Influence of Urbanization and Industries on the Pollution of Rivers of Gjilan Municipality , Kosovo

Gjilan (42 ̊28’08” V, 21 ̊27’48” L) is one of the seven largest cities in Kosovo. Throughout the city flow three rivers: Mirusha and Stanishor which mix and discharge into the largest river called Morava. The reason for the research of these rivers is the extreme pollution resulting from the discharge of industrial waters. Analysis of these rivers shows that they are extremely polluted and some physicochemical parameters are not in accordance with the regulations of the European Union (EU) and the World Health Organization (WHO). Parameters analysed are: pH, CW, NTU, DO, COD, BOD5, A-HCl, HCO3, GH, CS, Cl−, Cl2, Ca2+, Mg2+, NO2, NO3, PO4, and NH3.


Introduction
The increment in the world's population and the overwhelming industrial development has made water supply a problem on our planet, thus imposing the need for rapid long-term solutions. 1Today it is acknowledged that environmental protection should be given the highest priority, because the preservation of the continuity of life depends on it.Our knowledge of the environment is increasing constantly, and we now have enough knowledge about the chemical composition of our planet and developing processes.Resources (natural resources) of land are finite, and the exploitation and contamination of its systems on the regenerative possibilities have important implications for life on it. 2Water pollution from chemical substances can be divided into two groups: inorganic and organic chemical contamination.Inorganic pollutants include: nitrates, nitrites, sulphates, heavy metals, etc. Organic pollutants include oil and its derivatives, such as soaps, detergents, textile industry effluents, paper, phenols, radioactive materials, etc. 3 Water is a substance with a number of unique properties of great environmental significance.Water quality standards have legislative support and specify the characteristics for water. 4In order to prove the quality of these rivers, physicochemical parameters were determined by international methods, as presented in the Table 1.
Alkalinity refers to the capability of water to neutralize acid.This is really an expression of buffering capacity.A buffer is a solution to which an acid can be added without changing the concentration of available H + ions (without changing the pH) appreciably.Ammonia appears in different contrition in groundwater, surface water, and wastewater.Its appearance in water and in loess is described as a result of the reduction of nitrogen-containing organic matter, deamination of amines, hydrolysis of corn, etc., where all nitrogen appears as NH 4 or NH 3 .Orthophosphates (PO 4

3−
) are soluble salts of phosphoric acid, which dissolve into tinctures in humans, depending on the pH of the environment.Orthophosphates are used as artificial fertilizers in land, which dissolve and flow into surface water.
Chlorides are anions distributed in surface water and wastewater, while their concentration in natural water varies greatly.The chloride ion (Cl − ) with appropriate oxidizing agents has a higher redox potential than chlorine (Cl 2 ). 5 The characteristic of primary importance in many water systems is the amount of dissolved oxygen (DO), which can be quickly expended by the oxidation of organic material.In addition, the oxygen in water can even be consumed by bio-oxidation of dissolved ammonia or chemical iron oxidation Fe 2+ or SO 3 2− .
Nitrites, which are produced by nitrogen oxidation, are polyanion monovalent (NO 3 − ).Most of the metal nitrates are soluble in water and appear in very small quantities.They appear in trace amounts in surface and groundwater.The main source of nitrite ions (NO 2 − ) in unpolluted surface water is the process of mineralization of organic matter and nitrification from bacteria. 6The most important parameters for determination of organic pollution, also applied in wastewater and surface water, is 5-day biochemical oxygen demand (BOD5).BOD is not a measurement of a specific pollutant, but the measurement of the amount of oxygen required by aerobic bacteria and other microorganisms for the decomposition of organic matter.Most of all, organic substances, which are biologically difficult to oxidize, can be chemically oxidized.Thus, chemical oxygen demand (COD) is generally higher than BOD. 7Water containing a larger amount of dissolved salts of alkaline earth metals is called strong water as opposed to mild water in which the amount of these salts is small. 1The calcium ions are very important only for euchroites.The quantity of calcium in organisms is used only for support and to build structures such as teeth.Magnesium ions are ions dominated by 2 + in the cytoplasm and the only ions found free, unrelated to the minimum levels. 8Determination of these physicochemical parameters in water allows us to determine the pollution from industry, urban sewage, farms, etc. Extreme pollution is an expression of biological pollution from industry when BOD and COD exceeds the allowed values prescribed by European Union (EU) and World Health Organization (WHO) standards.
In ancient times, water pollution was low, perhaps because of smaller population.The industrial revolution and large population growth have led to serious environmental pollution. 9

Physicochemical parameters and methods of analysis
Absorption spectrometry in the ultraviolet and visible region is based on the electromagnetic radiation absorption of molecules in the UV spectra of 160-400 nm and VIS 400-780 nm range.UV-VIS radiation absorption causes the excitation of the electrons of chemical bonds by passing the molecules to higher energy levels. 11The absorption of UV-VIS radiation from complex molecules and inorganic salts of transitional metals, as well as of lanthanides and actinides, causes the molecule to move from its basal to its excited state. 12The Hach Model DR/2010 Spectrophotometer is a microprocessor-controlled single-beam instrument for colorimetric testing in the laboratory or in the field.The instrument is precalibrated for over 120 different colorimetric measurements and allows convenient calibrations for user-entered and future Hach methods. 13e pH, conductivity of water (CW), and dissolved oxygen (DO) were determined at the sampling points using a portable multiparameter analyser.Other chemical parameters were determined according to the standard analytical methods for the examination of water and wastewater according to the WHO and EU standards (see Table 1).The value of pH was determined using a portable multiparameter analyser, WTW 3010.Conductivity of water (CW), also known as specific conductivity, represents the ability of water to convey electricity, and is related to the concentration of ionized substances in water. 2 CW was determined with WTW Cond 3110, DO was determined with WTW Oxi 315i, and NTU was determined with 2100N ISC Turbidimeter (ISO Method 7027).
The chemical oxygen demand (COD) represents the amount of oxygen from organic matter, which is subjected to oxidation by any strong oxidizing agent. 6 As a result of the oxidation of organic matter by microorganisms, the biochemical oxygen demand in the well-preserved water sample decreases in time.Empirically, BOD5 is the amount of the consumed oxygen needed to oxidize the organic matter into the sample.The most commonly used test, BOD5, is based on a 5-day incubation of sample at 20 °C ± 1 °C.The tool used was "OxiTop", which was filled with water up to 250 ml.
For the determination of chlorine (Cl 2 ), DPD Total Chlorine reagent (Chlorine Test 0.02-2 mg l −1 , Method 8167) was used.The absorbance level did not exist and was then measured using a Pocket Colorimeter II (HACH, USA).
The determination of chlorides was carried out in an Erlenmeyer flask containing 100 ml of water sample (adjust pH 7-10 if necessary).With the addition of 1 ml of K 2 CrO 4 , the sample turned yellowish.Titration was done with silver nitrate (AgNO 3 (c = 0.01 mol l −1 )) and it stopped at the moment when the solution gets light red. 1 The value of the chlorides in the sample was calculated according to Eq. (1): , where V 1 is the volume of the titre for the sample (ml), V 2 is the volume of the titre for blind sample (ml), c is molarity AgNO 3 (c = 0.01 mol l −1 ), and V s is the volume of the sample used (100 ml in our case).
Water sample alkalinity (A) is the measurement of its capacity to neutralize the acids.Water accumulation is mainly due to weak acid salts.In 100 ml of the analysed sample, 4 drops of phenolphthalein were added.If the 100 ml solution became purple, that meant the water contained bases due to pH above 8.3, and if the solution did not turn purple, 2 to 3 drops of methylorange were added, which turned the solution yellow.The solution was then titrated with HCl (c = 0.01 mol l −1 ) until it turned orange, and the amount of titre used was recorded. 1ter hardness or general hardness (GH) was achieved by pouring 100 ml of sample into a 250-ml flask, adding 2-5 ml of buffer and indicator (black erythromycin) in very small quantities.Following the addition of the indicator, the solution became red or light red, and the titration was done with complexon III or EDTA (c = 0.01 mol l −1 ) until the solution changed its colour to intensive blue. 1 The calculation was made based on Eq. ( 2): where V EDTA is the titration volume (ml) with ethylenediaminetetraacetic acid, c EDTA is the concentration of EDTA (c = 0.01 mol l −1 ), and V s is the volume of the sample used.
Carbonate strength (CS) is defined as the alkalinity to methylorange.A volume of 100 ml water sample was transferred to 500-ml Erlenmeyer flask and 2-3 drops of methylene chloride were added.The titration was performed with standard solution HCl (c = 0.01 mol l −1 ) until the colour changed to orange.The analysis results were calculated in German degrees (°dH) water hardness scale according to Eq. ( 3) where 2.8 value is the constant, V HCL is consumed volume of HCl, and c HCL is the concentration of HCl (c = 0.01 mol l −1 ).
First, we get 100 ml of water, add 5 ml of buffer solution (in this case NaOH (c = 2 mol l −1 )) and a black murexide indicator (black murexide is prepared from ammonia purities mixed with NaCL (c = 0.01 mol l −1 ), and titrated with EDTA (c = 0.01 mol l −1 ) to change the colour from red to purple.The titration should be carried out for 5 min after the addition of NaOH. 1 The determination of Ca 2+ was calculated by the following Eq.(4): where V EDTA is the volume (ml) of the titre with ethylenediaminetetraacetic acid, c EDTA is the concentration of EDTA (c = 0.01 mol l −1 ), and V s is the volume of the sample used.
Determination of Mg 2+ was calculated with the following Eq.( 5): .
3 Results and discussion

Location of the analysed samples
Mirusha and Stanishor rivers are surface waters, characterized by low volumes during the summer, while during the winter season, the waters of these rivers are more voluminous.These two rivers flow into the rapid-flowing river called "Morava e Binçës".These rivers are highly polluted because sewage and industrial waters are discharged into them (Fig. 1).The source of the Mirusha River is in the village of Koretisht, and is called "holy water" by the inhabitants of this village, but the problem is that during its flow, it collects various impurities and sewage.The Stanishor River is also polluted, while its source is clean.The river rises in the suburbs of Gjilan and takes the name Stanishor accord-ing to the village from which it springs.Morava e Binçës belongs to the Black Sea basin.It joins the Western Morava, which merges and flows into the Danube and then into the Black Sea.The description of the sampling locations of the Mirusha, Stanishor, and Morava rivers is very important in explaining the network of monitoring the physical and chemical parameters of these rivers.Sample SP 1 belongs to the Mirusha River resource, sample SP 2 was taken after the river passes Koretisht village, while sample SP 3 was taken after the river passes the town of Gjilan.Sample SP 4 was taken from the Stanishor River basin, and sample SP 5 was taken after passing the Gjilan City.Sample SP 6 was taken at the merging point of the two rivers.Sample SP 7 was taken further downstream from sample SP 6 , and sample SP 8 belongs to the Morava River.

Results of pH determination
These contaminated rivers have pH varying between 7.2 and 7.39, which does not express concern.In SP 1 , pH was 7.2, but as the water flows and passes through the village, the pH of SP 2 increased to 7.28.In addition, the pH of SP 3 was 7.33.Again, pH increased to 7.33.SP 4 was taken from the Stanishor River, which was pH 7.38, but at the entrance to the city, after passing through the village and the city, pH increased to 7.39 in sample SP 5 , while in SP 6 , which was taken where the two rivers merge, the pH reduced to 7.37.In SP 7 , the pH was reduced to 7.25, while in SP 8 , of the Morava River the pH rose again to 7.3 (Table 2).The pH of these water samples are in accordance with WHO and EU regulations (Table 1).

Results for the conductivity of water (CW)
Conductivity of water (CW) from the source of the Mirusha River to the exit of the city increased from 14.9 to 28.5 S m −1 .In sample SP 1 , CW was 14.9 S m −1 , in SP 2 at the exit of the village CW increased to 24.3 S m −1 , while in SP 3 CW was 28.5 S m −1 (Fig. 1).Thus, an increase in electrical conductivity of the water is obvious.On the other hand, in the source of the Stanishor stream SP 4 , CW was 31.7, while in SP 5 the CW dropped to 27.3 S m −1 , but at the merging point of the two rivers at SP 6 the value of CW was 24.8 S m −1 , which was lower in comparison to samples SP 3 and SP 5 .CW value of sample SP 7 was 27.5 S m −1 , so we see it rising, while in Morava River the CW value in sample SP 8 was 24.1 S m −1 , which is lower compared to SP 2 , SP 3 , SP 4 , SP 5 , SP 6 , and SP 7 .CW values in these rivers are in accordance with EU and WHO regulations (Table 1).

Results for nephelometric turbidity unit (NTU)
Nephelometric turbidity unit (NTU) is a measure of relative purity or water turbidity.Turbidity is a feature of absorbing light or distributing it from suspended water. 14 the SP 1 sample, the value of NTU was 0.295 at the Mirusha River site and within the allowed criteria, but the obtained value of NTU in SP 2 sample was 42.2, which is not in accordance with EU and WHO regulations (Table 1).The sample SP 3 taken out of the city had NTU value of 57.8, so while passing through the village and the city, NTU value increases more and more due to uncontrolled urban and industrial wastewater.In sample SP 4 or in the Stanishor River basin, the NTU value was 0.626, but that river in the city or sample SP 5 had NTU value 53.6.NTU value at the merging point of the two rivers, sample SP 6 , was 14.5, thus, a decrease in turbulence is obvious.In sample SP 7 , NTU was 66.1, and the Morava River SP 8 sample NTU value was 27.5 (Fig. 1).
(i) In first group of samples SP 1 and SP 4 , the NTU values are in the accordance with the EU and WHO regulations.(ii) In the second set of samples -SP 2 , SP 3 , SP 5 , SP 6 , SP 7 , and SP 8 , NTU values are not in accordance with the EU and WHO regulations.

Results for dissolved oxygen (DO)
Dissolved oxygen (DO) is a very important parameter for biotin.A too low amount of oxygen in water suggests that the water sample taken as in our case may exhibit a very high degree of pollution due to the very high presence of microorganisms.In the SP 1 sample taken at the Mirusha River reservoir, DO was 4.67 mg l −1 indicating that it is below the EU and WHO allowed value >5 mg l −1 .In the sample SP 2 at the exit of the Koretisht village, DO value was 1.18 mg l −1 , suggesting a significant decrease in DO.
In the SP 3 sample at the exit of the Mirusha River from Gjilan, DO value was 0.61 mg l −1 .Comparison of SP 1 and SP 3 dissolved oxygen (DO) samples revealed a drop to 4.06 mg l −1 , and this decline is due to the microorganisms that need oxygen to perform their biological and chemical activities.In the SP 4 sample at the Stanishor River basin, DO value was 4.53 mg l −1 indicating that it is below the allowed value, while in the SP 5 sample at the exit of the city of Gjilan, DO value was 0.6 mg l −1 .Therefore, if we compare DO from SP 1 and SP 5 , the value of DO decreased to 3.93 mg l −1 .At the merging point of the rivers Mirusha and Stanishor in sample SP 6 , DO value was 1.32 mg l −1 .
In sample SP 7 (Fig. 1), DO value was 3.36 mg l −1 , whereas in sample SP 8 of Morava River, DO was 0.32 mg l −1 .The highest and the lowest values in the mentioned locations are divided into two groups: (i) The first group in the SP 1 and SP 4 samples are not in accordance with the EU and WHO regulations (Table 2).(ii) The second SP 2 , SP 3 , SP 4 , SP 5 , SP 6 , SP 7 and SP 8 sampling group is not in accordance with the EU and WHO regulations (Tables 1 and 2).Chemical oxygen demand (COD) as a chemical parameter indicates in some way whether a sample is chemically contaminated or not.In our case, during the COD research on rivers (Fig. 1), there is no chemical contamination based on the results obtained in the laboratory.In the SP 1 sample, COD value was 0.12 mg l −1 , but at the exit of the village, the COD in the SP 2 sample was 3.36 mg l −1 , so there was a rapid increase in COD, while in SP 3 sample at the exit of the city, COD value was 1.7 mg l −1 (Table 2).In the Stanishor River basin, COD was higher than in the samples contaminated with water, and the COD value in the SP 4 sample reached 4.94 mg l −1 .In the SP 5 samples, COD was 0.13 mg l −1 , while in the SP 6 sample, the amount of COD was 3.1 mg l −1 .The COD of sample SP 7 was 2.7 mg l −1 and this sample was taken from a greater distance compared to sample SP 6 .Sample SP 8 was taken in the Morava River, in which COD value was 1.34 mg l −1 .Therefore, according to all mentioned results, the highest COD value was found in sample SP 4 of the Stanishor River, but COD as a chemical parameter was higher in the Mirusha River than in the Stanishor River.In conclusion, all of these values are not in accordance with EU and WHO regulations (Table 1).

Results for 5-day biochemical oxygen demand (BOD5)
Biochemical oxygen demand (BOD) is a very important parameter to determine the biological level of water pollution.BOD5 in sample SP 1 was 0 mg l −1 , but during the flow of water from the Mirusha River site to the village exit, the amount of BOD5 in sample SP 2 was as high as 20 mg l −1 .In sample SP 3 , BOD5 was 18 mg l −1 , so from SP 2 to SP 3 sampling site, the amount of BOD5 reduced by 2 mg l −1 .BOD5 in sample SP 4 , which was the source of the Stanishor River, was 0 mg l −1 , while in sample SP 5 the amount of BOD5 was 17 mg l −1 , a very large increase compared to the BOD5 of the Stanishor River basin.In sample SP 6 , BOD5 was 21 mg l −1 (Table 2).BOD5 in sample SP 7 was 0.2 mg l −1 .This is a very large drop in the biochemical consumption of oxygen, but in the Morava River, unfortunately, the quantity of BOD5 was 29 mg l −1 and the value was higher than all other analysed samples.The lower and higher values of BOD5 are divided into two groups: (i) In the first group with the locations SP 1 , SP 4 and SP 7 (Fig. 1), BOD5 values range from 0 to 0.2 mg l −1 , which is in accordance with EU and WHO regulations.(ii) In the second group with SP 2 , SP 3 , SP 5 , SP 6 and SP 8 locations, BOD5 values range from 18 to 29 mg l −1 , indicating extreme contamination because >10 mg l −1 was calculated as extreme contamination.These values are not in accordance with EU and WHO regulations (Tables 1 and 2).

Results for alkalinity
All samples from SP 1 to SP 8 had HCl values from 5.5 to 7.8 ml (Table 2), so there was no need for analysis of this parameter, because all the values were in accordance with EU and WHO regulations (Table 1).

Results for bicarbonates HCO 3 −
During the determination of HCO 3 − , it can be seen that from one sampling point to another, its value had increased.In sample SP 1 , HCO 3 − value was 372.1 mg l −1 , while in sample SP 2 , HCO 3 − was 414.8 mg l −1 .In sample SP 3 , there was a decrease in HCO 3 − value (408.7 mg l −1 ) compared to the SP 1 and SP 2 samples.At the SP 4 site, HCO 3 − was 335.5 mg l −1 , but at the exit of the city where sample SP 5 was taken, HCO 3 − value was 427 mg l −1 , i.e., a higher HCO 3 − value compared to sample SP 4 , which was taken at the Stanishor River basin.The amount of HCO 3 − in sample SP 6 was 457.5 mg l −1 , while sample SP 7 showed an increase in HCO 3 − up to 475.8 mg l −1 .Morava River possess lower HCO 3 − value compared to all other samples, while only in sample SP 8 the value reached 341.6 mg l −11 (Table 2).Bicarbonates in all samples from SP 1 to SP 8 are in accordance with EU and WHO regulations (Table 1).

Results for general hardness and carbon strength
Water containing a large amount of dissolved salts of alkaline earth metals is called strong water as opposed to soft water in which the amount of these salts is low.General hardness (GH) in all samples from SP 1 to SP 8 enters the strongest water category, where GH value ranges from 15.28 to 21 °dH.In sample SP 1 , the GH value was 19.3 °dH, but this value began to drop in samples SP 2 (17.41 °dH) and SP 3 (17.92°dH).In sample SP 4 , GH value was 19.42 °dH, but was lower in sample SP 5 with a value of 18.42 °dH.The GH in sample SP 6 was 20.16 °dH, and in sample SP 7 it was 21 °dH, which is higher compared to sample SP 5 , while in sample SP 8 the GH value decreased to 15.28 °dH.All GH values of the aforementioned samples SP 1 -SP 8 (Fig. 1) are not included in the category of very strong water at the German °dH degree.The water of Stanishor River was harder compared to the GH of Mirusha River.
Large amounts of sodium bicarbonate or potassium in water will result in greater carbonate hardness than total strength (GH).Carbon strength (CS) values in the analysed samples ranged from 15.4 to 21.8 °dH to SP 1 -SP 8 samples (Fig. 1).In sample SP 1 , CS value was 17.08 °dH, in sample SP 2 , CS value was 19.4 °dH.It can be seen that sodium or potassium bicarbonates are higher in SP 2 than in SP 1 , while CS is reduced in sample SP 3 at 18.7 °dH compared to SP 2 .The CS value in sample SP 4 at the Stanishor River was 15.4 °dH, but in SP 5 at the exit of the Stanishor River, CS value was 19.6 °dH, thus, the CS increased compared to that of SP 4 .In sample SP 6 , CS value again increased to 21 °dH compared to SP 3 and SP 5 .The CS value of SP 7 was 21.8 °dH, but in SP 8 of the Morava River, CS value was reduced at 15.28 °dH.Finally, CS was the highest in the Stanishor River and the lowest in the Mirusha and Morava Rivers (Table 2).GH and CS values in SP 1 -SP 8 samples do not present a risk and are in accordance with EU and WHO regulations (Table 1).

Results for calcium (Ca 2+ )
Calcium (Ca 2+ ) is a very important parameter for water.In our case, its value ranged from 61.7 to 140.28 mg l −1 for SP 1 -SP 8 (Fig. 1).In SP 1 of the Mirusha River basin, Ca 2+ value was 61.7 mg l −1 , in SP 2 the value of Ca 2+ was 126.2 mg l −1 , and in SP 3 near the merging point with the Stanishor River, the value of Ca 2+ was 129.05 mg l −1 .In SP 4 at the Stanishor River basin, the amount of Ca 2+ was 122.88 mg l −1 , and in SP 5 the Ca 2+ value was 140.28 mg l −1 , thus, the amount of calcium increased in value from the river source to the interconnection between the two rivers -Mirusha and Stanishor.The Ca 2+ value in SP 6 was 140.8 mg l −1 and, compared to the sample of the Mirusha and Stanishor River after mixing these two rivers, Ca 2+ value increased.In SP 7 , the amount of Ca 2+ did not change significantly compared to SP 5 and SP 6 .In SP 8 of the Morava River, the Ca 2+ content was 102 mg l −1 , so the amount of Ca 2+ in this river was reduced to 38 mg l −1 compared to SP 7 (Table 2).The Ca 2+ values in this river are in accordance with EU and WHO regulations (Table 1).

Results for magnesium (Mg 2+ )
Magnesium (Mg 2+ ) ions values in samples SP 1 -SP 8 (Fig. 1) were not very high, ranging from 20.6 to 56.7 mg l −1 .In SP 1 of the Mirusha River basin, Mg 2+ value was 56.7 mg l −1 , which was higher than that of all other samples analysed in the laboratory.In sample SP 2 , Mg 2+ value decreases (20.6 mg l −1 ) compared to SP 1 .The value of Mg 2+ in SP 3 was 21.6 mg l −1 , which was higher by 1 mg l −1 in comparison to SP 2 .In SP 4 of the Stanishor River basin, the amount of Mg 2+ was 31.02mg l −1 , but in SP 5 of the Stanishor River, the amount of Mg 2+ decreased to 18.9 mg l −1 .In SP 6 , Mg 2+ value was 26.4 mg l −1 , much lower compared to SP 1 and SP 4 at the Mirusha and Stanishor River basins (Table 2).In SP 7 , Mg 2+ value was 30.07 mg l −1 , which was higher than that of SP 6 .In SP 8 of Morava River, Mg 2+ value was 21.9 mg l −1 .Mg 2+ values of the river waters are in accordance with EU and WHO regulations (Table 1).

Results for chlorides (Cl − )
During laboratory analysis, chlorides (Cl − ) were 12.3-73.9mg l −1 in SP 1 -SP 2 (Fig. 1).In SP 1 , Cl − value was 12.3 mg l −1 , and in SP 2 Cl − was 72 mg l −1 .It can be seen that the amount of Cl − increased in SP 2 by 59.7 mg l −1 compared to SP 1 .In SP 3 , the amount of Cl − was 68 mg l −1 , so there was a decrease in the amount of Cl − in comparison to SP 2 .In SP 4 taken at the Stanishor River basin, Cl − value was 29.9 mg l −1 , so the amount of Cl − was higher compared to the Mirusha River basin in SP 1 (Table 2).In SP 5 , Cl − value was 51.9 mg l −11 , so the value was higher compared to SP 4 .The amount of Cl − in SP 6 that was collected after the merging of the Mirusha and Stanishor rivers, was 52.2 mg l −1 , while in SP 7 , the amount of Cl − was 73.9 mg l −1 which was higher than that in SP 6 , while in the SP 8 sample of the Morava River, the value of Cl − was 36 mg l −1 , which is very low compared to SP 7 (Table 2).The value of Cl − poses no pollution risk, and is in accordance with the allowed EU and WHO values (Table 1).

Results for chlorine (Cl 2 )
Chloride (Cl 2 ) was determined at sites where SP 1 -SP 8 samples were taken (Fig. 1).Cl 2 was defined because if in these waters Cl 2 exceeds 0.5 mg l −1 , the potential to form trihalomethans would be very high.Trihalomethans are very dangerous and are formed by the very high amount of chlorine used in the regional water supply system.Sample SP 1 cannot normally be Cl 2 because it is the source of the Mirusha River that originates from the subsoil.In sample SP 2 , the Cl 2 value was 0.21 mg l −1 , while in SP 3 the value of Cl 2 increased to 0.26 mg l −1 compared to SP 2 , and this increase in Cl 2 in sample SP 3 occurred due to the release of domestic waters supplied by the regional water supply.In SP 4 , Cl 2 value was 0 mg l −1 because it is the source of the Stanishor River that originates from the subsoil.In SP 5 , the amount of Cl 2 was very low at 0.01 mg l −1 , while in SP 6 , where the two rivers meet, the amount of Cl 2 was 0.07 mg l −1 .In SP 7 , Cl 2 value was 0.39 mg l −1 , which is very high compared to SP 6 , and SP 6 -SP 7 are not at a very large distance.In SP 8 of Morava River, Cl 2 value was 0.19 mg l −1 , lower compared to sample SP 7 (Table 2).Cl 2 value in these samples are in accordance with allowed EU and WHO values (Table 1).

Results for nitrites (NO 2 − )
The laboratory analysis of nitrite (NO 2 − ) raised concerns, because high values in all the samples, SP 1 -SP 8 , were determined.In SP 1 of the Mirusha River basin, NO 2 − value was 1 mg l −1 , whereas the EU and WHO standards permit NO 2 − amounts up to 0.6 mg l −1 (Table 1).In sample SP 2 , NO 2 − value increased to 16 mg l −1 , while in SP 3 taken at the exit of the city, NO 2 − value was 11 mg l −1 .If we compare NO 2 − values from the Mirusha River basin, the amount of nitrite increased significantly, which is very disturbing (Table 2).In SP 4 taken at the Stanishor River basin, NO 2 − value was 4 mg l −1 , which is a very high value from a non-polluted wastewater source, while in SP 5 the NO 2 − value was 13 mg l −1 .If we compare the NO 2 − value from the Stanishor River source with sample SP 4 up to peak SP 5 , NO 2 − value increased by 9 mg l −1 .In SP 6 taken at the intersection of the two rivers (Fig. 1), NO 2 − value was 12 mg l −1 , while at a greater distance in SP 7 the nitrite value was 2 mg l −1 .In sample SP 7 , the nitrites significantly decreased, but still exceeded the permitted regulatory range for this parameter.In sample SP 8 taken from the Morava River, NO 2 − value was 13 mg l −1 , so even in this river, the amount of nitrite is high.In conclusion, NO 2 − values in these samples are not in accordance with EU and WHO regulations (Table 1).

Results for nitrates (NO 3 − )
The laboratory analysis of nitrates (NO 3 − ) showed that NO 3 − values ranged from 2 to 7 mg l −1 in SP 1 -SP 8 .NO 3 − value in SP 1 was 2 mg l −1 , while in SP 2 , the NO 3 − value was 6 mg l −1 , which shows an increase in the amount of nitrate compared to SP 1 at the Mirusha River source.In SP 3 , nitrates were 7 mg l −1 .Compared to SP 2 , the NO 3 − value increased by 1 mg l −1 in SP 3 .In SP 4 of the Mirusha River basin, the nitrate value was 2 mg l −1 , whereas (Table 2) NO 3 − value in SP 5 was 4.4 mg l −1 , so in SP 5 the nitrate value increased to 2.2 mg l −1 compared to SP 4 .In SP 6 (Fig. 1), NO 3 − value was 6 mg l −1 , so it can be seen that after merging of the Mirusha and Stanishor rivers, the nitrate values increased, while in SP 7 the value of NO 3 − again rose to 6.3 mg l −1 .In SP 8 , the NO 3 − value was 5.6 mg l −1 , which was less than that of SP 7 (Table 2).The NO 3 − values are in accordance with EU and WHO regulations (Table 1), and present no concern. 3− in the laboratory, as referred to in method 8048, the maximum measuring range of the instrument with this method is 2.5 mg l −1 .In SP 1 of the Mirusha River basin, PO 4 3− value was 0.35 mg l −1 , whereas in SP 2 , the PO 4 3− value was outside the instrument's measuring range, i.e. it was higher than 2.5 mg l −1 , and in SP 3 it was impossible for the spectrophotometer to give a value of PO 4 3− because the value was outside the measuring range.In SP 4 taken from the Stanishor River basin, the value of PO 4 3− was 0.33 mg l −1 , while in SP 5 , SP 6 , SP 7 , and SP 8 , the values of phosphates (PO 4

3−
) were immeasurable as mentioned above.The phosphate was divided into two groups of samples due to the high pollution present in these rivers (Fig. 1): (i) The first group of samples that included SP 1 and SP 3 taken from the Mirusha and Stanishor river basins are not in accordance with EU and WHO regulations, but reveal lower values compared to the second group (Table 2); (ii) The second group of samples SP 2 , SP 4 , SP 5 , SP 6 , SP 7 , and SP 8 includes values over 2.5 mg l −1 that are not in accordance with EU and WHO regulations (Table 1).
3.17 Results for ammonia (NH 3 − ) Ammonia (NH 3 − ) is a very important parameter to define in waters or sewage because amounts exceeding the limits should raise great concern.In SP 1 of the Mirusha River basin, NH 3 − value was 0.09 mg l −1 and in SP 4 of the Stanishor River basin, it was 0.03 mg l −1 , whereas in other samples it was immeasurable because it was outside the metering range or spectrophotometric determinant.The lowest and the highest values of NH 3 − are divided into two groups: (i) The first group that includes SP 4 of the Stanishor River is in accordance with EU and WHO regulations (Table 1).(ii) The second group, all samples including SP 1 , SP 2 , SP 3 , SP5, SP 6 , and SP 7 are not in accordance with EU and WHO regulations (Tables 1 and 2).

Conclusion
Based on the results, the studied river waters are heavily contaminated with nitrites, ammonium ions, phosphate ions, and BOD5.The water pollution of these rivers, as mentioned above, is caused by discharges from households, the food industry, and the application of chemicals in agriculture.Concentrations beyond the reference values of these pollutants directly affects the flora and fauna of the river waters, and thus are fatal for aquatic life.The primary goal of every state, and of Kosovo, is to protect the quality of water, and precisely for this reason, the state institutions, both at local and central level, should not only be committed to the permanent monitoring of these river waters, but should also construct an implant structure, where the Mirusha and Stanishor rivers merge with the waters of Morava River.
Discussion of the results and comparison of different parameters of SP 1 -SP 8 samples was very important in order to gain insight into how the parameters deviate.According to our research, the main problem of deviation was the purification of industrial pipes with the CIP system, since all the waters containing a large number of microorganisms are released into these rivers, resulting in extreme pollution due to the lack of wastewater treatment plants in the processing industry.

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During spectrophotometric analysis of phosphate PO 4