Nitrogen pollution in streams can be controlled by serially constructing natural wastewater treatment (NWT) systems inside streams. Therefore, a pilot-scale hybrid NWT system consisting of gravel filtration (GF), sedimentation pond (SP), gravel filtration-free water surface constructed wetland (GF-FWSCW), and gravel filtration-overland flow (GF-OF) was installed in order to prevent contamination in a stream (Nigde stream) that feeds and pollutes surface water source (Akkaya lake). The pilot-scale system was installed on a new 60 m-long channel which was located off the stream. Changes in ammonium (NH₄⁺-N), organic nitrogen (N_org.), total nitrogen (TN), and biochemical oxygen demand (BOD) concentrations was routinely monitored in influent and effluent of all stages of the hybrid NWT system and the bottom sediment of the SP over a one-year operation period. According to the study results, while NH₄⁺-N plus N_org. was reduced by an average of 75% (from 49,1 mg L⁻¹ to 7,1 mg L⁻¹), TN was reduced by an average of 85% (from 50,2 mg L⁻¹ to 12,4 mg L⁻¹). Colder seasons and higher hydraulic loading rates (HLRs) negatively affected nitrogen removal efficiency of the pilot-system. The use of vegetation and filter medium had a positive effect on the average removal efficiencies. The results showed that nitrogen pollution in polluted streams could be greatly reduced by establishing a NWT system in series within them.

河流中的氮污染可通过在河流内部顺序构建天然废水处理（NWT）系统来控制。因此，安装了由砾石过滤（GF），沉淀池（SP），无砾石过滤的水面人工湿地（GF-FWSCW）和砾石过滤-陆面流量（GF-OF）组成的中试混合NWT系统。为了防止流入和污染地表水源（阿卡亚湖）的溪流（Nigde溪流）中的污染。中试规模的系统安装在一条新的60 m长的河道上，该河道位于河的下游。铵（NH ₄ ⁺ -N），有机氮（N _org。在一年的运行时间内，常规监测混合NWT系统所有阶段的进水和出水以及SP底部沉积物中的总氮（TN）和生化需氧量（BOD）浓度。根据研究结果，NH ₄ ⁺ -N加N _org。平均减少75％（从49,1 mg L ^-1到7,1 mg L ^-1），TN平均减少85％（从50,2 mg L ^-1到12,4 mg L ^-1）。较冷的季节和较高的水力负荷率（HLR）对中试系统的脱氮效率产生负面影响。植被和过滤介质的使用对平均去除效率有积极影响。结果表明，通过在其中建立串联的NWT系统，可以大大减少污染流中的氮污染。