Abstract

This six-month study aimed to evaluate the removal of total nitrogen (TN) in two duplicated partially saturated (PS) vertical flow (VF) wetlands added with corncob in two different heights of the free-drainage zone (FDZ) after two years in operation. Both PS VF wetlands efficiently removed organic matter measured as biochemical oxygen demand (BOD₅) and chemical oxygen demand (COD) as well as total suspended solids (TSS) achieving average mass removal efficiencies of 95.3%, 83.2% and 92.9%, respectively, in system I (SI) and 96.3%, 84.0% and 94.9%, respectively, in system II (SII); with no significant differences (p > 0.05) between the systems. Measurements of oxidation-reduction potential (ORP), dissolved oxygen (DO), pH and electrical conductivity (EC) showed suitable conditions in the saturated zone (SZ) of the systems for denitrification process. TN removal was similar in both systems (p > 0.05) (51.5% and 52.9% in SI and SII), and decreased in 15% with respect to the first year. This decrease was due to the lower denitrification capacity of the FDZ as a result of the reduction in the supply of biodegradable carbon by corncob. Denitrification occurred in the SZ, but not at a sufficient level to increase TN removal.

Novelty

First, the use of lignocellulosic residues in partially saturated vertical wetlands to promote total nitrogen removal is very recent. Furthermore, to the best of our knowledge, this is the first study evaluating TN removal after two years of operation in this type of wetland. Therefore, this study allows us to better understand the function of these systems, in a relatively long term. Thanks to this study: it is possible to confirm that the main process of TN elimination is through the simultaneous nitrification-denitrification process in the free drainage zone (denitrification in the saturated zone is irrelevant) and that TN elimination decreases due to the reduction in carbon supply from the corn, in this area.

摘要

这项为期六个月的研究旨在评估在两年后在自由排水区 (FDZ) 的两个不同高度添加玉米芯的两个重复的部分饱和 (PS) 垂直流 (VF) 湿地中的总氮 (TN) 去除情况。手术。PS VF 湿地均能有效去除以生化需氧量 (BOD ₅ ) 和化学需氧量 (COD) 以及总悬浮固体 (TSS)衡量的有机物，平均去除效率分别为 95.3%、83.2% 和 92.9%，在系统 I (SI) 和系统 II (SII) 中分别为 96.3%、84.0% 和 94.9%；无显着差异（p > 0.05) 系统之间。氧化还原电位 (ORP)、溶解氧 (DO)、pH 值和电导率 (EC) 的测量表明，反硝化过程系统的饱和区 (SZ) 条件合适。两种系统的 TN 去除率相似（p  > 0.05）（SI 和 SII 分别为 51.5% 和 52.9%），并且与第一年相比下降了 15%。这种下降是由于玉米芯可生物降解碳的供应减少导致 FDZ 的反硝化能力降低。SZ 中发生了反硝化作用，但没有达到足以增加 TN 去除的水平。

新奇

首先，在部分饱和的垂直湿地中使用木质纤维素残留物来促进总氮去除是最近的事情。此外，据我们所知，这是在此类湿地运行两年后评估 TN 去除率的第一项研究。因此，这项研究使我们能够在相对较长的时间内更好地了解这些系统的功能。由于这项研究：可以确认TN消除的主要过程是通过自由排水区的同时硝化-反硝化过程（饱和区的反硝化无关紧要），并且由于碳的减少，TN消除减少供应来自该地区的玉米。