以好氧顆粒正滲透膜生物反應器從污水處理回收磷程序評估

Abstract

磷是無法再生也無可取代的珍貴資源，由於磷的使用量日益增加，地球正面臨磷礦耗竭和過多磷排入環境造成的水質優養化問題，因此越來越多研究投入磷回收方法設計。結晶沉降法以可同時去除水中的磷酸根和氨氮而富有前景，然而當廢水中養分濃度改變，回收利潤需隨操作成本變動而重新評估，本研究旨於提出一新式膜生物反應器以和既有反應器比較效益。具有優良沉降性、不易膨脹且能承受高有機負荷的好氧顆粒在本研究中用來取代絮狀活性污泥，模組件則採用正滲透TFC薄膜。75日操作過程中，前期（30日）反應器使用絮狀汙泥，後期（45日）使用好氧顆粒，每星期取出2.5公升上清液使用氫氧化鈉法以期反應生成含磷結晶，達到磷回收之目的。前期反應器之磷酸根、氨氮和總有機碳去除率分別為95.8%、 37.4% 和 100%；後期則為95.5%、 46.0% 和 100%。與直接從合成廢水回收磷之效益相比，前期可節省40.9%，後期則是45.0%鹼用量。由於實驗中觀察到溶質滲透現象，本研究同時測試了TFC薄膜的選擇性，結果顯示陽離子較可能通過TFC薄膜，其中又以單價（鋰、鈉）和原子序小（硼）的陽離子最容易滲透。

Phosphorus recovery has been a global issue due to the depletion of phosphorus resource and the contamination of its release to the aquatic environment. Precipitation formation is a promising approach to recover phosphorus by extracting phosphate and ammonium ions in wastewaters; however, the operating costs need to be considered when the nitrogen and phosphorus loading increase. In this study, a modified process is suggested, using an aerobic granule forward osmosis membrane bioreactor (AG-FOMBR) to estimate the recovery efficiency. In this bioreactor, organic matters were digested by the biological process while phosphate ions were rejected by the Thin-film Composite (TFC) FO membrane and accumulated. Aerobic granules, as a compact form of microbial aggregates with good settleability and capability to treat high-strength wastewaters, were seeded to compare the membrane water fluxes with the sludge form. The AG-FOMBR showed 95.8%, 37.4%, and 100% overall removal of PO43--P, NH4+-N, and TOC in the first stage, and 95.5%, 46.0%, and 100% in the second stage, respectively. The solutes leakage of TFC membrane is measured and discussed. Recovery benefits through AG-FOMBR, OMBR, and FO (directly removing phosphorus from synthetic wastewater by FO) are evaluated. The global phosphorus recovery efficiency in this suggested reactor was 97.0% in average during the 75-day operation.