High concentrations of nitrate-nitrogen degrade the quality of aquatic environments. The primary mechanism by which nitrate-nitrogen is removed (denitrification) requires anoxic conditions and electron donors. While removal of total and ammonium-nitrogen is often high in stormwater biofilters, poor removal or even the release of nitrate-nitrogen in the outflow has often been observed. Five Perspex biofilter columns (94 mm internal diameter) were fabricated with a filter layer that contained 8% organic material. Columns were operated at 875 mm/h 875 mm/h and fed with simulated stormwater with different antecedent dry days (ADDs) and concentrations of nitrate-nitrogen. Samples were collected from the outflow at different time intervals between 2 and 150 min and were tested for nitrate-nitrogen. The removal of nitrate-nitrogen varied during an event from a high removal percentage (60–90%) in the initial outflow that gradually decreased in the first 30 min and settled at 0–15% removal thereafter. This remained consistent during all simulated events independent of the number of ADDs or inflow concentrations. ADDs and previous event feed concentrations affected the outflow nitrate-nitrogen concentration in the first 30 min of the current event. Therefore, from this study it is concluded that denitrification within stormwater biofilters occurs mainly during drying periods rather than wetting periods.
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机译：高浓度的硝酸盐-氮会降低水生环境的质量。去除硝酸盐氮（反硝化）的主要机理需要缺氧条件和电子给体。尽管雨水生物滤池中总氮和铵氮的去除率通常很高，但经常观察到去除效果不佳甚至流出物中的硝酸盐氮释放。用含有8％有机材料的过滤层制造了五个Perspex生物过滤柱（内径94毫米）。色谱柱以875 mm / h的速度运行875 mm / h，并以模拟的雨水供入，模拟雨水具有不同的前干旱天数（ADD）和硝酸盐氮浓度。在2至150分钟之间的不同时间间隔从流出液中收集样品，并进行硝酸盐氮测试。在事件期间，硝酸盐氮的去除量有所不同，最初的流出物中的去除率很高（60–90％），在最初的30分钟内逐渐降低，此后稳定在0–15％的去除率。在所有模拟事件中，这与ADD数量或流入浓度无关，保持一致。在当前事件的前30分钟内，ADD和先前事件的进料浓度影响流出硝酸盐氮的浓度。因此，从这项研究得出的结论是，雨水生物滤池内的反硝化主要发生在干燥时期而不是润湿时期。
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