- 期刊
以沉澱槽及上流式流體化結晶床回收廢水中的磷成磷酸銨鎂的比較
Comparison of the Recovery of Phosphorus from Wastewater into Magnesium Ammonium Phosphate by Sedimentation Tank and Up-flow Fluidized Crystallization Bed
摘要
若排放的廢水中含有過高的磷，會造成河川、湖泊的優養化，因此，有效的降低磷含量，是廢水處理中重要的處理方法。磷酸銨鎂，又稱作鳥糞石，是一種緩釋性磷肥，施用時不會像化肥的磷會大量的溶洗出來，因此對環境友善。在此研究中，我們進行實場試驗，測試如何有效的以磷酸銨鎂的方式回收放流水中的磷。將厭氧消化後的廢水流出液以傳統式沉澱槽及上流式磷酸銨鎂流體化結晶床實際進行鳥糞石試量產測試。在傳統沉澱槽的結果中，雖然能回收約八成的磷，但磷酸銨鎂的純度約為50%，其他的多為鈣、鎂的碳酸鹽（dolomite）沉澱。單獨使用上流式磷酸銨鎂流體化結晶床時，能提高純度。若加上脫鈣槽時，透過草酸沉澱法，可以選擇性移除鈣離子，且不對磷酸銨鎂生合成所需之鎂離子產生作用。將脫鈣後的發酵液進行pH值調整，約能移除廢水中80－90%的磷，且可將磷以磷酸銨鎂的形式沉澱下來。因此，經過脫鈣處理後，上流式磷酸銨鎂流體化結晶床能將溶解態磷有效以磷酸銨鎂的形式回收，增加純度及產率。
並列摘要
High contents of phosphorus in discharged wastewater can cause eutrophication of rivers and lakes. Therefore, how to reduce phosphorus content effectively is important in wastewater treatment. Magnesium ammonium phosphate (MAP), also known as struvite, is a slow-release phosphate fertilizer. MAP does not dissolve well like chemical fertilizers, so it is friendly to the environment. In this research, we conducted a field study to test the recovery of phosphorus from wastewater as MAP. Anaerobic digestion effluent was used for the mass production test of struvite using a traditional sedimentation tank, and an up-flow type MAP fluidized crystallization bed. By using a traditional precipitation tank, 80-90% of the phosphorus could be recovered. However, the product contained only about 50% struvite and the others were mostly calcium and magnesium carbonate (dolomite) precipitates. MAP recovery rate can be improved when the up-flow MAP fluidized crystallization bed was used. When a decalcification tank was added, calcium ions, but not the magnesium ions, could be selectively precipitated by addition of oxalic acid. Consequently, 80-90% of the phosphorus could be recovered as MAP after pH adjustment of the decalcified fermentation broth. Therefore, after the decalcification treatment, the up-flow MAP fluidized crystallization bed can effectively recover the dissolved phosphorus from wastewaters in the form of MAP with higher purity and yield.