污水厂二级出水中难凝聚有机物的臭氧化特性

以城市污水处理厂二级出水为原水,研究臭氧化处理对水中难凝聚有机物的去除效果.结果表明单独混凝对水中有机物的去除率较低,混凝过程中未被去除的有机物属于难凝聚有机物,加入臭氧进行氧化,随着臭氧投加量的增加,二级出水色度和UV254去除率逐渐增大,而DOC去除率变化较小.当臭氧投加量(以O3/DOC计)增加至1.5 mg·mg-1时,色度、UV254和DOC的去除率分别为45%、34%和20%,说明臭氧易于与不饱和结构有机物反应,而直接氧化的矿化能力较弱.为进一步明确二级出水有机物种类和含量的变化,测定了混凝和不同臭氧投加量下有机物的相对分子质量和三维荧光光谱.结果表明混凝对有机物含量的影响很小,而臭氧能够优先氧化分解难凝聚有机物中的大分子物质,明显减弱腐殖质类物质的荧光峰强度,但不改变荧光峰位置.同时采用光电子能谱分析有机物结构的变化规律,结果表明混凝能够去除含羧基类官能团有机物,而臭氧则易于与含苯环类难凝聚有机物反应,随着臭氧投加量的增大,脂肪类饱和有机物含量有所升高.

Ozonation Characteristics of Low Coagulability Organic Matter from the Secondary Effluent of WWTPs

The aim of this study was to investigate the effectiveness of ozonation on the removal of organic matter with low coagulability from municipal secondary effluent. The results revealed that the removal efficiency of coagulation generally remained quite low. The residual organic matter belonged to low coagulability organic matter. The presence of the ozone increased the removal efficiency of color and UV₂₅₄ gradually for low coagulability organic matter, whereas DOC had no noticeable change; the efficiencies were 45%, 34%, and 20%, respectively, at a dosage (denoted as O₃/DOC) of 1.5 mg·mg^-1. It could be concluded that ozone easily reacted with unsaturated organic matter, and the mineralization of organic matter was less effective. In order to further define the variation in organic matter of the secondary effluent, the differences between the relative molecular weight distribution and fluorescence characteristics of coagulation and ozonation with different zone dosages were monitored in this study. The findings showed that coagulation had little effect on organic content. Nonetheless, ozone might have preferentially reacted with high-molecular-weight substances of organic matter with low coagulability and reduced the fluorescence intensity in the humic-like regions significantly. The shift of fluorescence peak was not changed by ozonation. In addition, via X-ray photoelectron spectroscopy (XPS) analysis, it was identified that coagulation could remove carboxylic organic matter. On the other hand, with the increasing ozone dosage (from 0 to 1.5 mg·mg^-1), ozone could preferentially react with low coagulability organic matter with aromatic structure, thus the amount of aliphatics increased gradually.