零价铁PRB修复硝酸盐和铬复合污染地下水

通过连续流动试验研究了Fe0(零价铁)-PRB(渗透反应格栅)修复受NO₃--N、Cr(Ⅵ)以及NO₃--N和Cr(Ⅵ)复合污染模拟地下水的反应特性,分析了Fe0对NO₃--N和Cr(Ⅵ)的氧化还原产物,并且对NO₃--N和Cr(Ⅵ)的相互影响进行了研究. 采用粒径为0.15～0.42 mm的Fe0和粒径为0.15 mm的活性炭作为PRB反应介质,二者的质量比为1∶1. 结果表明,Fe0单独与NO₃--N反应情况下,当进水中ρ(NO₃--N)为20 mg/L时,去除率达95%,NO₂-为还原过渡状态,NH₄+是主要产物,出水pH从原水的7.1升至9.0左右,出水中ρ(TFe)<0.60 mg/L. Fe0处理Cr(Ⅵ)情况下,对Cr(Ⅵ)有较高的去除效果,进水中ρ〔Cr(Ⅵ)〕为10 mg/L时,去除率达96%,反应产物Fe3+和Cr(Ⅲ)可以形成沉淀附着在反应介质上,不会迁移到“下游”水体中,出水pH从原水的7.0升至8.0左右,出水中ρ(TFe)<0.30 mg/L. Fe0去除NO₃--N和Cr(Ⅵ)复合污染时,共存的NO₃--N对Cr(Ⅵ)的去除效果没有影响,Cr(Ⅵ)的存在降低了NO₃--N的去除效果. 

Remediation of Ground Water Contaminated by Nitrate Nitrogen and Chromium Using Zero-Valent Iron PRB Technology

Through continuous flow experimentation, the reactivity characteristics of zero-valent iron (Fe0)-PRB with ground water contaminated by nitrate, chromium and the combination of nitrate and chromium were investigated. The products of nitrate and chromium deoxidized by zero-valent iron were also analyzed. The interaction between the nitrate and chromium which were synchronously deoxidized by zero-valent iron was also studied. In this paper, zero-valent iron with 0.15-0.42 mm particle size and activated carbon with 0.15 mm particle size were used as reaction packing media; their mass ratio was 1∶1. The results showed that nitrate could be effectively deoxidized by zero-valent iron. The NO₃--N removal efficiency was 95% when the influent NO₃--N mass concentration was 20 mg/L. NO₂--N was the transitional deoxidization product, while NH₄+-N was the main final product in the effluent. The pH increased from 7.1 in the influent to 9.0 in the effluent, and the total iron mass concentration in the effluent was below 0.60 mg/L. Chromium could be deoxidized by zero-valent iron more effectively for the chromium contaminated ground water which was treated by PRB. The Cr(Ⅵ) removal efficiency was 96% when the influent Cr(Ⅵ) mass concentration was 10 mg/L. The redox products such as Fe3+ and Cr(Ⅲ) precipitated on the packing media during the process. Thus, they could not be transported into the downstream. The pH increased from 7.0 in the influent to 8.0 in the effluent, and the total iron mass concentration in the effluent was below 0.30 mg/L. For the treatment of ground water contaminated by both nitrate and chromium, the results showed that the Cr(Ⅵ) removal efficiency by the zero-valent iron was not affected by the co-existence of NO₃--N, while the NO₃--N removal efficiency decreased with the existence of Cr(Ⅵ).