a critical evaluation of the water stability indices for the...

American Journal of Environmental Engineering and Science 2018; 5(1): 8-16 http://www.aascit.org/journal/ajees ISSN: 2381-1153 (Print); ISSN: 2381-1161 (Online)

Keywords Aggressiveness Index, Corrosion, Groundwater, Langelier Saturation Index, Larson-Skold Index, Puckorius Scaling Index, Ryznar Scaling, Stability Index Received: June 12, 2017 Accepted: January 16, 2018 Published: January 25, 2018

A Critical Evaluation of the Water Stability Indices for the Groundwaters of Bommasandra Industrial Area in Bangalore, India

Bangalore Shankar1, *

, Usha Arcot2

1Department of Civil Engineering, Alliance College of Engineering and Design, Alliance University, Bangalore, Karnataka, India

2Department of Mathematics, Alliance College of Engineering and Design, Alliance University, Bangalore, Karnataka, India

Email address [email protected] (B. Shankar) *Corresponding author

Citation Bangalore Shankar, Usha Arcot. A Critical Evaluation of the Water Stability Indices for the Groundwaters of Bommasandra Industrial Area in Bangalore, India. American Journal of

Environmental Engineering and Science. Vol. 5, No. 1, 2018, pp. 8-16.

Abstract Depending upon its specific chemistry, water can promote scaling, corrosion or both, and these two aspects remain to be one of the most critical water quality issues in India. Corrosion and scaling tendency of water is an etiology of economic and health concerns in the water supply systems. The present study aims to evaluate to the water stability with respect to corrosion and scaling, in the groundwaters of Bommasandra industrial area in Bangalore, India. Thirty groundwater samples were drawn from the area and subjected to physico-chemical analysis and the analysis results were used to evaluate the Langelier saturation index (LSI), Ryznar Stability index (RSI), Puckorius scaling index (PSI), Larson-Skold index (LS), and Aggressiveness index (AI). Based on the investigation, the corrosion tendency in the study area was seen to be 33.33, 30, 80, 93.33 and 20 percent as per the values of LSI, RSI, PSI, LS and AI respectively, while the scaling tendency in the same sequence was observed to be 66.67, 60, 20, 6.67 and 80% respectively. A brief note on the measures that could be employed to mitigate these issues has been indicated.

1. Introduction

While most people in urban cities of the developing countries have access to piped water, several others still rely on groundwater for domestic use [1]. Industrial effluents, if not treated and properly controlled can pollute ground water [2]. Therefore, the groundwaters generally have poor quality water in the affected areas Scaling is one of the most critical water quality issues in India. Scale can be formed from a variety of dissolved chemical species, but two reliable indicators are hardness and alkalinity. Calcium carbonate is the most common form of scale deposition attributable to ground water [3]. Stability of water is the tendency of water to either dissolve or deposit minerals varying with its chemical makeup. Water that tends to dissolve minerals is considered corrosive and that tends to deposit mineral is considered scaling. Corrosive water can dissolve minerals like calcium and magnesium, also can dissolve harmful metals such as lead and copper from plumbing utilities whereas scaling waters deposit a film of minerals on pipe walls and may prevent corrosion of metallic surfaces. If the scale deposition is too rapid, it also can be harmful and can damage appliances, such as

American Journal of Environmental Engineering and Science 2018; 5(1): 8-16 9

water heaters, and increase pipe friction coefficients; in extreme cases, scale may clog pipes [4].

The economic and health aspects of corrosion, which may not be obvious without network observation, is a significant concern for water supply [5]. Monitoring of water stability is an appropriate tool for preventing water leaks and decreasing the cost of replacing pipes, pumps, and equipment [6, 7].

Water scaling can cause staining, block nozzles and coat internal wall of pipework [8]. Deposits can also greatly impact the efficiency of boilers and heat exchangers substantially increasing energy and maintenance costs [9, 10].

Corrosion indices have been developed by researchers, which easily calculate and predict corrosion or scaling tendency and can be useful in corrosion control program. LSI is one of the most common scale prediction tools for calcium carbonate scaling [11]. Unlike the RSI, LSI has no theoretical basis and is defined by a simple empirical relationship that was found by trial and error.

Another empirical equation, PSI, is a variation of the RSI, but differs by using equilibrium pH instead of measured pH. From an empirical study, Larson and Skold developed an index based upon chloride and sulfate aggressiveness toward pitting corrosion and alkalinity as minimizing factor toward aggression, called LI [12]. In an attempt to govern proper type of Asbestos-Cement pipe type and its wholeness during operation, AI was developed. [13].

Evaluation of the Indices: A brief note on the five indices, along with their computations have been briefly illustrated below:

1.1. Langelier Saturation Index (LSI)

The Langelier saturation index (LSI) is probably the most widely used indicator of cooling water scale potential. This index indicates the driving force for scale formation and growth in terms of pH as a master variable [14]. The LSI is an equilibrium model derived from the theoretical concept of saturation and provides an indicator of the degree of saturation of water with respect to calcium carbonate. It can be shown that the Langelier saturation index approximates the base 10 logarithm of the calcite saturation level. The Langelier saturation level approaches the concept of saturation using pH as a main variable. Thus, the LSI can be interpreted as the pH change required to bring water to equilibrium.

The algebraic difference between the actual pH of a sample of water and its computed pHs is called the Calcium Carbonate Saturation Index. Hence, Saturation Index equals pH minus pHs.

LSI = pH - pHs

Calculation of the value for pHs can be done using the nomograph or through the use of the following equation

pHs = (9.3 + A + B) - (C + D) [10] Where: A = [log (TDS) -1)/10], TDS in ppm

B = [-13.12 log (T + 273)) + 34.55], Temperature, T in °C

C = [log (calcium hardness) - 0.4], Ca hardness in ppm (as CaCO3)

D = log (alkalinity), alkalinity in ppm as (CaCO3) It is apparent that the temperature at which the calculation

is made has considerable impact upon the results. This index is a qualitative indication of the tendency of calcium carbonate to deposit or dissolve. If the index is positive, calcium carbonate tends to deposit. If it is negative, calcium carbonate tends to dissolve. If it is zero, the water is at equilibrium.

1.2. Ryznar Stability Index (RSI)

The Ryznar stability index (RSI) uses a correlation established between an empirical database of scale thickness observed in municipal water systems and associated water chemistry data. Like the LSI, the RSI has its basis in the concept of saturation level. The Ryznar index takes the form:

RSI = 2(pHs) − pH

This index is often used in combination with the Langelier index to improve the accuracy in predicting the scaling or corrosion tendencies of water.

1.3. Puckorius Scaling Index (PI)

The Puckorius scaling index (PSI) is based on the buffering capacity of the water, and the maximum quantity of precipitate that can form in bringing water to equilibrium. Water high in calcium, but low in alkalinity and buffering capacity, can have a high calcite saturation level. The high calcium level increases the ion activity product. Such water might have a high tendency to form scale due to the driving force, but scale formed might be of such a small quantity as to be unobservable. The water has the driving force, but not the capacity and ability to maintain pH as precipitate matter forms.

The PSI index is calculated in a manner similar to the Ryznar stability index.

Puckorius uses an equilibrium pH rather than the actual system pH to account for the buffering effects:

PSI = 2(pHs) − pHeq

where pHs is still the pH at saturation in calcite or calcium carbonate

pHeq = 1.465 × log10 [Alkalinity] + 4.54 If PSI < 6, Scaling is unlikely to occur and > 7, it is Likely

to dissolve scale.

1.4. Larson–Skold Index (LS)

The Larson–Skold index is based upon evaluation of in situ corrosion of mild steel lines transporting Great Lakes waters. The index is the ratio of equivalents per million (epm) of sulfate (SO4

2−) and chloride (Cl−) to the epm of alkalinity in the form bicarbonate.

Larson–Skold index = (epm Cl− + epm SO42−) /(epm HCO3)

10 Bangalore Shankar and Usha Arcot: A Critical Evaluation of the Water Stability Indices for the Groundwaters of Bommasandra Industrial Area in Bangalore, India

The index has proven to be a useful tool in predicting the aggressiveness of once through cooling waters. The LS might be interpreted by the following guidelines:

Index < 0.8 chlorides and sulfate probably will not interfere with natural film formation, while

0.8 < index < 1.2 chlorides and sulfates may interfere with natural film formation. Higher than desired corrosion rates might be anticipated and Index > 1.2 the tendency toward high corrosion rates of a local type should be expected as the index increases. [14].

1.5. Aggressive Index (AI)

The Aggressive Index (AI), originally developed for monitoring water in asbestos pipe, is sometimes substituted for the Langelier Index as an indicator of the corrosivity of

water. The LSI was simplified without the involvement of temperature and ionic strength as AI. It is simple to use and convenient to apply because it does not include the complicating effects of temperature or dissolved solids [15]. The Aggressiveness index (AI) is defined as follows

AI = pH + log (AH)

Where: AI = Aggressiveness index, A = total alkalinity, mg/L as calcium carbonate, and H = calcium hardness, mg/L as calcium carbonate. AI >12 is deemed to be Non aggressive, a value between 10 and 12 is considered Moderately aggressive and <10 is deemed Very aggressive.

Table 1 illustrates the Interpretation of the Saturation Indices and criteria for categorizing the stability of the water.

Table 1. Interpretation of the Saturation Indices and criteria for categorizing the stability of the water.

Index Index Ranges Indications/Water condition

Langelier Saturation Index (LSI)

LSI <- 2 Intolerable corrosion

-2.0 <LSI < -0.5 Serious corrosion

-0.5 <LSI < 0 Slightly corrosive but non-scale forming

LSI = 0 Balanced but pitting corrosion possible

0 < LSI < 0.5 Slightly Scale forming and corrosive

0.5 < LSI < 2 Scale forming but non corrosive

Ryznar Stability Index (RSI)

RSI < 5.5 Heavy scale formation

5.5 < RSI < 6.2 Moderate scale formation

6.2 < RSI < 6.8 Non-scaling or corrosive

6.8 < RSI < 8.5 Water is aggressive and corrosion is likely

RSI > 8.5 Water is considered very aggressive, and substantial corrosion is possible

Puckorius scaling Index (PSI) PSI < 6.0 Scaling is unlikely to occur

PSI >7.0 Likely to dissolve Scale

Aggressive Index (AI)

AI < 10.0 Water is very aggressive

10.0 < AI < 12.0 Water is moderately aggressive

AI > 12.0 Water is non-aggressive

Larson-Skold Index (LS)

LS < 0.8 Chloride and sulfate will not interfere with natural film formation

0.8 < LS < 1.2 Chloride and sulfate may interfere with natural film formation, corrosion may occur

LS > 1.2 High corrosion rates are anticipated

Hither-to, quite a few studies have been carried out across

the world to evaluate these indices, but in India, hardly any such investigation has been taken up, which serves as an additional motivation to take up this work and understand the prevailing situation in the groundwaters of Bangalore, India.

2. Details of the Study Area

The Bommasandra Industrial area lies to the left of Bommasandra Village, on the Bangalore- Hosur Road, at a distance of about 12kms from the City. It covers an area of about 3.84 Square Km and lies between 12° 471 5211 to 12° 491 1211 E Latitude and 77° 41 2011 to 77° 421 2011 N Longitude and is covered under Survey of India topo sheet number 57 H/9. The area has a network of nearly 600 industries over an extent of 3.84SqKm. The drinking water

needs of the area is met by about 180 borewells drilled in and around the area.

3. Materials and Methods

Thirty water samples were collected from the groundwaters (borewells, open wells and hand pumps) in and around the area, in two litre PVC containers, sealed and were analyzed for 20 major physico-chemical parameters in the lab. However, the table 2 shows the analysis results of only those parameters which are essential for the computation of the stability indices. Figure 1 shows the location map of study area with the sampling stations. The chemical characteristics including metals were determined as per the Standard methods for examination of water and wastewater of American Public Health Association [16].


Figure 1. Location map of Bommasandra industrial area showing the sampling stations.


Table 2. Results of Physico-Chemical analysis of Groundwater Samples of Bommasandra Industrial area.

Sample

number pH

Calcium hardness,

mg/L as CaCO3 TDS, mg/L

Alkalinity,

mg/L as CaCO3 Temperature, °C Cl-, mg/L

SO4-,

mg/L

HCO3-,

mg/L

1 7.29 490 961 214 25 280 34 204 2 6.9 1000 2198 183 25 1012 180 183 3 6.92 320 715 291 25 272 54 275 4 7.1 370 867 327 25 300 84 327 5 7.18 750 1961 550 25 740 226 550 6 7.32 510 1197 360 25 404 40 360 7 6.5 230 388 153 25 60 75 153 8 7.01 320 982 293 25 280 290 275 9 7.06 840 2151 348 25 1012 210 348 10 7.47 630 1415 426 25 508 174 420 11 7.2 940 2141 350 25 1020 290 346 12 7.5 720 2183 214 25 1010 404 324 13 7.31 690 1926 506 25 700 402 488 14 7.9 700 1927 648 25 640 240 608 15 7.1 250 481 275 25 130 40 275 16 6.48 380 807 113 25 200 288 113 17 7.4 240 506 214 25 190 33 214 18 7.61 430 773 342 25 200 189 336 19 7.3 600 1408 551 25 410 238 519 20 7.32 600 1285 380 25 450 180 380 21 7.52 370 766 340 25 272 40 340 22 7.48 760 1426 555 25 610 30 516 23 7.62 340 1203 310 25 508 140 370 24 7.71 380 1379 398 25 530 152 398 25 7.8 890 2178 358 25 1044 350 458 26 8.02 1100 2616 400 25 1440 220 396 27 8.22 250 573 358 25 104 40 358 28 7.46 895 1734 472 25 682 176 472 29 7.1 260 578 244 25 200 30 244 30 7.42 770 2018 488 25 770 350 488

4. Results and Discussion

Investigation on the Stability indices to evaluate the scaling and corrosion potential in the ground waters of Bommasandra Industrial area revealed the following, depicted briefly, as under;

From the analysis based on Langelier Saturated index, only 33.33% of the water samples showed corrosion tendency while 66.67% of samples showed scale formation in which water tends to precipitate calcium carbonate.

Based on Ryznar Stability index, 40% of the water samples showed corrosion tendency while 60% of samples showed scale formation. This result is in perfect agreement with the LSI index.

According to the Puckorius Scaling Index, 80% showed corrosion tendency, while just 6.67% of the samples showed scale formation tendency. PSI considers scaling as unlikely to occur if the value is < 6. It is considered as likely to dissolve scale if it is > 7.

As per Larson-Skold Index, a whopping 94% of the samples have LS values greater than 1.2 and point towards high corrosion, while 3.33% of samples reveal that both chloride and sulphate ions do not interfere with the natural film formation another 3.33% of the samples have both chloride and sulfate interference resulting in more pronounced corrosion.

Aggressive index calculations showed that 80% of the

samples did not exhibit corrosion, showing scale forming tendency, whilst 20% of the samples were found to be mildly aggressive.

A composite understanding of all the stability indices in a nut shell reveal that the corrosion tendency in the study area was seen to be 33.33, 30, 80, 93.33 and 20 percent as per the values of LSI, RSI, PSI, LS and AI respectively, while the scaling tendency in the same sequence was observed to be 66.67, 60, 20, 6.67 and 80% respectively. Table 3 depicts the Drinking water stability of the study area, while the variations of all five stability indices have been presented in Figure 2.

The analysis results agree well with the multiple studies that have been carried out hither-to in different parts of the world. Taghipour et al. evaluated the water stability indices in Tabriz, Iran using different corrosion indices. They found that the water resources mostly tended to be corrosive [17].

A study of Evaluation of corrosion and scaling potential in rural water distribution network of four villages located in Urmia, Iran reveal that based on the LSI, RSI, and PSI values, water samples in the three of villages were highly corrosive, however for one of these villages, LRI as a suitable index showed that the water of distribution network has tendency to scaling [18].

In another study, water stability condition of 31 rural distribution networks, located in Tabas county (Middle-East of Iran) were evaluated by Shams et al. [19]. Based on LSI, RSI, PSI, LS and AI indices results showed 29.03, 90.32,


96.78, 96.77 and 12.1 percent of drinking water distribution networks have corrosion tendency. They concluded that water temperature is a key factor in corrosion and scaling potential of water, so increasing water temperature can shift the water tendency toward scaling. The results in the present study match with these observations.

In 2014, a study of the water quality supplied to a hospital in Chacas village (Peru) was also carried out. The results showed negative values of LSI ranging from - 1.04 to - 3.07. RSI values ranged from 10.04 to 12.34. Dolomite limestone filter was used to mitigate the effect of corrosion in the water reaching the hospital. The limestone filter modified both the LSI and RSI to values of - 1.2 and 10.0, respectively. These values indicated a positive effect of the filter on the corrosion tendency of the distributed water. Therefore, the LSI and RSI indices were useful tools for pipe corrosion evaluation even if both LSI and RSI were not suitable for the quantification of water corrosiveness [20].

Some considerable variations have been noticed in the present study with respect to the values amongst some indices. As per Taghipour H, et al., difference among indices results at months may be related to different in water chemistry caused by composition of ground layers. The study of relationship between chemical water quality and layer ground material showed if the geologic structure is made up of layers of calcareous the water hardness increases and resulting in the scaling of water increases [21]. Mahvi et al. studied corrosion and scaling in “Bandar Abbas city (Southern Iran) pipe water network” and they obtained the same results. They showed that, Bandar Abbas water network

has corrosion potential. Evaluation of indices in their study showed that there were significant differences among indices findings; therefore, it seems that mono-index evaluation is unlikely to determine the corrosion status or scaling condition [22]. The present study findings support these observations strongly too.

Further, in order to evaluate the effect of water temperature on water stability, Water Stability indices have been calculated at T – 10°C, T – 5°C, T + 5°C, and T + 10°C, where T refers to the mean temperature of 25°C used in the study. According to the obtained results, as water temperature increased, LSI increased, but RSI and PSI decreased. This means that the tendency of water toward scaling has been accelerated by increasing the water temperature. The previous studies too have confirmed these results [5].

The effect of water temperature on LSI, RSI and PSI has been depicted in Table 4.

Corrosive potential of water will affect the aesthetic aspects, adversely. Since the corrosion and scaling control goals include protecting public health, water quality, longevity of water utility and providing national standards for water quality, taking logical steps in this regard would also be beneficial. Monitoring of chemical quality, scaling and corrosion potential of water should be considered in quality control programs [8]. As the choice of any index, maybe, propose a different description of the water stability condition, selecting the most appropriate index conforming with actual situation of any system, is one of the most critical aspects whilst making predictions.

Table 3. Drinking water stability of the Study area.

Index Index and Water Stability

Sampling locations LSI RSI AI PSI LI LSI RSI AI PSI LI

1 0.32 6.64 12.31 6.01 2.62 CT CT NA ST CT 2 0.14 6.62 12.16 5.70 10.96 CT CT NA CT CT 3 -0.08 7.09 11.89 5.90 1.99 CT CT MA CT CT 4 0.20 6.70 12.18 5.61 1.94 CT CT NA CT CT 5 0.78 5.62 12.80 4.29 2.89 ST ST NA CT CT 6 0.59 6.14 12.58 5.22 2.11 ST ST NA CT CT 7 -0.90 8.30 11.05 7.09 1.32 CT CT MA ST CT 8 -0.01 7.02 11.98 5.91 2.82 CT CT MA CT CT 9 0.50 6.05 12.53 4.89 5.87 ST ST NA CT CT 10 0.90 5.68 12.90 4.80 2.66 ST ST NA CT CT 11 0.70 5.81 12.72 4.78 6.25 ST ST NA CT CT 12 0.67 6.17 12.69 5.75 11.24 ST ST NA CT CT 13 0.84 5.64 12.85 4.49 3.44 ST ST NA CT CT 14 1.54 4.82 13.56 4.10 2.36 ST ST NA CT CT 15 -0.02 7.14 11.94 6.16 1.02 CT CT MA ST ST 16 -0.87 8.21 11.11 7.18 5.95 CT CT MA ST CT 17 0.15 7.10 12.11 6.58 1.75 CT CT NA ST CT 18 0.80 6.01 12.78 5.40 1.66 ST ST NA CT CT 19 0.82 5.67 12.82 4.45 1.98 ST ST NA CT CT 20 0.68 5.96 12.68 5.00 2.69 ST ST NA CT CT 21 0.64 6.23 12.62 5.54 1.55 ST CT NA CT CT 22 1.10 5.28 13.11 4.24 2.14 ST ST NA CT CT 23 0.65 6.33 12.64 5.79 3.41 ST CT NA CT CT 24 0.89 5.94 12.89 5.34 2.83 ST ST NA CT CT 25 1.28 5.24 13.30 4.79 6.19 ST ST NA CT CT 26 1.63 4.75 13.66 4.46 7.09 ST ST NA CT CT 27 1.21 5.80 13.17 5.78 0.65 ST ST NA CT ST 28 1.07 5.31 13.09 4.36 3.01 ST ST NA CT CT


Index Index and Water Stability

Sampling locations LSI RSI AI PSI LI LSI RSI AI PSI LI

29 -0.06 7.22 11.90 6.32 1.59 CT CT MA ST CT 30 0.98 5.47 12.99 4.45 3.69 ST ST NA CT CT

*: ST: Scaling tendency; CT: Corrosion tendency; NA: Non aggressive; MA: Moderately aggressive.

Table 4. Water Stability indices studied as a function of temperature.

Indices LSI RSI PSI LS Al LSI LSI LSI LSI

Temperature T T T T T T-10 T-5 T+5 T+lO

1 0.32 6.64 6.01 2.62 12.31 0.13 0.23 0.42 0.51 2 0.14 6.62 5.70 10.96 12.16 -0.05 0.04 0.23 0.33 3 -0.08 7.09 5.90 1.99 11.89 -0.28 -0.18 0.01 0.10 4 0.20 6.70 5.61 1.94 12.18 0.01 0.10 0.30 0.39 5 0.78 5.62 4.29 2.89 12.80 0.58 0.68 0.87 0.97 6 0.59 6.14 5.22 2.11 12.58 0.39 0.49 0.68 0.78 7 -0.90 8.30 7.09 1.32 11.05 -1.10 -1.00 -0.81 -0.71 8 -0.01 7.02 5.91 2.82 11.98 -0.20 -0.10 0.09 0.18 9 0.50 6.05 4.89 5.87 12.53 0.31 0.41 0.60 0.69 10 0.90 5.68 4.80 2.66 12.90 0.70 0.80 0.99 1.08 11 0.70 5.81 4.78 6.25 12.72 0.50 0.60 0.79 0.88 12 0.67 6.17 5.75 11.24 12.69 0.47 0.57 0.76 0.85 13 0.84 5.64 4.49 3.44 12.85 0.64 0.74 0.93 1.02 14 1.54 4.82 4.10 2.36 13.56 1.35 1.44 1.63 1.73 15 -0.02 7.14 6.16 1.02 11.94 -0.21 -0.12 0.08 0.17 16 -0.87 8.21 7.18 5.95 11.11 -1.06 -0.96 -0.77 -0.68 17 0.15 7.10 6.58 1.75 12.11 -0.04 0.06 0.25 0.34 18 0.80 6.01 5.40 1.66 12.78 0.61 0.70 0.90 0.99 19 0.82 5.67 4.45 1.98 12.82 0.62 0.72 0.91 1.00 20 0.68 5.96 5.00 2.69 12.68 0.48 0.58 0.77 0.87 21 0.64 6.23 5.54 1.55 12.62 0.45 0.55 0.74 0.83 22 1.10 5.28 4.24 2.14 13.11 0.91 1.00 1.20 1.29 23 0.65 6.33 5.79 3.41 12.64 0.45 0.55 0.74 0.83 24 0.89 5.94 5.34 2.83 12.89 0.69 0.79 0.98 1.08 25 1.28 5.24 4.79 6.19 13.30 1.09 1.18 1.38 1.47 26 1.63 4.75 4.46 7.09 13.66 1.44 1.54 1.73 1.82 27 1.21 5.80 5.78 0.65 13.17 1.01 1.11 1.30 1.40 28 1.07 5.31 4.36 3.01 13.09 0.88 0.98 1.17 1.26 29 -0.06 7.22 6.32 1.59 11.90 -0.26 -0.16 0.03 0.13 30 0.98 5.47 4.45 3.69 12.99 0.78 0.88 1.07 1.16

Table 4. Continued.

Indices RSI RSI RSI RSI PSI PSI PSI PSI

Temperature T-10 T-5 T+5 T+lO T-10 T-5 T+5 T+lO

1 7.03 6.83 6.45 6.27 6.40 6.21 5.82 5.64 2 7.01 6.81 6.43 6.24 6.09 5.89 5.51 5.32 3 7.48 7.28 6.90 6.71 6.29 6.09 5.71 5.52 4 7.09 6.89 6.51 6.32 6.00 5.81 5.42 5.24 5 6.01 5.82 5.43 5.25 4.68 4.48 4.10 3.91 6 6.53 6.34 5.95 5.77 5.61 5.41 5.03 4.84 7 8.69 8.49 8.11 7.93 7.48 7.29 6.90 6.72 8 7.41 7.21 6.83 6.64 6.30 6.11 5.72 5.54 9 6.44 6.24 5.86 5.68 5.28 5.08 4.70 4.51 10 6.07 5.87 5.49 5.30 5.19 4.99 4.61 4.42 11 6.20 6.00 5.62 5.43 5.17 4.97 4.59 4.40 12 6.56 6.36 5.98 5.79 6.14 5.94 5.56 5.37 13 6.03 5.83 5.45 5.26 4.88 4.68 4.30 4.11 14 5.21 5.01 4.63 4.44 4.49 4.30 3.91 3.73 15 7.53 7.33 6.95 6.76 6.55 6.35 5.97 5.79 16 8.60 8.40 8.02 7.84 7.56 7.37 6.99 6.80 17 7.49 7.29 6.91 6.72 6.97 6.77 6.39 6.20 18 6.40 6.20 5.82 5.63 5.79 5.60 5.22 5.03 19 6.06 5.86 5.48 5.29 4.84 4.65 4.26 4.08 20 6.35 6.16 5.77 5.59 5.39 5.19 4.81 4.63 21 6.62 6.43 6.04 5.86 5.93 5.74 5.35 5.17 22 5.67 5.47 5.09 4.90 4.63 4.43 4.05 3.86 23 6.72 6.52 6.14 5.95 6.18 5.99 5.60 5.42


Indices RSI RSI RSI RSI PSI PSI PSI PSI

Temperature T-10 T-5 T+5 T+lO T-10 T-5 T+5 T+lO

24 6.32 6.13 5.75 5.56 5.72 5.53 5.15 4.96 25 5.63 5.43 5.05 4.86 5.18 4.99 4.60 4.42 26 5.14 4.95 4.56 4.38 4.85 4.65 4.27 4.08 27 6.19 6.00 5.61 5.43 6.17 5.97 5.59 5.41 28 5.70 5.51 5.12 4.94 4.74 4.55 4.17 3.98 29 7.61 7.42 7.03 6.85 6.71 6.52 6.13 5.95 30 5.86 5.66 5.28 5.09 4.84 4.64 4.26 4.07

a

b

c

d

e

Figure 2. Variation of (a) LSI, (b) RSI, (c) PSI, (d) LI and e) AI in the Study

area.

5. Conclusion

Groundwater analysis in the study area revealed that the corrosion tendency was seen to be 33.33, 30, 80, 93.33 and 20 percent as per the values of LSI, RSI, PSI, LS and AI respectively, while the scaling tendency in the same sequence was observed to be 66.67, 60, 20, 6.67 and 80% respectively. Based on the investigations, it is apparent that waters with high corrosive property cannot be transported in metallic pipes and non-corrosive PVC pipes may have to be used. Both the scaling as well as corrosive nature of groundwater render them unfit for regular domestic use, unless otherwise properly treated, and it thus becomes highly imperative for the civic authorities to pay due attention to this and reduce the adverse effects that may be caused.


Acknowledgements

The authors are extremely grateful to Prof. Sudhir Angur, Chancellor, Alliance University, Bangalore, for his perpetual support, encouragement and inspiration along with the excellent library facilities provided to the authors during the course of this work.

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a critical evaluation of the water stability indices for the...

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