EDTA-2Na/Fe(Ⅱ)对自养生物体系下硝酸盐还原过程的影响

Effect of EDTA-2Na/Fe(Ⅱ)on nitrate reduction in autotrophic biological system

采用厌氧序批式生物膜反应器(ASBBR),以固定浓度的硝酸盐和硫酸亚铁为基质,按不同梯度条件添加EDTA-2Na,进行长时间的培养驯化,研究铁盐脱氮的启动过程,同时探究不同EDTA-2Na/Fe(Ⅱ)对铁自养反硝化过程以及硝酸盐异化还原为铵(DNRA)的影响.结果表明:经过65d的培养驯化,反应器成功稳定运行.当EDTA-2Na/Fe(Ⅱ)<1.50时,反应器只进行铁自养反硝化过程,NO_(3)^(-)-N去除率最高仅为71.70%;当EDTA-2Na/Fe(Ⅱ)≥1.50时,反应器同时进行铁自养反硝化与DNRA过程,NO_(3)^(-)-N去除率最高为99.70%.值得注意的是,在EDTA-2Na/Fe(Ⅱ)=1.50时,铁自养反硝化速率达到最大值1.63mg/(L·h)的同时,DNRA的产氨量也达到最大值9.75mg/L.Visual MINTEQ模拟结果表明:EDTA-2Na与Fe(Ⅱ)的摩尔比会影响进水中EDTA-2Na与Fe(Ⅱ)的存在形态,物质的量比越大,FeEDTA^(2)度越高,Fe(Ⅱ)的生物可利用性越强.通过对不同样本进行微生物种群分析,发现优势菌属有Brucella、Castellaniella、Ochrobactrum、Pseudomonas、Citrobacter,前4种菌属均与反硝化过程有关,Citrobacter菌属与DNRA过程有关,且该菌属只在EDTA-2Na/Fe(Ⅱ)=1.50和1.75两个条件下出现.上述研究结果可为更深入探究DNRA与反硝化之间的作用关系提供参考.

The initiation of iron mediated denitrification was studied in an anaerobic sequenced batch biofilm reactor(ASBBR)with a fixed concentration of nitrate and ferrous sulfate,supplemented with EDTA-2Na according to different gradient conditions for a long period of cultivation domestication.Meanwhile,the effects of different EDTA-2Na/Fe(Ⅱ)on iron autotrophic denitrification process and the dissimilatory nitrate reduction to ammonium(DNRA)were also explored in this study.The results showed that after 65days of cultivation and domestication,the reactor operated successfully and stably,and the removal rate of NO_(3)^(-)-N was up to 99.70%.When EDTA-2Na/Fe(Ⅱ)<1.50,only iron autotrophic denitrification was performed with the highest removal rate of NO_(3)^(-)-N of 71.70%;When EDTA-2Na/Fe(Ⅱ)≥1.50,iron autotrophic denitrification and DNRA were carried out simultaneously in the reactor,and the highest removal rate of NO_(3)^(-)-N was 99.70%.It was worth noting that when EDTA-2Na/Fe(Ⅱ)=1.50,the iron autotrophic denitrification rate reached the maximum value of 1.63mg/(L·h),and the ammonia production of DNRA also reached the maximum value of 9.75mg/L.Visual MINTEQ simulation results showed that the molar ratio of EDTA-2Na to Fe(Ⅱ)affected the existing forms of EDTA-2Na and Fe(Ⅱ)in the influent.The larger the molar ratio,the higher the concentration of FeEDTA^(2) and the stronger the bioavailability of Fe(Ⅱ).Through microbial population analysis,it was found that the dominant bacteria were Brucella,Castellaniella,Ochrobactrum,Pseudomonas as well as Citrobacter.Among them the first four bacteria were related to denitrification process,while Citrobacter was related to DNRA process and was only appeared under the conditions of EDTA-2Na/Fe(Ⅱ)=1.50 and 1.75 in this research.Therefore,the above results could throw light on further exploring the relationship between DNRA and denitrification.