纳米铁-微生物耦合体系去除硝酸盐的影响因素研究

Study of influential elements on nitrate reduction by nanoscale iron particles integrated with microorganisms

采用液相还原法制备出纳米铁粒子,并与自养反硝化细菌耦合,以解决单独使用生物反硝化和纳米铁还原法的不足。本实验在纳米铁-微生物耦合体系可以有效还原硝酸盐的基础上,研究了pH、温度和DO等环境因素对该耦合体系脱氮速率和产物的影响,以期通过优化参数达到最好的脱氮效果。结果表明,该体系在中性条件下能够快速将硝酸盐还原,随pH升高,氨氮比例无显著变化,均在40%左右,但还原速率有所下降;随温度的升高,氨氮比例有所上升,而反应速率明显升高,但该体系在5℃时仍能将硝酸盐完全去除;耦合体系中的DO过高或过低都会导致产物中氨氮比例的增加,0.4 mg/L左右为较适宜DO水平,但对硝酸盐还原速率的影响不大,当DO为0.8 mg/L时,硝酸盐仍可以在8 d内完全去除。因此,该耦合脱氮体系对pH、温度和DO的适应能力较强,有利于实际地下水的原位修复。

Use of nanoscale zero-valent iron（NZVI） integrated with Alcaligenes eutrophus for nitrate reduction has been proved to counterbalance the shortages associated with traditional denitrification processes and maintain the unique features of nanoparticle technology such as higher surface energies and functionality in suspensions.Based on the former research that nitrate was found to be removed completely by NZVI particles combined with A.eutrophus with a lower reduction rate but generate a smaller proportion of ammonium,batch tests were conducted in the system to investigate the factors affecting the removal of nitrate,such as pH,temperature as well as DO.The results indicated that increasing pH did not have a distinguishable effect on the generation of ammonium in the range of pH 7~10,but decreased the reduction rate slightly.With the temperature increasing,the generation of ammonium and the rate of the nitrate removal increased.Moreover,too high or too low DO enhanced the generation of ammonium,so the proper DO may maintain around 0.4 mg/L.However,the rate of the nitrate reduction had no change with increasing DO level in the solution.Therefore,the system under high pH,low temperature and high DO conditions can still remove nitrate,and thus,the integrated system is more practical for in situ groundwater denitrification.