| 臭氧预氧化强化混凝对二级出水中DON作用机制探讨 |
| 摘要点击 1698 全文点击 592 投稿时间：2017-05-15 修订日期：2017-07-20 |
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| 中文关键词 二级出水 氯化消毒副产物 溶解性有机氮 臭氧预氧化 强化混凝 三维荧光光谱 |
| 英文关键词 secondary effluent disinfection by-products(DBPs) dissolved organic nitrogen(DON) pre-ozonation enhanced coagulation 3DEEM |
| 作者 | 单位 | E-mail | | 刘冰 | 信阳师范学院地理科学学院, 水土环境污染协同防治重点实验室, 信阳 464000
中国科学院城市环境研究所, 厦门 361021 | liubing_982002@163.com | | 郑煜铭 | 中国科学院城市环境研究所, 厦门 361021 | | | 王大祥 | 信阳水文水资源勘测局, 信阳 464000 | | | 李清飞 | 信阳师范学院地理科学学院, 水土环境污染协同防治重点实验室, 信阳 464000 | | | 赵承美 | 信阳师范学院地理科学学院, 水土环境污染协同防治重点实验室, 信阳 464000 | | | 余国忠 | 信阳师范学院地理科学学院, 水土环境污染协同防治重点实验室, 信阳 464000 | | | 古励 | 重庆大学城市建设与环境工程学院, 重庆 400044 | |
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| 中文摘要 |
| 城市污水厂出水越来越多被中水回用或排入河流间接地作为下游水源水，其中所包含的溶解性有机氮（dissolved organic nitrogen，DON）被认为是含氮消毒副产物（nitrogenous disinfection by-products，N-DBPs）的前体物，受到国内外学者的高度关注.为探讨臭氧预氧化强化混凝对二级出水中DON作用机制，不仅分析了不同相对分子量和亲疏水性DON组分变化，而且还考察氯化消毒副产物（disinfection by-products，DBPs）生成潜势；最后结合三维荧光（3DEEM）分析技术，对强化混凝前后DON组成、化学结构特征进行研究.结果表明，臭氧预氧化可以显著提高混凝对DON、DOC和UV254去除效果，其中DON最大去除率提高到3.7倍；pH对臭氧预氧化强化混凝有着重要的影响.随着pH值的增加，DON、DOC和UV254去除率呈下降趋势；Ca2+是臭氧预氧化提高混凝效果的关键因素.随着臭氧浓度增加到8 mg·L-1时，ζ电位由-33 mV上升到-8 mV，Ca2+浓度则从116 mg·L-1下降到89 mg·L-1.ζ电位和溶解性Ca2+浓度的线性关系（R2=0.97）可以表明，只有当Ca2+浓度较高时臭氧预氧化才能显著地提高混凝效果；臭氧预氧化强化混凝处理后，相对大分子量（> 20×103）和疏水性DON所占比例显著下降，相对小分子量（< 6×103）和亲水性DON所占比例增加.DBPs的生成潜势总和明显降低，由120.1 μg·L-1下降到65.2 μg·L-1；最后，经3DEEM光谱分析可知，在臭氧预氧化强化混凝过程中DON浓度和DBPs生成潜势变化与3DEEM光谱中3个主要荧光峰有关，分别代表色氨酸类蛋白质、芳香族类蛋白质和富里酸类物质. |
| 英文摘要 |
| Municipal wastewater effluent is increasingly used as reclaimed water and source water for downstream areas. Scholars are beginning to study the potential of dissolved organic nitrogen (DON) as a precursor to the formation of nitrogen disinfection by-products (DBP). In order to explore the mechanism of pre-ozonation coupled with enhanced coagulation on DON in the secondary effluent, the distributions of molecular weight and hydrophobicity/hydrophilicity of DON were analyzed. Disinfection by-product formation potential from chlorination was also investigated. Lastly, the composition and chemical structure of DON before and after coagulation were studied in combination with 3DEEM. Our results showed that pre-ozonation followed by coagulation with PACl significantly enhanced the removal of DON and mitigated DBP formation potentials. The following conclusions can be drawn from this study:① The tested effluent was very hard as indicated by total hardness and high calcium concentrations, and the pH had an important effect on pre-ozonation enhanced coagulation. As pH was decreased, the rates of DON, DOC and UV254 removal increased. At pH 6.2, the rate of DON removal was maximal, and a 3.7 fold increase in removal-rate was achieved. ② Calcium played a critical role in pre-ozonation enhanced coagulation. Zeta potentials and calcium concentrations were substantially affected at higher ozone doses. At ozone dosage of 8 mg·L-1, Zeta potentials increased from -33 to -8 mV, and calcium concentrations decreased from 116 to 89 mg·L-1. The ratio of calcium hardness to DOC was relatively high in this study, approaching 24 mg·mg-1 (CaCO3/DOC). Thus, pre-ozonation promoted the removal of DON by coagulation. ③ Large molecular weight and hydrophobic DON were easier to remove by coagulation. Ozonation modified the DON characteristics to become more hydrophilic and smaller in molecular weight. Coagulation reduced overall DBP formation potentials to less than 20%. Pre-ozonation enhanced coagulation decreased overall DBP formation potentials by more than 45%. ④ Finally, the 3DEEM spectra indicated that the formation potentials and DON characteristics, due to disinfection, were related to three main peaks, which corresponded to tryptophan-based proteins, aromatic proteins, and fulvic acids. |
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