Optimization of Primary Wastewater Treatment from the Fishing Industry using Chitosan and Aluminum Sulfate

Abstract

Wastewater from primary processing of hydrobiological resources, characterized by its high pollutant load, represents an environmental and sanitary risk. Although coagulation-flocculation with chemical agents has traditionally been the method used, its use is associated with negative adverse impacts, which has prompted the search for more sustainable natural alternatives. The purpose of this research was to evaluate the effect of a natural coagulant (chitosan), in comparison with aluminum sulfate, a chemical coagulant, in the reduction of turbidity and its adverse effects in fishery effluents. For this purpose, wastewater samples were collected from an Artisanal Fishing Landing Site (DPA) and coagulation-flocculation tests were performed using the jar test method, applying different doses of coagulant (5, 12.5 and 25 mg/L) and adjusting specific times for fast mixing, slow mixing and sedimentation. The results indicated that aluminum sulfate achieved the highest turbidity reduction (74.01 %) with an optimum dose of 20 mg/L, while chitosan, with a lower dose (12.5 mg/L), achieved a comparable reduction (61.72 %). Furthermore, chitosan had a lower influence on the pH of the treated water (0.03 variation) and a lower sludge generation (1.70 mL/L) in contrast to aluminum sulfate (pH variation of 0.17 and 5.50 mL/L of sludge produced). These findings show that chitosan, in addition to being a natural and sustainable alternative, has a performance comparable to that of aluminum sulfate in reducing turbidity in fishery effluents.