Chitosan Production from Fish Scales and Its Application as a Natural Coagulant for Surface Water Treatment: Experimental and Statistical Evaluation

The progressive deterioration of surface water quality due to natural and anthropogenic factors, together with the limitations associated with conventional chemical coagulants, has driven the development of natural coagulants as sustainable alternatives for water treatment. In this context, the present study analyzed the production and application of a chitosan-based natural coagulant obtained from Oreochromis niloticus fish scales through a chemical method. The first phase involved biopolymer extraction through depigmentation, deproteinization, demineralization, and deacetylation; the second phase evaluated its performance as a coagulant using jar tests with water from the Magdalena River; and the third phase consisted of statistical analysis of the results using ANOVA. Yields of 78%, 78.20%, 88.52%, and 30% were obtained for each processing stage, and the chitosan achieved a degree of deacetylation of 76.87%, confirming its potential for water treatment applications. Optimal conditions were determined as a coagulant dosage of 300 mg/L and a flocculation time of 30 min, while ANOVA results indicated that both variables significantly influenced turbidity removal (p < 0.05). Under these conditions, a turbidity reduction of 76.30% was achieved. However, the final turbidity and color values did not meet Colombian regulatory standards, which was attributed to the presence of residual minerals and a moderate degree of deacetylation. Overall, the results demonstrate that chitosan derived from fish scales represents a sustainable alternative to chemical coagulants; however, process optimization and complementary treatment stages are required to meet drinking water standards.