Sistemas de dessalinização do semiárido do Rio Grande do Norte: percepção social e avaliação da qualidade da água para atividades agropecuárias

Abstract

Most of the territory of the state of Rio Grande do Norte (RN) is inserted within the drought polygon, a region where more than half of the population live in rural areas. To improve the drinking water in the region, desalination equipment was installed, however, this equipment has generated a large amount of brackish waste. Thus, the present work aimed to assess the quality of groundwater and the desalination by-product for use in productive agricultural activities, as well as to evaluate the community's perception of the technology implemented. The database used, which was mostly provided by the Programa Água Doce (PAD), consisted water quality reports and semi-structured interviews carried out in 33 municipalities in RN. An evaluation of groundwater for irrigation purposes, which is discussed in the first chapter, revealed that the pH, conductivity, total dissolved solids (TDS), chloride, manganese, uranium, and zinc levels were above the limits recommended to cultivate vegetables. The waters in almost half of the wells presented high risks of soil salinization (43%), but low risks of sodification (45%). All the water sources analyzed were inadequate to cultivate most sensitive plants as they had sodium levels (> 115 mg/L) that can cause some degree of leaf damage. With respect to farming livestock, TDS, the concentrations of magnesium, sulphate and manganese were above the maximum recommended values. In the second chapter, the physical-chemical composition of the groundwater and concentrate was used to determine quality indices, given their use in irrigation and livestock watering. Well water (51%) and concentrate (65%) qualities were found to have higher percentages classified as poor and very poor for plant growth, respectively. Conversely, most of the groundwater (87%) and brackish waste (71%) were classified in the best quality classes (excellent and good) for livestock farming. A diagnosis of the desalination systems, which is carried out in the third chapter, revealed that in 42 locations 53% of the families used the desalination systems. Fixed monthly expenses such as: electricity (62%), operator salaries (90%) and reserve funds (100%) were mostly paid by communities themselves. After the desalinizators were implanted, an evaluation of the management model and service performance was carried out and revealed a 90% satisfactory response rate (excellent and good) for each aspect and/or variable analyzed. With respect to perceptions on the quality of sources of consumed water (cisterns and desalinated water), which were evaluated in four locations, 46% of respondents reported perceiving changes in the organoleptic properties of the water, mainly that they could taste chlorine and/or salts. About half of the respondents said they had received information on good hygiene and sanitary practices. Diseases, such as diarrhea and verminosis, were the most frequently cited examples. Community management tools proved to be important to maintaining desalinizators. However, this study found that there is a need for greater awareness among the population, for example through educational approaches and social communication, on the risks associated with this water for human consumption.