EVALUATION OF THE COAGULANT CAPACITY OF STARCH OBTAINED FROM TOPOCHO PELIPITA PLANTAIN CLONE (Musa ABB) FOR TURBIDITY AND COLOUR REMOVAL IN RAW WATER

摘要

Flocculation and coagulation of organic material contained in raw water samples were evaluated by using starch as coagulation agent. The starch was obtained from topocho pelita ( Musa ABB) plantain clone, which is grown in the south area of the Department of Bolivar (Colombia). Native starch (NS) was chemically modified with acetic anhydride obtaining a 18.3% degree of acetylation (low acetylated starch, LAS) and 23.7% (high acetylated starch, HAS). The chemical structure of these biomaterials was analysed by FTIR spectroscopy. Characteristic peaks were observed at 1350 cm -1 (C-O stretching) and 950 cm -1 (C-O-C bending). Scanning Electron Microscopy (SEM) was used to determine morphology and size of the starch samples. Elongated grain shapes with sizes of 37±8 mm (NS), 35±11 mm (LAS) and 307±85 mm (HAS) were observed through this technique, suggesting a relationship between degree of acetylation and agglomeration of grains. Analysis of variance indicated that concentration of the starch samples is the only factor which has a statistically significant effect on the response variables (colour and turbidity) at a 95% confidence level. Colour removal capacities of 94%, 93% and 89% were estimated using the NS, LAS and HAS samples, respectively at a concentration of 200 mg/L. Additionally, a turbidity removal capacity of 96% was estimated for the NS sample, which compares very well with the 95% turbidity removal capacity obtained from the acetylated starches, indicating that native starch presents suitable properties to be used as coagulation agent for water treatment.