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Risk evaluation for pathogenic bacteria and viruses in sewage sludge compost
1Department of Civil Engineering, Graduate School of Engineering, Tohoku University, Aoba-yama 06, Sendai 980-8579, Japan.
Summary
Pathogenic bacteria and viruses were undetectable in tested compost samples. Risk assessments determined acceptable limits for contamination, establishing criteria for safe compost use in agriculture and gardening.
Area of Science:
- Environmental microbiology
- Public health
Background:
- Sewage sludge composting is a common recycling method.
- Limited data exists on pathogen presence and infectious risks in compost.
Purpose of the Study:
- To detect pathogenic bacteria (Salmonella spp., E. coli O157) and enteric viruses in compost.
- To evaluate infectious risks associated with compost use.
- To establish safety criteria for compost contamination.
Main Methods:
- Compost samples analyzed for bacterial and viral pathogens.
- Monte Carlo simulation used to assess infectious risks.
- Risk assessment based on acceptable risk levels (10^-4 per year).
Main Results:
- Pathogenic bacteria and viruses were not detected in 1.0 g-wet of compost samples.
- Simulation determined acceptable contamination criteria for Salmonella spp., E. coli O157, and Poliovirus 1.
- 1.0 CFU or PFU/g-wet is acceptable for E. coli O157 and Poliovirus 1.
Conclusions:
- Compost samples tested were free from detectable levels of specific pathogens.
- Safety criteria were established for compost contamination to mitigate infectious risks.
- Lower Salmonella spp. limits ( < 0.001 CFU/g-wet) are recommended for compost safety.