| 摘要: | 磷酸鹽從自然環境或污水中釋放至河川、湖泊、水庫等水體，會導致水質優養化的問題。多層複合濾料水質淨化系統(multi-soil-layering system, MSL)是一種現地污水處理技術，對於鄉村偏遠地區具有應用潛力，且能有效去除污水中的有機物與營養鹽。雖然此技術已成功地應用於世界上的許多國家，如：日本、泰國、印尼，但MSL系統去除磷酸鹽的機制還未被完全理解。
本研究探討初始磷酸鹽濃度、曝氣、微生物以及添加鐵對於MSL系統去除磷酸鹽的影響，使用large pilot MSL (L-MSL)系統與benchtop-MSL (B-MSL)系統進行實驗。為了清楚理解各參數對於去除磷酸鹽的貢獻，實驗採用砂替代混合土磚包中的土壤，配製合成污水，以減少其他參數如：土壤中的有機物、微生物、污水中的其他物質對於去除磷酸鹽造成的影響；另外也將混合土磚包與出流水中的鐵物質做進一步的分析與討論。
添加鐵粒能在MSL系統中提升固定磷酸鹽的效果，但是在缺乏微生物與有機物的條件下，出流水中的磷酸鹽濃度隨著時間明顯上升。而在含鐵的MSL系統中添加微生物、葡萄糖的組別，在運作的40天中，磷酸鹽的濃度穩定維持在0.05 mg-P/L以下。在pH值於6.5 – 8的範圍下，MSL系統中主要以纖鐵礦、磁鐵礦、磁赤鐵礦的形態存在，且有部分氧化鐵會結晶在砂的表面；在B-MSL6運作約一周後，釋出的鐵濃度逐漸上升，並觀察到出流水中有奈米磁赤鐵礦的沉澱。總體而言，MSL系統在添加鐵、有機物、微生物的條件下，去除磷酸鹽的效能良好，推測微生物與有機物可能有助於系統中磷酸鹽的去除，或是能與鐵、磷酸鹽共同作用提升MSL系統固定污水中磷酸鹽的效果。
;Release of phosphate from environment or wastewater can undermine water quality and cause eutrophication in lakes, rivers and reservoirs. Multi-soil layering (MSL) system as an attractive technology for rural area can effectively treat organic contaminants and nutrients in wastewater. Although it has been successfully applied in Japan, Thailand and Indonesia, the mechanism of phosphate removal in MSL system have not been fully understand.
In this research, the effects of concentration, aeration, microorganisms and addition of iron on the performance of phosphate removal in MSL system were investigated using large pilot MSL system (L-MSL) and benchtop-scale MSL system (B-MSL). To clearly understand the contribution of factors, the filling media was prepared sand instead of local soil in soil mixture blocks, and synthetic wastewater was prepared as the influent in experiments. In addition, the species of iron in soil mixture blocks and in effluent were unveiled. The iron beads in MSL system provide a major contribution to fix phosphate in MSL system. However, the phosphate concentration in effluent gradually increased with time in B-MSL without microorganisms and organic matters. In contrast, the MSL system with addition of microorganisms and organic matters stably maintained the phosphate concentration below 0.05 mg-P/L in effluent under 40 days of operation. Maghemite, lepidocrocite, magnetite are major iron oxides in MSL system in the pH range of 6.5 to 8, and a portion of them form crystallization coating on the surface of sand. Release of iron concentration had gradually increased after operation for a week in B-MSL6, and the nanoscale particles of maghemite were found in the effluent. Overall, MSL system with addition of iron, microorganisms and organic matters has effective performance on phosphate removal. The organic matter and microorganisms could assist iron to fix phosphate in MSL system. |
