Treatment of Wastewater from Fish Processing Industry using Chitosan Acid Salts

The effect of chitosan acetate and chitosan lactate prepared from chitosan obtained by N-deacetylation of chitin from common lobster (Panulirus argus), as coagulants/flocculants for depurating wastewater of fish processing industry was evaluated. Experiments were carried out by Jar tests varying chitosan acid salts concentration and pH. The results were evaluated in terms of reduction of total suspended solids (TSS) and chemical oxygen demand (COD) of the wastewater. Response surface methodology was applied to obtain quadratic and second-degree response surface model equations. With both chitosan acid salts, it was obtained a decrease in TSS and COD between 70-90% and 26-30%, respectively was observed. Optimal values for coagulation-flocculation process, found it by numerical optimization, were: a) for chitosan lactate, pH=6.0 and salt dose of 29.50 mg/L, with values for COD of 30.4% and TSS of 89.5%; and b) for chitosan acetate, pH=7.13 and salt dose of 28.29 mg/L, with values for COD of 23.9% and TSS of 84.0%. Chitosan lactate was more effective as coagulant than chitosan acetate for decreasing the COD and TSS, due to that lactate ion exerts a higher electrostatic force over the electric charges of the particles in suspension, favoring the flocculation process.