Díaz-García Carolina, Martínez-Sánchez Juan J, Álvarez-Rogel José
Department of Agricultural Engineering of the ETSIA & Institute of Plant Biotechnology, Technical University of Cartagena, 30203 Cartagena, Spain; Department of Crop Sciences, University of Illinois at Urbana-Champaign. AW-101 Turner Hall, MC-046, 1102 South Goodwin Avenue, Urbana, IL, USA 61801-4730.
Department of Agricultural Engineering of the ETSIA & Institute of Plant Biotechnology, Technical University of Cartagena, 30203 Cartagena, Spain.
J Environ Manage. 2023 Apr 1;331:117292. doi: 10.1016/j.jenvman.2023.117292. Epub 2023 Jan 17.
Leachates from intensive agriculture containing high nitrate have been identified as a major cause of the severe eutrophication crisis that impacts Mar Menor (SE Spain), the largest hypersaline coastal lagoon in the Mediterranean basin. A best management practice for removing NO-N is denitrifying bioreactors. This is the first study to assess the efficiency of citrus woodchips bioreactors in treating agricultural leachates that flow to the Mar Menor via surface discharges. Denitrification capacity, woodchip degradation (by weight loss), formation of potentially harmful compounds, and greenhouse gas (GHG) emissions were assessed. Three bioreactors (6 m × 0.98 m x 1.2 m) filled with citrus woodchips (3 m d per bioreactor) through which the untreated ditch water over 1.5 years. Bioreactors were operated at 8 h, 16 h, and 24 h hydraulic residence time respectively, in each bioreactor. The main characteristics of the ditch water were: pH ≈ 7.5-8.0, electrical conductivity ≈ 5-8 dS m, dissolved organic carbon ≈6-10 mg L, and NO-N ≈ 22-45 mg L. Bioreactors were highly efficient in reducing NO-N. The average R in effluents was for the complete experimental period 8 g N m d, 10.9 g N m d, and 12.6 g N m d for 8, 16 and 24 h residence time, respectively. Nitrate reduction efficiency was modulated by seasonal changes in temperature, with an increasing efficiency in warmer periods (maximum ≈ 85-90% for all hydraulic residence time) and decreasing in colder ones (minimum ≈ 12%, 23% and 41% for hydraulic residence time 8, 16 and 24 h respectively). Woodchips degradation was greatest during the first six months (average ≈ 29% weight loss) in the material above the water level, attributable to aerobic mineralization of the organic carbon, while weight loss was ≈11% in woodchip media continuously below the water level. Dissolved organic carbon, sulfide, ammonium, and soluble phosphorus concentrations in the effluents were mostly low, although some peaks in concentrations occurred. Design consideration must be taken to avoid environmental impacts due to the occasional presence of harmful compounds in the effluents.
集约化农业产生的含有高硝酸盐的渗滤液已被确定为影响地中海盆地最大的超咸水沿海泻湖——马莫尔湖（西班牙东南部）的严重富营养化危机的主要原因。去除硝态氮的最佳管理实践是反硝化生物反应器。这是第一项评估柑橘木片生物反应器处理通过地表排放流入马莫尔湖的农业渗滤液效率的研究。评估了反硝化能力、木片降解（通过重量损失）、潜在有害化合物的形成以及温室气体（GHG）排放。三个生物反应器（6米×0.98米×1.2米）填充有柑橘木片（每个生物反应器3立方米），未经处理的沟渠水在1.5年的时间里流经这些生物反应器。每个生物反应器分别在水力停留时间为8小时、16小时和24小时的条件下运行。沟渠水的主要特征为：pH值约为7.5 - 8.0，电导率约为5 - 8 dS/m³，溶解有机碳约为6 - 10毫克/升，硝态氮约为22 - 45毫克/升。生物反应器在降低硝态氮方面效率很高。在整个实验期间，8小时、16小时和24小时停留时间的出水平均反硝化速率分别为8克氮/立方米·天、10.9克氮/立方米·天和12.6克氮/立方米·天。硝酸盐还原效率受温度季节性变化的调节，温暖时期效率增加（所有水力停留时间下最高约为85 - 90%），寒冷时期效率降低（8小时、16小时和24小时水力停留时间下最低分别约为12%、23%和41%）。木片降解在水位以上的材料中前六个月最大（平均重量损失约为29%），这归因于有机碳的好氧矿化，而在持续低于水位的木片介质中重量损失约为11%。出水中溶解有机碳、硫化物、铵和可溶性磷的浓度大多较低，尽管浓度出现了一些峰值。必须考虑设计因素，以避免由于出水中偶尔存在有害化合物而对环境造成影响。
