前趨滲透應用於高營養鹽污泥濃縮脫水之研究

Application of forward osmosis on dewatering of high nutrient sludge

楊弘胤(Hung-Yin Yang)

指導教授 ： 陳孝行

國立臺北科技大學/工程學院/環境工程與管理研究所/碩士(2013年)

https://doi.org/10.6841/NTUT.2013.00242

摘要

前驅滲透程序(Forward osmosis, FO) 是一種利用溶液滲透壓差驅動的薄膜技術，與傳統薄膜程序如RO、NF 膜等比較，有著無需外加壓力的優點，在一切以節能為首要條件的時代，能同樣使用薄膜程序但是大幅降低能量消耗，是非常重要的課題。但是在實務應用上，還是有兩個問題須要克服，第一是從驅動液(draw solution) 中分離清水的問題。當清水進入高濃度驅動液，會使濃度降低而減少滲透壓差。第二是FO膜傳遞中的濃差極化使得FO膜實際水通量要遠遠小於理論水通量，因此如何減小濃差極化，也是一個需要解決的問題。過去研究中，高滲透壓如單價鹽類，是最常用的驅動液，但是也必須使用耗能的RO膜且單價鹽類還是會通過薄膜。部分研究開始嘗試用溶解性顆粒當成驅動液，但是通量還是不好。
前趨滲透(Forward Osmosis)為一種新興處理技術應用於污泥脫水同時去除營養鹽之低耗能程序。本研究使用美國HTI公司製造之三乙酸纖維FO膜進行試驗，膜的活性層(active layer)面對進流水(feed solution)，並使用NaCl作為驅動液，濃度分別為36 g/L及70 g/L進行高營養鹽污泥脫水之研究。污泥中含有DOC =200 mg/L、NH4+- N =100 mg/L,及PO43--P=100 mg/L並含有混合液懸浮固體物(MLSS) 5000 mg/L將使用FO程序進行脫水並取代沉澱池，同時去除有機物、氮、磷營養鹽以改善出流水水質。實驗結果顯示，在最初15小時操作時間其最高滲透水通量為4.5 L/m2h，在操作32小時後逐漸下降至1.6 L/m2h，此時MLSS從初始的5000 mg/L升至25,000 mg/L，此外，DOC、NH4+- N及PO43--P去除率分別為99.90%、97.15%和99.89%。

關鍵字

前趨滲透 ； 污泥脫水 ； 驅動液 ； 活性污泥 ； 污泥脫水 ； 滲透壓

並列摘要

Forward osmosis (FO) is a process of water driven by the osmotic pressure difference across the semipermeable membrane without the aid of external energy. Unlike other membrane process such as NF and RO, the no/less energy consumption of FO makes it possible to be a promising technology. However, the application of FO relies on two critical concepts: (1) an ideal draw solutes should have high osmotic pressure and should be easily separated and (2) a good FO membrane process should be able to reduce the concentration polarization to enhance permeate flux. Therefore, it is still a pressing demand to find an ideal FO draw solution and way to reduce concentration polarization. Monovalent ions are commonly used as draw solution, but high energy RO is required; some of the researches also used soluble particles as draw solution, but the resulting flux was low.
A novel approach was designed to simultaneously apply low energy sludge dewatering and nutrient removal for the centrate using Forward Osmosis (FO). This study used a flat-sheet cellulose triacetate FO membrane for high nutrient sludge dewatering under orientation membrane of active layer facing feed solution and using NaCl of 36g/L as the draw solution. The sludge was spiked with DOC = 200mg/L, NH4+- N = 100mg/L, PO43--P= 100mg/L and the mixed liquor suspended solids (MLSS) of 5000mg/L for FO dewatering performance to replace second sedimentation tank and enhance removal efficiency of organic contaminants, nitrogen and phosphorus in the final effluent. The preliminary results from the FO module showed that the highest permeate water flux was achieved as 4.5 L/m2h during first operating 15 hr, but gradually declined to 1.6 L/m2h at 28 hr where MLSS concentration reached 25,000mg/L from the initial concentration of 5000mg/L. Moreover, nutrients and organic compounds in the sludge solution were also successfully removed by FO membrane with 97.15% of NH4+- N, 99.89% of PO43--P and 99.90% of DOC.

並列關鍵字

Forward osmosis ； Draw solution ； Activated sludge ； Sludge dewatering ； Osmotic pressure

參考文獻

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