近年來，台灣光電半導體業等嶄新的高科技產業發展蓬勃，其中薄膜液晶螢幕(Thin Film Transistor Liquid Crystal Display, TFT-LCD)由於可應用在許多相關科技上而使需求與日俱增。但是隨著需求與產量增加，光電產業的廢水量也逐日劇增。其中的顯影劑中的氫氧化四甲基胺(Tetramethylammonium hydroxide, TMAH)經過處理後，產生高濃度氨氮，如果排入河川，會造成水體難以抹滅的衝擊。有鑑於此，眾多工業開始發展降低氨氮濃度技術。
本研究以針對實廠(I廠)所產生之高濃度氨氮廢水結合磷酸銨鎂沉澱法(MAP, Magnesium ammonia phosphate hexhydrate, struvite) 來降低氨氮濃度並且回收氨氮。為了使其可以實際應用，所採用之原料以最低成本考量採用。在此研究中，低成本是指使用同一家公司產的磷酸為以及滷水為磷及鎂的來源。其磷酸來源為使用同一家公司(I廠)之磷酸蒸發液，以及苗栗通霄精鹽場所使用的苦滷水提供鎂離子來源，以降低成本。在本研究中，找出回收氨氮之最佳氨氮、鎂離子、磷酸之莫爾數比及pH值，並且評估其經濟效益，並且以種植葉萵苣(Arden lettuce)來觀察其施肥效益。並且檢驗其重金屬含量以確認其食用安全性，並提供建議此方法是否可行。
此研究之目的可分為四個，第一，以氨氮的莫爾數比為1，並且以磷酸的莫爾數分之鎂離子的莫爾數之P/M值建議最佳配比。第二，建議最佳pH值。第三，成本效益評估。第四，推估其MAP品質。
針對第一點之結果所得，其對應之莫爾數比混合所得之氨氮、鎂離子、磷酸之最佳配比為1: 1.0 : 1.0 至 1: 1.0: 1.2，氨氮回收率之各批次之範圍則為68.53%~96.12%，其中位數為89.78%。針對第二點結果所得，在最佳pH值為9.0~9.9，氨氮回收率為95.22%~96.89%，其中位數為96.29%。針對第三點結論所得，以原本處理方法所消耗的金額，及原先滷水販售價格以及磷酸蒸發塔販售價格之總額和以磷酸銨鎂沉澱法所產出之肥料總和來比較是否符合經濟效益。以產出一公斤的鳥糞石來計算，以原本的方法來處理氨氮廢水需要耗費以及回收的磷酸可販賣之價格的總和需消耗14,260元新台幣，以磷酸氨鎂沉澱法之價格的總和需要消耗70新台幣，故磷酸氨鎂法符合經濟效益。針對第四點其結論所得，此實驗所產出的最高之鳥糞石純度為59.13%，其營養成分之氮成分含4.45％、磷酐含32.59％、氧化鉀含1.8％以及有機質含32％。重金屬檢測結果Ni及Cu等重金屬超過肥料標準。並且以盆栽實驗來試驗種植之植物是否會有重金屬汙染，並且來以重金屬是否超過標準來決定其食用安全性，其檢驗結果為植體中的Cd及Cu超過法定標準。故其種植出來之蔬菜不具食用安全性。
綜合以上三點結論，最佳P/M 值是1.0~1.2，最佳pH值為9.0~9.9，MAP沉澱法暫時為不可行。若能夠去除光電沸水中之懸浮固體中即可降低肥料中之重金屬，如此一來，極有可能符合有機肥料及植物體中重金屬標準。若能夠解決重金屬的問題，MAP沉澱法即為可行。

Optoelectronic semiconductor and high technology industries are growing in recent years in Taiwan. Among these industries, Thin Film Transistor Liquid Crystal Display (TFT-LCD) can be applied in many relative high technology products so it made the demand and output become higher and higher. As the output higher, the volume of wastewater becomes higher. The wastewater contains tetra-methyl-ammonium-hydroxide (TMAH), which processes with upflow anaerobic sludge blanket reactor (UASB). The TMAH transferred to ammonia then made the wastewater contains high concentration of NH4+. If the high concentration NH4+ of wastewater effluent to water body, it will cause irreversible impact. Therefore, TFT-LCD industries start to develop new technologies for reducing ammonia concentration.

In this work, we evaluate the effectiveness and feasibility of applying a magnesium phosphate precipitation (MAP) method for further reducing the level of NH4+ by recovery of nitrogen from the effluent of UASB treating TFT-LCD wastewater, and generating struvite (MgNH4PO4‧6H2O) solids as slow-released fertilizer. Additionally, with an intention to cost down the MAP approach, source materials including magnesium from concentrated seawater brine, and phosphate recovered from the TFT-LCD manufacturing process, were applied in this study. First, the operational pH value and optimum molar ratio between ammonia from the UASB effluent, magnesium from the concentrated seawater brine and recovered phosphate, were determined to maximize the recovery rate of ammonia. Second, the cost of generating struvite from the proposed approach was evaluated. Third, the quality of generated struvite was assessed by analyzing the nutrient content, and the concentration of heavy metals in soils and vegetation when applying it as fertilizer.

First, the highest median ammonia recovery rate of 89.78% (68.53% to 96.12%) was attained when the range of molar ratio (NH¬4+: PO43- : Mg2+) was adjusted to between 1: 1.0 : 1 to 1: 1.2: 1. The best pH value for synthesizing struvite solids using the proposed MAP approach is between 9.0 to 9.9. Second, the cost for generating 1 kg struvite solids (59% purity) is estimated to be 2 NTD/Kg-struvite by taking both the cost of adjusting pH value 44 NTD/Kg-struvite and purchasing concentrated seawater brine is 28 NTD/kg-struvite. The generated struvite solids (59% purity) consist of 4.5% nitrogen, 32.6% phosphorous, 1.8% potassium oxide and 32% organic matter. The concentration of Ni and Cu within the struvite solids exceed the limits of fertilizer standard in Taiwan. The heavy metal resource of Ni and Cu is from suspend solid in TFT-LCD wastewater. The original way to treat wastewater have to spend 14,260 NTD/Kg-struvite. The MAP precipitate method to treat wastewater have to spend 70 NTD/Kg-struvite. Therefore, the MAP precipitate method is cost effective. If the problem of heavy metal can be solve, it is feasible to apply to the nowadays society.

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簡道南，新創事業處，肥料與植物生長，合肥月刊，第四十四卷第二期，2003年2月15日出刊

中華肥料協會，作物施肥手冊，2005年，ISBN 986-00-3335-8