本研究以平鎮及板新淨水場快濾池為對象，建立其反洗廢水之水質特性。並以不同操作條件處理濾池反洗廢水，探討超濾(UF)程序之滲透液水質、通量及膜面阻塞的情形。最後，以不同薄膜(微濾MF、超濾UF、奈濾NF及逆滲透RO)組合程序，評估回收處理反洗廢水的可行性。 研究結果顯示，兩淨水場快濾池反洗廢水屬中等濁度(156~390NTU)或懸浮固體物濃度(193.1~380.7mg/L)，且99％以上的濁度顆粒，粒徑大於1μm。廢水中的溶解性物質，大部分來自原反洗清水，故有機物濃度低(DOC為2.02~6.66mg/L)，且導電度亦不高(216~275μs/cm)。UF程序操作條件中，以1μm MF前處理可去除廢水中大部分濁度顆粒，進而提高UF滲透液通量。在3kg/cm2操作壓力下，可獲得最大的滲透液總通量。根據SEM觀測及模式模擬結果，反洗廢水經UF程序，其UF薄膜阻塞機制偏向於濾餅過濾。 薄膜組合程序中，MF程序可去除反洗廢水中99.87％的濁度；接續的UF程序可使廢水中殘餘的濁度顆粒完全地被去除，且可去除廢水中約30％的DOC；UF程序之後的NF或RO程序，能進一步去除部分DOC及無機離子。反洗廢水經MF過濾後的水質，初步顯示可符合飲用水水質標準，故可考量就近直接回收再利用作為快濾池反洗水。如考量作為清水補充或生活用水，基於用水安全，為避免致病菌穿透MF薄膜及有機物污染的風險，仍須接續UF程序。 This study investigated the characteristics of filter backwash wastewater (FBW) from Pingjan and Bansin water treatment plants (WTP).The effects of ultrafiltration process parameters on the quality and flux of the FBW permeate as well as membrane fouling were discussed. Also, the feasibility of recovery and reuse of the FBW by the combination of various membrane processes including microfiltration (MF), ultrafiltration (UF), nanofiltration (NF) or reverse osmosis (RO) was evaluated. The results of this study revealed that the FBWs from the two WTPs were both characterized as medium level of turbidity (156-390 NTU) and SS (193.1-380.7 mg/L) with 99% particle size larger than 1 μm. The dissolved substances presented in the FBWs were majority from the original backwash water, indicating low dissolved organic carbon (DOC = 2.02-6.66 mg/L) and conductivity (216-275 μs/cm). For UF process, the pretreatment of FBW by 1 μm MF could remove most of turbidity particles and enhance permeate flux of UF. It also found that the maximum total permeate flux occurred at 3 kg/cm2 UF operating pressure. The mechanism of UF membrane fouling was prone to cake filtration according to SEM analysis of membrane surface and blocking model simulation. The pretreatment of FWB by MF could remove 99.87% of turbidity. After MF process, the residual turbidity particles in FBW were almost completely removed along with about 30% of DOC removal by the following UF process. In comparison, the NF and RO process had ability to further remove DOC and inorganic ions after UF process. The experimental results of membrane filtration showed that the water quality of FBW after MF treatment had potential to meet the drinking water quality standard of Taiwan. Thus, the MF permeate could be directly recycled and reused as the makeup of filter backwash water in WTPs. However, if FBW was reused as a portion of clean water supply, the combination of MF and UF should be considered in order to prevent the penetration of pathogenic bacteria and reduce the risk of organic pollutants for safety use.
