污水中溶解性有机氮类化合物的氯化反应特性及其消毒副产物生成潜能

Chlorination Characteristic and Disinfection By-product Formation Potential of Dissolved Organic Nitrogen Compounds in Municipal Wastewater

为探讨城市污水厂二级出水中溶解性有机氮(dissolved organic nitrogen,DON)类化合物的氯化消毒副产物生成潜能及其化学结构变化,首先测定DON、溶解性有机炭(dissolved organic carbon,DOC)、NH4+-N和UV254等指标以及与氯反应前后DON相对分子质量分布,并采用气相色谱测定消毒副产物(disinfection by-products,DBPs)质量浓度,最后应用红外光谱和三维荧光光谱对与氯反应前后的水样进行表征.结果表明,城市污水厂二级出水中DON、DOC、UV254和NH4+-N分别为2.47mg·L-1、14.45 mg·L-1、15.88 m-1和5.42 mg·L-1,DOC与DON比值[m(DOC)/m(DON)]为5.85 mg·mg-1,SUVA为1.09L·(m·mg)-1;与氯反应后,小相对分子质量(Mr<6 000)DON所占比例由70%提高到78%,大相对分子质量(Mr>20 000)DON所占比例从21%降到14%,占较小比例的中等相对分子质量(Mr6 000～20 000)DON基本不变;氯化消毒副产物生成潜能中一氯一溴乙腈(BCAN)质量浓度最大为6.887μg·L-1,三氯乙腈(TCAN)质量浓度最小仅为0.217μg·L-1;与氯反应前,水样的红外光谱出现6个主要吸收区域分别在3 500～3 400、2 260～2 200、1 700～1 640、1 500～1 450、1 150～1 100和850～800 cm-1;与氯反应后水样的红外光谱在1 380～1 350 cm-1和600～550 cm-1增加两个吸收区域;三维荧光光谱证实,与氯反应前后水样中变化与3个主要特征峰有关,分别代表色氨酸类蛋白质、芳香族类蛋白质和富里酸类等物质.

In order to explore the chlorinated disinfection by-product formation potential and chemical structure of dissolved organic nitrogen compounds in municipal wastewater,the water quality parameters,such as DON,DOC,NH＋4-N and UV254 etc,were determined in the secondary effluent and the molecular weight distribution of the DON was investigated before and after the reaction with chlorine.DBPs were determined by gas chromatography,and the changes of DON were characterized using fourier transform infrared spectroscopy and three-dimensional fluorescence spectroscopy before and after the reaction with chlorine.The results showed that DON,DOC,NH＋4-N and UV254 were 2.47 mg·L-1,14.45 mg·L-1,5.42 mg·L-1 and 15.88 m-1,and m（DOC）/m（DON） and SUVA were 5.85 mg·mg-1 and 1.09 L·（m·mg）-1 in the secondary effluent.After the reaction with chlorine,the proportion of small molecular weight（Mr6 000） DON increased from 78% to 70%,and the proportion of large molecular weight（Mr20 000） DON decreased from 21% to 14%.The medium molecular weight（Mr 6 000-20 000） DON accounted for a small proportion and was unchanged.Among the DBPs,the concentration of bromochloroacetonitrile was the highest,which was 6.887 μg·L-1,and the concentration of trichloroacetonitrile was the lowest,which was only 0.217 μg·L-1.In FTIR spectrum,the dominating bands were at 3 500-3 400,2 260-2 200,1 700-1 640,1 500-1 450,1 150-1 100 and 850-800 cm-1 respectively before the reaction,and the 1 380-1 350 cm-1 and 600-550 cm-1 bands were the dominating bands in addition to the original absorbing regions after the reaction.3DEEM revealed that the variation of DON depends intimately on tryptophan protein-like substances,aromatic protein-like substances and fulvic acid-like substances.