The biosolids resulting from the sludge treatment from sewage treatment plants improve soil conditioning and are rich in nutrients. However, despite the benefits to soil and plants, as well as the sustainable appeal, the agricultural use of biosolids in Brazil is still not widespread. In this Technical Note (TN), the objective is to present some Brazilian experiences with biosolids in the light of relevant legislation, as well as to discuss aspects and potential related uses. Paraná and São Paulo states are the main references in agricultural use, with experiences of sanitization with alkaline stabilization and composting. In this TN the criteria for the use of biosolids are presented, according to the new CONAMA Resolution 498/2020, as well as the challenges related to the agricultural sector and public acceptance. Public policies to support rural producers for the application of biosolids are also discussed, to promote transformation of a rich by-product of sewage treatment into a resource for agricultural use, in a vision of circular economy.

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.

The effluent from sewage treatment plants (STPs) used in fertigation is a source of nutrients for plants, reducing mineral fertilizers applied to agricultural crops, and partially supplying the water demanded by the plants. The use of this effluent in agroforestry is also favoured because of its availability all year long, especially in cities with sewage treatment systems. Some criteria, hould be considered when using effluent from STP in crops, such as: type of plant that will be used, method of application, physicochemical and biological characteristics of the effluent, as well as the doses to be applied. Such criteria are covered in this technical note. The potential use of the effluent in the agroforestry segment is illustrated by some experiments using different treatment levels. In these experiments, the effects on the productivity of the essential oil extracted from coriander seeds and on the productivity of forage (elephant grass), by using different methods of fertigation, were evaluated.

Sewage treatment plants (STPs) generate solid by-products that need to be managed safely so as not to compromise the environment and public health. Among these by-products, of special interest is the sludge generated in the primary, biological and physical-chemical treatment units, which concentrates a large amount of the pollutants and contaminants removed during sewage treatment. However, the sludge is also a reservoir of compounds that can be recovered or reused (e.g.: organic matter, phosphorus, and nitrogen), which are of agronomic interest and can be used for the recovery of degraded areas. This technical note (TN), the first of the collection “Valorization and management of solid by-products of sewage treatment. Part A: Sanitization and use of sewage sludge in soil”, presents topics of interest related to modern management of the sludge generated in STPs, with emphasis on the legal aspects and forms of treatment for its transformation into biosolid for use in soils and other possibilities. The other TNs that are part of this collection deepen the topics briefly addressed in this first TN.