Introduction

Incrustation is the process of deposition of precipitate from groundwater onto well installation materials or into the surrounding aquifer. The implications include reduction in open area of well screen in wells and reduction of aquifer permeability adjacent to the well in addition to causing blockages in convey pipes and increase in operational and maintenance costs. Incrustation relates directly to supersaturation of groundwater with respect to certain compounds, like calcite, carbonates, iron compounds, sulphates or manganese compounds. Water being a universal solvent dissolves many constituents from atmosphere, soil and strata in contact. These chemical constituents are directly responsible for causing corrosion, fouling and scaling.

Scaling and fouling indices have been used to predict the extent of calcium carbonate deposition onto heat transfer surfaces in industries. Once calcium carbonate is supersaturated, it precipitates as salt with an increase in temperature. Saturation indices of calcium carbonate have been determined mainly by saturation Indices (Nalco 1979) even though sophisticated methods are available (Hasson 1981).

Some authors have calculated the scale deposition and corrosion in tap waters (Al-Rawajfeh and Al-Shamaileh 2007), whereas others have described the same for river waters (Haritash et al. 2016) and others have described its usefulness in water supply networks and water treatment and supply plants (Davil et al. 2009; Mirzabeygi et al. 2017).

The study area

Mahoba district lies at the southernmost extent of Bundelkhand region of Uttar Pradesh state between 25°01′30″ to 25°39′40″ North latitude and 79°15′00″ to 80°10′30″ East longitude. The district experiences semiarid climate with low precipitation of around 864 mm/year and covers an area of 2884 km2 and is divided into 4 blocks, namely Kabrai, Charkhari, Panwari and Jaitpur.

Mahoba is an agriculture-dominated district, and 72% area is actively cultivated. About 80% of the total geographical area of the district is cultivated area. The main Rabi crops include wheat, barley, red lentil, gram, pea, pigeon pea and mustard. The main Kharif crops are mung beans, millets, sesame, maize, urad, jowar, groundnut and black gram. Zaid crops are maize, black gram, mung beans and potato (CGWB 2020).

The map of the study area is attached in Fig. 1.

Fig. 1
figure 1

Map of the study area

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Geology and hydrogeology of study area

The district can be broadly classified into two physiographic units—southern portion with high relief and northern portion with relatively low relief and low hillocks. Geologically, the northern portion of the district comprises Quaternary alluvium underlain by Bundelkhand Granites of Precambrian age. Dolerite dykes and Quartz reefs are also seen at places but form only a fraction when compared to Granites and Alluvium, and they too were formed during Precambrian age. Granites are observed as isolated or clustered hillocks. Granites occurring in the district reflect considerable heterogeneity in colour, texture, grain size and composition. Most common Granite in the district is Alkali feldspar Granite, and less common variety is grey coloured Leucogranite. Occasionally, Quartz veins are also encountered in Granite. The Quartz reef trending NE–SW occurs as narrow ridges. These reefs are composed of fine grained compact silica material and are milky white in colour. Dolerite dykes intruding the Granite mainly display trend in EW to NW–SE direction (CGWB 2014).

Surface water from Madan Sagar, Kirat Sagar, Vijay Sagar and Kalyan Sagar lakes is a possible source of potable water but it is only fit for agriculture (Pal et al. 2013). All villages and towns depend solely upon groundwater for sustenance, since surface water bodies have either disappeared or have been polluted. Groundwater occurs up to 35 mbgl (metres below ground level) in the form of phreatic aquifer and is mainly tapped by dug wells, Indian Mk. II handpumps and shallow borewells for supplying drinking water and irrigation water, wherever possible.

Yield of dug well and shallow borewell ranges from 100 to 300 lpm. Deeper groundwater is tapped by borewells that access fractures and joints below 35 mbgl. The Granites are profusely and extensively jointed and fractured, forming good conduit for groundwater movement. Groundwater occurs in deeper fracture zones in semi-confined to confined condition. Quartz reefs act as a barrier impeding the subsurface movement of groundwater.

Geological map of Mahoba is attached in Fig. 2.

Fig. 2
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Geological map of Mahoba district

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Materials and methods

The sampling was carried out during May 2019 as a part of NAQUIM programme under the aegis of CGWB at Mahoba district that lies in the Bundelkhand region of Uttar Pradesh State. A total of 105 ground water samples were collected from Indian Mk. II handpumps tapping shallow aquifer (~ 20 mbgl) from different locations that were used by locals for analysis of basic parameters like pH, TDS, EC, ions like calcium, magnesium, sodium, potassium, chloride, carbonate, bicarbonate, sulphate, etc.

Sampling locations with chemical data are given in Appendix 1.

The samples were collected after removal of water column by pumping out the water from the handpumps for at least 5–10 min, and the water samples were collected in HDPE sample bottles of 1 L capacity. It was ensured that the sample bottles were free from air bubbles and they were immediately closed, labelled and transported to a NABL accredited laboratory at Panipat for analysis. Map displaying sampling locations is attached in Fig. 3.

Fig. 3
figure 3

Map displaying sampling locations at Mahoba district

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Hydrogeochemistry

The groundwater samples collected were plotted on the Hill-Piper trilinear diagram (Piper 1944), and the samples were classified into the following categories based on the dominant cation and anion.

  • 76 samples are of magnesium bicarbonate water type;

  • 24 samples are of mixed type wherein no dominant cation or anion can be identified;

  • 4 samples are of calcium chloride water and

  • 1 sample is of sodium chloride water type.

Kabrai block is dominated by Mg-HCO3 hydrochemical facies (62.50 %), followed by Mixed facies (31.25 %) and CaCl2 facies (3.125 %) and NaCl facies (3.125 %).

Charkhari block is dominated by Mg-HCO3 hydrochemical facies (74.07 %), followed by Mixed facies (22.22 %) and CaCl2 facies (3.70 %). Jaitpur block is dominated by Mg-HCO3 hydrochemical facies (79.16 %), followed by Mixed facies (16.66 %) and CaCl2 facies (4.16 %).

Panwari block is dominated by Mg-HCO3 hydrochemical facies (77.27 %), followed by Mixed facies (18.18 %) and CaCl2 (4.54 %).

A closer look at the data reveals Ca> Na> Mg > K in cations and HCO3> Cl> SO4 > CO3 in anions.

The plotted Hill-Piper trilinear diagrams are attached in Fig. 4.

Fig. 4
figure 4

a–e Hill-Piper trilinear diagrams of blocks of Mahoba district. a Piper plot of Charkhari block, b Piper plot of Jaitpur block, c Piper plot of Panwari block, d Piper plot of Kabrai block

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Calculation of corrosion indices

The following indices were calculated.

Langelier saturation index

Langelier 1936 had proposed a formula to predict calcium carbonate scaling in water based on pH, TDS, temperature, total alkalinity and hardness that affect calcium carbonate solubility and was calculated by the following formula

$$ LSI \, = \, pH \, {-} \, pHs $$

where

  • pH is the actual pH of water and

  • pHs is the pH at saturation and is calculated by pHs = (9.3+A+B)–(C+D).

  • A = TDS (mg/l),

  • B = temperature in Celsius,

  • C = calcium hardness (mg/l of CaCO3),

  • D = alkalinity (mg/l of CaCO3).

  • LSI value > 0 indicates water is supersaturated and CaCO3 layer precipitates,

  • LSI value = 0 indicates water is in equilibrium with CaCO3, and no precipitation or corrosion is possible,

  • LSI value < 0 indicates water is under-saturated, dissolves solid CaCO3 and causes corrosion.

Puckorius scaling index

Puckorius and Brooke 1991 also proposed a formula that is calculated by the following formula

$$ PSI \, = \, 2\left( {pH_{s} } \right) \, {-} \, pH_{eq} $$

where

  • pHs is the pH at saturation and pHeq is the pH at equilibrium and calculated by pHeq = 1.465 * log10(Alkalinity) + 4.54

  • PSI value < 6 indicates CaCO3 scale will be dissolved by water and is corrosive,

  • PSI value > 6 indicates CaCO3 scaling may occur.

Ryznar stability index

Ryznar 1949 also proposed a formula to predict calcium carbonate scaling in water that overcame deficiencies in LSI and is calculated by the following formula

$$ RSI \, = \, 2 \, pH_{s} {-} \, pH $$

  • RSI value < 6 indicates increasing tendency for scaling with decreasing index,

  • RSI value between 6-7 indicates formation of no corrosion-protective film by water,

  • RSI value > 8 indicates tendency for corrosion by water.

Larson-Skold index

Larson and Skold 1958 gave a formula to predict the corrosivity of water towards mild steel which is calculated by the following formula

$$ Larson{ - }Skold \, Index\; = \;\frac{Cl\; + \;SO4}{{HCO3}} $$

All ionic concentrations in meq/l.

  • LS value < 0.8 indicates chloride and sulphate may not interfere with natural scale formation,

  • LS value between 0.8 to 1.2 indicates chloride and sulphate may interfere with scale formation and higher than desired corrosion rates expected,

  • LS value > 1.2 indicate very high corrosion rate by the action of chloride and sulphate.

Potential to Promote Galvanic Corrosion (PPGC)

Edwards et al. (2007) proposed a formula to calculate possibility of release of lead from copper pipes wherein lead was used as solder

$$ PPGC\; = \;\frac{Cl}{{SO4}} $$

PPGC > 0.50 indicates susceptibility of galvanic corrosion by groundwater.

All ionic concentrations are in mg/l.

Computed data of corrosion indices is attached in Appendix 2.

Results and discussion

  1. (1)

    The Langelier Saturation Index values range from −0.92 to 1.01 with mean value of 0.46.

    4.76% samples display negative values wherein groundwater is under-saturated with respect to calcium carbonate and removes existing protective covering of pipes.

    95.24% of samples display possible scale formation due to deposition of calcium carbonate.

    Sample nos. 9, 10, 12, 17 and 100 display negative values, and the underlying geological formations mainly include Precambrian Granite with minority from Quartz reefs.

  2. (2)

    The Puckorius Scaling Index values range from 4.12 to 7.66 with mean value of 5.83.

    60.95% of samples display values less than 6.0 indicating calcium carbonate scaling might occur.

    30.05% of samples are indicative of calcium carbonate scale dissolved by groundwater.

    Sample nos. 9, 10, 12, 17, 28, 41, 42, 43, 51 and 60 display values greater than 6.0, and the underlying geological formations mainly include Precambrian Granite with minority from Quartz reefs.

  3. (3)

    The Ryznar Stability Index values range from 5.55 to 8.55 with mean value of 6.58.

    12.38% of samples display value greater than 7.0 indicating groundwater is of corrosive nature.

    87.62% of samples display value lesser than 6.0 indicating possibility of scale formation due to deposition of calcium carbonate.

    Sample nos. 1, 3, 9, 10, 12, 17, 42, 51, 58, 61, 78, 100 and 105 display values greater than 7.0, and the underlying geological formations mainly include Precambrian Granite with minority from Quartz reefs and Quaternary alluvium.

  4. (4)

    The Larson-Skold Index values range from 0.05 to 5.89 with mean value of 0.62.

    73.33% of samples indicate chlorides and sulphates may not interfere with natural film formation.

    13.3% of samples indicate tendency for high corrosion.

    13.33% of samples indicate higher than desired corrosion rates wherein chlorides and sulphates may interfere with natural film formation.

    Sample nos. 5, 9, 12, 21, 22, 23, 52, 53, 54, 55, 60, 88, 97 and 101 display values between 0.8 and 1.2, and the underlying geological formations mainly include Precambrian Granite with minority from Quartz reefs and Quaternary alluvium.

    Sample nos. 9, 15, 32, 33, 35, 48, 57, 58, 71, 73, 78, 86, 91 and 100 display values greater than 1.2, and the underlying geological formations mainly include Precambrian Granite with minority from Quartz reefs and Quaternary alluvium.

  5. (5)

    The PPGC or chloride–sulphate mass ratio values range from 0 to 31.90 with mean value of 3.42.

    94.28% of samples indicate possibility of galvanic corrosion.

    5.71% of samples rule out the possibility of galvanic corrosion.

The groundwater samples mainly obtained from Precambrian Granites display possibility of corrosion with reference to Langelier Saturation Index, Puckorius Scaling Index, Ryznar Stability Index and Larson-Skold Index, whereas very few groundwater samples collected from Quartz reefs and Quaternary alluvium mirror the possibility of corrosion with respect to indices stated above.

It is also observed that the underlying geology has little to no bearing on corrosion with respect to PPGC (index that indicates possibility of galvanic corrosion) and about 94.28% of samples display possibility of galvanic corrosion across varied lithologies barring a few samples that possess low sulphate content.

Overall, majority of the groundwater samples display tendency to deposit calcium carbonate within the pipes, chlorides and sulphates not interfering with natural film formation in pipes and possibility of galvanic corrosion, whereas minority of samples indicate the alternate scenario.

The map of GW samples classified with respect to different corrosion indices is attached in Fig. 5.

Fig. 5
figure 5

Map displaying GW sampling locations classified with respect to various corrosion indices

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Conclusion

It is observed that groundwater samples collected from Precambrian Bundelkhand Granites display tendency to deposit calcium carbonate as per 3 indices—Langelier Saturation Index, Puckorius Scaling Index and Ryznar Stability Index in addition to possibility of corrosion of mild steel as defined by Larson-Skold Index.

The geology of the study area was found to have none to near negligible influence on Potential to Promote Galvanic Corrosion (PPGC) index as the quantum of sulphate ion varies across different lithologies and no relation between the two is observed.

The various indices can be utilized to plan for materials used in construction of Indian Mk. II handpumps in addition to deciding the material used for borewell casing that is resistant to corrosion as calculated by different indices. The groundwater samples will require collection every month or every quarter in order to calculate values as defined by each index. Galvanic pipes containing lead as solder should be avoided since the index indicates high possibility of leaching of lead into water.

The data computed from various corrosion indices can also be utilized prior to establishment of industries that require stringent water quality standards for production, and areas free from corrosive potential of groundwater can be demarcated for investment in infrastructure in the future.