Waste Water Management – Indications ad interim regarding the sewage sludge management and the spread prevention of virus SARS-CoV-2
The report explored the safe management of sewage sludge, for the prevention of the spread of Coronavirus (SARS-CoV-2). The authors take account of current knowledge in the transmission of the SARS-Cov-2 infection, as well as the regulatory provisions and the current knowledge and practices applied to the integrated water cycle are considered, with particular regard to the purification of waste water from civil and productive settlements. In sum, the study recommends the following:
- Composting plants, anaerobic digestion: The times and temperatures of treatment make the risk of transmission of SARS-CoV-2 infection irrelevant.
- Incineration or thermal dehydration: The conditions and temperatures of treatment make the risk of transmission of the SARS-CoV-2 infection irrelevant.
- Landfill disposal: Landfilling (with a controlled deposit) must be carried out in strict compliance with the rules of good technique and hygiene and public health within the plants and in all the phases of transfer and use of the sludge. In particular, the collection of sludge at the treatment plants must take place with suitable mechanical means and in compliance with the hygienic conditions for those involved in these operations and for the environment, avoiding the formation of aerosols and dust. The transport of sludge must be carried out with suitable means to avoid any dispersion during the transfer and to guarantee maximum safety from a hygienic-sanitary point of view.
- Reuse in agriculture (spreading or production of soil improvers and corrective agents): Sewage sludge need to be applied in compliance with good agricultural practices. To proceed with this practice, stabilization treatment with lime, sulfuric acid, ammonia, soda or a combination of these, anaerobic digestion (mesophilic and thermophilic) or aerobic (mesophilic and thermophilic), thermal dehydration, thermal hydrolysis with a temperature above 100 ° C for at least 20 minutes, the pasteurization of the liquid sludge for a minimum of 30 minutes at 70 ° C or in any case a minimum retention time (including treatment and storage times) of the sludge must be guaranteed before using it in compliance with the treatment and storage temperatures, and following the formula reported in Annex 18, ensuring that the sludge to be reused is not integrated or mixed with treated sludge that does not ensure the retention conditions in the plant as established above. Sludge coming from purification plants operating with prolonged oxidation in the absence of primary treatment with residence times of the waste in the oxidation tank of at least 24 hours and residence times of the sludge of at least 15 days and concentration of volatile solids in the excess sludge of less than 60% of the total solids, can also be considered sanitized.