Evaluación de la capacidad del quitosano extraído de la cáscara de cangrejo como coagulante para potabilización

Abstract

This research work evaluated the coagulating capacity of chitosan for removing turbidity and color in water for human consumption. The biopolymer was extracted from shell waste of red crab (Ucides occidentalis), by chemical treatments of deproteinization, demineralization, purification and deacetylation, obtaining biopolymer of up to 37,76% performance, 57,34% ash content and 79,70% degree of deacetylation. Jar-tests were carried out using synthetic raw water with initial turbidities of 10, 50 and 90 NTU. Optimal doses of chitosan less than 7 mg/L were obtained for all three analyzed turbidities; an optimal coagulation pH range of 5,7 - 10; optimal gradients and times of flocculation of 15 s-1 and 20 min for 10 NTU, 25 s-1 and 20 min for 50 NTU and 35 s-1 and 30 min for 90 NTU; with removals greater than 80% at the first minute of sedimentation. Finally, the feasibility study concluded that the use of chitosan as a coagulant is viable for water treatment plants that treat a flow rate of 176 L/s, from the generation of crab shell waste of 57 kg/d, with a treatment cost saving of 47,92%, compared to the conventional coagulant (Al2(SO4)3).