都市污水處理廠RO濃排液及MBR排放水以薄膜蒸餾產製再生水之實驗探討

An experimental study on membrane distillation for reverse osmosis concentrate and membrane bioreactor effluent from municipal wastewater treatment plant

黃彥瑋(Yan-Wei Huang)

指導教授 ： 莊清榮

中原大學/工學院/化學工程研究所/碩士(2019年)

https://doi.org/10.6840/cycu201900396

摘要

由於氣候變遷與工業用水需求增加，導致臺灣常有缺水問題，近年來發展再生水產製是重要課題。基於生活及工業廢水量大且較穩定，利用其產製再生水具有發展潛力。
本研究利用直接接觸式薄膜蒸餾 ( DCMD ) 針對桃園北區水資源回收中心之RO濃排液及MBR放流水進行試驗，其中試驗水樣大多以前者為主，目標產製高純度之再生水且達至工業使用標準，及減少RO濃排液體積與提高水回收率，最後也嘗試估算DCMD產製此再生水之成本。
首先探討進料溫度變化對通量的影響，以RO濃排液為進料，當進料溫度從50 ºC提升至70 ºC時，其六小時平均通量從5.04提升至8.43 kg / m2hr。接續比較RO濃排液與MBR放流水為進料之通量變化，結果顯示，在不同進料溫度( 50 ºC及60 ºC )及長時間操作下，後者為進料時有較高的通量，以進料溫度60 ºC操作六小時為例，當進料為MBR放流水時，其平均通量為9.24 kg / m2hr；進料改為RO濃排液時，其平均通量為7.48 kg / m2hr。根據滲透端氯離子濃度下降之結果，顯示薄膜對離子有良好阻擋效果。接著以RO濃排液為進料進行批次濃縮實驗，操作二十四小時通量由9.24降至4.39 kg / m2hr，後續進行MD操作後之膜面積垢成分分析及膜清洗效能的評估，經SEM-EDS分析顯示膜面上附著排列緊密結晶物，膜面積垢主要來自碳酸鈣，以檸檬酸溶液掃流清洗膜面可有約98%之通量回復，而若以氫氧化鈉及清水溶液掃流清洗則通量回復分別約94及84%。本研究最後亦嘗試估算以DCMD產製再生水之成本，當有充足廢熱作為MD進料熱源之條件下，於RO濃排液與MBR放流水為進料所評估之單位產水成本分別為NT$ 29.04及21.96 / m3。

關鍵字

薄膜蒸餾 ； 都市生活污水 ； 薄膜生物反應器 ； 逆滲透濃縮液 ； 再生水

並列摘要

Due to climate change and increased demand in water for industry, Taiwan has often faced water shortage problems in recent years. Therefore, promoting the reuse of reclaimed water for industry is an important issue for the government. Based on the large and stable amount of domestic sewage and industrial wastewater, the use of these wastewater to produce reclaimed water should have the potential for future development. In this study, direct contact membrane distillation (DCMD) with tubular module was used to conduct experiments with RO concentrate and MBR effluent from Taoyuan North District Water Resources Recycling Center. The aim was to produce high-purity reclaimed water and meanwhile reduce the discharged volume of RO concentrate. Finally, the cost of producing reclaimed water from these waste streams with DCMD was also evaluated in this study.
First, the effect of feed temperature on flux was investigated. When the RO concentrate was used as the feed for DCMD, experimental results showed that the six-hour average flux increases from 5.04 to 8.43 kg / m2hr as the feed temperature varied from 50 ºC to 70 ºC. A comparison of fluxes between the feed with RO concentrate and that with MBR effluent showed that the latter has a higher flux. The measurements of permeate conductivity and chloride ion concentration indicate that the ions in these feeds are almost completely rejected. A continuous concentration experiment carried out with RO concentrate showed that the flux decreases from 9.24 to 4.39 kg / m2hr for 24 hours operation. SEM-EDS analysis for the fouled/scaled membrane surface after 24 hours operation with RO concentrate showed the inorganic deposit is mainly the CaCO3 crystallization. In the study, three types of solutions such as NaOH ( 1 wt% ), citric acid ( 1 wt% ) and Deionizer water were used for crossflow over the fouled/scaled membrane to test the cleaning performance. The results showed that the flushing of the fouled/scaled membrane by citric acid can restore a higher flux to near 98% the initial flux of virgin membrane. Finally, we also estimate the cost of producing reclaimed water by DCMD with these waste streams. When there is sufficient waste heat as heat source, the water production cost by MD with RO concentrate and MBR effluent are NT$ 29.04 and 21.96 / m3, respectively.

並列關鍵字

Membrane distillation ； Effluent of urban sewage treatment ； MBR ； RO concentrate ； Reclaimed water

參考文獻

Al-Karaghouli, A. & Kazmerski, L. L. (2013). Energy consumption and water production cost of conventional and renewable-energy-powered desalination processes. Renewable and Sustainable Energy Reviews, 24, 343-356.

An, A. K., Guo, J., Jeong, S., Lee, E. J., Tabatabai, S. A. A. & Leiknes, T. (2016). High flux and antifouling properties of negatively charged membrane for dyeing wastewater treatment by membrane distillation. Water Research, 103, 362-371.

Banat, F. A. & Simandl, J. (1998). Desalination by membrane distillation: a parametric study. Separation Science and Technology, 33, 201-226.

Chew, N. G. P., Zhao, S., Loh, C. H., Permogorov, N. & Wang, R. (2017). Surfactant effects on water recovery from produced water via direct-contact membrane distillation. Journal of Membrane Science, 528, 126-134.

Edwie, F. & Chung, T. S. (2012). Development of hollow fiber membranes for water and salt recovery from highly concentrated brine via direct contact membrane distillation and crystallization. Journal of Membrane Science, 421-422, 111–123.