The Effect of Bentonite and Municipal Wastewater Effluent on Some Soil and Alfalfa and Clover Plant Characteristics

Iran is one of the countries in the Middle East that is facing a shortage of renewable water resources. As one of the governmentchr('39')s socio-economic policies, the emphasis has been on the optimal use of renewable resources, in particular refined human and industrial wastewater. One of the limiting factors of using these wastewater is the presence of heavy metals in them. Therefore, soil remediation is important to reduce this pollution or to deactivate heavy metals.  This study was conducted to investigate the effect of bentonite modification on soil elements concentration irrigated with municipal wastewater under cultivation of Alfalfa and clover in a completely randomized design. In this study, essential and toxic elements of the plant, soil properties and elements in soil under different effluent ratios (0%, 25%, 50%, 75% and 100%) were investigated. Also, due to the presence of heavy metals in wastewater, bentonite modifier was used as immobilizer of heavy metals in soil at two levels of 1% and 3%. The results showed that 100% effluent-3% bentonite treatment had the highest amount of soil organic carbon, organic matter, lime, pH and EC for both alfalfa and clover species (p<0.05). Also, increasing the level of effluent application significantly increased the concentration of essential elements (NPK) in soil and plants. On the other hand, application of 3% bentonite resulted in a significant decrease in the toxicity of lead and cadmium in plants and soils. In general, it can be concluded that application of proper wastewater treatment can be used as a potential source of water to enhance plant growth and yield, as well as the use of bentonite as an immobilizing agent of heavy metals in wastewater in forage production methods.