Research Article Open Access

Application of Gamma irradiation in treatment of Waste Activated Sludge to Obtain Class a Biosolids

  • Mohammed I. AL-Ghonaiem
  • Abdelnasser Salah Shebl Ibrahim
  • Ali Abdullah Al-Salamah

American Journal of Environmental Sciences
Volume 6 No. 6, 2010, 500-504


Problem statement: The main objective of the current study was investigation of the possible application of Gamma irradiation for treatment of the activated sludge generated wastewater treatment stations, to achieve the standard requirements in term of pathogens content. Approach: Activated sludge samples were collected from Riyadh wastewater plant and analyzed quantitatively for the presence of important bacterial parameters including fecal coliforms and Salmonella spp. The collected samples were treated with various doses of Gamma irradiation and bacterial count was determined. Results: The results indicated that all tested sludge samples were positive for the presence of fecal coliforms and Salmonella spp, with different counts in different stages of wastewater treatment. The raw sludge showed to have the highest coliforms and Salmonella spp counts of 1.1×108 and 2×103 MPN g-1 dry sludge, respectively. Furthermore, coliforms and Salmonella spp were detected in final resulted sludge with count of 2.5×107 and 6×102 MPN g-1 dry sludge, respectively. It was found that treatment of samples with gamma irradiation was able to reduce the fecal coliforms and Salmonella spp effectively and the reduction efficiency was increased by increasing the irradiation dose. Fecal coliforms and Salmonella counts were reduced to less than 100 MPN g-1 dry sludge by exposing to 1.5 and 0.25 kGy respectively. Furthermore, Gamma radiation dose of 2.0 kGy was able to remove both fecal coliforms and Salomnella spp completely. In addition, D10 values were determined and was found to be 0.25 and 0.24 kGy for fecal coliforms and Salmonella spp., respectively. Conclusion/Recommendations: The results indicating that the resulted activated sludge generated from Riyadh wastewater plant are rich with important pathogens and therefore further treatment procedures are necessary to achieve the required standards, before any land application. Application of Gamma irradiation in treatment of the activated sludge showed to be a promising safe technology for this purpose.

How to Cite

AL-Ghonaiem, M. I., Ibrahim, A. S. S. & Al-Salamah, A. A. (2010). Application of Gamma irradiation in treatment of Waste Activated Sludge to Obtain Class a Biosolids. American Journal of Environmental Sciences, 6(6), 500-504.



  • Colony Forming Units (CFU)
  • Most Probable Numbers (MPN)
  • Dry Solids content (DS)
  • Gamma radiation
  • gamma irradiation
  • bacterial parameters
  • fecal coliforms
  • generated wastewater
  • pathogens entering
  • dry sludge
  • Salmonella spp