Agronomic potential of biosolids for a sustainable sanitation management in Brazil: Nutrient recycling, pathogens and micropollutants

Abstract

Abstract The agricultural recycling of biosolids is a sustainable option and part of a circular economy. Some countries still face difficulties in expanding cleaner production. Studies pointing out the agronomic potential of biosolids and the level of pollutants might encourage the development of more efficient public policies within the scope of the water-energy-food nexus concept. The purpose of this paper was to evaluate the agronomic potential of biosolids in nutrient recycling, and its chemical, pathogen, and micropollutant characteristics, regarding meeting the Brazilian and international legal requirements. Drying bed samples were analyzed for nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur, as well as the demand for these macronutrients in eucalyptus, soy, orange, and tomato crops. The pathogens present and their limits established by the Conama Resolution 498/20 (Brazil), Norm 503 (United States), and Directive 86/278 (European Union) were analyzed. The same reference basis was adopted to evaluate inorganic contaminants (metals), with the addition of the Normative Instruction 7 (Brazil). For emerging organic pollutants (EOPs) the Conama Resolution 375/06 (Brazil) and EU Directive 2007 were used. Results evidenced that biosolids had the agronomic potential to meet the nutritional needs of the analyzed crops, especially for phosphorus, and they conformed to legal determinants for agricultural recycling. Based on the levels of Escherichia coli, biosolids were categorized as Class B. Inorganic contaminants were all within limits established by the Conama 498 Resolution and the Norm 503, although regarding Directive 86 there was an excess of zinc. Finally, results of EOPs were below minimum detectable limits, according to limits established by the Conama 375 Resolution, which is an old resolution, although it presents values for EOPs and EU Directive 2007. Consequently, the agricultural recycling potential of biosolids was evident, mainly because of the phosphorus recovery. It requires less landfill and transport and reincorporates nutrients into the production chain, which reduces the exploitation of natural reserves.