Su Chunming, Puls Robert W
Ground Water and Ecosystems Restoration Division, National Risk Management Research Laboratory, Office of Research and Development, United States Environmental Protection Agency, Ada, OK 74820, USA.
Chemosphere. 2007 Apr;67(8):1653-62. doi: 10.1016/j.chemosphere.2006.09.059. Epub 2007 Jan 25.
Recent research has shown that carbonaceous solid materials and zerovalent iron (Fe(0)) may potentially be used as media in permeable reactive barriers (PRBs) to degrade groundwater nitrate via heterotrophic denitrification in the solid carbon system, and via abiotic reduction and autotrophic denitrification in the Fe(0) system. Questions arise as whether the more expensive Fe(0) is more effective than the less expensive carbonaceous solid materials for groundwater nitrate remediation, and whether there is any synergistic effect of mixing the two different types of materials. We carried out batch tests to study the nature and rates of removal of added nitrate in the suspensions of single, binary, and ternary systems of cotton burr compost, Peerless Fe(0), and a sediment low in organic carbon. Cotton burr compost acted as both organic carbon source and supporting material for the growth of indigenous denitrifiers. Batch tests showed that cotton burr compost alone removed added nitrate at a greater rate than did Peerless Fe(0) alone on an equal mass basis with a pseudo-first-order rate constant k=0.0830+/-0.0031 h(-1) for cotton burr compost and a k=0.00223+/-0.00022 h(-1) for Peerless Fe(0); cotton burr compost also removed added nitrate at a faster rate than did cotton burr compost mixed with Peerless Fe(0) and/or the sediment. Furthermore, there was no substantial accumulation of ammonium ions in the cotton burr compost system, in contrast to the systems containing Peerless Fe(0) in which ammonium ions persisted as major products of nitrate reduction. It is concluded that cotton burr compost alone may be used as an excellent denitrification medium in a PRB for groundwater nitrate removal. Further study is needed to evaluate performance of its field applications.
近期研究表明，含碳固体材料和零价铁（Fe(0)）有可能用作渗透反应墙（PRB）中的介质，通过固体碳系统中的异养反硝化作用，以及Fe(0)系统中的非生物还原和自养反硝化作用来降解地下水中的硝酸盐。由此产生了一些问题，比如价格较高的Fe(0)在修复地下水中的硝酸盐方面是否比价格较低的含碳固体材料更有效，以及将这两种不同类型的材料混合是否存在协同效应。我们进行了批次试验，以研究在棉籽壳堆肥、Peerless Fe(0)和低有机碳沉积物的单一、二元和三元系统悬浮液中添加硝酸盐的去除性质和速率。棉籽壳堆肥既作为有机碳源，又作为本地反硝化菌生长的支撑材料。批次试验表明，在等质量基础上，单独的棉籽壳堆肥去除添加硝酸盐的速率比单独的Peerless Fe(0)更快，棉籽壳堆肥的假一级速率常数k = 0.0830±0.0031 h⁻¹，Peerless Fe(0)的k = 0.00223±0.00022 h⁻¹；棉籽壳堆肥去除添加硝酸盐的速率也比与Peerless Fe(0)和/或沉积物混合的棉籽壳堆肥更快。此外，与含有Peerless Fe(0)的系统不同，在棉籽壳堆肥系统中铵离子没有大量积累，在含有Peerless Fe(0)的系统中，铵离子作为硝酸盐还原的主要产物持续存在。得出的结论是，单独的棉籽壳堆肥可作为PRB中去除地下水中硝酸盐的优良反硝化介质。需要进一步研究来评估其现场应用性能。
