Literature DB >> 29896499

Evaluation of water quality and stability in the drinking water distribution network in the Azogues city, Ecuador.

Fernando García-Ávila1,2, Lía Ramos-Fernández1, Damián Pauta2, Diego Quezada2.   

Abstract

This document presents the physical-chemical parameters with the objective of evaluating and analyzing the drinking water quality in the Azogues city applying the water quality index (WQI) and to research the water stability in the distribution network using corrosion indexes. Thirty samples were collected monthly for six months throughout the drinking water distribution network; turbidity, temperature, electric conductivity, pH, total dissolved solids, total hardness, calcium, magnesium, alkalinity, chlorides, nitrates, sulfates and phosphates were determined; the physical-chemical parameters were measured using standard methods. The processed data revealed that the average values ​​of LSI, RSI and PSI were 0.5 (±0.34), 6.76 (±0.6), 6.50 (±0.99) respectively. The WQI calculation indicated that 100% of the samples are considered excellent quality water. According to the Langelier, Ryznar and Pukorius indexes showed that drinking water in Azogues is corrosive. The quality of drinking water according to the WQI is in a good and excellent category.

Entities:  

Year:  2018        PMID: 29896499      PMCID: PMC5996164          DOI: 10.1016/j.dib.2018.03.007

Source DB:  PubMed          Journal:  Data Brief        ISSN: 2352-3409


Specifications table Value of the data The dates presented are used to calculate the water quality indexes, as well as the corrosion and scaling indexes, emphasizing the importance of continuous monitoring of water quality. Determine the corrosion potential and quality of drinking water in all distribution systems is important to avoid adverse effects on health and economic losses due to deterioration of the infrastructure. The water quality indexes (WQI) serve to provide a clear picture of the quality of water distributed and used for human consumption, therefore, these data could be useful for communities, or cities that have similar drinking water quality. The pipes, fittings and valves in the distribution networks deteriorate due to corrosive water and cause some health, aesthetic and economic problems. Then, the determination of the corrosion and incrustation potential of drinking water allows decision making and adoption of guidelines for the management of water quality by those who are related to engineering and water quality management. Sharing such data can allow a much earlier rectification of the problem of corrosion and scaling.

Data

The data presented in this article deals with the quality of drinking water distributed in the Azogues city, Ecuador. Data include in this document, indicate about the situation of drinking water saturation, three stability indexes were determined: Langelier, Ryznar, and Pockorius, were calculated using special equations that are summarized in Table 1. Other data parameters such as turbidity (Tur), pH, total dissolved solids (TDS), electrical conductivity (EC), total hardness (TH), calcium (Ca), magnesium (Mg), alkalinity (Alk), sulfate (SO), chloride (Cl), nitrate (NO), phosphate (PO), free chlorine (Cl2). The physical and physical characteristics of drinking water are shown in Table 2, Table 3. The corrosion indexes values obtained are presented in Table 4.
Table 1

Equations and classifications of Langelier, Ryznar and Pockorius indexes [2], [3], [4].

IndexEquationDescriptionValueWater condition
LangelierLSI = pH-pHsLSI = Langelier Saturation IndexLSI > 0Tend to precipitate
LSIpH = pH measured in situ.











pHs = pH at saturation







pHs = 9.3 + A + B - C - DLSI = 0Equilibrium







A=(log10TDS1)10
B = [−13.12log10(273 °C+T)]+34.55 C = log10[Ca+2mg/L as CaCO3]−0.4LSI < 0Tend to corrosion







D = log10 [Alk. mg/L as CaCO3]
TDS = Total Dissolved Solids mg/L
RyznarRSI = 2 pHs-pHRSI = Ryznar Stability IndexRSI < 5.5Highly scale-forming











RSIpHs = pH at saturation
pH = pH measured in situ5.5 < RSI < 6.2Relatively scale-forming







6.2 < RSI < 6.8Balanced





6.8 < RSI < 8Low corrosion
RSI > 8High corrosion
PuckoriusPSI = 2pHs−pHeqPSI < 5.5Tend to precipitate











PSIpHs = pH at saturation5.5<PSI<6.5Optimal range
pHeq = 1.456 Log(Alk) + 4.54PSI > 6.5Tend to corrosion
Table 2

Values of the physico-chemical parameters analyzed.

Number SampleTurbidity NTUpHTemp. °CTDS mg/LEC µS/cmTotal hardness mg/L CaCO3Ca2+mg/L CaCO3Ca2+mg/L
S10.567.4217.5281.17129.9668.3351.0020.40
S20.557.3819.1382.17131.8370.0052.1720.87
S30.517.2016.6863.67102.4969.3352.1720.87
S40.617.1720.0980.67129.4978.0057.8323.13
S50.597.4618.4670.40111.8972.0056.0022.40
S60.577.2617.3273.60117.6275.6058.0023.20
S70.517.2218.2575.67119.4770.6753.6721.47
S80.507.2116.7875.60120.8274.0056.0022.40
S90.597.2018.3364.83103.2769.0052.6721.07
S100.477.2016.8866.17106.0969.8352.0020.80
S110.457.1715.9371.17112.9671.1753.0021.20
S120.497.2215.3066.83106.3371.5052.6721.07
S130.447.1614.8558.6794.6156.3342.0016.80
S140.547.2618.1372.00115.0170.8355.0022.00
S150.557.3516.9572.50115.3773.1754.6721.87
S160.557.1619.7574.83119.1172.0054.3321.73
S170.537.2017.2071.00112.8971.1053.5021.40
S180.547.2218.1070.17111.1672.4254.7521.90
S190.507.2317.3269.00110.5874.8355.6722.27
S200.507.1818.5771.33112.5770.8353.5021.40
S210.527.2217.6255.6788.3655.5042.1716.87
S220.507.1917.5364.17103.9265.1750.8320.33
S230.487.2717.0366.50106.2969.8354.0021.60
S240.487.2419.0868.83109.2968.0052.6721.07
S250.477.2216.7563.6799.9665.6750.5020.20
S260.477.2618.5867.50106.8565.3349.3319.73
S270.497.2616.6767.17107.0767.6751.3320.53
S280.477.2815.7266.83106.0867.3350.6720.27
S290.537.2020.0873.50117.7267.1752.0020.80
S300.507.2717.9755.6788.6858.5044.1717.67
Mean0.517.2417.669.29110.4768.9452.1920.88
Min0.397.1614.855.6788.3655.5042.0016.80
Max0.617.4620.182.17131.8378.0058.0023.20
S.D.0.050.071.36.5510.525.123.841.54
Table 3

Values of the physico-chemical parameters analyzed.

Number sampleMg2+mg/L CaCO3Mg2+mg/LFree chlorine mg/LSO42−mg/LAlkalinity mg/L CaCO3Clmg/LNO3mg/LPO43−mg/L
S117.334.160.4722.3346.835.300.550.07
S217.834.280.5921.0050.005.580.580.07
S317.174.120.7619.1746.335.020.480.07
S420.174.840.8223.0048.675.220.370.07
S516.003.840.5320.2048.005.220.380.07
S617.604.220.7119.8054.805.240.440.07
S717.004.080.4518.6752.505.120.500.11
S818.004.320.7518.9056.605.880.500.09
S916.333.920.5617.3350.005.470.380.07
S1017.834.280.6918.0051.335.650.420.07
S1118.174.360.7115.8351.175.550.520.08
S1218.834.520.9016.5053.334.880.430.06
S1314.333.440.5512.1740.337.270.670.06
S1415.833.800.6220.6747.675.250.580.06
S1518.504.440.6420.5048.835.630.500.08
S1617.674.240.7521.8345.835.280.350.24
S1717.604.220.8620.0046.605.720.440.08
S1817.674.240.8619.3350.005.550.470.07
S1919.174.600.6619.8347.505.350.630.08
S2017.334.160.8018.6746.685.750.530.08
S2113.333.200.5811.0040.826.520.530.07
S2214.333.440.8417.8346.335.850.370.07
S2315.833.800.8520.1748.505.250.350.07
S2415.333.680.7818.0046.505.900.500.07
S2515.173.640.8617.0047.175.400.370.08
S2616.003.840.8216.1748.835.880.380.09
S2716.333.920.8117.0048.176.080.430.08
S2816.674.000.8616.6750.676.150.650.10
S2915.173.640.7717.0049.335.670.600.08
S3014.333.440.4810.1740.336.430.470.08
Mean16.754.020.7118.1248.255.640.480.08
Min13.333.200.510.1740.334.880.350.06
Max20.174.840.923.0056.607.270.670.24
S.D.1.600.380.13.023.700.500.090.03
Table 4

Corrosion and scaling indexes in drinking water of Azogues city.

Number sampleLangelier index LSIRyznar index RSIPuckorius index PSI
S1−1.259.9210.38
S2−1.229.8110.19
S3−1.4210.0410.21
S4−1.389.9210.09
S5−1.159.7610.25
S6−1.289.8210.00
S7−1.359.9310.11
S8−1.349.8910.00
S9−1.399.9810.16
S10−1.4210.0410.21
S11−1.4610.0910.23
S12−1.4110.0310.20
S13−1.6810.5210.79
S14−1.359.9710.26
S15−1.269.8810.23
S16−1.4410.0310.23
S17−1.4410.0810.32
S18−1.369.9410.15
S19−1.3910.0110.26
S20−1.4310.0410.25
S21−1.5510.3210.65
S22−1.4710.1210.34
S23−1.359.9810.26
S24−1.379.9810.24
S25−1.4410.1010.34
S26−1.369.9910.25
S27−1.3910.0410.31
S28−1.3710.0310.29
S29−1.379.9310.13
S30−1.4810.2310.61
Equations and classifications of Langelier, Ryznar and Pockorius indexes [2], [3], [4]. Values of the physico-chemical parameters analyzed. Values of the physico-chemical parameters analyzed. Corrosion and scaling indexes in drinking water of Azogues city. Also in this document the drinking water quality indexes (WQI) are presented, to evaluate the water quality through WQI, the recommended standards by the World Health Organization (WHO) 2011 were considered [1] the relative weight (Wi) was assigned for water quality parameters according to their relative importance to water quality for consumption purposes (Table 5). The calculation obtained from WQI for drinking water samples is presented in Table 7. The classification of drinking water quality based on WQI values is shown in Table 8. Azogues city where the study was realized is shown in Fig. 1.
Table 5

Relative weight of chemical of physico-chemical parameters [2], [8], [9], [10], [11].

Chemical parameterUnitFactor weight (wi)WHO standard (si)Relative weights (Wi)
TurbidityNTU50.50.12
pH48.50.10
TDSmg/L35000.07
Total Hardnessmg/L22000.05
Calcium Ca2 +mg/L3750.07
Magnesium Mg2+mg/L2500.05
Sulfatemg/L42500.10
Alkalinitymg/L32000.07
Chloridemg/L32500.07
Nitratemg/L5500.12
Phosphatemg/L20.50.05
Free Chlorinemg/L510.12
Table 7

Data of sub-index (SI).

N° sampleTur.pHTDSTHCaMgSO42−AlkClNO3PO43−Cl2WQI
S113.668.521.191.671.990.410.871.710.160.130.630.0330.96
S213.418.471.201.712.040.420.821.830.160.140.650.0430.89
S312.448.260.931.692.040.400.751.700.150.120.700.0529.22
S414.888.231.181.902.260.470.901.780.150.090.720.0532.61
S514.398.561.031.762.190.370.791.760.150.090.720.0331.84
S613.908.331.081.842.260.410.772.000.150.110.680.0431.60
S712.448.291.111.722.090.400.731.920.150.121.020.0330.02
S812.208.281.111.802.190.420.742.070.170.120.840.0529.98
S914.398.260.951.682.060.380.681.830.160.090.680.0331.20
S1011.468.260.971.702.030.420.701.880.170.100.720.0428.45
S1110.988.231.041.742.070.430.621.870.160.130.730.0428.03
S1211.958.290.981.742.060.440.641.950.140.110.600.0528.96
S1310.738.220.861.371.640.340.471.480.210.160.590.0326.10
S1413.178.331.051.732.150.370.811.740.150.140.590.0430.27
S1513.418.441.061.782.130.430.801.790.160.120.730.0430.91
S1613.418.221.101.762.120.410.851.680.150.092.310.0532.14
S1712.938.261.041.732.090.410.781.700.170.110.800.0530.08
S1813.178.291.031.772.140.410.751.830.160.110.700.0530.41
S1912.208.301.011.832.170.450.771.740.160.150.760.0429.58
S2012.208.241.041.732.090.410.731.710.170.130.750.0529.23
S2112.688.290.811.351.650.310.431.490.190.130.700.0428.07
S2212.208.250.941.591.980.340.701.700.170.090.630.0528.63
S2311.718.340.971.702.110.370.791.770.150.090.700.0528.76
S2411.718.311.011.662.060.360.701.700.170.120.700.0528.54
S2511.468.290.931.601.970.360.661.730.160.090.760.0528.06
S2611.468.330.991.591.920.370.631.790.170.090.860.0528.27
S2711.958.330.981.652.000.380.661.760.180.110.800.0528.86
S2811.468.360.981.641.980.390.651.850.180.160.960.0528.66
S2912.938.261.081.642.030.360.661.800.170.150.810.0529.93
S3012.208.340.811.431.720.340.401.480.190.110.800.0327.84
Table 8

Standard WQI values for water to human consumption.

WQI rangeType of waterExplanation
< 50Excellent WaterGood for human health
50.1–100Good WaterFit for human consumption
100.1–200Poor WaterWater not in good condition
200.1–300Very Poor WaterNeed attention before use
> 300.1InappropriateNeed too much attention
Fig. 1

Map and location of Azogues city.

Map and location of Azogues city. Relative weight of chemical of physico-chemical parameters [2], [8], [9], [10], [11]. From Fig. 2, Fig. 3, Fig. 4 the variation of the physical-chemical parameters in the 30 sampling points is shown. Fig. 5 shows the variation of the corrosion indexes in the 30 sampling points. Fig. 6 show the Water Quality Indexes at the 30 sampling points.
Fig. 2

Variation of turbidity, pH, Temperature, Dissolved Total Solids and Electric Conductivity in the sampling points of the drinking water network.

Fig. 3

Variation of Total Hardness, Calcium and Magnesium in the sampling points.

Fig. 4

Variation of Free Chlorine, Alkalinity, Sulphates, Chlorides, Nitrates, Phosphates in the sampling points of the drinking water network.

Fig. 5

Trend of Langelier, Ryznar and Pockorius indexes.

Fig. 6

Trend of water quality indices in the 30 sampling points.

Variation of turbidity, pH, Temperature, Dissolved Total Solids and Electric Conductivity in the sampling points of the drinking water network. Variation of Total Hardness, Calcium and Magnesium in the sampling points. Variation of Free Chlorine, Alkalinity, Sulphates, Chlorides, Nitrates, Phosphates in the sampling points of the drinking water network. Trend of Langelier, Ryznar and Pockorius indexes. Trend of water quality indices in the 30 sampling points.

Experimental design, materials and methods

Study area description

The Azogues city is located south of the Republic of Ecuador, its geographic coordinates are: latitude 2° 44'22 "S, longitude: 78° 50'54" W, they cover an area of approximately 1200 km2, the average altitude of the city is 2518 m above sea level, the average temperature is 17 °C. Fig. 7 shows the location of the drinking water network.
Fig. 7

Location of the water sampling sites in the Azogues city drinking water network.

Location of the water sampling sites in the Azogues city drinking water network.

Collection of samples and analytical procedures

Monthly samples were collected at 30 points of the drinking water network for six months, 180 samples in total were collected, stored and transferred to the laboratory using standard methods and drinking water quality; turbidity, pH, temperature, total dissolved solids, total hardness, calcium hardness, alkalinity, nitrate, phosphate, chloride, sulfate and free chlorine were measured. Fig. 7 shows the study area and the sampling locations, the samples were collected in polyethylene bottles (1 L) and transported immediately at 4 °C to the central laboratory of the drinking water company. The alkalinity, total hardness and hardness of calcium were measured by the titration method; concentration of hydrogen ion (pH), temperature and total dissolved solids were analyzed with HACH Multiparameter HQ 40d, turbidity was measured using turbidimeter (model P2100 HACH); nitrate, phosphate, chloride and sulfate were determined with the HACH DR 2500 spectrophotometer, free chlorine was measured with HACH DR 890. All the water samples were analyzed according to the standard methods for the analysis of drinking water [5], [6], [7]. The data obtained after the laboratory analysis is presented in Table 2, Table 3.

Drinking water stability indexes calculation

Table 1 presents the equations and criteria to calculate and categorize the water stability indexes. The Langelier saturation index, Ryznar saturation index, and the Puckorius scale index were calculated and classified into three categories: scale, stabilized and corrosive [2], [3], [4]. The results are presented in Table 4.

Water quality index calculation

For calculation of WQI, the following four steps have been taken into account [8], [9], [10], [11]. In the first step, each of the analyzed parameters has been assigned a weight (wi) according to its relative importance in the overall quality of water for drinking purposes (Table 5). In the second step, the relative weight (Wi) is calculated as per the established method as follows.Where ‘Wi’ is the relative weight, ‘wi’ is the weight of each parameter and ‘n’ is the number of parameters. In the third step a quality rating scale (qi) for each parameter is calculated by following equation (Table 6);Where ‘Ci‘ is the concentration of each chemical parameter in each water sample and ‘si’ is the standard value for each chemical parameter according to the Guide lines of WHO. In the fourth step the sub index (Sli) of each chemical parameter is estimated by using the equation;
Table 6

Data of quality rating (qi).

Number sampleTur.pHTDSTHCa2 +Mg2 +SO42−Alk.ClNO3PO43−Cl2
S111287.2916.2334.1727.208.328.9323.422.121.1013.000.23
S211086.8216.4335.0027.838.568.4025.002.231.1713.330.29
S310284.7112.7334.6727.838.247.6723.172.010.9714.330.38
S412284.3516.1339.0030.849.689.2024.332.090.7314.670.41
S511887.7614.0836.0029.877.688.0824.002.090.7614.800.26
S611485.4114.7237.8030.938.457.9227.402.100.8814.000.35
S710284.9415.1335.3428.638.167.4726.252.051.0021.000.23
S810084.8215.1237.0029.878.647.5628.302.351.0017.200.37
S911884.7112.9734.5028.097.846.9325.002.190.7714.000.28
S109484.7113.2334.9227.738.567.2025.672.260.8314.670.34
S119084.3514.2335.5928.278.726.3325.582.221.0315.000.35
S129884.9413.3735.7528.099.046.6026.671.950.8712.330.45
S138884.2411.7328.1722.406.884.8720.172.911.3312.000.27
S1410885.4114.4035.4229.337.608.2723.832.101.1712.000.31
S1511086.4714.5036.5929.168.888.2024.422.251.0015.000.32
S1611084.2414.9736.0028.978.488.7322.922.110.7047.330.37
S1710684.7114.2035.5528.538.458.0023.302.290.8816.400.43
S1810884.9414.0336.2129.208.487.7325.002.220.9314.330.43
S1910085.0613.8037.4229.699.207.9323.752.141.2715.670.33
S2010084.4714.2735.4228.538.327.4723.342.301.0715.330.40
S2110484.9411.1327.7522.496.404.4020.412.611.0714.330.29
S2210084.5912.8332.5927.116.887.1323.172.340.7313.000.42
S239685.5313.3034.9228.807.608.0724.252.100.7014.330.43
S249685.1813.7734.0028.097.367.2023.252.361.0014.330.39
S259484.9412.7332.8426.937.286.8023.582.160.7315.670.43
S269485.4113.5032.6726.317.686.4724.422.350.7717.670.41
S279885.4113.4333.8427.377.846.8024.082.430.8716.330.40
S289485.6513.3733.6727.038.006.6725.332.461.3019.670.43
S2910684.7114.7033.5927.737.286.8024.672.271.2016.670.38
S3010085.5311.1329.2523.566.884.0720.172.570.9316.330.24
Data of quality rating (qi). The data obtained of SI are presented in Table 7. The overall Water Quality Index was calculated by adding together each sub index values of each water samples as follows; Data of sub-index (SI). The WQI values presented in the last column of Table 7 were compared with the standard values of Table 8. The WQI values at the 30 sampling sites clearly indicate that drinking water in all areas of Azogues is safe to drink. Therefore, based on the general results, drinking water in Azogues is of excellent quality. Standard WQI values for water to human consumption.
Subject areaEnvironmental Engineering
More specific subject areaWater treatment
Type of dataTable and figure
How data was acquiredIn 30 points of the drinking water network for six months, 176 water samples were collected, stored and transferred to the lab using standard methods and the drinking water quality; turbidity, pH, temperature, total dissolved solids, total hardness, calcium hardness, alkalinity, nitrate, phosphate, chloride, sulfate and free chlorine were measured. Alkalinity, total hardness and calcium hardness were measured by titration method; the hydrogen ion concentration (pH), temperature and total dissolved solids were analyzed with the HACH Multiparameter HQ 40d. Turbidity were measured with turbidimeter (model P2100 HACH); nitrate, phosphate, chloride, and sulfate were determined with HACH DR 2500 spectrophotometer, free chlorine were measured with HACH DR890 and compared with internal standards.
Data formatRaw, analyzed
Experimental factorsThe mentioned parameters above, in abstract section, were analyzed according to the standards for water and wastewater treatment handbook.
Experimental featuresThe levels of physical and chemical parameters drinking water were determined.
Data source locationAzogues, Ecuador 2°44'22" S, 78°50'54" O
Data accessibilityData are available in the article.
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