Departamento de Ingeniería Agronómica, E.T.S. de Ingeniería Agronómica, Universidad Politécnica de Cartagena, Paseo Alfonso XIII, 48, Cartagena, 30203, Murcia, Spain.
J Environ Manage. 2021 Jul 1;289:112521. doi: 10.1016/j.jenvman.2021.112521. Epub 2021 Apr 8.
Woodchip bioreactors are widely known as a best management practice to reduce excess nitrate loads that are discharged with agricultural leachates. The aim of this study was to evaluate the performance of citrus woodchip bioreactors for denitrification of brine (electrical conductivity ≈ 17 mS cm) from groundwater desalination plants with high nitrate content (NO-N ≈ 48 mg L) in the Campo de Cartagena agricultural watershed, one of the main providers of horticultural products in Europe. The performance was evaluated relative to seasonal changes in temperature, dissolved organic carbon (DOC) provided by woodchips, hydraulic residence time (HRT) and woodchip aging. Bioreactors (capacity 1 m) operated for 2.5 years (121 weeks) in batch mode (24 h HRT) with three batches per week. Denitrification efficiency was modulated by DOC concentration, temperature, hydraulic residence time and the drying-rewetting cycles. High salinity of brine did not prevent nitrate removal from occurring. The high DOC availability (>25 mg C L) during the first ≈48 weeks resulted in high nitrate removal rate (>75%) and nitrate removal efficiency (until ≈ 25 g N m d) regardless of temperature. Moreover, the high DOC contents in the effluents during this period may present environmental drawbacks. Denitrification was still high after 2.5 years (reaching ≈9.3 g N m d in week 121), but dependence on warm temperature became more apparent with woodchips aging from week ≈49 onwards. Nitrate removal efficiency was highest on the first weekly batch, immediately after woodchips had been unsaturated for four days. It was attributable to a flush of DOC produced by aerobic microbial metabolism during drying that stimulated denitrification following re-saturation. Hence, alternance of drying-rewetting cycles is an operation practice that increase bioreactors nitrate removal performance.
木屑生物反应器被广泛认为是减少农业渗滤液中过量硝酸盐负荷的最佳管理实践。本研究的目的是评估柑橘木屑生物反应器在去除高硝酸盐含量（NO-N≈48mgL）的地下水脱盐厂盐水（电导率≈17mScm）中的硝酸盐的性能，该研究位于卡塔赫纳农业流域，该流域是欧洲主要园艺产品供应商之一。相对于季节性温度变化、木屑提供的溶解性有机碳（DOC）、水力停留时间（HRT）和木屑老化，评估了生物反应器的性能。生物反应器（容量为 1m）以批处理模式（24h HRT）运行了 2.5 年（121 周），每周进行三批。通过 DOC 浓度、温度、水力停留时间和干燥-再润湿循环来调节反硝化效率。盐水的高盐度并没有阻止硝酸盐的去除。在最初的≈48 周内，高 DOC 可利用性（>25mgCL）导致高硝酸盐去除率（>75%）和硝酸盐去除效率（直到≈25gNm），而与温度无关。此外，在此期间，废水中高含量的 DOC 可能会带来环境问题。2.5 年后，反硝化作用仍然很高（在第 121 周达到≈9.3gNm），但随着木屑老化（从第≈49 周开始），对温暖温度的依赖变得更加明显。在每周第一批中，硝酸盐去除效率最高，即在木屑经过四天不饱和后立即达到最高。这归因于在再饱和后，干燥过程中好氧微生物代谢产生的 DOC 冲洗刺激了反硝化作用。因此，交替进行干燥-再润湿循环是一种可以提高生物反应器硝酸盐去除性能的操作实践。
