Analysis of Leachate Characteristics to Study Coal Ash Usability - Management of Natural Resources in a Changing Environment - page 236

Table 5 Calcium, potassium, sodium, sulphate and phosphate analysis of leachate
Sample no. Na + (mg/L) K + (mg/L) Ca 2+ (mg/L) Sulphate (mg/L) Phosphate (mg/L)

1 3.3 3.2 2.4 5.57 0.002

2 2.2 3.4 1.8 4.66 0.002

3 4.6 4.3 3.3 28.9 0.002

4 3.2 3.8 2.6 6.15 ND

5 4.7 4.9 3.9 3.38 0.001

ND not detected

Table 6 Indian standards for discharge of effl uents into surface water and public sewers

Into surface water
(IS 2490-1974)

Into public sewers
(IS 3306-1974) Parameter and unit

pH 5.5-9.0 5.5-9.0

Sulphates (mg/L) 1,000 1,000

Phosphates (mg/L) 5 -

Copper (mg/L) 3 3

Iron (mg/L) 3 3

Manganese (mg/L) 2 2

Lead (mg/L) 0.1 1

Cadmium (mg/L) 2 1

Chromium (mg/L) 2 2

Sodium (%) - 60

Nickel (mg/L) 3 3

Source : Garg ( 2010 )

Sulphate and Phosphate Ions Analysis

Due to dominant surface association in fly ash and the marked solubility of
most sulphate-bearing compounds, sulphur is the major soluble element in fl y ash.
In environmental conditions, reduced S species are generally present in negligible
quantities and sulphate is the dominant species (Fruchter et al. 1990 ). The leach-
ability in terms of absolute levels varies over one order of magnitude, depending
upon the nature (i.e. pH) of the ash. Result in Table 5 shows that in samples 1, 2, 4
and 5 sulphates leached in very low amount i.e. 3.38-6.15 mg/L and in sample 3
sulphates leached in high amount that is 28.9 mg/L, indicating the presence of high
sulphur in the ash sample. Research shows that P remained immobile over 2 years-
long column leaching test and concluded that this element occurs within the silicate
matrix or as adsorbed constituents (Dudas 1981 ).
However, this evidence comes from very limited data available in the literature
(Moreno et al. 2005 ). Results shows very low amount of phosphorus has been
leached from all the samples i.e. 0.001-0.002 mg/L.
Table 6 shows the Indian standards for discharge of effl uents. The concentrations
of all the metals, salts and ions under this study of the leachate when compared with
the Indian standards for discharge of effl uents were found to be within the limit.