Eficiencia de coagulantes orgánico, inorgánico y mixto, en la recuperación ex situ de la calidad del agua de la laguna San Martín del cantón Girón (Ecuador)

Abstract

This study was conducted in San Martin Lagoon, canton Girón (Ecuador), with the objective of evaluating the efficiency of organic, inorganic, and mixed coagulants applied ex situ, analyzing their effect on turbidity, color, dissolved oxygen, pH, biochemical oxygen demand (BOD), electrical conductivity, nitrates, and phosphates. The methodology included an initial physicochemical characterization through sampling at eight points and, subsequently, the application of the jar test with four formulations: organic (banana peel powder), inorganic (aluminum sulfate), and two mixtures (75 % organic - 25 % inorganic and 25 % organic - 75 % inorganic), evaluated at doses of 33.33 mg/L and 250.5 mg/L. Removal efficiency was determined through analysis of variance, complemented by a cost analysis per cubic meter treated. The technical-economic analysis determined that treatment feasibility depends on the balance between performance and cost. The organic coagulant at low dose was the most economical (0.0262 USD/m3) but showed technical efficiencies with negative results in color, nitrates, and BOD. In contrast, the inorganic coagulant at 33.33 mg/L presented the best cost-benefit balance (0.0443 USD/m3), achieving phosphate removals exceeding 97 % and BOD reduction of 80.17 %, without significantly altering pH or conductivity and avoiding the high costs of elevated doses. Finally, it is concluded that the lagoon presents marked seasonal degradation; in this context, the use of inorganic coagulants at low doses or mixed formulations optimizes treatment efficiency and improves water quality.