Part A: Sanitization and use of sewage sludge in soil Technical Note 7 - Use of biosolids to recover degraded areas

Organic matter (OM) is fundamental in the rrecovery of degraded areas (RDA), particularly when concerning the soils’ chemical and physical properties. The biosolid obtained from sewage sludge is an important source of OM and nutrients. This technical note discusses the influence of both on RDA, as well as the potential for using biosolids for that purpose. OM acts as a reservoir of nutrients, which are gradually released; it improves the cation exchange capacity of the soil; and it can complex or chelate metals potentially toxic to plants. It is also highlighted its influence on the reduction of the specific mass of the soil, the formation of micro and macro aggregates, the improvement of soil stability, and the increase of soil specific surface. The practical aspects of biosolids use in RDA are discussed in the light of CONAMA Resolution 498/2020, mainly about the criteria for calculating the application doses. Two case studies are also presented.