(Eco)toxicological impact potential from inorganic substances in biosolids: Real data-based suggestions for regulatory improvements

Abstract

Sewage sludge (SS) can be applied in soil for its nutrient recycling in agriculture and forestry, but the presence of toxic substances may prompt environmental and human health risks. Brazilian Resolution (CONAMA 498/2020) establishes thresholds for biosolid (i.e., treated sludge) quality for application in soils. We have evaluated the (eco)toxicological impact potential of such practice regarding the mentioned thresholds, and the concentration of inorganic substances in sludge from three different Wastewater Treatment Plants (WWTP) in São Paulo, Brazil. The assessment relied on USEtox®, a model that estimates the potential toxicological impact on humans and ecosystems. According to the evaluation of the regulatory thresholds, Zn are responsible for an ecotoxicological impact potential of 2.33E + 02 PAF.m3.day/kg (potentially affected species), which represents 48.2% of the aggregated impact for the scenario, while Hg potential is of 1.25E-04 cases/kg for non-cancerous diseases in humans – corresponding to 54% of this scenario. The assessment of the SS samples has confirmed to be critical for Zn, Hg, and Cr, and indicated potential ecotoxicological risks for concentrations found of Fe and Al, which do not have regulatory thresholds. Results were discussed along with related literature and international regulation. The study supports sustainable management of sewage in Brazil, and the analytical framework is replicable in other regions.