College of Chemistry and Materials Science, Sichuan Normal University, Chengdu, Sichuan, 610066, PR China; Department of Civil and Environmental Engineering, University of Delaware, Newark, DE, 19716, USA.
Department of Civil and Environmental Engineering, University of Delaware, Newark, DE, 19716, USA.
Water Res. 2019 Jan 1;148:378-387. doi: 10.1016/j.watres.2018.10.030. Epub 2018 Oct 17.
Nitrogen (N) removal in conventional bioretention systems is highly variable owing to the low nitrate (NO) elimination efficiency. We hypothesized that amending bioretention cells with biochar and zero-valent iron (ZVI) could improve the NO removal performance. A well-instrumented, bi-layer pilot-scale bioretention cell was developed to test the hypothesis by investigating its hydrologic performance and NO removal efficacy as affected by biochar and ZVI amendments. The cell containing 18% (v/v) wood biochar in the vadose zone and 10% (v/v) ZVI in the saturation zone was monitored for 18 months of field infiltration tests using synthetic stormwater amended with bromide (tracer) and NO. Compared to the Control cell without amendments, the Biochar/ZVI cell increased water retention by 11-27% and mean residence time by 0.7-3.8 h. The vadose zone of the Biochar/ZVI cell removed 30.6-95.7% (0.6-12.7 g) of NO-N from the influent, as compared with -6.1-89.6% (-0.1-2.9 g) by that of the Control cell. While the performance varied with synthetic storm events and seasons, in all cases the Biochar/ZVI cell resulted in greater NO removal than the Control cell. This improvement was presumably due to biochar's ability to improve water retention, facilitate anoxic conditions, increase residence time, and provide electrons for microbial denitrification. The saturation zone with ZVI amendment further promoted NO removal: removal was 1.8 times greater relative to the control in the first infiltration test, but was minimal in following tests. The reduction in performance of the ZVI amendment in subsequent tests might be due to diminished NO-N input to the saturation zone after treatment by the biochar-amended vadose zone. The redox potential and dissolved oxygen content at the vadose/saturation zone interface also indicated more favorable denitrification conditions in the Biochar/ZVI cell. Biochar amendment demonstrated significant promise for increasing nitrate removal in bioretention systems.
在传统的生物滞留系统中，氮（N）的去除率变化很大，因为硝酸盐（NO）的去除效率很低。我们假设通过在生物滞留池中添加生物炭和零价铁（ZVI）可以提高 NO 的去除效果。通过调查水力性能和 NO 去除效果，开发了一种装备齐全的双层中试规模生物滞留池来验证这一假设，该中试规模生物滞留池受到生物炭和 ZVI 添加剂的影响。含有 18%（v/v）木质生物炭的非饱和区和 10%（v/v）ZVI 的饱和区的池在使用添加了溴化物（示踪剂）和 NO 的合成雨水进行了 18 个月的现场渗透测试。与未添加生物炭和 ZVI 的对照池相比，Biochar/ZVI 池的水保留量增加了 11-27%，平均停留时间增加了 0.7-3.8 小时。与对照池相比，Biochar/ZVI 池的非饱和区从进水去除了 30.6-95.7%（0.6-12.7g）的 NO-N，而对照池的去除率为-6.1-89.6%（-0.1-2.9g）。尽管性能随合成雨水事件和季节而变化，但在所有情况下，Biochar/ZVI 池的 NO 去除效果均优于对照池。这种改善可能是由于生物炭提高了水的保留能力、促进了缺氧条件、增加了停留时间并为微生物反硝化提供了电子。添加 ZVI 的饱和区进一步促进了 NO 的去除：在第一次渗透试验中，与对照相比，去除率增加了 1.8 倍，但在随后的试验中，去除率最低。在随后的试验中，ZVI 添加剂的性能降低可能是由于生物炭处理后的非饱和区向饱和区输入的 NO-N 减少。非饱和/饱和区界面的氧化还原电位和溶解氧含量也表明，在 Biochar/ZVI 池中反硝化条件更为有利。生物炭的添加为提高生物滞留系统中硝酸盐的去除效果提供了重要的前景。
