活性汙泥對水中消毒副產物前質及其生成特性之影響

Abstract

為了避免水中病原菌的孳生，進而影響到人以及環境生態系統的健康，在水處理流程中加入消毒劑是必要的流程。但是消毒過程所衍生消毒副產物的生成會對人類造成健康上的風險，包括癌症或是生殖方面的疾病，因而近幾年來水中消毒副產物的課題越來越受到大家的重視。最常見的水處理消毒劑包括氯及氯氨，這兩種消毒劑所產生消毒副產物的特性及種類亦有所不同。本研究的目的即在比較在不同的汙水消毒情況下，消毒副產物生成的差異。 本研究進行主要以實驗室模擬為主。汙泥以及汙水樣本由台北內湖汙水廠取得，所使用的消毒劑為次氯酸鈉及一氯氨，這兩種消毒劑也被使用於消毒副產物生成潛能試驗。批次氧化模擬實驗皆持續二十四小時，並於不同反應時間採樣，以觀察後續有機物質和消毒副產物濃度的變化。 研究結果顯示，消毒副產物濃度會隨著溶解性有機碳濃度(NPDOC)變化而有所不同。若是以次氯酸鈉消毒汙泥，則消毒副產物濃度會隨溶解性有機碳濃度之上升而上升，但相同的現象卻無法從汙水樣本中觀察到。在pH值較高的環境之下反應，THMs的濃度會增加，但對於HAAs、HANs和HKs而言，則會產生相反的趨勢。在水消毒處理過程中，若水體裡有溴離子的存在，會造成含溴消毒副產物物種濃度的增加。氯氨的氧化能力較低，實驗結果顯示以氯氨取代氯作為消毒劑時，可以減少THMs和HAAs的生成。 不論是使用哪一種消毒劑(次氯酸鈉或是一氯氨)，隨著接觸時間增加，在活性汙泥樣本部分，NPDOC濃度也會隨著反應時間而增加，但在汙水樣本中，卻未觀察到此種情形，活性汙泥樣本NPDOC濃度上升可能是來自汙泥細胞被氧化而釋出小分子有機物而導致。

Water disinfection has been widely applied to prevent the spreading of waterborne diseases. However, the formation of disinfection by-products (DBPs) has caused the great attention due to the potential DBPs-related health risks, e.g., cancer and reproductive defects, in the past decades. The most commonly used disinfectants are chlorine and chloramines, which have been shown to form different types of DBPs during the treatments. The objective of this study is to compare the differences in DBPs formation characteristics from disinfected sludge and wastewater effluents between different wastewater treatment conditions. For laboratory simulations, activated sludge and domestic sewage were sampled from Neihu Wastewater Treatment Plant in Taipei. Chlorine and chloramines were used as the disinfectants and oxidants for disinfection byproducts formation potential (DBPFP) tests. The chlorination and chloramination time were lasted for 24 hours, and samples were taken at designated intervals during the experiments to assess the changes on non-pergeable dissolved organic carbon (NPDOC) and DBPFPs of disinfected samples. The results showed that the DBPs formations were related to the change of NPDOC concentrations after treatments. For solutions with higher pH, the concentration of trihalomethanes (THMs) was increased; however, the formation of haloacetic acids (HAAs), haloacetonitriles (HANs), and haloketones (HKs) were decreased. The presence of bromide ion leads to the formation of brominated DBPs during water disinfection. AS expected, disinfection with chloramine reduces the THMs and HAAs formation. For both chlorine and chloramines, a longer contact time with the disinfectants result in higher NPDOC and DBPs concentrations from water samples containing activated sludge. However, no apparent changes were observed after treatments for NPDOC concentrations for domestic sewage without sludge. This difference may be due to the lysis of sludge to form organic molecules with smaller particle sizes.