| 摘要: | 本研究利用位於台南縣二行村為全國首座用來處理社區生活污水的示範實場，於民國90年開始操作至今已有三年，針對實場區之自由表面流動(FWS)系統作底泥特性的探討，再另選一處自然溼地作背景值。茲將兩系統的分析數據作比較，以瞭解人工溼地利用土壤介質作為植物媒介來淨化污水，期能探討系統經長期性處理生活污水之污染物最終沉積於底泥的累積與變化，且研究在不同深度底泥特性中污染物停留分佈形態及植物體攝取的狀況。
本研究先分析兩系統水中的總懸浮固體、生化需氧量、總氮和總磷等污染物，其污染物經由物理淨化過程，而部份污染物因化學反應形成非溶解性物質則沉積於介質上；再者，底泥長期處於厭氧還原形態環境中，影響到土壤基本性質的變化；而本研究主要探討之參數包括質地分析、容積密度、陽離子交換容量、底泥含水量、底泥酸鹼值、有機物含量、溶解性總有機碳、硝酸態氮、總氮、總磷及重金屬等，以分析各參數的累積情況與變化；最後進行人工溼地的植物對營養鹽之攝取含量等分析。
初步研究結果顯示，自然溼地土壤性質分析底泥在長期淹澇的結果，會使累積於介質上的沉積物在形成有機土過程，造成底泥特性有很大的變化，像底泥孔隙小且緊密度增加到1 g/cm3 左右，而底泥上下層質地呈現均質化及色澤相似、屬中性偏鹼性、吸附有機物能力強和ORP負值高等性質；最後礦質土轉為有機的富營養之底泥，而底泥挖除後亦可回收再利用。然而在人工溼地FWS系統，由於系統中物質轉換累積等行為未穩定，底泥上層有機土的形成尚不明顯，所以研判底泥特性的變化較小，可能需長時間才會像自然溼地一樣的性質，故人工溼地系統底泥吸附污染物之能力與貯存量尚有很大的空間。
This experiment of this research was performed in the first full-scale constructed wetland system (CW) built in Erh-Hang village, Tainan and has been operated since 2001. The goal of this research is focused on the study of sediments taken from the free water surface flow (FWS) of the CW and natural wetland. By comparing the sediment characteristics of these two different types of wetland to understand the media behavior in a CW while treating wastewater, so that further understand pollutants accumulation and variation in the sediment of CW after a long-term operation. Furthermore, a distribution of pollutants along the depth of sediment and absorption by macrophytes were also investigated.
Total suspend solid, biological oxygen demand, total nitrogen, and total phosphorus were measured in this research work. Part of those constituents in wastewater were removed via physical mechanism and chemical precipitation to settle on the bottom media in CW. Meanwhile, in the continuously anaerobic condition in the sediment, the soil characteristics were changed. The parameters investigated in this research includes soil texture analyses, volumetric density, cationic exchange capacity, water content of sediment, pH of sediment, organic content, soluble total organic carbon, nitrate nitrogen, total nitrogen, total phosphorus, and heavy metals. The accumulation and variation of these measures were analyzed. The nutrient contents in the macrophytes in CW were also analyzed.
The initial research results indicate that the characteristics of sediment varied significantly in natural wetlands due to the process of accumulation of materials on the surface of media during long-term merged in water, such as the density would increase to 1 g/cm3, upper and lower layers become similar in color and weak base, the adsorption of organics becomes stronger, and oxidation- reduction potential becomes highly negative, etc. Eventually, the mineralized soil turns to be more nutritious organic from and suitable for recycled. However, the materials transforming behaviors in the FWS wetland system were still not stabilized and the organic layer was not yet formed on sediment. The variation of the soil characteristics in FWS wetland. Therefore, the adsorption and the storage capacities for pollutants in constructed wetland system are still remained very high potential. |
