Simplification and sensitivity study of Alamar Blue bioassay for toxicity assessment in liquid media

Abstract

Bacteria, as an essential component of most wastewater treatment plants (WWTPs), play a critical role in the biological stage of WWTPs due to their role in cycling mineral compounds and in the decomposition of organic material. In this study, a modified Alamar Blue-based bioassay was used to evaluate the toxicity of metal plating wastewaters on sequence batch reactor (SBR) bacteria. For confirming the robustness, reproducibility, and efficiency of the optimized method, it was compared with the standard colony count protocol and oxygen consumption method. The influence of pH on the Alamar Blue reduction was examined over a pH range of 1.0-13.0. The optimum pH for Alamar Blue bioassay using SBR bacteria was 6.5-7. The correlation between the reduction of Alamar Blue by SBR bacteria and their oxygen consumption coefficient was 0.945. According to our optimized bioassay, Alamar Blue was rapidly reduced by active SBR bacteria. This protocol successfully assessed the toxicity of metal plating wastewaters. As most of the WWTPs are inefficient for elimination of toxic effect of metals, it is desirable to use bioassays that can determine the toxicity of such pollutants. We simplified and optimized such an assay that can be manipulated for real metal plating wastewater samples.