Impact of flow on woodchip properties and subsidence in denitrifying bioreactors
Impact of flow on woodchip properties and subsidence in denitrifying bioreactors
复制标题
反硝化生物反应器中流动对木片特性和沉降的影响
DOI：
10.1002/agg2.20149
复制
发表时间：
2021
影响因子：
1.5
通讯作者：
M. Soupir
中科院分区：
文献类型：
--
作者：
A. Schaefer;Kyle Werning;Natasha L. Hoover;U. Tschirner;G. Feyereisen;T. Moorman;A. Howe;M. Soupir
木屑生物反应器是从农业排水中去除营养物质的边缘实践，有效寿命估计在10到30年之间。沉降，或生物反应器沉降和随后的凹陷形成，是生产商和利益相关者关注的问题，关于其对生物反应器性能的影响知之甚少。六个木片生物反应器设置在三个不同的水力停留时间（HRT 2，8，和16小时）挖掘后，2年的操作，从多个深度和距离生物反应器入口收集的木材样品。在所有六个生物反应器中均观察到沉降，并且在入口附近沉降更大。粒度分布在研究期间没有变化，表明较小的木片没有优先降解或从生物反应器中冲洗出来，而大孔空间同时减少。流路分析显示，莫里尔分散指数和短路增加，可排水孔隙度和水力效率降低;这些变化在所有三个HRT中是一致的，表明水力特性的下降与流量无关。此外，尽管与8 h和16 h HRT系统（分别为90.3 ± 19.0，95.6 ± 27.2）相比，2 h HRT生物反应器（平均值± SD = 64.9 ± 13.7）中的C/N比测量的木片分解增加，但根据分批脱氮试验的结果，在所有HRT下仍支持脱氮。为了抵消木材老化，可以在不挖掘整个生物反应器的情况下补充最接近入口的生物反应器填充材料。
Woodchip bioreactors are edge‐of‐field practices that remove nutrients from agricultural drainage water, with an effective lifespan estimated between 10 and 30 yr. Subsidence, or bioreactor settling and subsequent depression formation, is a concern of producers and stakeholders and little is known regarding its effect on bioreactor performance. Six woodchip bioreactors set at three different hydraulic residence times (HRTs 2, 8, and 16 h) were excavated after 2 yr of operation, with wood samples collected from multiple depths and distances from the bioreactor inlet. Subsidence was observed in all six bioreactors and was greater near the inlet. Particle‐size distribution did not change over the study period, indicating that smaller woodchips were not degrading preferentially or washing out of the bioreactor while the macropore space was simultaneously decreasing. Flow path analysis showed an increase in Morrill Dispersion Indices and short‐circuiting as well as decreases in drainable porosity and hydraulic efficiency; these changes were uniform across all three HRTs, suggesting that the decline in hydraulic properties was independent of flow. Further, despite increased woodchip decomposition as measured by C/N ratio in the 2‐h HRT bioreactors (mean ± SD = 64.9 ± 13.7) compared with the 8‐ and 16‐h HRT systems (90.3 ± 19.0, 95.6 ± 27.2, respectively), denitrification was still supported at all HRTs based on the results from a batch denitrification test. To offset wood aging, bioreactor fill material nearest the inlet could be replenished without excavation of the entire bioreactor.