Inactivation of biohazards in healthcare wastewater by E-Beam and Gamma irradiation: a comparative study.

The main objective of this study is to evaluate the effect of irradiation by Gamma rays and Electron Beam (E-Beam) on naturally occurring microorganisms shed in healthcare wastewater issued from multi-specialties hospital. We examined the susceptibility of naturally occurring total indicator bacteriophages towards Gamma rays and E-Beam irradiation to evaluate their appropriateness as viral indicators for healthcare wastewater quality control. Results showed that healthcare wastewater is a rich matrix containing bacteriophages surrogates of pathogenic waterborne viruses (4.5 Log PFU/100 mL for SOMCPH and 2.3 Log PFU/100 mL for FRNAPH), antibiotic resistant bacteria (Mean concentrations from 2.3 to 5.5 Log CFU/100 mL), molds and yeasts (2.7 Log CFU/100 mL), and spores of Clostridium perfringens (Mean concentration of 3.3 Log CFU/100 mL). After E-Beam irradiation, naturally occurring bacteria in healthcare wastewater showed lower resistance patterns (D values ranging between 0.21 ± 0.005 and 0.59 ± 0.005) compared to those obtained after Gamma irradiation (D values ranging between 0.25 ± 0.015 and 0.70 ± 0.0001). Spores of Clostridium perfringens were the most resistant assayed microbes either after E-Beam (D values of 3.74 ± 0.005) or Gamma irradiation (D values of 4.77 ± 0.025) of collected samples. According to inactivation patterns, a dose of 10 kGy was sufficient for a complete inactivation of spores. Bacteriophages isolated from healthcare wastewater showed the same resistance patterns as those previously obtained in urban treated sewage and were inactivated using higher doses than waterborne bacteria (D values of SOMCPH 1.46 ± 0.057; D values of FRNAPH 1.03 ± 0.057). Their resistance to irradiation treatment in such complex matrix corroborates their use to survey the viral quality of healthcare wastewater before their discharge in the urban sanitation network. D value analysis showed that bacteria and bacteriophages inactivation by E-Beam irradiation required lower doses than those required for their inactivation using Gamma rays. According to inactivation patterns, a dose of 7 kGy was sufficient for total inactivation of both pathogenic bacteria and viruses. Thus, E-Beam irradiation seems to be an efficient physical pre-treatment process for healthcare wastewater treatment prior to its discharge in urban sanitation system to ensure compliance with environmental standards and protect public health.