二級處理廢水之出流水有機物對臭氧處理程序去除新興污染物之影響

Abstract

廢水中新興污染物的去除對於環境健康已經成為重要的議題。臭氧處理程序是一個可行的技術，但廢水的特性會影響臭氧的處理效率，而這部分的影響尚未被闡明。二級放流水含有出流有機物(effluent organic matter, EfOM)，這些有機物質可以直接與臭氧反應，亦可以在臭氧降解過程中的氫氧自由基鏈狀反應裡扮演起始劑(initiator)、促進劑(promoter)以及抑制劑(inhibitor)的角色。這四種不同的反應機制會影響臭氧的降解、氫氧自由基的形成及消耗以及新興污染物的去除。本研究的目的為：(1)利用氫氧自由基的瞬時穩定態模式、Rct概念以及臭氧的擬一階速率模式測定出流水有機物於臭氧直接反應、起始反應(initiation)、促進反應(promotion)以及抑制反應(inhibition)的速率常數。(2)測定pH值及溫度對出流水有機物的四個速率常數之影響。(3)測定及模擬出流水有機物對於選定的新興污染物去除之影響。本研究所使用的二級放流水取自迪化及內湖污水處理場，並測定其出流水有機物之速率常數。結果顯示直接反應及起始反應(都源自出流水有機物與臭氧之反應)的速率常數會隨著pH值的升高而增加，然而在促進反應及抑制反應(都源自出流水有機物與氫氧自由基反應)的速率常數則沒有顯著的變化。在溫度影響方面，所有的速率常數皆隨著溫度的升高而增加。在稀釋的內湖二級處理出流水中, ibuprofen、acetylsulfamethoxazole以及metoprolol的去除皆可利用測定的出流水有機物速率常數加以模擬而得到良好的去除效率預測。

Removal of emerging contaminants such as pharmaceutical compounds in wastewater treatment is essential to ensure the ecological health of the receiving water bodies. Ozonation is a promising technology to achieve this purpose but important wastewater characteristics affecting the optimal removal efficiency has not been fully elucidated. The secondary effluent contains effluent organic matter (EfOM), which can react directly with ozone as well as react as the initiator, promoter and inhibitor in the hydroxyl radical (·OH) chain reactions resulting from ozone decomposition. These different reaction modes of EfOM collectively determine the ozone and ·OH exposures and the degradation of pharmaceutical compounds. The objectives of this study were (1) to determine the rate constants of EfOM in terms of direct ozone reaction, initiation, promotion and inhibition reactions using a new experimental procedures that integrate the transient steady-state ·OH model, the Rct concept and the pseudo first-order ozone decomposition model, (2) to investigate the influences of pH value and temperature on these rate constants, and (3) to determine and model the effects of EfOM on the removal of selected model pharmaceutical compounds. The rate constants of EfOM in secondary effluents collected from Neihu and Dihua wastewater treatment plants were determined in this study. It was found that the rate constants of direct reaction and initiation (both resulting from the reaction with ozone) generally increase with the increasing pH value while the rate constants of promotion and inhibition (both resulting from the reaction with ·OH) do not vary significantly. All rate constants increase with the increasing temperature. The removal of ibuprofen, acetylsulfamethoxazole and metoprolol in diluted Neihu secondary effluent using ozonation can be fairly-well modeled by using the determined rate constants of EfOM.