نوع مقاله : مقاله پژوهشی
عنوان مقاله English
نویسندگان English
Introduction: Nitrate contamination of groundwater poses significant environmental and health concerns, particularly in arid and semi-arid regions where brackish groundwater is widely exploited for non-potable uses or as feed water for desalination systems.
Material and Methods: In this study, biofilm-based nitrate removal from brackish groundwater with EC ranging from 851 to 3150 µS/cm was investigated using a pilot-scale up-flow biofilter system. Seven different filter media, including Kaldnes, coarse Leca , fine Leca, fine sand, palm fiber, multi-media, and plastic baskets, were evaluated in parallel pilot units operated under identical conditions. The experimental program was conducted under varying influent nitrate concentrations (112.0–279.5 mg/L), flow rates (13.0–52.0 L/h), and HRTs (from 1.0 h for fine sand to 7.6 h for plastic baskets) during three periods from June to November 2021. Nitrate removal performance was assessed primarily in terms of removal efficiency (%).
Results: Among the evaluated media, coarse Leca demonstrated the highest performance, achieving a nitrate removal efficiency of 82.1% followed by Kaldnes (68.1%) during Period 2. Notably, palm fiber exhibited considerable removal efficiency (61.2%), which may be attributed not only to its physical support function but also to its lignocellulosic nature. To evaluate the non-linear relationships between operational parameters, an XGBoost machine learning model was applied using independent variables including flow rate, pH , EC, temperature, and influent nitrate. The SHAP analysis revealed that the flow rate was the most critical determinant of nitrate removal efficiency, followed by pH and EC.
Conclusion: Overall, the findings indicated that biofilm-based nitrate removal using pilot-scale up-flow biofilters can provide an effective and low-energy treatment or pre-treatment option for nitrate-contaminated brackish groundwater.
کلیدواژهها English
