Evidences on the application of biosolids and the effects on chemical characteristics in infertile tropical sandy soils

Abstract Biosolids are generated at Wastewater Treatment Plants (WWTPs) and they enable closing the loop of valuable resources that are beneficial to the soil-plant system, however, the legal aspects of viability and the principles of the circular economy must be considered. Studies that evaluate the chemical properties of tropical soils subjected to long-term applications of biosolids are scarce, especially with regards to Emerging Organic Micropollutants (EOPs), which makes the present work original. Thus, the present study aimed to statistically evaluate through the Tukey test and Principal Component Analysis (PCA) six years of biosolids‘ application (2012 to 2018), with different application rates, in five areas of infertile tropical soils. The study also evaluated the Potentially Toxic Elements (PTEs) and EOPs in relation to the legal viability aspects of Brazil and the European Union. The results showed that the biosolids can improve the chemical properties of the soil right after the first annual application, without risk of PTEs accumulation. The EOPs that were analyzed from 2016 to 2018, remained below the detection limits, consequently complying with the legislation. Further, the PCA showed that biosolids can replace the use of commercial fertilizers in tropical soils when applied at agronomic rates to meet plant nutrient requirements (mainly N and P), which consequently diverts the biosolids from landfills, and reduces the operational costs of Brazilian WWTPs. In this way, the cleaner production of agricultural systems in tropical soil can promote the circular economy and sustainable development in WWTPs in Brazil and other tropical climate regions.