BIOREMEDIATION OF SEWAGE SLUDGE FOR LAND APPLICATION AS A FERTILIZER USING BIOLEACHING

Öz

Huge amount of sewage sludge is generated worldwide that needs a proper discharge strategy, which retains both future sustainability and present needs. Land application of sewage sludge can be a good solution, whereas it is cost-effective disposal method for treatment plants and also can provide a favorable fertilizer for farm lands. It provides an economical alternative for the final disposal of the sewage sludge, but heavy metals in sewage sludge is always an issue restricting its general use. Therefore, removal of heavy metals prior to land application is likely to be a possible and practical means for reducing metal content in sewage sludge. Bioleaching appear to be a promising technology in removing heavy metals from contaminated sewage sludge. The effect of bioleaching on heavy metals solubilization and also their DTPA-extractable (Diethylene Triamine Pentaacetic Acid) form changes was investigated in this work. The samples of activated sludge were collected from three of most important sewage sludge treatment plant of Tehran. Total metal concentration and DTPA-extractable metal content of samples were determined. Bioleaching using Acidithiobacillus ferrooxidans was carried out in two experiments to study solubilization rate and changes in DTPA-extractable Fe, Cu, Ni and Pb. Results showed that bioleaching could affect metal DTPA-extractable form significantly but, there was no definite behavior for each metal and also each metal in different samples. However, bioleaching can efficiently remove mentioned metals from sewage sludge solid phase. Bioleaching removed approximately 24.73 % of Fe, 83.96 % of Cu, 81.46% of Ni and 38.96 % of Pb from sewage sludge samples. In fact, bioleaching is more efficient and economic than chemical leaching. Indeed Acidithiobacillus ferrooxidans is a powerful bacterium in metals removal and environmental remediation programs.

Anahtar Kelimeler

• Bioleaching, Heavy metal, Sewage sludge, Bioremediation, Acidithiobacillus ferrooxidans, DTPA-extractable

USI G BIOLEACHI G

Öz