Bench-scale columns were used to test the impact of depth, alkalinity, and nitrogen/hydraulic loading on nitrification performance and microbial community abundance in a sand filter treating onsite wastewater. The extent of nitrification was independent of the column depth at the test hydraulic loading rate (20.5 L m⁻² d⁻¹), as full nitrification was observed at 15 cm of the column. The nitrification performance was less sensitive to nitrogen loading increase (0.15 to 0.53 mg N cm⁻² d⁻¹), while increased hydraulic loading (from 20.5 L m⁻² d⁻¹ to 32.8 L m⁻² d⁻¹) and insufficient alkalinity caused reduced nitrification at shallow column depth. Microbial analysis suggested the majority of biomass and functional species were present at the top 15 cm, with several orders of magnitude lower microbial density was observed at 45 cm depth. In addition, the microbial community present in the aged sand matrix could sustain efficient nitrification when treating synthetic wastewater. Collectively, these findings reveal the precise conditions for optimizing for complete nitrification of wastewater by sand filters.

台式色谱柱用于测试深度，碱度和氮/液压负荷对处理现场废水的沙滤池中硝化性能和微生物群落丰度的影响。在试验液压负载率（20.5 L m ^-2 d ^-1）下，硝化程度与色谱柱深度无关，因为在色谱柱的15 cm处观察到完全硝化。硝化性能对氮负荷增加（0.15至0.53 mg N cm ^-2 d ^-1）较不敏感，而对水力负荷增加（从20.5 L m ^-2 d ^-1至32.8 L m ^-2 d ^-1）不敏感。）和碱度不足会导致浅柱深度的硝化作用降低。微生物分析表明，大部分生物量和功能物种都存在于顶部15 cm处，在45 cm深度处观察到的微生物密度降低了几个数量级。另外，在处理合成废水时，存在于老化的砂基质中的微生物群落可以维持有效的硝化作用。总的来说，这些发现揭示了通过砂滤器优化废水完全硝化的精确条件。