AGRONAUT

Is the reuse of sewage sludge for agricultural purposes a safe procedure? This is a key issue that must be addressed, especially when this practice has been fostered over the last 30 years as the most suitable for sludge disposal. In the last years, the number of wastewater treatment plants has increased and consequently, sludge production. Sewage sludge and compost contains a high organic matter content and nutrients that are extremely valuables for soils. These characteristics make them prone to be used as fertilisers. However, the potential presence of significant amounts of organic contaminants has raised concern. In fact, the land application of sewage sludge or compost may be considered as a risk to humans and the environment due to their persistence, bioaccumulation and toxicity.

The AGRONAUT project aims to contribute to increase the knowledge on the safe use of sewage sludge and compost in cropland and to promote improvements in these practices, trying to increase its use in Portugal (up to 10%), promoting a circular economy. It will be focused on the analysis of emerging organic pollutants, namely synthetic musks and volatile methylsiloxanes. To the authors’ best knowledge, this work will fill an important gap, being the first study of its kind to be performed in Portugal.

A national monitoring plan will be established (sewage sludge and/or compost) in different urban wastewater treatment plants and those collected samples will be physicochemical and agronomically characterised. The potential variations of their quality will be assessed taking into account their origin, sociodemograhic aspects and seasonality. This is crucial to define new procedures and crop management conditions, trying to minimise pollutants uptake. Then, application of sewage sludge/compost to agricultural fields will be studied and plant uptake assessed using three crops - Solanum lycopersicum (tomato), Zea mays (maize) and Phaseolus vulgaris (bean) – those with a higher production/consumption in Portugal.