Urban water management has been increasingly relying on infiltration to limit the environmental impact of stormwater, secondary treated effluent and gray water. The infiltration systems used are generally based on non-renewable drainage materials featuring a pronounced ecological footprint (i.e., excavation and transport), such as gravel. This paper investigates the possibility of using woodchips instead of traditional drainage materials. Our study examines flow dynamics in woodchip-filled infiltration trenches at four decentralized gray water sites, on a silty clay soil. Infiltration tests were conducted using the Beerkan method to measure soil infiltration capacity both beneath the woodchip-filled trenches and in adjacent soil. Soil hydraulic functions were determined according to the BEST method, then comparisons were drawn between the woodchip-filled trench and natural soil. Results indicate that woodchips locally maintain or enhance soil infiltration rates, with a hydraulic conductivity up to 200 times higher in woodchip-treated soil. Additional soil measurements and analyses serve to formulate hypotheses on how the woodchips actually contribute to these effects. Dye tracer experiments revealed preferential pathways facilitated by macro fauna (earthworms) and, most likely, plant roots. This last information input has been corroborated since earthworm counts did prove to be significantly higher in the woodchips than in the soil. A chemical analysis of the soils also showed a significant enrichment of carbon and nitrogen under the trench, which may also improve soil structure and stability and perhaps indirectly enhance water infiltration capacity. In summary, the presence of woodchips in infiltration trenches improves the soil hydraulic conductivity at saturation for systems that have been in use for 5 to 10 years. These findings underscore the potential of woodchips in sustainable urban water management in order to enhance the functionality and efficiency of drainage materials by means of limiting the clogging effect.

中文翻译：

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木屑填充的沟渠：提高城市水渗透能力的解决方案？


城市水务管理越来越依赖渗透来限制雨水、二级处理污水和灰水对环境的影响。使用的渗透系统通常基于不可再生的排水材料，具有明显的生态足迹（即挖掘和运输），例如砾石。本文研究了使用木屑代替传统排水材料的可能性。我们的研究在粉质粘土上检查了四个分散的灰水地点的木屑填充渗透沟中的流动动力学。使用 Beerkan 方法进行渗透测试，以测量填充木屑的沟槽下方和相邻土壤中的土壤渗透能力。根据 BEST 方法确定土壤水力函数，然后在木屑填充的沟槽和天然土壤之间进行比较。结果表明，木屑局部维持或增强土壤渗透率，在木屑处理的土壤中，水力传导率高出 200 倍。额外的土壤测量和分析有助于制定关于木片实际上如何导致这些影响的假设。染料示踪剂实验揭示了大型动物群（蚯蚓）和最有可能的植物根系促进的优先途径。最后一条信息输入得到了证实，因为事实证明木屑中的蚯蚓数量明显高于土壤中的蚯蚓数量。对土壤的化学分析还显示，沟槽下碳和氮的显著富集，这也可能改善土壤结构和稳定性，并可能间接增强水的渗透能力。 总之，渗透沟中存在木屑可以提高已使用 5 到 10 年的系统在饱和时的土壤水力传导率。这些发现强调了木屑在可持续城市水管理中的潜力，以便通过限制堵塞效应来提高排水材料的功能和效率。