Estimation of corrosive and scaling trend in drinking water systems in the city of Azogues, Ecuador

García-Ávila, Fernando; Ramos-Fernández, Lía; Zhindón-Arévalo, César

doi:10.4136/ambi-agua.2237

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ARTICLES • Rev. Ambient. Água 13 (5) • 2018 • https://doi.org/10.4136/ambi-agua.2237 copy

Estimation of corrosive and scaling trend in drinking water systems in the city of Azogues, Ecuador

Estimativa da tendência corrosiva e de escala no sistema de água potável

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

The quality of drinking water flowing in a distribution network can possess corrosive characteristics that may cause the material degradation of pipes and accessories. This problem can result in reduction of the service life of pipes and create a major public health problem. The agreement between the physical-chemical water quality analysis and national standards are not enough to confirm the balance of the water quality in terms of corrosion. In order to predict pipe corrosion in water distribution system networks, the corrosive trend was evaluated using the Langelier (LSI), Ryznar (RSI), and Larson-Skold (LRI) indexes based on measurements of pH, temperature, total dissolved solids, alkalinity, calcium hardness, sulfate and chloride. This study was setup with 180 samples collected in six zones of the distribution network, from July to December of 2017, according to the standard methods for the analysis of drinking water. The results indicate a variation of the LSI from -1.22 to -1.68; RSI from 9.75 to 10.52 and LRI from 0.46 to 0.77. A linear model was fitted for each index to predict the corrosion with the water quality conditions of this study case. Therefore, the drinking water of the city of Azogues, Ecuador has a corrosive tendency from significant to severe. Corrosion indices were calculated to provide useful information on the water's corrosiveness. These results indicate the need to constantly monitor the corrosion rate in the distribution network and conduct a laboratory study to adjust effective parameters such as pH, in order to control corrosion.

Keywords:
Azogues city; corrosion rates; potabilization; water quality.

Index	Equation	Value	Water Feature
LSI	LSI = pH-pHs ISL = Langelier Saturation Index pH = pH measured in situ. pHs = pHat saturation pHs = 9.3 + A + B - C - D Where: $A = \frac{(l o g 10 T D S - 1)}{10}$ B = [-13.12 log10 (273°C + T)] + 34.55 C = log10 [ ${C a}^{+ 2}$ mg L^-1 as ${C a C O}_{3}$ ]-0.4 D = log10[Alcal. mg L^-1 L as ${C a C O}_{3}$ ] TDS = Total Dissolved Solids (mg L^-1)	LSI > 0	Scale forming
		LSI = 0	Neutral
		LSI < 0	Corrosive
		-0.4 to +0.4 is considered as a "zero"
RSI	RSI = 2 pHs-pH RSI = Ryznar Stability Index pHs = pH at saturation pH = pH measured in situ.	RSI< 5.5	Heavy scale likely to form
		5.5<RSI<6.2	Moderate scale-forming
		6.2<RSI<6.8	Is considered neutral
		6.8<RSI<8	Low corrosion
		RSI > 8	High corrosion
LRI	$L R I = \frac{[({C l}^{-}) + ({S O}_{4}^{- 2})]}{[({H C O}_{3}^{-}) + ({C O}_{3}^{- 2})]}$	LRI <0.8	Chloride and sulfate are unlikely to interfere with the formation of protecting film
		0.8<LRI <1.2	Corrosion rates may be higher than expected
		LRI> 1.2	High rates of localized corrosion may be expected.

N° Sample	pH	Temperature °C	TDS mg L^-1	Calcium mg L^-1 as CaCO₃	Alkalinity mg L^-1 as CaCO₃	Sulphate mg L^-1	Chloride mg L^-1
1	7.42 ± 0.07	17.66 ± 0.6	81.17 ± 7.02	20.40 ± 1.91	46.83 ± 6.30	22.33 ± 2.73	5.30 ± 0.47
2	7.38 ± 0.08	18.96 ± 0.4	82.17 ± 5.33	20.87 ± 1.49	50.00 ± 6.32	21.00 ± 2.45	5.58 ± 0.55
3	7.2 + 0.06	16.72 ± 1.0	63.67 ± 4.54	20.87 ± 2.01	51.33 ± 5.33	19.17 ± 1.96	5.33 ± 0.59
4	7.17 ± 0.05	19.44 ± 0.7	80.67 ± 7.82	23.13 ± 1.79	48.67 ± 5.81	23.00 ± 2.27	5.22 ± 0.54
5	7.41 ± 0.12	18.02 ± 0.5	71.50 ± 6.48	21.80 ± 2.80	46.67 ± 6.27	19.50 ± 2.91	5.05 ± 0.96
6	7.23 ± 0.07	17.3 ± 0.6	70.50 ± 5.16	22.47 ± 1.54	52.50 ± 5.90	19.17 ± 2.01	5.12 ± 0.57
7	7.2 ± 0.06	17.44 ± 08	72.33 ± 6.01	21.67 ± 2.01	52.5 ± 6.05	18.83 ± 2.06	11.58 + 0.6
8	7.18 ± 0.06	16.3 ± 0.6	72.33 ± 4.24	21.73 ± 1.79	53.67 ± 5.65	18.58 ± 1.70	4.57 ± 1.05
9	7.2 ± 0.05	17.72 ± 1.0	64.50± 5.91	21.00 ± 1.43	49.50 ± 5.14	17.33 ± 2.33	5.38 ± 0.71
10	7.22 ± 0.05	16.1 ± 1.4	66.33 ± 4.76	20.20 ± 1.63	50.50 ± 6.04	17.33 ± 1.96	5.70 ± 0.48
11	7.16 ± 0.05	15.78 ± 0.3	72.67 ± 6.50	21.33 ± 1.66	51.00 ± 4.92	15.50 ± 2.08	5.58 ± 0.97
12	7.26 ± 0.05	15.66 ± 0.8	68.83 ± 4.69	21.47 ± 1.14	53.67 ± 6.06	17.00 ± 2.77	4.95 ± 0.6
13	7.11 ± 0.08	16.16 ± 1.2	60.00 ± 3.66	17.47 ± 0.98	40.67 ± 2.53	13.50 ± 2.77	7.27 ± 1.56
14	7.25 ± 0.10	18.06 ± 0.8	70.00 ± 5.66	22.23 ± 2.16	47.00 ± 6.47	21.00 ± 2.39	5.30 ± 0.41
15	7.3 ± 0.08	16.36 ± 0.4	70.33 ± 6.54	21.57 ± 1.48	48.67 ± 4.98	20.17 ± 1.66	5.67 ± 0.46
16	7.17 ± 0.06	18.2 ± 1.3	72.67 ± 7.29	21.33 ± 1.35	45.67 ± 4.90	21.17 ± 2.24	5.22 ± 0.4
17	7.21 ± 0.07	17.64 ± 0.2	69.83 ± 5.55	20.60 ± 1.39	46.00 ± 4.50	18.83 ± 1.89	5.62 ± 0.74
18	7.24 ± 0.06	17.8 ± 0.7	68.67 ± 6.99	22.00 ± 1.78	48.83 ± 5.08	19.00 ± 2.82	5.58 ± 0.4
19	7.23 ± 0.09	17.76 ± 0.6	71.00 ± 6.04	21.87 ± 1.90	47.50 ± 5.66	19.67 ± 2.38	5.58 ± 0.65
20	7.18 ± 0.06	17.52 ± 1.2	69.67 ± 7.22	21.20 ± 1.48	46.52 ± 4.27	17.67 ± 2.69	5.57 ± 0.61
21	7.22 ± 0.06	18.7 ± 0.4	58.17 ± 2.33	17.47 ± 1.0	40.82 ± 1.87	12.50 ± 2.79	6.63 ± 1.03
22	7.24 ± 0.04	17.3 ± 0.5	63.50 ± 4.92	20.13 ± 1.54	46.50 ± 4.15	18.50 ± 2.17	5.72 ± 0.80
23	7.24 ± 0.09	17.62 ± 0.7	68.17 ± 5.13	21.33 ± 1.78	49.17 ± 5.24	19.50 ± 2.11	5.47 ± 0.47
24	7.26 ± 0.07	17.22 ± 1.1	66.83 ± 6.77	21.07 ± 1.73	47.50 ± 2.96	17.50 ± 2.62	5.80 ± 0.58
25	7.2 ± 0.05	17.1 ± 0.7	64.33 ± 3.8	20.07 ± 1.56	46.33 ± 3.48	17.00 ± 2.28	5.30 ± 0.82
26	7.26 ± 0.09	18.1 ± 0.6	67.83 ± 5.15	20.67 ± 1.37	48.83 ± 4.43	16.33 ± 2.33	5.88 ± 0.74
27	7.28 ± 0.07	16.24 ± 1.1	65.17 ± 6.99	20.13 ± 1.54	47.67 ± 4.72	15.83 ± 2.21	6.03 ± 0.68
28	7.31 ± 0.06	17.16 ± 1.2	67.83 ± 5.70	20.2 ± 1.51	51.33 ± 4.72	17.33 ± 2.17	6.00 ± 0.86
29	7.26 ± 0.05	18.56 ± 0.8	72.50 ± 6.84	20.13 ± 1.43	49.00 ± 5.49	16.17 ± 2.70	5.93 ± 0.67
30	7.27 ± 0.06	17.26 ± 1.2	59.83 ± 2.64	17.33 ± 0.91	40.00 ± 2.54	14.00 ± 3.2	5.97 ± 1.22

Zone	LSI	RSI	LRI
Alta	-1.40	10.03	0.52
Mahuarcay	-1.58	10.38	0.53
Media	-1.4	10.03	0.67
Zhigzhiquin	-1.31	9.94	0.63
Principal	-1.43	10.09	0.54
Zhapacal	-1.34	9.93	0.60
Average	-1.39	10.07	0.58
p	<0.0001	<0.0001	<0.0001

Authors	LSI	RSI	LRI
Abbasnia et al.(2018)ABBASNIA, A.; ALIMOHAMMADI, M.; MAHVIA, A. H.; NABIZADEH, R.; YOUSEFI, M.; MOHAMMADI, A. A. et al. Assessment of groundwater quality and evaluation of scaling and corrosiveness potential of drinking water samples in villages of Chabahr city, Sistan and Baluchistan province in Iran. Data Brief, v. 16, p. 182-192, 2018. https://doi.org/10.1016/j.dib.2017.11.003 https://doi.org/10.1016/j.dib.2017.11.00...	0.5	6.76	2.71
Yousefi et al.(2018)YOUSEFI, M.; SALEH, H. N.; MAHVI, A. H.; ALIMOHAMMADI, M.; NABIZADEH, R.; MOHAMMADI,A. A. Data on corrosion and scaling potential of drinking water resources using stability indices in Jolfa, East Azerbaijan, Iran. Data Brief, v. 16, p. 724-731, 2018. https://dx.doi.org/10.1016/j.dib.2017.11.099 https://dx.doi.org/10.1016/j.dib.2017.11...	1.15	6.92	0.85
Alimoradi et al.(2018)ALIMORADI, J.; NAGHIPOUR, D.; KAMANI, H. Data on corrosive water in the sources and distribution network of drinking water in north of Iran. Data Brief, v.17, p.105-118, 2018. https://doi.org/10.1016/j.dib.2017.12.057 https://doi.org/10.1016/j.dib.2017.12.05...	-1.31	9.73	0.24
Khorsandi et al.(2015)KHORSANDI, H.; MOHAMMADI, A.; KARIMZADEH, S.; KHORSANDI, J. Evaluation of corrosion and scaling potential in rural water distribution network of Urmia, Iran. Desalination and Water Treatment, p. 1-8, 2015. http://dx.doi.org/10.1080/19443994.2015.1042058 http://dx.doi.org/10.1080/19443994.2015....	-1.94	12.05	0.68
Tavanpour et al.(2016)TAVANPOUR, N.; NOSHADI, M.; TAVANPOUR, N. Scale Formation and Corrosion of Drinking Water Pipes: A Case Study of Drinking Water Distribution System of Shiraz City. Modern Applied Science, v. 10, n. 3, p. 166-177, 2016. http://dx.doi.org/10.5539/mas.v10n3p166 http://dx.doi.org/10.5539/mas.v10n3p166...	0.08	7.15	1.1

Coef	Est.	E.E.	LI (95%)	LS (95%)	T	P-Value	CpMallows	VIF
Const	-9.84	0.06	-9.96	-9.71	-155.32	<0.0001
PH	1.01	0.01	0.99	1.03	106.29	<0.0001	11236.03	1.96
T	0.02	6.60E-04	0.02	0.02	28.91	<0.0001	836.03	1.36
SDT	-4.30E-04	1.60E-04	-7.50E-04	-1.20E-04	-2.69	0,008	12.18	3.91
Calcium	0.02	5.50E-04	0.02	0.02	38.61	<0.0001	1487.2	3.42
Alkalinity	0.01	1.80E-04	0.01	0.01	44.71	<0.0001	1992.51	3.49

Coef	Est.	E.E.	LI (95%)	LS (95%)	T	P-Value	CpMallows	VIF
Const	19.7	0.12	13.67	19.95	157.76	<0.0001
PH	-1.02	0.02	-1.06	-0.99	-54.61	<0.0001	2969.87	1.96
T	-0.04	1.30E-03	-0.04	-0.04	-29.55	<0.0001	873.33	1.36
SDT	8.40E-04	3.20E-04	2.10E-04	1.50E-03	2.64	0.0091	11.94	3.91
Calcium	-0.04	1.10E-03	-0.04	-0.04	-39.07	<0.0001	1522.9	3.42
Alkalinity	-0.02	3.60E-04	-0.02	-0.02	-45.06	<0.0001	2023.09	3.49

Instituto de Pesquisas Ambientais em Bacias Hidrográficas Instituto de Pesquisas Ambientais em Bacias Hidrográficas (IPABHi), Estrada Mun. Dr. José Luis Cembranelli, 5000, Taubaté, SP, Brasil, CEP 12081-010 - Taubaté - SP - Brazil
E-mail: ambi.agua@gmail.com

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[1] ^*Corresponding author: Fernando García-Ávila, e-mail: garcia10f@hotmail.com