Soil Quality as Affected by Wastewater Irrigation in a Semi-arid Agricultural Land

The shortage of fresh water and the urgent reuse of wastes have made necessary to use unconventional water sources, such as municipal wastewater for irrigation. The main obstacle for extending its use results from its quality. The standardized urban effluents contain, from a chemical point of view, relatively high concentrations of dissolved organic matter, nutrients, salts and detergents. Prolonged irrigation of a calcareous soil with municipal effluents was performed. Specific potential effects of surfactants, one of the most common components found in wastewater, were also investigated. The results showed that application of wastewater deteriorates the soil quality parameters related to plant nutrition (increase salinity and reduce cation exchange capacity) but does not alter significantly soil physical properties. However, flow pattern could be affected since before the last irrigation steps, less leachate was collected and water ponded on the soil surface. Higher surfactant contents result in less soil buffering ability, increase soil electrical conductivity and induce soil physical deterioration. Aggregate stability seems to improve after application of solutions richer in organic carbon specially surfactants at 10 cmc.