Downing Leon S, Nerenberg Robert
Department of Civil Engineering and Geological Sciences, University of Notre Dame, Notre Dame, Indiana 46556, USA.
Biotechnol Bioeng. 2007 Oct 15;98(3):543-50. doi: 10.1002/bit.21442.
Bromate (BrO(3)(-)) is an oxidized contaminant produced from bromide (Br(-)) during ozonation and advanced oxidation of drinking water. Previous research shows that denitrifying bioreactors can reduce bromate to innocuous bromide. We studied a hydrogen-based, denitrifying membrane-biofilm reactor (MBfR) for bromate reduction, and report the first kinetics for a hydrogen-based bromate reduction process. A mixed-culture MBfR reduced up to 1,500 microg/L bromate to below 10 microg/L with a 50-min hydraulic residence time. Kinetics were determined using short-term tests on a completely mixed MBfR at steady state with an influent of 5 mg N/L nitrate plus 100 microg/L bromate. Short-term tests examined the impact of pH, nitrite, nitrate, and bromate on bromate reduction rates in the MBfR. Kinetic parameters for the process were estimated based on the short-term bromate tests. The q(max) for bromate reduction was 0.12 mg BrO(3)(-) x mg(x)(-1) x day(-1), and the K was 1.2 mg BrO(3)(-)/L. This q(max) is 2-3 times higher than reported for heterotrophic enrichments, and the K is the first reported in the literature. Nitrite and nitrate partially inhibited bromate reduction, with nitrite exerting a stronger inhibitory effect. Bromate was self-inhibitory at concentrations above 15 mg/L, but up to 50 mg/L of bromate had no inhibitory effect on denitrification. The optimum pH was approximately 7. We also examined the performance of an MBfR containing pure culture of the denitrifying bacterium Ralstonia eutropha. Under conditions similar to the mixed-culture tests, no bromate reduction was detected, showing that not all denitrifying bacteria are active in bromate reduction. Our results suggest the presence of specialized, dissimilatory bromate-reducing bacteria in the mixed-culture MBfR.
溴酸盐（BrO₃⁻）是饮用水臭氧化和高级氧化过程中由溴化物（Br⁻）产生的一种氧化型污染物。先前的研究表明，反硝化生物反应器可将溴酸盐还原为无害的溴化物。我们研究了一种基于氢气的反硝化膜生物反应器（MBfR）用于溴酸盐还原，并报告了首个基于氢气的溴酸盐还原过程的动力学。一个混合培养的MBfR在50分钟的水力停留时间内可将高达1500微克/升的溴酸盐还原至10微克/升以下。动力学是通过在稳态下对完全混合的MBfR进行短期试验确定的，进水为5毫克氮/升硝酸盐加100微克/升溴酸盐。短期试验研究了pH值、亚硝酸盐、硝酸盐和溴酸盐对MBfR中溴酸盐还原速率的影响。基于短期溴酸盐试验估算了该过程的动力学参数。溴酸盐还原的最大比反应速率（q(max)）为0.12毫克BrO₃⁻×毫克⁻¹×天⁻¹，半饱和常数（K）为1.2毫克BrO₃⁻/升。这个q(max)比异养富集报道的值高2至3倍，且K值是文献中首次报道。亚硝酸盐和硝酸盐对溴酸盐还原有部分抑制作用，亚硝酸盐的抑制作用更强。溴酸盐在浓度高于15毫克/升时具有自抑制作用，但高达50毫克/升的溴酸盐对反硝化没有抑制作用。最佳pH值约为7。我们还研究了含有反硝化细菌真养产碱菌纯培养物的MBfR的性能。在与混合培养试验相似的条件下，未检测到溴酸盐还原，表明并非所有反硝化细菌在溴酸盐还原中都有活性。我们的结果表明在混合培养的MBfR中存在专门的异化溴酸盐还原细菌。
