Department of Civil and Environmental Engineering, South Dakota State University, Brookings, SD 57006, USA.
Department of Civil and Environmental Engineering, South Dakota State University, Brookings, SD 57006, USA.
Water Res. 2016 Oct 1;102:180-189. doi: 10.1016/j.watres.2016.06.022. Epub 2016 Jun 11.
Woodchip bioreactors have been increasingly used as an edge-of-field treatment technology to reduce the nitrate loadings to surface waters from agricultural subsurface drainage. Recent studies have shown that subsurface drainage can also contribute substantially to the loss of phosphate from agricultural soils. The objective of this study was to investigate nitrate and phosphate removal in subsurface drainage using laboratory woodchip bioreactors and recycled steel byproduct filters. The woodchip bioreactor demonstrated average nitrate removal efficiencies of 53.5-100% and removal rates of 10.1-21.6 g N/m(3)/d for an influent concentration of 20 mg N/L and hydraulic retention times (HRTs) of 6-24 h. When the influent nitrate concentration increased to 50 mg N/L, the bioreactor nitrate removal efficiency and rate averaged 75% and 18.9 g N/m(3)/d at an HRT of 24 h. Nitrate removal by the woodchips followed zero-order kinetics with rate constants of 1.42-1.80 mg N/L/h when nitrate was non-limiting. The steel byproduct filter effectively removed phosphate in the bioreactor effluent and the total phosphate adsorption capacity was 3.70 mg P/g under continuous flow conditions. Nitrite accumulation occurred in the woodchip bioreactor and the effluent nitrite concentrations increased with decreasing HRTs and increasing influent nitrate concentrations. The steel byproduct filter efficiently reduced the level of nitrite in the bioreactor effluent. Overall, the results of this study suggest that woodchip denitrification followed by steel byproduct filtration is an effective treatment technology for nitrate and phosphate removal in subsurface drainage.
木屑生物反应器已被越来越多地用作一种田间处理技术，以减少农业地下排水对地表水的硝酸盐负荷。最近的研究表明，地下排水也会导致农业土壤中磷酸盐大量流失。本研究的目的是利用实验室木屑生物反应器和回收的钢铁副产品过滤器研究地下排水中的硝酸盐和磷酸盐去除。木屑生物反应器在进水硝酸盐浓度为 20mg/L、水力停留时间（HRT）为 6-24h 的情况下，平均硝酸盐去除效率为 53.5-100%，去除率为 10.1-21.6gN/m(3)/d。当进水硝酸盐浓度增加到 50mg/L 时，生物反应器在 HRT 为 24h 的情况下，硝酸盐去除效率和去除率平均为 75%和 18.9gN/m(3)/d。木屑中的硝酸盐去除遵循零级动力学，当硝酸盐不受限时，其速率常数为 1.42-1.80mgN/L/h。钢铁副产品过滤器可有效去除生物反应器出水中的磷酸盐，在连续流动条件下，总磷酸盐吸附容量为 3.70mgP/g。在木屑生物反应器中发生亚硝酸盐积累，随着 HRT 的降低和进水硝酸盐浓度的增加，出水中的亚硝酸盐浓度增加。钢铁副产品过滤器可有效降低生物反应器出水中的亚硝酸盐水平。总的来说，本研究结果表明，木屑反硝化后进行钢铁副产品过滤是去除地下排水中硝酸盐和磷酸盐的有效处理技术。
