Treatment wetlands for raw wastewater from small communities (< 2000 p.e.) represent 20% of the wastewater treatment plants in France today. The classical French Vertical Flow Treatment Wetland consists of two stages filter beds intermittently fed with raw wastewater (inflow concentrations TSS 387 ± 70 mg/L, COD 880 ± 188 mg/L, TKN 110 ± 16 mg/L). The system has a good removal performance for TSS and COD with > 90% and TKN of approx. 85% after filter maturation (months 12 to 24 of the trial), but efficiencies can vary between 10 and approx. 20% according to the material type, filter age, and filter depth. This study presents how these systems can be costly optimized when outlet requirements are not too stringent or when carbon is required for a subsequent denitrification step. The study shows the effectiveness of using different gravel depths and types (pea and crushed gravel) over almost 2 years regarding removal performances, carbon source availability, and nitrification. Core samples were taken to evaluate the dry matter accumulation. Tracer tests using fluorescein were performed to assess the internal hydrodynamics related to filter depth. The removal performance was not significantly affected by the filter depth, but the filter filled with 30 cm of pea gravel performed significantly better than the one with 30 cm of crushed gravel: for COD with a removal of 83% compared to 76%, TSS of 87% to 81%, and TKN of 64% to 57%, respectively. This is another indication that the shape of crushed gravel affects biofilm attachment and hydrodynamics in the filters due to irregular compaction.

处理来自小社区（< 2000 pe）的原始废水的湿地处理占当今法国废水处理厂的 20%。经典的法国垂直流处理湿地由两级滤床组成，间歇性地向原废水进料（流入浓度 TSS 387 ± 70 mg/L，COD 880 ± 188 mg/L，TKN 110 ± 16 mg/L）。该系统对 TSS 和 COD 具有良好的去除性能，> 90% 且 TKN 约为 过滤器成熟后为 85%（试验的第 12 至 24 个月），但效率可在 10 至约 10 个月之间变化。20% 根据材料类型、过滤器年龄和过滤深度。本研究介绍了当出口要求不太严格或后续反硝化步骤需要碳时，如何对这些系统进行成本优化。该研究表明，在近 2 年的时间里，使用不同深度和类型的砾石（豌豆和碎砾石）在去除性能、碳源可用性和硝化作用方面的有效性。采集岩心样品以评估干物质积累。进行了使用荧光素的示踪剂测试以评估与过滤器深度相关的内部流体动力学。去除性能不受过滤深度的显着影响，但填充 30 cm 豌豆砾石的过滤器的性能明显优于填充 30 cm 碎砾石的过滤器：对于去除 83% 与 76% 的 COD，TSS 为87% 到 81%，TKN 分别为 64% 到 57%。这是另一个迹象，表明由于不规则压实，碎石的形状会影响过滤器中的生物膜附着和流体动力学。