Evaluación del consumo de oxígeno por bacterias aeróbicas en aguas residuales de la planta de tratamiento de Ambato contaminadas con arsénico y cromo

Abstract

Industrial activities and population growth have led to an increase in the use of water resources and, therefore, the generation of wastewater. These have a high pollution load, both biological and non-biological (heavy metals, organic matter). For this reason, the objectives of this curricular integration project were to characterize the wastewater obtained from three secondary treatment points (the clarified effluent from the primary reactor, the mixed liquor from the biological reactor and the biosolids recirculation tank) of the Ambato wastewater treatment plant. Toxicity bioassays were also conducted by adding arsenic and hexavalent chromium, to verify how these metals affect the oxygen uptake rate and the inhibition of 20, 50 and 80 percent of microbial metabolism and growth. Determining that, as the concentration of the elements increased, the oxygen uptake rate decreased in both cases, as they decreased from 277 to 152 (arsenic) and from 288 to 68 milligrams of oxygen per liter per day (chromium). Furthermore, chromium was more toxic than arsenic, since the latter metal needed higher concentrations (1000 milligrams per liter) to achieve a 20 percent inhibition, as opposed to chromium, which needed only 13 milligrams per liter. Finally, these studies have been carried out with the purpose of providing alternatives to optimize wastewater treatment in future research.