ABSTRACT Water deficit is a current problem of global relevance. This is a problem in Brazil, especially in the Semiarid region, which undergoes severe droughts for much of the year. This requires the search for alternatives, such as the planned wastewater use, which is a successful alternative in developed countries that is applied for various purposes, including agriculture. However, despite the increasing growth of agriculture in Brazil, there are no established control and monitoring policies to minimize its impacts on the environment and human health. The country does not have specific legislation that defines wastewater quality parameters for domestic sewage. The objective of this work was to compile international guidelines and legislations that address this issue and compare them with the national normative resolutions for quality of wastewater and its different uses. The most relevant and locally applicable parameters described in these documents were listed, and the reference limits were defined by comparing them with those found in the scientific literature applied to the Brazilian context. This compilation represents the first step towards the incorporation of regulations for water reuse, having the Brazilian Semiarid region as a first test field, but with expandable application to different regions of the country. | RESUMO O déficit hídrico é uma problemática atual de relevância mundial. No Brasil, em especial no semiárido, essa realidade alcança níveis elevados de seca em boa parte do ano, sendo necessária a busca de alternativas mitigadoras, como o reúso planejado de águas residuárias, alternativa instaurada com sucesso nos países desenvolvidos, aplicado para diversos fins, inclusive na agricultura. No cenário nacional, mesmo diante do acentuado crescimento dessa atividade, não existem, políticas definidas de controle e monitoramento que visam minimizar impactos causados ao meio ambiente e à saúde humana. Ademais, o país não dispõe de legislação específica que contemple parâmetros da qualidade de água de reúso proveniente de esgoto doméstico. Nesse sentido, este trabalho teve como objetivo analisar as diretrizes e legislações internacionais que tratam dessa temática associadas às normativas nacionais que discorrem sobre a qualidade da água de reúso em suas diversas aplicações. Foram elencados os parâmetros de maior relevância e aplicabilidade local, descritos nesses documentos, e os limites de referência definidos a partir da comparação com a bibliografia científica aplicada ao contexto brasileiro. Essa compilação representa o primeiro passo para uma futura incorporação regulamentar da atividade de reúso de águas, tendo como campo primário de aplicação o semiárido, mas expansível às diversas regiões do país.

ABSTRACT Water scarcity is one of the main problems in the Semiarid region of Brazil, which can be mitigated by water resource management strategies. The objective of this work was to classify waters of a watershed in the Semiarid region of Brazil and select the water attributes that most affect the quality of waters used for irrigation (QWI), using multivariate statistics. The study area was the Riacho da Bica watershed, which is between the municipalities of Portalegre and Viçosa, Rio Grande do Norte, Brazil. The QWI was determined using water samples from 15 collections carried out from 2016 to 2018, in five specific points of the watershed, starting in the spring and following the water course. The water attributes evaluated were: electrical conductivity (EC), potential hydrogen (pH), and sodium (Na+), potassium (K+), magnesium (Mg2+), calcium (Ca2+), carbonate (CO32-), chloride (Cl-), and bicarbonate (HCO3-) contents. The water quality data were subjected to multivariate statistics through factorial analysis (FA) and principal component analysis (PCA). The application of multivariate statistics through FA-PCA generated four principal components. The attributes that most explained the QWI variation were potassium, calcium, and pH for Factor 01, and sodium and RAS for Factor 02. The watershed waters were classified as low risk of salinity and medium risk of sodicity (C1S2) for irrigation purposes.

ABSTRACT The objective of this study was to evaluate the effect of the conversion of secondary native vegetation (NV) to conventional systems (agriculture and pasture) in soil organic carbon (SOC) and carbon of fractions particulate organic matter (POM) and mineral-associated organic matter (MAOM) in the Brazilian semi-arid region. The study was carried out in the municipalities of Delmiro Gouveia, Inhapi and Pariconha, in Alagoas, Brazil. Soils were collected in the layers of 0-0.1, 0.1-0.2 and 0.2-0.3 m. The treatments analyzed were: agricultural crops with 4, 15 and 30 years and pasture with 10 years. As a reference, the secondary Caatinga was used. The results show that in soils with sandy texture (Neossolos Quartzarênico and Regolítico – Arenosols and Regosols, respectively), there were reductions in SOC levels and carbon in the compartment associated with minerals. The inverse can be observed in the clay-textured Argissolo (Acrisols), with 30 years of cultivation, in which there was an increase in SOC and C in the quantitative fractions of soil organic matter. In addition, despite the sandy texture of the Neossolo Regolítico, POM levels were increased in the pasture system in comparison to native vegetation, but it was not enough to recover the original SOC content of this system.