Study of the possibility of using gamma - irradiated sewage sludge in different plants production

sewage sludge is an organic fertilizer and in addition to pathogens, containing macronutrients (including nitrogen, phosphorus, potassium) and micronutrients (for example iron, zinc, copper, manganese, molybdenum) and heavy metals such as arsenic, cadmium, chromium, lead, mercury, nickel, selenium, and etc. Using ionizing radiation is the best way for disinfection of sewage sludge and absorption of radiation energy by water molecules of sewage sludge causes the ionization of their and formation of oxidizing and reducing free radicals. A comprehensive report does not exist on the effects of ionizing radiation such as gamma rays on the changes in chemical properties of sewage sludge; however, irradiation of sewage sludge could remove dangerous pathogenic organisms and plant growth inhibitors and could increase plants yield. In Iran due to the low cost of sewage sludge it was used in the cultivation of plants particularly fresh vegetables. The existence of various organic and inorganic pollutants in sewage sludge used in the cultivation of vegetables increased the risk of various diseases in consumers due to their direct consumption. Therefore, the use of risk assessment models have been suggested to predict the risks of crops consumption by various consumers and vegetables production with organic fertilizers containing pollutants such as sewage sludge. Lack of study about comparing plants grown in irradiated and non-irradiated sludge with risk assessment equations, reveals necessity of these equations and their mechanisms.