Evaluación la inhibición tóxica de Cd2+ y Cr6+ en la actividad metanogénica de un inóculo bacteriano proveniente de biosólidos del biodigestor de la planta de tratamiento de aguas residuales de Ambato

Abstract

The generation of sludge (biosolids) in wastewater treatment plants (PTAR) poses a problem for human health and the environment due to its high level of contamination. Treating biosolids through anaerobic digestion helps reduce contaminants while generating methane gas. However, the presence of heavy metals such as chromium or cadmium can lead to toxic inhibition and hinder the treatment process. For this reason, the objective of the project was to evaluate the toxic inhibition of cadmium (II) and chromium (VI) on the specific methanogenic activity (AME) of a bacterial inoculum derived from biosolids in Ambato's PTAR biodigester. Analytical methods were used to determine the main characteristics of the biosolids, and bioassays were conducted to monitor the AME. The results revealed that the biosolids contained contaminants such as organic matter, nutrients, and metals. Additionally, the AME of the inoculum (without the addition of metals) was 0.6 moles of methane per gram of bacterial biomass per day. The inhibitory effect caused a reduction in AME by 20, 50, and 80 percent with the addition of 15, 28.4, and 50 mg of cadmium per liter, respectively. These reductions in AME were observed for chromium (VI) with the addition of 75, 100, and 200 mg per liter, resulting in a reduction of 20, 50, and 80 percent, respectively. Finally, it was demonstrated that increasing concentrations of cadmium and chromium (VI) significantly decreased the AME, which would represent a potential risk for biosolids treatment in the PTAR.