تاثير پساب نيروگاه شهيد مفتح همدان بر افزايش درصد سديم تبادلي خاك

The Effect of Hamedanʹs Shahid Mofatteh Power Plant Sewage Sludge on the Increase in Exchangeable Sodium Percentage (ESP) of the Surrounding Soils

An Evaluation of the effect of industrial sewage sludge on soil, in terms of soil contamination, and fertility as well as on groundwater quality is quite important. In order to study the effect of sewage sludge of Shahid Moffateh Power Plant on chemical properties of the agricultural soils around this Power Plant, leaching experiments were conducted in soil columns, namely soil compacted piecemeal in the poly-vinyl chloride (P.V.C) columns (9 cm in diameter and 25 cm height). Effluent was collected and concentrations of sodium, calcium, magnesium, potassium, chlorine and sulphate were measured. Also, column of the soil were lcached using distilled water. The experiment was performed in two replicates. The experiments were continued until the concentration of output and input cations became equal. At the end of the experiment, soil columns were cut into 2cm thick layers for which the concentration of exchangeable sodium, electrical conductivity as well as pH in the layers of soil were measured. The results showed that sodium ions in sewage sludge, replaced calcium, magnesium and potassium ions from the exchange sites, resulted in the appearance of the peak concentration of these ions in effluent after 1 to 2 pore volumes. Peak concentration of chloride appeared following one pore volume after which the concentration equaled the chlorine concentration in input sewage sludge. This pattern was not true for sulphate ions, which can be accounted for by low rate of sulphate salt solubility in comparison with chlorine salts. Hence, sulphate release continued with the passage of time, peak concentration of sulphate appearing in third pore volumes. The leached potassium from the soil is partly compensated for, by input potassium. Bccausc the concentration of input calcium, in comparison with calcium carbonate solubility, is high, calcium carbonate was not dissolved during the proces of the experiment. The final mean exchangeable sodium percentage of the soil was 28.3. Thus, the percentage increase in exchangeable sodium in this soil was 4. Sewage sludge application also increased the electrical conductivity of this soil, preventing it from serious structural damage.