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Disinfection kinetics of pathogens in physicochemical sludge treated with ammonia

J M Mendez1, B Jimenez, C Maya

  • 1Orizaba Institute of Technology (ITO), 852 Tecnológico, Zapata 94320, Orizaba, Mexico. jmendez@itorizaba.edu.mx

Water Science and Technology : a Journal of the International Association on Water Pollution Research
|December 8, 2004
PubMed

Insights

Ammonia effectively disinfects wastewater sludge, significantly reducing pathogens like E. coli and Salmonella, and nearly eliminating helminth ova. Combining ammonia with heat ensures complete ova inactivation and enhances biosolid value.

Area of Science:

  • Environmental microbiology
  • Water treatment technologies
  • Public health

Background:

  • Wastewater sludge often contains high levels of pathogens, including helminth ova, posing risks to public health and the environment.
  • Conventional disinfection methods may be insufficient for highly resistant structures like helminth ova.
  • Ammonia's disinfectant properties and ability to penetrate resistant structures suggest its potential as an alternative sludge treatment.

Purpose of the Study:

  • To investigate the efficacy of ammonia as a disinfectant for wastewater sludge.
  • To quantify the inactivation kinetics of faecal coliforms, Salmonella spp., and helminth ova using ammonia.
  • To evaluate the combined effect of ammonia and elevated temperature on pathogen inactivation and biosolid quality.

Main Methods:

  • Wastewater sludge from Advanced Primary Treatment (APT) or Chemical Enhanced Primary (CEP) processes was treated with ammonia alone and in combination with heat.
  • The Hom model was applied to determine kinetic parameters for the inactivation of faecal coliforms, Salmonella spp., and helminth ova.
  • Pathogen reduction and helminth ova viability were assessed over a 2-hour contact time at varying ammonia concentrations and temperatures.

Main Results:

  • A 20% w/w ammonia concentration reduced faecal coliforms by 7 logs, Salmonella spp. by 6 logs, and viable helminth ova by 83% within 2 hours.
  • Complete inactivation (100%) of helminth ova (88-132 ova/g TS) required combining 20% ammonia with 50°C.
  • Kinetic analysis indicated helminth ova possess higher resistance to inactivation than bacteria, and ammonia treatment outperformed lime stabilization.

Conclusions:

  • Ammonia is a potent disinfectant for wastewater sludge, effective against bacteria and helminth ova, especially when combined with elevated temperatures.
  • The ammonia disinfection process offers advantages over lime stabilization in terms of microbial inactivation and biosolid agricultural value.
  • Ammonia treatment presents a viable alternative for disinfecting sludge with high pathogenic loads, enhancing biosafety and resource recovery.

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