Phytoremediation for soils contaminated with heavy metals using the symbiosis between Astragalus Sinicus with rhizobia

Bioremediation has evolved frommanagement and treatment ofmu-nicipal and industrial wastewater and solid wastes. Land disposal of wastewaters on sewage farms began in the late 19th century and in-volved the use of soil bacteria. In decontamination processes more sophisticated methods of contaminant treatment, such as tricking filters, activated sludge, and anaerobic fermentation, were advanced in the first half of the 20th century. Since 1960, biological treatment processes have continued to include newmethods of land treatment and processes for biodegradation of particular types of compounds. Developments in wastewater and solid-waste treatment have been transferred to the treatment of contaminated soils and groundwater. In recent years, most of the works on bioremediation has been on the treatment of soils contaminated with petroleum products, since most petroleum hydrocarbons are relatively easy to degrade and are amenable to bioremediation, and the large number of sites conta-minated with petroleum hydrocarbons from leaking underground storage tanks.