Toxicity assessment of selected heavy metals in water using a seven-chambered sulfur-oxidizing bacterial (SOB) bioassay reactor

초록

A seven-chamber reactor was developed for a 2-h batch toxicity assessment in water using sulfur-oxidizing bacteria (SOB) based bioassay. The optimum sulfur to water ratio (g:mL) was evaluated using a constant 20 g of sulfur and varying volumes of water at ratios of 1:1, 1:1.5, 1:2, and 1:2.5. Sulfur particles with 20 g sulfur and 20 mL water (1:1 ratio) proved the most efficacious and led to higher electrical conductivity (EC) values. Air flow rates may hinder the effectiveness of EC as the indicator since rates greater than 300 mL/min were shown to lead to higher ECs, most likely through evaporation resulting in higher concentrations. Once optimal conditions were established, the toxicity of Cr6+, Cu2+, Zn2+, Hg2+, and Ag2+ were assessed. The toxicity values (EC50) were decreased as exposure time was increased. A 2-h EC50 of 1.78 mg/L for Cr6+, 5.0 mg/L for Cu2+, 1.55 mg/L for Zn2+, 0.21 mg/L for Hg2+, and 1.76 mg/L for Ag2+ was calculated. The toxicity was compared in decreasing manner as Hg2+ > Zn2+ > Ag2+ > Cr6+ > Cu2+. The results suggest that SOB was effective for detecting heavy metals in a short period of time (2-h). (C) 2017 Elsevier B.V. All rights reserved.

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