Electrolysis within anaerobic bioreactors stimulates breakdown of toxic products from azo dye treatment
- 456 Downloads
Azo dyes are the most widely used coloring agents in the textile industry, but are difficult to treat. When textile effluents are discharged into waterways, azo dyes and their degradation products are known to be environmentally toxic. An electrochemical system consisting of a graphite-plate anode and a stainless-steel mesh cathode was placed into a lab-scale anaerobic bioreactor to evaluate the removal of an azo dye (Direct Black 22) from synthetic textile wastewater. At applied potentials of 2.5 and 3.0 V when water electrolysis occurs, no improvement in azo dye removal efficiency was observed compared to the control reactor (an integrated system with electrodes but without an applied potential). However, applying such electric potentials produces oxygen via electrolysis and promoted the aerobic degradation of aromatic amines, which are toxic, intermediate products of anaerobic azo dye degradation. The removal of these amines indicates a decrease in overall toxicity of the effluent from a single-stage anaerobic bioreactor, which warrants further optimization in anaerobic digestion.
KeywordsAnaerobic treatment Electric potential Azo dye Direct Black 22 Aromatic amines Toxicity Electrolysis eAD
The authors thank the Brazilian agency CNPq for a Post-Doctorate Scholarship (Process number 202290/2012-3) granted to S.G. and the National Science Foundation through CAREER Grant No. 0939882 to L.T.A. We also thank anonymous reviewers for helpful comments.
- American Public Health Association, American Water Works Association, and Water Environment Federation (2005) Standard methods for the examination of water and wastewater. American Public Health Association, Washington, DCGoogle Scholar
- Dillalo R, Albertson OE (1961) Volatile acids by direct titration. J Water Pollut Control Fed 3:356–365Google Scholar
- Fernando E, Keshavarz T, Kyazze G (2013) Simultaneous co-metabolic decolourisation of azo dye mixtures and bio-electricity generation under thermophillic (50 °C) and saline conditions by an adapted anaerobic mixed culture in microbial fuel cells. Bioresour Technol 127:1–8. doi: 10.1016/j.biortech.2012.09.065 CrossRefPubMedGoogle Scholar
- Franciscon E, Zille A, Fantinatti-Garboggini F, Serrano Silva I, Cavaco-Paulo A, Durrant LR (2009) Microaerophilic-aerobic sequential decolourization/biodegradation of textile azo dyes by a facultative Klebsiella sp. strain VN-31. Process Biochem 44:446–452. doi: 10.1016/j.procbio.2008.12.009 CrossRefGoogle Scholar
- Kawasaki S, Watamura Y, Ono M, Watanabe T, Takeda K, Niimura Y (2005) Adaptive responses to oxygen stress in obligatory anaerobes Clostridium acetobutylicum and Clostridium aminovalericum. Appl Environ Microbiol 71(12):8442–8450. doi: 10.1128/AEM.71.12.8442-8450.2005 CrossRefPubMedCentralPubMedGoogle Scholar
- Vanýsek P (2012) Electrochemical series. In: Haynes WM (ed) Handbook of chemistry and physics, 93rd edn. Chemical Rubber Company, ClevelandGoogle Scholar