## 3 Results and Discussion
### Pathogens  
Table 3 presents the average pathogenic microorganism concentration found in biosolids, disposed of in the soil, throughout the three years of the IBRS WWTP monitoring. In comparison with the legislation of Brazil, the United States, and the European Union, the three norms establish two classes of quality, class A and class B. Biosolids in the WWTP of the present research were classified in three norms as class B. The biosolids had a concentration of _Escherichia coli_ higher than the threshold concentration allowed for class A (\(<\)10\({}^{3}\) MPN g\({}^{-1}\) TS), as well as enteric viruses above the class A limit (\(<\)0.25 PFU g\({}^{-1}\) of TS). The average result of 381.5 \(\pm\) 23,955 (MPN g\({}^{-1}\) of TS) for _Escherichia Coli_ and enteric viruses \(<\)1 (PFU g\({}^{-1}\) of TS), according to [56], may be caused by the fact that the samples had been collected with biosolid freshly disposed of in the soil. However, several processes help the biosolids achieve adequate microbiological conditions, such as liming, thermal drying, or composting maintaining a thermal condition above 60 \({}^{\circ}\)C for at least three days [27]. Thus, there are no restrictions to the class B biosolids of the WWTP of the present study to being recycled in planted forests and recovery of soils and degraded areas, only to growing food products consumed raw, according to Conama Resolution 498/20 [27]. As regards the crops used as references to evaluate the agronomic potential of biosolids in this study, forage grasses cannot receive applications of biosolids two months before the grazing of animals. Furthermore, corn, rice, wheat, coffee, sugar cane, beans, and cotton can be fertilized with biosolids, as long as the interval between application and harvest is of 24 months [27]. In the old resolution, the 375/06 [26], class B biosolids only could be applied in coffee plantations, fiber, and oilseed crops, or in forestry, as long as they were incorporated into the soil mechanically and restrictions of harvest and public access were obeyed. According to EU legislation, the interval between application and harvest must be from 12 to 30 months for all edible crops [30]. In the USA, in turn, the interval between application and harvest must be of 14 months for food crops grown close to the ground, including vegetables, and 20-38 months for edible roots [28]. Class B biosolids of tropical climate WWTPs containing 30 helminth eggs (g TS\({}^{-1}\)), 10\({}^{6}\)_Escherichia coli_ (g TS\({}^{-1}\)), and 10\({}^{5}\)_Salmonella_ (g TS\({}^{-1}\)) were tested in the cultivation of carrot and spinach. At the time of harvest of the spinach and carrots, respectively, seven and twelve weeks after planting, no _Salmonella_ was detected in the soil, but about 10\({}^{3}\)-10\({}^{5}\)_Escherichia coli_ g TS\({}^{-1}\) were found and around 1-6 helminth eggs (g TS\({}^{-1}\)), according to the study of [57], in South Africa. Ref. [58] applied class B biosolids to grow lettuce and carrot, with up to 2 \(\times\) 10\({}^{6}\) of _Escherichia coli_ (g TS\({}^{-1}\)), which resulted in lettuce and carrot contamination levels below the limit of Brazilian regulation about the sanitary quality of consumed raw vegetables [59]. Thus, it is evident that in Brazil, the Conama 498/20 legislation is aligned with international law, toward promoting a circular economy and the nexus concept (water, energy, and food), except with respect to crops that are consumed raw, which cannot receive class B biosolids.