values for drinking water. The amount of calcium perchlorate in the range of 5–10 mg (optimal value) is sufficient for the total clearance of all microorganisms in contaminated water taken from Araz River and the accumulated amount of residual chlorine does not exceed the maximum permissible value.

Figure 1 shows the results of disinfection experiments involving ionizing radiation of water samples taken from the Araz River.

Figure 1.

Reducing the microorganism’s count in water samples taken from the Araz River, depending on the value of the absorbed dose of ionizing radiation.

As shown in Figure 1, the irradiation by absorbed dose 5 kGy of ionizing radiation ensures complete extermination of all microorganisms in water samples taken from the Araz River, which were contaminated with organic emissions and microorganisms.

Thus, both chemical (chlorination with perchlorates) and radiolytic (irradiation with ionizing radiation) methods of disinfection of the contaminated water of the Araz River are highly efficient methods of purification.

Based on the experimentally obtained results and considering the observed process of slow natural self-purification of water, particularly the partial adsorption of inorganic pollutants on the silt soils along the Araz River on its way to the territory of the Beylagan-Imishli region, it becomes evident that there is potential to implement deep purification of the Araz River water in Nakhchivan AR.

This can be achieved by passing the river water through a thermally regenerated and periodically updated large adsorbent sand filter after chemical or radiolytic disinfection of the river’s water. This approach would help enhance the quality of the water supply in Nakhchivan AR, ensuring safer and cleaner drinking water for the population.

3. Conclusions

In this chapter, we analyzed the sensory, physical-chemical, and microbiological properties of water samples collected from drinking water sources to determine the distributions of heavy metals, trace natural radionuclides, and other inorganic components. The chemical composition and microbiological parameters of waters transported to Baku through the Shollar and Oguz-Gabala pipelines adhere to the drinking water standards 2874-82, AZS 216-2006, and AZS 282-2007. Thus, these waters meet the criteria for safe consumption.

The radioactive radon concentration in the thermal springs of the Istisu sanatorium, located in the Kalbajar region of Azerbaijan, remains below the recommended threshold (60 Bq/l). These waters are deemed suitable for medical applications as prescribed by healthcare professionals. Conversely, the radioactive radon levels in both cold and thermal springs situated at an altitude of 2385 m above sea level in the western territories of the region exceed the directive indicator by 100 times, rendering them unsuitable for drinking.

In conjunction with measuring background radiation in adjacent areas along the Araz River watercourse, we conducted an extensive analysis of the river’s polluted water.

During the irradiation of contaminated water reservoirs, notably high values of removed petroleum products have been observed. This observation suggests the presence of chemical sorption alongside physical adsorption on the surface of wood chips added to the reservoir. This crucial phenomenon should be considered in the radiation purification of water contaminated with various organic compounds, crude oil, and phenol. Moreover, we identified the optimal parameters for chemical and radiological purification of water polluted by harmful emissions and pathogenic microorganisms. Additionally, we discussed the mechanisms of chemical and radiation-chemical processes involved in water purification.

Conflict of interest

The author declared no conflict of interest.