Iron (Fe), manganese (Mn), and ammonium (NH₄⁺) removal from groundwater using rapid sand filtration is a widely employed method in drinking water production. Over time, Fe and Mn oxides accumulate in the filter, which necessitates frequent backwashing to avoid clogging. In this study, we investigated the impact of backwashing on the microbial community and filter chemistry in a dual-media filter comprising anthracite and sand layers. Specifically, we focused on the removal of Fe, Mn, and NH₄⁺ over the runtime of the filter. With increasing runtime, depth profiles of dissolved and particulate Fe revealed the buildup of Fe oxide flocs, causing Fe²⁺ and Mn²⁺ oxidation and nitrification to occur at greater depths within the filter. Towards the end of the filter runtime, breakthrough of suspended Fe oxides was observed, likely due to preferential flow. Backwashing effectively removed metal oxide flocs and restored the Fe removal efficiency in the top layer of the filter. While the two layers remained separate, the anthracite and sand layers themselves fully mixed during backwashing, leading to a homogenous distribution of the microbial community within each layer. Methyloglobulus and Gallionella were the predominant organisms in the anthracite layer, likely catalyzing methane and Fe²⁺ oxidation, respectively. The nitrifying community of the anthracite consisted of Nitrosomonas, Candidatus Nitrotoga, and Nitrospira. In contrast, the nitrifying community in the sand layer was dominated by Nitrospira. Backwashing minimally affected the microbial community composition of the filter medium except for Gallionella, which were preferentially washed out. In conclusion, our research offers a molecular and geochemical basis for understanding how backwashing influences the performance of rapid sand filters.

中文翻译：

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过滤器反冲洗对饮用水生产用双介质快速砂过滤器中铁、锰和铵去除的影响


使用快速砂过滤从地下水中去除铁 （Fe）、锰 （Mn） 和铵 （NH₄⁺） 是饮用水生产中广泛采用的方法。随着时间的推移，Fe 和 Mn 氧化物会在过滤器中积累，这需要频繁的反冲洗以避免堵塞。在这项研究中，我们调查了反冲洗对由无烟煤和沙层组成的双介质过滤器中的微生物群落和过滤化学的影响。具体来说，我们专注于在滤波器运行期间去除 Fe、Mn 和 NH₄⁺。随着运行时间的增加，溶解和颗粒 Fe 的深度剖面揭示了 Fe 氧化物絮凝体的堆积，导致 Fe²⁺ 和 Mn²⁺ 氧化和硝化发生在过滤器内的更深处。在过滤器运行时间接近尾声时，观察到悬浮的 Fe 氧化物突破，这可能是由于优先流动。反冲洗有效去除金属氧化物絮凝物，恢复过滤器顶层的 Fe 去除效率。虽然两层保持独立，但无烟煤层和沙层本身在反冲洗过程中完全混合，导致每层内的微生物群落均匀分布。甲基球菌和加里奥氏菌是无烟煤层中的主要生物，可能分别催化甲烷和 Fe²⁺ 氧化。无烟煤的硝化群落由 Nitrosomonas、Candidatus Nitrotoga 和 Nitrospira 组成。相比之下，沙层中的硝化群落以 Nitrospira 为主。 反冲洗对过滤介质的微生物群落组成的影响最小，但 Gallionella 除外，Gallionella 被优先冲刷掉。总之，我们的研究为了解反冲洗如何影响快速砂滤器的性能提供了分子和地球化学基础。