Document Type : Research Article
Authors
1 Department of Soil Science, College of Agriculture, Ferdowsi University of Mashhad
2 Department of Water Engineering, College of Agriculture, Ferdowsi University of Mashhad
Abstract
Increasing population, limitation of water resources, and also enormous volume of municipal wastewater and need to dispose of these wastewaters safety, has been increased of necessity of reuse of wastewater. Disposal of wastewater in soil is one of the most economical methods of their disposal. Different soil characteristics, type of wastewater and method of its application are issues that affect wastewater treatment efficiency in the soil. For this purpose, an experiment was carried out in 12 polyethylene columns during 7 periods of 15 days in Ferdowsi University of Mashhad. A statistical “factorial design” was used. Raw and treated wastewaters from Parkandabad Treatment Plant were applied under continuous and intermittent flood conditions in columns filled with silty loam soil. At the end of experiment, soil columns were divided and soil samples from depths of 0-25, 25-50 and 50-100 cm each column were collected. Properties such as pH, salinity, concentration of NO3, PO4, TOC, Ni and Cd were measured in soil solution samples and also Leachates were taken in each period of experiment. The result showed that the mean values of each of the above mentioned parameters, with exception of pH and salinity, were lower in leachate compared to the wastewaters entering the soil. However, with continuous application of wastewaters increase in the amount of these components (with exception of salinity and Ni) were observed. The amount of Cd in leachate samples of any periods was undetected. Considering the effect of wastewater application on soil chemical properties, value of all parameters (except salinity) in comparison to their initial values have increased in the soil solution. Based on the above results, disposal of wastewaters (especially raw wastewater) on soil should be managed carefully. So that by sound usage of wastewaters, environmental risks resulting from disposal of them are reducing to the lowest level in nature.
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