溫度及鈣離子對生物膜生成效應與水中消毒副產物前質貢獻之研究

Effects of Temperature and Calcium Ions on Biofilm Formation and its Contribution to DBP Precursors in Water

洪郁欣(Yu-Hsin Hung)

指導教授 ： 王根樹

國立臺灣大學/公共衛生學院/環境與職業健康科學研究所/碩士(2021年)

https://doi.org/10.6342/NTU202103563

摘要

為了確保飲用水水質安全，在水處理的過程中加氯消毒是必要的步驟。然而在這同時，氯也會和水中的天然有機質、水中的微生物以及所生成的生物膜反應進而生成消毒副產物。這些消毒副產物會對人體健康造成負面效應。
過去的研究顯示水溫以及水中的硬度，其中尤其是鈣離子，對於細菌的生長以及生物膜的生成有著顯著的影響。本研究利用實驗室模擬方式，針對水溫及硬度的變化探討其是否會影響細菌和生物膜增生，進而增加水中消毒副產物生成潛能。在研究中，戀臭假單胞菌 (Pseudomonas putida, ATCC 47054) 被用於模擬水中微生物的活動，並培養於未額外添加鈣離子，以及每公升水中含有40毫克、120毫克以及200毫克鈣離子濃度的培養液中，以評估鈣離子對生物膜生成的影響。除探討鈣離子之效應外，樣本同時也分別放置於15°C、25°C以及30°C的環境下培養30天，以探討溫度變化對生物膜生成的影響。在培養完畢後，針對各水樣分析其微生物濃度、相關水質參數以及消毒副產物生成潛能。
根據重複模擬結果顯示，相較於未添加鈣離子的樣本，鈣離子濃度的提升會促進戀臭假單胞菌細菌及生物膜的增生。在考量到溫度與鈣離子的綜合效應後，結果顯示在25°C下，以每公升水中含40毫克的鈣離子濃度進行培養後，戀臭假單胞菌的細菌及生物膜濃度達到最高。同時，隨著微生物的增長，其對於水中有機質的貢獻也隨之上升，例如：水中腐植質及蛋白質含量。消毒副產物生成潛能的實驗結果顯示，在研究中所測量的消毒副產物，相較於未添加鈣離子之樣本，其濃度皆因鈣離子濃度增加而上升，其中又以鹵乙酸（HAA）生成為最大宗。同時，依據溫度對於微生物生長之影響，在鹵乙晴（HAN）的濃度變化上亦可觀察到相同的趨勢。另外，為了進一步了解微生物活動所貢獻之有機質成分比例，我們同時也針對過濾後的樣本進行比較分析。結果顯示，在培養液中的有機質主要為溶解態，而來自生物膜的有機質，則主要被歸類於顆粒狀態。
綜合以上，本研究結果顯示水中硬度的增加以及在適當的溫度下，微生物的活動會因此上升。其後在進行加氯消毒時，會伴隨更多的消毒副產物生成。然而針對一富含生物膜的水體，在進行加氯消毒前，可以藉由過濾等前處理去除生物膜所貢獻到水體的有機質，進而有效降低消毒副產物生成潛能。

關鍵字

消毒副產物 ； 水溫 ； 鈣離子 ； 消毒副產物前質 ； 生物膜

並列摘要

Disinfection is a necessary process in water treatments to ensure the water safety. However, disinfection by-products (DBPs) may be formed from reactions between the disinfectants (e.g., chlorine) and DBP precursors, mainly comprised of natural organic matters. Ingestion of these DBPs poses health threats as they are suggested to associate with bladder cancer, colorectal cancer, adverse reproductive outcome, etc. In addition to natural organic matters, bacteria residing in water can form biofilm and contribute to additional organic substances (e.g., extracellular polymeric substance) that are also DBP precursors.
Water temperature and hardness are both critical parameters in water quality, especially under the attention of global climate change. The change of temperature and hardness of water also affects growth of bacteria and biofilm in water. Yet, only few studies are available to demonstrate the interactions among water temperature, calcium levels, bacterial activities, and DBP precursor alterations. Therefore, the objective of this study is to assess DBP formation attributed to bacteria activities by simulating environmental water conditions under different temperature and calcium levels. Pseudomonas putida (ATCC 47054), due to its inclination of formulating biofilm and ubiquity in environmental water, was chosen as the representative species to monitor the microbial growth and DBP formation potential. P. putida was incubated in water enriched with natural organic matters and different levels of calcium (40, 120, or 200 mg-Ca/L final concentration) under 15°C, 25°C, or 30°C. The incubated samples were analyzed for planktonic and biofilm P. putida concentrations, dissolved organic matters, fluorescence excitation emission matrix and disinfection by-product formation potential (DBPFP). The result revealed that, when sample was incubated with 40 mg-Ca/L under 25°C, the bacterial growth and biofilm formation was most induced, compared to the samples without calcium spiked. As the promotion of bacteria growth, more contents of proteins, which potentially contribute to DBP precursors, in the water were observed. The results of DBPFP measurements showed that elevation of calcium levels generally resulted in higher concentration of DBP precursors. Among these, HAAs were generated predominantly and the yields of HANs also elevated with increase of the incubation temperature.
In addition, filtration was applied for the samples to differentiate whether the DBP precursors were under dissolved state or particles, by which may imply the efficacy of coagulation, flocculation and filtration processes to remove DBP precursors. The results showed that the organic matters from biofilm were mainly composed of particulate matters, while those suspended in the incubating solution were principally attributed to dissolved organic matters. We suggest that water utilities with uncontrolled biofilms should apply filtration or even more efficient treatment alternatives to remove particulate DBP precursors before chlorination; and microbe-related DBP precursors should be more emphasized as a side effect in performing disinfection.

並列關鍵字

disinfection by-product ； temperature ； calcium ； disinfection by-product precursor ； biofilm

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