改性剂添加量对改性微米铁-微生物耦合体系去除三氯乙烯效能的影响

Effect of Modifier Dosage on the Effectiveness of Modified Micron Zero-Valent Iron-Anaerobic Bacteria Coupling System for Trichloroethylene Removal

基于球磨法的硫化与碳改性是提高微米零价铁(Micron zero-valent iron,mZVI)对三氯乙烯(Trichloroethylene,TCE)还原选择性的有效手段,但其改性效果常受改性剂添加量的影响,且其对改性mZVI和微生物耦合体系修复效能的影响尚未明确。本文通过构建多个硫化mZVI-微生物体系(S-mZVI bm/AB)和碳改性mZVI-微生物体系(C-mZVI bm/AB),系统研究改性剂添加量对改性mZVI-微生物耦合体系去除TCE和代表性共存电子受体NO_(3)^(-)的影响。实验结果表明:不同改性剂添加量的S-mZVI bm/AB和C-mZVI bm/AB体系均可显著促进TCE的去除,且促进程度随改性剂添加量的增加呈现先上升后下降的趋势;S-mZVI bm/AB体系可抑制NO_(3)^(-)的去除,且抑制程度随S/Fe摩尔比的增加呈现上升趋势,而C/Fe质量比不会影响C-mZVI bm/AB体系中NO_(3)^(-)的去除;S-mZVI bm/AB和C-mZVI bm/AB体系均可调控TCE及NO-3的产物构成,并均促进了饱和碳烃化合物及N_(2)生成,且该促进作用与改性剂添加量成正比。通过分析微生物群落结构探究了耦合体系脱氯及其脱氮的影响机制,发现在S-mZVI bm/AB和C-mZVI bm/AB体系中均存在大量参与脱氯和反硝化的细菌,反硝化菌的丰度高于脱氯菌,是NO_(3)^(-)快速去除和较高浓度N 2产生的原因。

Sulfidation and carbon modification based on ball milling is an effective means to improve the selectivity of micron zero-valent iron(mZVI)for trichloroethylene(TCE)reduction,but its modification effect is often influenced by the modifier dosage.The effect of modifier dosage on the remediation performance of modified mZVI and anaerobic bacteria coupled systems is not yet clear.In this paper,we systematically investigated the effect of modifier dosage on the removal of TCE and the representative coexisting electron acceptor NO_(3)^(-) by setting up several sulfated mZVI-anaerobic bacteria systems(S-mZVI bm/AB)and carbon modified mZVI-anaerobic bacteria systems(C-mZVI bm/AB).The experimental results showed that both S-mZVI bm/AB and C-mZVI bm/AB systems with different modifier dosage could significantly improve the removal performance of TCE,and the TCE removal efficiency increased first and then decreased with the increase of modifier dosage;The S-mZVI bm/AB system inhibited the removal of NO_(3)^(-),the degree of inhibition showed an increasing trend with the increase of S/Fe molar ratio,while the C/Fe mass ratio did not affect the removal of NO_(3)^(-) in the C-mZVI bm/AB system.Both S-mZVI bm/AB and C-mZVI bm/AB systems modulated the product composition of TCE and NO_(3)^(-),and both promoted the formation of saturated hydrocarbon compounds and N_(2),and the promotion effect was proportional to the modifier dosage.The mechanisms affecting dechlorination and denitrification in the coupled systems were explored by analyzing the microbial community structure,and it was found that a large number of bacteria involved in dechlorination and denitrification existed in both S-mZVI bm/AB and C-mZVI bm/AB systems,and the abundance of denitrifying bacteria was higher than that of dechlorinating bacteria,which was responsible for the rapid removal of NO-3 and higher concentration of N 2 production.