[[alternative]]The basis of conducting SDI as evaluation tool in pretreatment efficiency of seawater desalination plants in Taiwan

[[abstract]]「問題多」、「操作複雜」為國內對海水淡化廠之普遍印象，主要造成此現象的原因在於實廠用以評估單元效能之指標過於缺乏，導致系統操作不易。目前僅有少數海淡廠以濁度或淤泥密度指數(silt density index , SDI)值評估水質進入逆滲透(reverse osmosis, RO)系統之適宜性，然僅此亦無法掌控前處理單元之效能。因此本研究欲推展SDI分析之應用，探討各種前處理程序於實廠之水處理成效，評估將系統中各單元產水之SDI分析列入實廠例行分析項目之必要性。結果顯示，SDI確實可反應出單元操作效能。此外，本研究藉由各海淡廠之評估結果，提出實廠常見之問題與建議解決方式；並藉由各廠之操作經驗，整理出在正常操作下，各種前處理單元組合其理想之SDI表現，此將為實廠操作之重要依據。本研究亦建議在考量操作之便利性、匣式濾材之廢棄物處理費及RO膜之生物性阻塞等面向下，超濾(ultra-filtration, UF)前處理為現階段新設海水淡化廠之最佳前處理方式之選擇。[[abstract]]Seawater desalination in Taiwan has been thought as complex and full of problem. Lack of comprehensive operation index is one of the major reason making systems not work well. Just several desalination plant have used RO feed turbidity and SDI to be the water quality control. However these still couldn’t help to express the efficiency of every pretreatment unit enough. Therefore, this study tried to extend the application of SDI to every pretreatment product. And evaluate the necessary of keeping SDI analysis to be one of the essential items in desalination plan. Results indicate that SDI could be a basic tool to reflect treatment unit conditions. Besides, according to the SDI evaluated results of eight desalination plants, this study provides recommendations against the common problems and to be reasonable guild for real plant operation. Overall, a consideration of stable permeate water quality according to SDI in this study, and other advantages of UF, such as operation convenient, cost of waste cartridge filter treatment, lower RO biofouling potential, this study concludes that UF is an idea pretreatment method in seawater desalination plant