Dataset on comparing the corrosion indices of alum and ferric chloride coagulants with phosphate dose elevation

The aim of this data was to assess and compare the corrosion indices of alum and ferric chloride coagulants in conventional coagulation process of water with elevation of phosphate dose. After preparing synthetic water samples, jar experiments were performed with elevation of different phosphate doses using alum and ferric chloride coagulants. Then, corrosion indices of Ryznar and Langelier of water samples were calculated. The results indicated that the values of Ryznar and Langelier index in the experimental samples were 7 and less than zero, and the water conditions were under saturated. The corrosion and precipitation indices indicated that the water samples can be considered as corrosive waters.


a b s t r a c t
The aim of this data was to assess and compare the corrosion indices of alum and ferric chloride coagulants in conventional coagulation process of water with elevation of phosphate dose. After preparing synthetic water samples, jar experiments were performed with elevation of different phosphate doses using alum and ferric chloride coagulants. Then, corrosion indices of Ryznar and Langelier of water samples were calculated. The results indicated that the values of Ryznar and Langelier index in the experimental samples were 7 and less than zero, and the water conditions were under saturated. The corrosion and precipitation indices indicated that the water samples can be considered as corrosive waters.
&  Table   Subject area  Water chemistry  More specific subject area  Corrosion and coagulation  Type of data  Tables, Figures  How data was acquired After preparing the synthetic water samples, different doses of phosphate were injected into jar glasses, 10 mg/L alum and ferric chloride were also added to the samples and finally the phosphate level of the samples was measured by DR/2000 Direct Read Spectrophotometer at the wavelength of 420 nm. Ryznar and Langelier corrosion indices were calculated for samples.

Data format
Raw, analyzed Experimental factors The qualitative parameters of the samples including alkalinity, electric conductivity, total suspended solids, temperature, bicarbonate and pH were performed by the instructions in Standard methods for the examination of water and wastewater, 20th edition [1][2][3][4].

Experimental features
The levels of physico-chemical parameters of the samples were determined. Data source location Tehran University of Medical Sciences, Tehran, Iran.

Data accessibility
The data are available with this article

Value of the data
The data can be beneficial for improving the quality of potable water with corrosion problems resulting from alum and ferric chloride coagulants.
The data can be helpful in the design and operation of conventional and advanced coagulation units in water treatment plants.
The data comparing the Langelier and Ryznar corrosion indices of alum and ferric chloride with elevation of phosphate dose in water samples indicated that the water conditions in the samples were under saturated.

Data
The datasets include 4 Tables and 8 Figures. The water corrosion indices used are summarized in Table 1. Table 2 indicates the mixing conditions and retention time of stages of coagulation, Table 1 A summary of the corrosion and water sedimentation indices used in this study [5][6][7][8][9][10][11][12].

Equation
Index value Water condition

Design of experiments
Synthetic water samples were used for comparing the corrosion indices of alum and ferric chloride coagulants in conventional coagulation processes of water with phosphate dose elevation, synthetic water samples were used. To prepare the synthetic water sample, natural clay soil water utilized. For this purpose, first this soil was passed through a sieve with mesh 120 and then 1.5 mg/L of it was weighed by a balance and poured into the water sample. For homogenization, it was then stirred for 10 min. Next, the solution was kept still for 24 h and then stirred again. After 30 min of sedimentation, the top water was used for the experiments.

Jar experiments
The jar experiments (coagulation, flocculation, and sedimentation) were performed by standard jar test device (Sedimentation Jar test, AZTEC Environmental Control LTD) using six 1-L beakers at room temperature. All jars and pedals of mixing were washed by HCl before doing any experiment and then rinsed off by distilled water [13][14][15]. Addition of phosphate compounds was also performed during rapid mixing, one minute before or after injecting the coagulant (alum or ferric chloride). The phosphate compounds were injected as 0.5, 1, 1.5, 2, 2.5, 3, and 3.5 mg/L into jar glasses. However, no phosphate was added to any of the jar glasses across all jar tests so that the extent of residual metal in every situation would be determined. Further, 10 mg/L doses of alum and ferric chloride were used for conventional coagulation. Eventually, the jar samples were filtered by a syringe filter with 0.45 μm pores and the phosphate level of the samples was measured by DR/2000 Direct Read Spectrophotometer at the wavelength of 420 nm. Eventually, the Langelier and Ryznar corrosion indices were calculated by the equations in Table 1. Table 2 The conditions of mixing and retention time of coagulation, flocculation, and sedimentation stages.

Parameter
Flash mixing Flocculation Sedimentation Mixing speed (rpm) 120 20 -Time (minute) 2 20 30 Table 3 The results of jar test for evaluating the effect of orthophosphate dose in altering the water corrosion indices; type of coagulant: aluminum sulfate (alum).           Furthermore, all of the qualitative parameters of the samples including alkalinity, electric conductivity, total suspended solids, temperature, bicarbonate and pH were performed by the instructions in Standard methods for the examination of water and wastewater, 20th edition. The pH of the samples was measured by pH meter (Metrohm Herisau) E520.