Natural coagulant for water treatment based on cationized tannins from Terminalia Catappa bark

Abstract

In a drinking water treatment plant, particles in the water must be destabilized in the coagulation stage after adding coagulants and performing intense stirring to remove impurities. Finding new alternatives to replace chemical coagulants and evaluating the turbidity and pH parameters to observe their effect on water treatment is essential to reduce costs and minimize environmental impacts. This study therefore aimed to develop and test a vegetable coagulant based on a tannin-rich extract of Terminalia catappa L. and to evaluate different coagulant concentrations at different stirring times. The extract was acquired from the tree bark for quantification and formulation of the coagulant. After this, the extract was cationized and employed in the coagulation test, with concentrations of 50, 100, 150, and 200 mg L^-1 and a chemical product as a comparison. Two different stirring times were performed (2 min followed by 10 min (T1) and 2 min and 20 min (T2). The turbidity and pH values were evaluated every 10 min up to 60 min. The data obtained were subjected to analysis of variance by Tukey's test at 5% probability to observe if there was a statistical difference. Terminalia catappa presented 10.01% of condensed tannin content. The natural coagulant treated the water efficiently. The best concentration found was 200 mg L^-1, with sedimentation of 30 min, and the best stirring time was T2. The coagulant reached the minimum turbidity values required by the Brazilian regulations for water for human consumption and did not alter the original water pH.

Keywords: forest species, phenolic compound, water quality.