Jaynes Dan B, Moorman Tom B, Parkin Timothy B, Kaspar Tom C
J Environ Qual. 2016 May;45(3):830-8. doi: 10.2134/jeq2015.07.0342.
There is a general understanding in the scientific community as to how denitrifying bioreactors operate, but we lack a quantitative understanding of the details of the denitrification process acting within them and comprehensive models for simulating their performance. We hypothesized that nitrate transport through woodchip bioreactors would be best described by a dual-porosity transport model where the bioreactor water is divided into a mobile domain (i.e., the water between the woodchips where it is free to flow and solute movement is by advection and dispersion) and an immobile domain of water (i.e., the water mostly within the woodchips that is stagnant and where solute movement is by diffusion alone). We calibrated the dual-porosity model contained in the HYDRUS model for a woodchip bioreactor using the results of a Br breakthrough experiment where we treated Br as a conservative nonadsorbing tracer. We then used the resulting model parameters to describe 2 yr of NO transport and denitrification within a bioreactor supplied by tile drainage. The only model parameters fitted to the NO data were either the zero- or first-order denitrification rate and its temperature dependence. The bioreactor denitrified 2.23 kg N (38%) of the NO entering it in 2013 and 3.73 kg N (49%) of the NO that entered it in 2014. The dual-porosity model fit the NO data very well, with fitted zero-order reaction rates of 8.7 and 6.8 mg N L d in 2013 and 2014, respectively, and corresponding first-order reaction rates of 0.99 and 1.02 d. For the 2-yr data set, both reaction rate models fit the data equally well. Consistent model parameters fitted for the 2 yr indicated that the model used was robust and a promising approach for modeling fate and transport of NO in woodchip bioreactors.
科学界对反硝化生物反应器的运行方式有一个总体的认识，但我们缺乏对其内部反硝化过程细节的定量理解以及用于模拟其性能的综合模型。我们假设，通过木片生物反应器的硝酸盐传输最好用双孔隙度传输模型来描述，其中生物反应器中的水被分为一个流动域（即木片之间的水，在这里水可以自由流动，溶质通过对流和扩散移动）和一个不流动的水域（即主要在木片中停滞的水，溶质仅通过扩散移动）。我们使用Br突破实验的结果对HYDRUS模型中包含的双孔隙度模型进行了校准，在该实验中我们将Br视为保守的非吸附性示踪剂。然后，我们使用得到的模型参数来描述由瓷砖排水供应的生物反应器内2年的NO传输和反硝化情况。唯一根据NO数据拟合的模型参数是零级或一级反硝化速率及其温度依赖性。该生物反应器在2013年反硝化了进入其中的NO的2.23 kg N（38%），在2014年反硝化了进入其中的NO的3.73 kg N（49%）。双孔隙度模型对NO数据的拟合非常好，2013年和2014年的拟合零级反应速率分别为8.7和6.8 mg N L d，相应的一级反应速率为0.99和1.02 d。对于2年的数据集，两个反应速率模型对数据的拟合效果相同。对这2年拟合的一致模型参数表明，所使用的模型是稳健的，并且是模拟木片生物反应器中NO归宿和传输的一种有前景的方法。
