7.4 What indicates foul odour release and vector insect appearance at biosolids land application sites?

Biosolid storage areas and application sites may be prone to infestation by vector insects, small rodents, and the release of foul odours. These problems are a consequence of poor stabilisation of organic matter and high volatile solids content in the biosolids, which supposedly should have been eliminated through aerobic or anaerobic sludge digestion treatment stages.

Letting those volatile substances be eliminated during biosolid storage or after its application, poses an open invitation to insects and small rodents, which may trigger the biosolid recontamination process, eventually spreading disease vectors.

It is therefore essential to ensure the proper treatment prior to application.

Some other recommendations are as follows:

• Proper covered storage: In case biosolids cannot be applied directly, but need to be stored, it is essential to establish a covered storage facility to prevent access by vector insects and minimize odour release. Nonetheless, timely application is important to reduce the attractiveness of biosolids to insects.
• Effective application methods: Using application methods such as injection or incorporation, which bury biosolids beneath the soil surface, can deter insects and minimize odour release. This method can also promote better soil incorporation and reduce surface runoff.
• Continuous monitoring: Monitoring and inspection of storage areas and application sites for signs of insect activity, odour release, and biosolid quality can help identify issues early and implement corrective actions. Prompt responses to insect infestations or odour complaints can prevent further problems.