不同莫耳氮磷比對微藻去除污水中氮磷營養鹽之影響

Different N/P Molar Ratios for Microalgae to Remove Nitrogen and Phosphorus Nutrients from Wastewater

蕭文暐(Wen-Wei Hsiao)

指導教授 ： 于昌平

國立臺灣大學/工學院/環境工程學研究所/碩士(2022年)

https://doi.org/10.6342/NTU202200452

摘要

目前污水放流水中含有超量的氮和磷營養鹽常導致承受水體產生優養化的問題，因此在前端的污水處理中即去除氮磷營養鹽刻不容緩。微藻膜生物反應器為近幾年提出結合微藻與薄膜以去除氮磷營養鹽的技術。本研究評估微藻應用於污水三級處理去除硝酸鹽和磷酸鹽的潛力，特別針對微藻膜生物反應器評估其操作參數包括藻種、莫耳氮磷比(4.5、10) 和pH值(7、8.5)。此外，本研究也進一步關注微藻膜生物反應器操作過程因為微藻有機物造成的薄膜積垢問題。本研究使用四種微藻：四尾柵藻、斜生柵藻、經紋球藻和迪化污水處理廠的二沉放流水的混藻群，分別進行硝酸鹽和磷酸鹽去除和薄膜積垢潛勢的探討。在為期 15 天的營養鹽去除批次實驗中，探討了氮磷營養鹽分別的去除效率和速率。而後續也採集第15天含有微藻有機物的上澄液並去除微藻，與陶瓷膜共運行5小時，藉由測量其薄膜通量下降程度，作為薄膜積垢潛勢的探討依據。
結果表明，混藻群在每組批次實驗中均能達到 100% 的硝酸鹽去除率，尤其在 pH=7 時對比其他藻種有著最高去除率。四尾柵藻在大多數批次測試中皆能達到 100% 的磷酸鹽去除率，並且在 pH=8.5 時表現出較快的去除速率。此外，混藻群雖然比四尾柵藻去除磷酸鹽速率稍慢，但在大部分組別也能達到 100% 的磷酸鹽去除率。實驗結果也顯示莫耳氮磷比確實會影響微藻對磷酸鹽的去除，但對硝酸鹽的去除影響則不明顯。在薄膜積垢實驗中，混藻群上澄液對薄膜造成的通量下降幅度較四尾柵藻小。此外，在莫耳氮磷比=10的條件下，上澄液造成的薄膜通量下降也較莫耳氮磷比=4.5的情況小。綜上所述，混藻群具有優秀的硝酸鹽和磷酸鹽去除能力，其上澄液含有的微藻有機物對薄膜積垢的影響也較小。因此，本研究推薦混藻群為未來微藻膜生物反應器最佳的應用藻種。

關鍵字

微藻 ； 混藻 ； 氮磷比 ； 薄膜積垢 ； 陶瓷膜

並列摘要

Excessive nitrogen and phosphorus nutrients in wastewater effluents cause eutrophication and hence the removal of nutrients is of great urgency. Algae-based membrane bioreactor was proposed to be a treatment process for nutrients removal combing microalgae and membrane recently. The objective of this study was to assess the microalgae species application to algae-based membrane bioreactor mainly for nitrate and phosphate removal in the condition of two molar N/P ratios (4.5, 10) and two pH values (7, 8.5). Also, this study further focused on the algal organic matter of microalgae which caused membrane fouling in the case of algae-based membrane bioreactor. Four microalgae cultures, Scenedesmus quadricauda, Scenedesmus obliquus, Coelastrella striolata and mixed microalgae from Di-Hua WWTP were studied for nutrients removal and potential of membrane fouling. The 15-day batch tests were conducted to reveal the nutrients removal efficiencies and rates. After the batch tests, the 15-day microalgae supernatant containing algal organic matter was separated from microalgae and operated with ceramic membrane for five hours to show the flux decline which was an indicator of membrane fouling.
The results showed mixed microalgae reached 100% nitrate removal in every batch test and with the highest removal rate at pH=7 compared to other species. Scenedesmus quadricauda revealed 100% phosphate removal in most batch tests and performed higher removal rate at pH=8.5. Furthermore, mixed microalgae did reach 100% phosphate removal but slightly slower than Scenedesmus quadricauda. Molar N/P ratio did affect microalgae phosphate removal but not nitrate removal. Mixed microalgae supernatant had slighter flux decline compared to Scenedesmus quadricauda. Also, the supernatant in the condition of molar N/P ratio=10 showed slighter flux decreasing compared to molar N/P ratio=4.5. To summarize, mixed microalgae had a better ability to remove both nitrate and phosphate, and less membrane fouling due to slighter flux decline. Consequently, this study suggests mixed microalgae as the optimal species for algae-based membrane bioreactor.

並列關鍵字

microalgae ； mixed microalgae ； nitrogen/phosphorus ratio ； membrane fouling ； ceramic membrane

參考文獻

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