溫度及微生物濃度對消毒副產物生成效應之研究

Effects of Temperature and Microorganism Densities on Disinfection By-product Formation

曾靖軒(Jing-Syuan Zeng)

指導教授 ： 王根樹

國立臺灣大學/公共衛生學院/環境衛生研究所/碩士(2019年)

https://doi.org/10.6342/NTU201902588

摘要

人為活動所引起的全球氣候變遷已經被討論許久，而氣候變遷所造成的影響也使我們的生活環境與生態系統產生了諸多改變。其中全球暖化是最早被觀察到的氣候變遷效應，在各地都觀察到類似的變化，也引起了許多後續的問題，像是地表溫度上升造成冰山融化，而進一步引起海平面上升。地表溫度上升也使得水體溫度上升，進而引起河川生態系改變、優養化或是水中溶氧下降等等問題。已有研究觀察到環境溫度上升與水中溶解性有機物碳(Dissolved organic matter, DOC)增加有關連性，而這些DOC又被認為是消毒副產物(Disinfection by-products, DBPs)重要的前驅物質之一。因此這些氣候變遷結果對於水資源的衝擊以及飲用水水質安全的潛在影響也是非常值得關注的議題之一。
而從先前的研究已得知溫度變化會造成原水水中DOC與DBP前質的改變，但只在原水含有微生物的水樣中可觀察到較明顯的變化。因此本研究之目的係以實驗室研究模擬溫度變化對微生物及消毒副產物生成效應的影響。整體研究架構以實驗室配置好的原水樣品，一部份先經過濾，而另一部份則未經過濾分別進行試驗。而過濾與未過濾兩組水樣再分別細分為添加菌液與不添加菌液兩組，以比較在含有不同菌量下的差別。經過不同前處理後的水樣再分別在15、25和 35°C環境下進行七天的培養，並在第0、1、4、7天進行採樣，分析基本水質參數與進行消毒副產物生成潛能(DBPFP)的測試。此外，也利用基隆河水作為原水以驗證先前實驗室模擬水樣所得到的結果。
實驗室模擬結果顯示，在25度培養且未將微生物濾除的水樣，在添加菌液的情況下，可以觀察到三鹵甲烷(THM)生成潛能測試(THMFP)結果，三鹵甲烷前質濃度降低了一半：但在未添加菌液的樣品則只減少了7.4%。而在未過濾的水樣中，雖然無額外添加菌液的水樣三鹵甲烷前質濃度也下降了13.1%，但在有添加菌液的情況下THM前質濃度下降幅度則高達61.9%。由培養結果可以推測在微生物活動力高時，會消耗較多的DOC，進而降低THMFP。此外，隨著溫度升高，DOC與DBP濃度的變化也變得更加明顯。而在微生物含量較多或者是溫度較高的情況下，甚至可以發現DBP濃度先降後升的情況，推測此現象與細菌在不同生長階段有著不同的代謝反應有關。但實際以基隆河水做實驗時在消毒物副產物生成潛能部分卻有不同的趨勢，可能是因為河水中的基質較複雜所導致。

關鍵字

氣候變遷 ； 溫度 ； 微生物 ； 消毒副產物 ； 水質 ； 實驗室模擬

並列摘要

The potential impacts of climate change have been observed in different aspects and have been of concern for decades. Intergovernmental Panel on Climate Change (IPCC) published its Fifth Assessment Report on Climate Change (AR5) in 2013. Among the different impacts mentioned in the report, surface temperature rising is the one which is the earliest observed and also the most obvious and ubiquitous result observed around the world.
Disinfection is a crucial step in water treatment process. However, disinfection may results in the formation of hazardous disinfection by-products (DBPs). Results of the previous study showed that rising temperature is correlated to the change of DOC and DBPFPs of unfiltered raw water in which microorganism was presented; however the correlation was not apparent when raw water was filtered prior to laboratory tests. The results of previous study also showed that, when the raw water was incubated at 35°C prior to chlorination, the THMFP decreases when it was not filtered. It was therefore reasonable to suspect that microorganisms in water played a role in consuming DOC, which is the precursor of different categories of DBPs, and thus decrease the corresponding THMFPs.
The objective of this study is to investigate the role of microbial activities on the relationship between temperature change and DBP formation. Laboratory simulation experiments were conducted with the water collected from Liugongjun Pond in National Taiwan University campus. After different pretreatments of filtration and spiking of bacteria concentrates, there were four kinds of raw water samples which contain different amounts of microorganisms. These samples were then incubated for 7 days under 15, 25 and 35°C, respectively. Samples were taken on the 0th, 1th, 4th and 7th day for analysis of different water quality parameters and DBPFPs were measured. For comparison, the water samples were also taken from Keelung River to verify the results obtained in laboratory simulations.
When the water samples were filtered prior to incubation and spiked with bacteria concentrate, the THMFP decreased by almost 50%; but only reduced by 7.4% when water sample was not spiked with bacteria concentrate. A similar result can also be observed in the unfiltered water samples; the results of THMFPs in non-spiking samples showed a 13.1% downward shift; however, there was a 61.9% downturn in water samples with spiking of bacteria concentrate. The samples added with bacteria showed a decreasing trend in DOC, THMFP and HAAFP no matter the water samples were filtrated or not, however this trend was not observed in water samples without addition of bacteria concentrate. It was thus inferred that higher microorganism activities contribute to more consumption of DOC and thus lower down the DBPFPs. As the incubation temperature increased, the change in the DBPFP of water samples became more distinct. However, the trend that DBPFP descended at the beginning stage and then rose again could also be observed in water samples added with more microorganisms. This tendency may be related to different metabolism rate of bacteria in different growth stages.

並列關鍵字

Climate change ； temperature ； microorganisms ； disinfection by-products ； water quality ； laboratory simulation

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