Haukelidsaeter Signe, Boersma Alje S, Kirwan Liam, Corbetta Alessia, Gorres Isaac D, Lenstra Wytze K, Schoonenberg Frank K, Borger Karl, Vos Luuk, van der Wielen Paul W J J, van Kessel Maartje A H J, Lücker Sebastian, Slomp Caroline P
Department of Earth Sciences, Faculty of Geosciences, Utrecht University, P.O Box 80021, Utrecht 3508 TA, the Netherlands.
Department of Microbiology, Faculty of Science, Radboud Institute of Biological and Environmental Science, Radboud University, P.O. Box 9010, Nijmegen 6500 GL, the Netherlands.
Water Res. 2023 Aug 15;242:120184. doi: 10.1016/j.watres.2023.120184. Epub 2023 Jun 10.
Rapid sand filtration is a common method for removal of iron (Fe), manganese (Mn) and ammonium (NH) from anoxic groundwaters used for drinking water production. In this study, we combine geochemical and microbiological data to assess how filter age influences Fe, Mn and NH removal in dual media filters, consisting of anthracite overlying quartz sand, that have been in operation for between ∼2 months and ∼11 years. We show that the depth where dissolved Fe and Mn removal occurs is reflected in the filter medium coatings, with ferrihydrite forming in the anthracite in the top of the filters (< 1 m), while birnessite-type Mn oxides are mostly formed in the sand (> 1 m). Removal of NH occurs through nitrification in both the anthracite and sand and is the key driver of oxygen loss. Removal of Fe is independent of filter age and is always efficient (> 97% removal). In contrast, for Mn, the removal efficiency varies with filter age, ranging from 9 to 28% at ∼2-3 months after filter replacement to 100% after 8 months. After 11 years, removal reduces to 60-80%. The lack of Mn removal in the youngest filters (at 2-3 months) is likely the result of a relatively low abundance of mineral coatings that adsorb Mn and provide surfaces for the establishment of a microbial community. 16S rRNA gene amplicon sequencing shows that Gallionella, which are known Fe oxidizers, are present after 2 months, yet Fe removal is mostly chemical. Efficient NH removal (> 90%) establishes within 3 months of operation but leakage occurs upon high NHloading (> 160 µM). Two-step nitrification by Nitrosomonas and Candidatus Nitrotoga is likely the most important NH removal mechanism in younger filters during ripening (2 months), after which complete ammonia oxidation by Nitrospira and canonical two-step nitrification occur simultaneously in older filters. Our results highlight the strong effect of filter age on especially Mnbut also NH removal. We show that ageing of filter medium leads to the development of thick coatings, which we hypothesize leads to preferential flow, and breakthrough of Mn. Use of age-specific flow rates may increase the contact time with the filter medium in older filters and improve Mn and NH removal.
快速砂滤是从用于饮用水生产的缺氧地下水中去除铁（Fe）、锰（Mn）和铵（NH）的常用方法。在本研究中，我们结合地球化学和微生物学数据，评估滤池使用年限如何影响双层滤池（由覆盖在石英砂上的无烟煤组成）中铁、锰和铵的去除情况，这些滤池已运行约2个月至约11年。我们发现，溶解态铁和锰的去除深度反映在滤料层中，滤池顶部（<1米）的无烟煤中形成了水铁矿，而水钠锰矿型锰氧化物主要在砂层（>1米）中形成。铵的去除是通过无烟煤和砂层中的硝化作用实现的，并且是氧气消耗的关键驱动因素。铁的去除与滤池使用年限无关，且始终高效（去除率>97%）。相比之下，对于锰，去除效率随滤池使用年限而变化，在更换滤池后约2 - 3个月时为9%至28%，8个月后达到100%。11年后，去除率降至60% - 80%。最年轻的滤池（2 - 3个月）中锰去除率低可能是由于吸附锰并为微生物群落建立提供表面的矿物涂层丰度相对较低。16S rRNA基因扩增子测序表明，已知的铁氧化菌嘉利翁氏菌在2个月后出现，但铁的去除主要是化学作用。高效的铵去除（>90%）在运行3个月内建立，但在高铵负荷（>160µM）时会发生泄漏。在滤池成熟初期（2个月），亚硝化单胞菌和硝化螺旋菌属的两步硝化作用可能是较年轻滤池中最重要的铵去除机制，之后在较老的滤池中硝化螺旋菌的完全氨氧化作用和典型的两步硝化作用同时发生。我们的结果突出了滤池使用年限对锰尤其是铵去除的强烈影响。我们表明，滤料老化会导致厚涂层的形成，我们推测这会导致优先流和锰的穿透。使用特定年限的流速可能会增加较老滤池中与滤料的接触时间，并改善锰和铵的去除。
