光電產業廢水處理單元中RO膜阻塞改善分析研究

Abstract

光電產業為一高耗用水量之產業，然台灣水資源匱乏，致使主管單位因節水緣故對於工廠水回收率之要求越來越嚴格，製程廢水回收再利用之利基日趨明顯，成為產業提高回收率之趨勢，工業用水回收處理的需求越來越大。RO膜系統為目前最為廣泛使用回收系統之一，然而產業廢水導致RO膜污垢的形成將會降低RO膜系統性能、減少RO膜的使用壽命、增加化學清理的次數並由此而引起的停工時間、從而提高系統的運行成本。本研究的目地除了對實際運轉廠製程廢水系統常用之RO膜對於廢水進水水質變化造成阻塞進行調查外，並針對系統提出改善方案，如各種阻塞與結垢之清洗方式、增設高濃度廢磷酸回收系統、加藥控制調整等。 最後將運轉多年且不堪使用之報廢RO膜作為解剖之分析，RO膜解剖後首先會初步鑑定外觀，其中包含硬度、氣味、黏性與結垢物之顏色，並藉由不同部位膜之樣本了解阻塞程度、種類與型態。經研究結果顯示，RO膜主要阻塞分為兩種，一為有機生物造成之阻塞，此狀況可藉殺菌劑添加及RO膜鹼洗去除之，而無機物阻塞主要因矽含量偏高可推斷玻璃碎屑堆積及含氟廢水之氟化鈣阻塞，此污染造成無機顆粒堆積於RO膜上不易清除且具有累積性，可藉由廢水來源加裝過濾器並將高濃度無機污染源單獨回收改善，另添加抑垢劑亦可有效改善無機物造成之阻塞。

Optoelectronics industries are the industries with high water-consumption, and the requirement for wastewater recovery rate by the authorities has become stricter. It’s not only a good chance but also an inevitable trend to the enterprise to prompt wastewater reuse. The RO system is one of the most widely used unit in the wastewater reuse system. Unfortunately, the fouling and scaling of RO membranes seriously deteriorate the performance, reduce the lifespan, and increase the durations of chemical cleaning and the downtime. Of course, its running cost also goes up. The aim of this study is not only to investigate the relation between the variation of inlet wastewater and the fouling/scaling of RO membranes which are regularly used in the process of wastewater reuse, but aslo to issue some improvement suggestions, including the fouling and scaling cleaning methods, constructing a new high concentration phosphoric acid recovery system and chemical dosing control method adjustment. Finally, three scrapped RO membranes which have been run for many years are dissected. By observing the appearance, including the strength of the structure, the odor, viscosity and color of the foulants, I learn of the degrees, species and types of the fouling at different locations in the membrane samples. Results have indicated that the fouling can be divided into two. One is caused by the microorganism, which can be removed by the adding of bactericide and alkali solution. The other is caused by the inorganic matters, including glass debris containing silicon and CaF2. This contamination causes the accumulation of inorganic particles on the RO membrane, which is not difficult to remove. The better way is to install the prefilter ahead of RO modules. Moreover, it is also shown that it is effective to improve the obstruction by adding antiscalant.