van der Zee F P, Bouwman R H, Strik D P, Lettinga G, Field J A
Wageningen University, Agrotechnology and Food Sciences, Sub-department of Environmental Technology, P.O. Box 8129, 6700 EV, Wageningen, The Netherlands.
Biotechnol Bioeng. 2001 Dec 20;75(6):691-701. doi: 10.1002/bit.10073.
Azo dyes are nonspecifically reduced under anaerobic conditions but the slow rates at which reactive azo dyes are converted presents a serious problem for the application of anaerobic technology as a first stage in the complete biodegradation of these compounds. As quinones have been found to catalyze reductive transfers by acting as redox mediators, the application of anthraquinone-2,6-disulfonic acid (AQDS) during continuous anaerobic treatment of the reactive azo dye, Reactive Red 2 (RR2), was evaluated. A mixture of volatile fatty acids was used as the electron-donating primary substrate. Batch experiments demonstrated that AQDS could increase the first-order rate constant of RR2 reductive cleavage by one order of magnitude. In the continuous experiment, treatment of RR2 containing synthetic wastewater in a lab-scale upflow anaerobic sludge blanket (UASB) reactor yielded low dye removal efficiencies (<30%). Consequently, severe toxicity problems occurred, eventually resulting in almost complete inhibition of the methanogenic activity. Addition of catalytic concentrations of AQDS (19 microM) to the reactor influent caused an immediate increase in the dye removal efficiency and recovery of biological activity. Ultimately, RR2 removal efficiency stabilized at 88%, and higher AQDS loads resulted in higher RR2 removal efficiencies (up to 98% at 155 microM AQDS). Examination of the RR2 decolorizing properties of dye-adapted reactor sludge and of nonadapted reactor seed sludge revealed that RR2 decolorization was principally a biologically driven transfer of reducing equivalents from endogenous and added substrates to the dye. Hydrogen, added in bulk, was clearly the preferred electron donor. Bacteria that couple dye decolorization to hydrogen oxidation were naturally present in seed sludge. However, enrichment was required for the utilization of electrons from volatile fatty acids for dye reduction. The stimulatory effect of AQDS on RR2 decolorization by AQDS-unadapted sludge was mainly due to assisting the electron transfer from endogenous substrates in the sludge to the dye. The stimulatory effect of AQDS on RR2 decolorization by sludge from the AQDS-exposed reactor was, in addition, strongly associated with the transfer of electrons from hydrogen and acetate to the dye, probably due to enrichment of specialized AQDS-reducing bacteria.
偶氮染料在厌氧条件下会发生非特异性还原，但活性偶氮染料的转化速率较慢，这给将厌氧技术作为这些化合物完全生物降解的第一阶段应用带来了严重问题。由于已发现醌类通过作为氧化还原介质来催化还原转移，因此评估了蒽醌 - 2,6 - 二磺酸（AQDS）在活性偶氮染料活性红2（RR2）的连续厌氧处理过程中的应用。挥发性脂肪酸混合物用作供电子的主要底物。批次实验表明，AQDS可使RR2还原裂解的一级速率常数提高一个数量级。在连续实验中，在实验室规模的上流式厌氧污泥床（UASB）反应器中处理含RR2的合成废水，染料去除效率较低（<30%）。因此，出现了严重的毒性问题，最终几乎完全抑制了产甲烷活性。向反应器进水添加催化浓度的AQDS（19 microM）导致染料去除效率立即提高，生物活性得以恢复。最终，RR2去除效率稳定在88%，更高的AQDS负荷导致更高的RR2去除效率（在155 microM AQDS时高达98%）。对适应染料的反应器污泥和未适应的反应器接种污泥的RR2脱色特性进行研究发现，RR2脱色主要是将还原当量从内源性和添加的底物生物驱动转移到染料上。大量添加的氢气显然是首选的电子供体。将染料脱色与氢氧化耦合的细菌天然存在于接种污泥中。然而，需要富集才能利用挥发性脂肪酸中的电子进行染料还原。AQDS对未适应AQDS的污泥RR2脱色的刺激作用主要是由于协助电子从污泥中的内源性底物转移到染料上。此外，AQDS对来自暴露于AQDS的反应器污泥RR2脱色的刺激作用与电子从氢气和乙酸盐转移到染料密切相关，这可能是由于专门还原AQDS的细菌富集所致。
