Research Regarding the Accumulation in Soybeans of Heavy Metals from Anaerobic Composted Sewage Sludge Used as Organic Fertilizer

Abstract

In sewage sludge from urban wastewater treatment stations can often be find high levels of Ni, Pb, Cu, Zn, Mn and Cd. Aerobic or anaerobic composting of this sewage sludge does not eliminate the possibility of bioaccumulation of these metals in plants through metabolic processes of phytoextraction type. Researches regarding the accumulation degree of heavy metals through phytoextraction processes were performed on soybean plants (Glycine max), Condor variety. Plants were fertilized with anaerobic composted sludge in amounts of 25 t of / ha, 50 t / ha and 100 t / ha. The chemical analysis was done on an average sample of three repetitions. Metal concentration in soybeans was analyzed by reporting to the maximum allowance level for sheep, considered one of the most sensitive farm species to heavy metal toxicity. Our results showed a higher level than normal with 5.8 mg / kg only in the case of copper ions. Zn, Pb, Mn and Cd concentration in soybeans was below the maximum allowance limits set by the rules of feeding farm animals. Also, heavy metal content of soybeans was not affected by the amount of composted sludge used as fertilizer.

Keywords

• anaerobic composted sludge
• bioaccumulation
• heavy metals
• soybean