臭氧與氯對水中微生物殺菌效率之評估

Abstract

飲用水與民眾健康息息相關，為了防止水媒疾病（water-born diseases）的傳播，消毒已成為飲用水處理中不可或缺的過程。加氯消毒因成本低、操作簡單、效果好，且是唯一有能力提供餘量的方法，因此為目前最普遍使用的消毒方式。臭氧因具有超強氧化力、反應速率快，且無副產物等優點，成為目前最具潛力的消毒方法之一。本研究的主旨便是評估臭氧與氯對水中微生物之殺菌效率。 本研究包括二部分：第一部分以培養方法評估水中臭氧與加氯消毒之劑量效應關係，探討各項參數（菌種、菌濃度、臭氧濃度、暴露時間）對殺菌效率之影響，並討論美國環境保護署水中臭氧與加氯消毒標準下，不同微生物的殺菌效率；第二部分為應用非培養方法（Non-culture Method）－螢光染色法搭配流式細胞儀（Flow Cytometry, FCM）評估水中臭氧與加氯消毒效率，且同時與傳統培養方法（Culture Method）比較。 培養方法結果顯示，對於臭氧與氯的抵抗力：枯草桿菌內孢子＞青黴菌孢子＞酵母菌＞大腸桿菌；對臭氧殺菌效率之影響：臭氧濃度＞菌種差異＞暴露時間＞菌濃度；對加氯消毒效率之影響：菌種差異＞餘氯濃度＞暴露時間＞菌濃度；在美國環境保護署水中臭氧與加氯消毒標準下，對於細胞型態微生物來說，足以達到良好的殺菌效果；但對於孢子型態微生物的殺菌效率卻不及99.9％。 非培養方法結果顯示，比起傳統培養方法，以螢光染劑搭配流式細胞儀評估水中臭氧與加氯消毒效率時，可在殺菌機制與過程上提供更多的資訊，例如微生物在殺菌過程中總濃度的變化、細胞膜的受損程度或變化等，為一快速又十分有用的評估方法。此外，研究結果顯示消毒過程中，當微生物失去在培養基上的生長能力時，仍能保有一定程度的活性，因此使用傳統培養方法確實會高估殺菌效率。

For preventing the spread of water-born diseases, disinfection has already become an essential part in drinking water treatment plant. Chlorine disinfection is the most popular disinfection method because of its cheap, simple, and efficient properties. On the other hand, Ozone is a very strong and fast-reacting oxidant without byproduct, as considered as a potential disinfection method. Our current study was to evaluate the inactivation efficiency of ozone and chlorine on microorganisms in water. By culture and non-culture（flow cytometry with fluorochrome, FCM/FL）methods, the influences of microorganism species, microorganism concentrations, ozone and chlorine concentrations, and exposure time on inactivation efficiencies of ozone and chlorine were evaluated. By culture method, it was found that the resistant abilities of tested microorganisms to both ozone and chlorine were as follows：endospore of Bacillus subtilis＞Penicillium citrinum spores＞Candida famata＞Escherichia coli. For ozone disinfection, the importance of the evaluated parameters were ozone concentration > species > exposure time > microbial concentrations. For chlorine disinfection, the importance was species, chlorine concentration, exposure time and microbial concentrations. Under the USEPA standards, the suggested doses could not provide efficient disinfection for spore type microorganisms. It is known that microorganism could be still viable when they lose their ability to grow on culture medium. In comparison with non-culture method, it was clearly demonstrated that inactivation efficiencies of ozone and chlorine on microorganisms were overestimated by culture method.