基于Fe^0的PRB去除地下水中硝酸盐的模拟研究

Simulation of nitrate removal from groundwater using PRB based zero-valent iron

由于地下水中硝酸盐污染的普遍性、难去除性和对人体健康的潜在危害性而引起人们的广泛关注。本研究通过柱实验,研究了不同条件(进水pH、砂/Fe0体积比和添加锯末)对基于Fe0的模拟渗透性反应墙(permeable reactivebarrier,PRB)去除地下水中硝酸盐的影响。结果表明,由于黄土的碱性和缓冲作用,进水pH的影响不显著;5~6∶1的砂/Fe0(S/Fe)体积比既可提高铁粉利用率,又有利于硝酸盐的还原并延长PRB的有效期;铁腐蚀产物引起铁粉粘固而导致PRB的渗透性和反应性降低,尤其在反应区的进水口端;虽然酸预处理Fe0有助于硝酸盐的还原,但更容易引起堵塞,而在Fe0体系中加入活性炭不仅可提高硝酸盐的去除率,还可延长PRB的有效期,是一种很好的辅助填料;同时添加锯末和Fe0的生物-化学联合法更有助于硝酸盐还原并提高出水水质,具有很好的应用潜力;不同条件下,出水中的氨和亚硝酸盐的浓度相差较大,但可溶性铁浓度均低于饮用水标准(0.3 mg/L)。Fe0的化学还原和锯末的生物反硝化是硝酸盐去除的主要机理。本研究表明,基于Fe0的PRB用于去除中性或偏碱性地下水中的硝酸盐污染具有很大的潜力。

Nitrate contamination in groundwater attracts extensive attention since it is very widespread in the world,hard removal and potential harm to people.Nitrate pollution remediation in the groundwater using simulated permeable reactive barrier（PRB） based zero-valent iron（Fe0） packed columns was evaluated under different conditions（influent water pH,the volume ratio of sand and Fe0 and adding sawdust）.The results indicated that the influent pH exhibited slight impact on nitrate reduction,in part because of the alkalinity and buffer effect of the tested soil.The volume ratio of sand and Fe0 of 5~6∶1 was wonderful,which not only enhanced the efficiency of Fe0 but also promoted nitrate removal and extended the longevity of PRB.The permeability and reaction of PRB decreased because of cementation induced by the accumulation of iron corrosion products,especially near the inlet of reactive zone.Although acid-pretreated Fe0 improved nitrate reduction,it also resulted in clog easily.But the addition of active carbon extended the longevity and efficiency of PRB.So it is a very good assistant material for nitrate reduction by Fe0.Nitrate was removed completely after adding sawdust and Fe0 as well as improved the quality of effluent water,which exhibited a good potential for field applications.In all treatments,the concentrations of ammonia and nitrite in the effluent,the product of nitrate reduction by Fe0,were very different,but the total dissoluble iron was almost below the drinking water standard（0.3 mg/L）.Chemical reduction by Fe0 and biological denitrification by sawdust are the main mechanisms.This study demonstrated that it is potential for in-situ remediation nitrate contamination in the neutral or alkaline groundwater using iron-based PRB.