Assessment of scaling and corrosion potential of drinking water resources of Iranshahr

Graphical abstract

The data presented in this article can be useful for managers of water and wastewater companies, water resources facilities and treatment plants operators and operation manager of water distribution system. Due to adverse health effect of corrosion potential of water resources as a results of solving of the materials and ingredient of pipes, fittings and valves in distribution networks and its consequence on human health effect, assessment of scaling and corrosion potential of water in distribution network is necessary. In dry climates, groundwater is almost the main source of drinking water, so, the continuous monitoring of the physic-chemical parameter of these valuable resources is very necessary. Sources of drinking water in Iranshahr have corrosion potential and can threaten the health of consumers in the long term.

Description of protocol
Experimental design, materials and methods

Study area description
Iranshahr city in Sistan and Baluchistan province and its aquifers are located in South-East Iran between the latitudes 25815 0 N and longitudes 60845 0 E, encompassing an area of about 30,200 km 2 (Fig. 6). The study area is a semi-flat plain region with a gentle slope toward the south has a warm, temperate climate. Also, the air's highest and lowest temperatures are 50 C and À6.2 C, respectively, with an annual average of 26.8 C.

Sample collection and analytical procedures
To calculate the corrosion indices, 36 samples of 1.5 l volume were collected from 18 sources, stored and transferred to lab according to standard method (stored in a dark cold box (4 C) and transferred to laboratory within less than 3 h). The pH measured by pH meter device and water temperature determined by thermometer at the sampling points. Water quality parameters such as electrical conductivity, total dissolved solids, pH, calcium hardness, and alkalinity were measured in water samples in laboratory upon arriving samples. Alkalinity and hardness were determined using titration method and total dissolved solids was determined by gravimetric method. Sulfate was measured based on turbidity measurement at 420 nm by DR5000 spectrophotometer [1]. The equation of corrosion indices and their interpretations were summarized in Table 1. Calculation of indices was done using Microsoft Excel 2010.

Results
Water quality assessment and safe drinking water supply is one of the most concerning issue in the world [3]. Data presented here deal with monitoring of physical and chemical parameter of drinking water in Iranshahr including pH, EC, TDS, Alkalinity, and EC which have shown in Table 2. The results of the calculations for Langelier, Ryzener, Puckorius and aggressive indices for drinking water resources of Iranshahr were presented in Table 3. Data on results of phsico-chemical parameter are compared with the National Iranian Water Standard (Figs. 1-5). Total hardness was equal to 225.11 mg/L as CaCO 3 and was lower than the standard limit of Iran. The mean of electrical conductivity also was lower than it national standard. However, the mean of alkalinity and total dissolved solids were exceeded from standards. The mean of pH value was in the range of its desired values based on national standards of Iran. The data showed that Langelier index ranged between À1.53 to À0.96, Ryznar index between 9.63-10.54, Aggressive index between 12.04 and 12.91, and Puckorius index between 9.05-10.68 for drinking water resources Iranshahr. Based on all indices, drinking water in Iranshahr is corrosive. Table 1 Summary of water stability indices in present study [2].

Index Equation Index value
Water condition Langelier saturation index (LSI) LSI = pH -pHs LSI > 0 Water has super saturated condition and tend to precipitate CaCO 3 in the system pHs = A + Blog (Ca 2+ ) log Water has saturated condition. It has no tendency to dissolve or precipitation of CaCO 3 (Alk) pH < = 9.3 pHs = (9.3 + A + B) -(C + D) Water is under saturated condition and tend to dissolve precipitated CaCO 3 (3) pH > 9.3 Ryznar stability index (RSI) RSI = 2pHs -pH RSI < 6 Water has super saturated condition and tend to precipitate CaCO 3 in the system 6 < RSI < 7 Water has saturated condition. It has no tendency to dissolve or precipitation of CaCO 3 . RSI > 7 Water is under saturated condition and tend to dissolve precipitated CaCO 3 Puckorius scaling index (PSI) PSI = 2 (pHeq) -pHs PSI < 6 Scaling likely will not occur pH = 1.465 + log PSI > 7 It likely tend to dissolve scale (T.ALK) + 4.54 pHeq = 1.465 Â log(T. ALK) + 4.54

Concluding remarks
In the present study, it was attempt to evaluate corrosion and scaling potential of drinking water resources Iranshahr. Studied indices indicated that the drinking water in Iranshahr can be considered as corrosive. Total hardness and pH were well below the standard limit of Iran. However, electrical conductivity, total dissolve solids and alkalinity were exceeded form their standard values in some cases.