微藻胞外有機物質的特性及對陶瓷膜積垢之影響

Characterization of microalgae extracellular organic matter and its effect on ceramic membrane fouling

吳泓宇(Hung-Yu Wu)

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(2021年)

https://doi.org/10.6342/NTU202101131

摘要

以微藻去除廢水的氮磷營養鹽是相當新穎的技術，但如何更有效率的使微藻去除氮磷仍是許多研究所努力的目標，微藻膜生物反應器是其中一種可以讓微藻水質處理更有效率的方式之一，但微藻造成的薄膜積垢問題仍有待解決，若能了解微藻的特性，將有益於微藻相關應用。本研究挑選兩種常見之微藻：四尾柵藻及小球藻，以人工合成的二級出流水進行批次實驗，以期能了解懸浮微藻/固定化微藻之比較及微藻的生長特性。結果分為三部分，不同pH值、不同藻種之影響及陶瓷膜過濾進行探討。
pH值影響方面，研究發現懸浮微藻在起始pH=7.7環境下培養，遲滯期較不明顯，而在起始pH=8.5條件下培養則較明顯。固定化技術可以提升微藻的磷酸鹽去除效率，起始pH=8.5時培養第三天，固定化四尾柵藻就有100%的PO43--P去除率，但固定化技術也會造成額外的溶解性有機碳(DOC)上升，在起始pH=8.5時固定化的小球藻培養至第15天時，甚至觀察到水中的DOC濃度=95.4 ± 21.2 mg/L。NO3--N的去除方面則在不同pH值表現略有不同，在起始pH=8.5時，固定化技術的微藻去除效果較佳，而在起始pH=7.7時，則是懸浮態的微藻較佳，總體來說，培養至第9天可以去除大部分的硝酸鹽氮，培養至第12天則硝酸鹽氮幾乎完全去除。
藻種比較的部分，四尾柵藻相比小球藻具有更快的生長速度、更低的DOC產生量，多醣及蛋白質產生量亦較少，根據螢光激發-發射矩陣(EEM)分析，四尾柵藻產生的有機物質更傾向於天然有機物，而小球藻則更傾向於微生物導向的有機物。
陶瓷膜過濾的結果顯示，海藻酸鈉並不會對陶瓷膜造成顯著的積垢問題，且固定化技術使不同微藻分泌的胞外有機物質特性差異減少，其性質更接近於海藻酸，使用齒輪泵提供掃流速度，有助於薄膜積垢的抑制。
關鍵字：四尾柵藻、小球藻、微藻固定化、胞外有機物質、陶瓷膜、薄膜積垢

關鍵字

四尾柵藻 ； 小球藻 ； 微藻固定化 ； 胞外有機物質 ； 陶瓷膜 ； 薄膜積垢

並列摘要

The application of microalgae to remove nitrogen and phosphorus nutrients in wastewater is a novel technology, but how to apply microalgae to remove nitrogen and phosphorus more efficiently is still the goal of many researches. Algae-based membrane bioreactor is one of the ways to make microalgae water treatment more efficient, but membrane fouling caused by microalgae is still a big challenge. A better understanding of the properties of microalgae will be beneficial to microalgae and related applications. In this study, two common microalgae were selected: Scenedesmus quadricauda and Chlorella vulgaris. The batch experiments were conducted with artificially prepared secondary effluent water. In order to understand the growth characteristics of these two microalgae and the comparison of suspended/immobilized microalgae. The results were divided into 3 parts, with different pH values, the influence of different algae species and ceramic membrane filtration.
In terms of the effect of pH value, this study found that when the suspended microalgae was cultured at the initial pH = 7.7, the lag phase was less obvious, while the culture at the initial pH = 8.5 was more obvious. Immobilization microalgae technology can improve the phosphate removal efficiency. On the third day of cultivation at the initial pH = 8.5, the immobilized S. quadricauda has a 100% removal rate of PO43--P, but the immobilization beads will additionally increase the release of dissolved organic carbon. When the immobilized C. vulgaris.was cultured to the 15th day(at initial pH = 8.5), the DOC concentration in the water was even observed to be 95.4 ± 21.2 mg/L. The removal performance of NO3--N has slightly different at different pH values. When the initial pH = 8.5, the immobilized microalgae removal efficiency is better, and when the initial pH = 7.7, suspended microalgae is better. In general, most of the nitrate can be removed at 9th day of cultivation, and almost completely removed at 12th day.
For the comparison of microalgae species, S. quadricauda has a faster growth rate, lower DOC production, and less polysaccharide and protein production than C. vulgaris. According to fluorescence excitation-emission matrix analysis, The organic matter produced by S. quadricauda is more inclined to natural organic matter(NOM), while C. vulgaris is more inclined to microorganism-oriented organic matters(MOOMs).
The results of ceramic membrane filtration show that sodium alginate does not cause significant fouling problems on ceramic membranes, and the immobilization technology reduces the difference of extracellular organic matter characteristic secreted by different microalgae, and the properties of immobilized microalgae are closer to alginate. Using gear pumps to provide the cross flow velocity(CFV) is helpful for the mitigation of membrane fouling.

並列關鍵字

Scenedesmus quadricauda ； Chlorella vulgaris ； Microalgae immobilization ； Extracellular organic matter ； Ceramic membrane ； Membrane fouling

參考文獻

Abdel-Raouf, N., Al-Homaidan, A. A., Ibraheem, I. B. M. (2012). Microalgae and wastewater treatment. Saudi Journal of Biological Sciences, 19(3), 257-275. doi:https://doi.org/10.1016/j.sjbs.2012.04.005

Acién, F. G., Molina, E., Reis, A., Torzillo, G., Zittelli, G. C., Sepúlveda, C., Masojídek, J. (2017). Photobioreactors for the production of microalgae. In Microalgae-based biofuels and bioproducts (pp. 1-44).

Ahmad, A., Yasin, N. M., Derek, C., Lim, J. (2012). Crossflow microfiltration of microalgae biomass for biofuel production. Desalination, 302, 65-70.

Almomani, F., Al Ketife, A., Judd, S., Shurair, M., Bhosale, R. R., Znad, H., Tawalbeh, M. (2019). Impact of CO2 concentration and ambient conditions on microalgal growth and nutrient removal from wastewater by a photobioreactor. Science of The Total Environment, 662, 662-671. doi:https://doi.org/10.1016/j.scitotenv.2019.01.144

Almomani, F., Judd, S., Bhosale, R. R., Shurair, M., Aljaml, K., Khraisheh, M. (2019). Intergraded wastewater treatment and carbon bio-fixation from flue gases using Spirulina platensis and mixed algal culture. Process Safety and Environmental Protection, 124, 240-250.