Análise da eficiência do gel extraído da semente de chia (salvia hispanica) como coagulante natural na clarificação de água em comunidade do semiárido baiano

Abstract

A large number of people in Brazil and around the world suffer from problems associated with water insecurity and the lack of basic sanitation. The northeast of Brazil is where this reality is most evident, since the drought polygon that encompasses a large part of the region suffers from irregular rainfall. Given this scenario, the quality of water for human consumption takes a back seat, since ensuring drinking water, especially for rural areas, is unfortunately not a priority. In the context of conventional water treatment logistics, one of the most important steps is coagulation. In the meantime, the most widely used coagulants are ferric sulfate and aluminum sulfate. The latter has raised questions regarding the residuals in treated water and its consequences for human health. In view of this, organic coagulants are considered as alternatives, since they do not pose a risk to human health and are low cost. This study aimed to analyze the efficiency of using the gel extracted from chia seeds (Salvia hispanica) as a natural coagulant in water clarification in a reservoir located in the rural area of the semi-arid region of Bahia, in the municipality of Malhadas de Pedras-BA. For this purpose, water samples were collected from a reservoir in the rural community of Lagoa do Mucambo, the samples were characterized, and then the gelatinous solution of chia (Salvia hispanica) was extracted for 3 (three) concentrations of chia, 2 g/L, 6 g/L and 10 g/L in a ratio of 1:40 weight/volume and the efficiency of turbidity removal after the application of aluminum sulfate and the gel was compared. The parameters analyzed were turbidity, pH, electrical conductivity and total dissolved solids. The experiments revealed that the chia gelatin solutions presented high efficiencies in removing turbidity from the reservoir water, with the solution with a concentration of 2.0 g/L presenting a removal percentage of 99.4%, meeting the maximum value allowed (<5 uT) by Ordinance No. 888/2021 of the Ministry of Health. The 6 g/L and 10 g/L chia gel solutions presented a turbidity reduction percentage above 98%. Meanwhile, among the tests using aluminum sulfate, the dosage of 2.82 mL presented the highest removal percentages with approximately 99.89%, while the dosage of 5.52 mL presented the lowest reduction with 99.74%. A small increase was observed for the pH, making it more basic, but the maximum values found were 8.04 for aluminum sulfate at a dosage of 4.23 mL and 7.93 for 10 g/L of chia gel solution. Significant reductions occurred for total dissolved solids, with values below 125 mg/L in all tests, meeting the maximum value permitted (<500 mg/L) by potability legislation. Thus, the results indicate that the chia seed gel solution is efficient as an organic coagulant for water treatment, enabling its future use in water purification, especially in communities in the semiarid region, through its improvement and analysis of its economic and logistical viability.