Efficiency of Cassia fistula Seed as a Natural Coagulant in Raw Water Treatment from Sinú River, Colombia

Objective: To evaluate coagulant activity of Cassia fistula seeds in turbidity removal of raw water from the Sinú River and its influence on pH of treated water. Methods/Statistical Analysis: Saline extracts of Cassia fistula seeds were tested in raw water samples with 10 different turbidity levels and different coagulant doses in a jar test, according to standardized techniques. ANOVA blanks and tables with a 95% confidence level were used to verify if there were statistically significant differences in pH after treatment. Findings: Turbidity removals in raw water reached up to 70% for highly turbid samples (500 to 800 NTU), with a 50 mg L-1 optimum dose. Coagulant activity reached up to 50% for samples with turbidity levels between 250 to 492 NTU, and it was less than 30% for levels from 158 to 241 NTU. No statistically significant change evidence was found in pH of water treated with Cassia fistula seeds as a coagulant. Application/Improvements: This work proved that use of Cassia fistula for raw water treatment from Sinú River could serve as a coagulation aid and not as a primary coagulant.