Efecto de la adición de cadmio y de plomo sobre el consumo de oxígeno en la degradación de materia orgánica del agua residual cruda de la Planta de Tratamiento de Aguas Residuales de Ambato

Abstract

The residuals water treatment contributes to environmental sustainability by removing contaminants present in water. However, the biological treatment in a wastewater treatment plant (WWTP) be affected due to the high concentration of inorganic contaminants, such as heavy metals, causing deterioration of the system. The objective of the project was to evaluate the impact of the addition of cadmium and lead on the oxygen of aerobic bacteria that degrade the organic material, doing respirometric tests in relation to the increase in heavy metal concentrations. For the tests, the mixed liquor from the WWTP-Ambato biological reactor was collected and exposed to different concentration levels of cadmium and lead. The results revealed that in a concentration up to 2000 mg per L, both heavy metals had an inhibitory effect on oxygen consumption, with a maximum inhibition of 97.75 percent and 85.07 percent for Cd and Pb, respectively. Also, the cadmium and lead toxicity index were determined in the activity of the PTAR-Ambato biological reactor that causes a 20 percent inhibition (IC20) to be 23.32 mg Cd per L and 390.39 mg Pb per L, a 50 percent inhibition (IC50) to be 147.40 mg Cd per L y 671.08 mg Pb per L and 80 percent inhibition (IC80) to be 731.12 mg Cd per L y 951.38 mg Pb per L. In conclusion, the high levels of cadmium and lead toxicity suggest that aerobic bacteria are developing tolerance to these metals.