Bioretention system with modified media has been increasingly used to control dissolved nutrients in stormwater runoff. However, complicated removal processes and improper design have made most of them hardly achieve comprehensive dissolved nutrient removal and even show by-product generation problem, especially during extreme stormwater events. Here, a modified biochar-pyrite (FeS₂) bi-layer bioretention system was developed and tested under various stormwater conditions with conventional sand-based and woodchip-based bioretention systems as controls. The modified system showed high stability and efficiency for dissolved nutrient treatment. The removal of dissolved organic nitrogen, ammonium, total dissolved nitrogen, and total dissolved phosphorus were 86.3–93.0%, 95.3–98.1%, 41.4–76.5%, and 69.7–88.2%, respectively. Stormwater conditions only influence nitrate removal which decreased with the increase of total received volume and increased with the extension of antecedent drying duration. Net sulfate and total iron generation were very low, less than 8 mg/L and 0.15 mg/L, respectively. Several microbiology, spectroscopy, and media related tests further demonstrated that the vadose zone and submerged zone showed synergy effects during operation. Biochar addition facilitated ammonium adsorption, nitrification, and in situ denitrification in the vadose zone. It also intercepted dissolved oxygen, which alleviated aerobic pyrite oxidation and created an anoxic condition for the submerged zone. Meanwhile, the pyrite-modified submerged zone achieved stable mixotrophic denitrification. The generated iron intermediate products further controlled phosphorus from both influent and vadose zone leaching into stable forms. Mixotrophic denitrification and potential sulfate reduction processes also reduce sulfate generation. Overall, the biochar-pyrite bi-layer bioretention is a highly promising technology for stormwater runoff treatment, with effective dissolved nutrient removal and minimal by-product generation in various stormwater conditions.

带有改良培养基的生物滞留系统越来越多地用于控制雨水径流中的溶解养分。然而，复杂的去除过程和不当的设计使得它们中的大多数难以实现全面的溶解养分去除，甚至出现副产品产生问题，尤其是在极端暴雨事件期间。在这里，改性的生物炭-黄铁矿（FeS ₂) 双层生物滞留系统是在各种雨水条件下开发和测试的，传统的基于沙子和木屑的生物滞留系统作为对照。改进后的系统在溶解养分处理方面表现出很高的稳定性和效率。溶解有机氮、铵、总溶解氮和总溶解磷的去除率分别为86.3-93.0%、95.3-98.1%、41.4-76.5%和69.7-88.2%。雨水条件只影响硝酸盐的去除，随着总接收量的增加而减少，随着前期干燥时间的延长而增加。净硫酸盐和总铁生成量非常低，分别低于 8 mg/L 和 0.15 mg/L。几种微生物学、光谱学、和介质相关的试验进一步证明，包气带和淹没带在运行过程中表现出协同效应。添加生物炭促进铵吸附、硝化和包气带中的原位反硝化作用。它还拦截了溶解氧，从而减轻了好氧黄铁矿氧化并为淹没区创造了缺氧条件。同时，黄铁矿改造的淹没区实现了稳定的混合营养反硝化。生成的铁中间产物进一步控制了从进水区和渗流区浸出到稳定形式的磷。混合营养反硝化和潜在的硫酸盐还原过程也减少了硫酸盐的生成。总体而言，生物炭-黄铁矿双层生物滞留是一项非常有前途的雨水径流处理技术，在各种雨水条件下都能有效去除溶解的养分，副产品的产生量最少。