污水生物处理过程中溶解性有机氮分布和转化特征

Distribution and transformation characteristics of dissolved organic nitrogen in wastewater biological treatment process

为研究太湖流域城镇污水处理厂溶解性有机氮(dissolved organic nitrogen,DON)的污染现状及迁移转化规律,选取数座典型污水处理厂(wastewater treatment plants,WWTPs),通过长期水质监测研究出水DON污染水平及其季节变化,并运用多种方法阐明WX-A工艺沿程中DON的分子质量(molecular weight,MW)、亲疏水及荧光光谱变化等特性.结果表明:出水中97.66%~99.22%的含氮化合物为溶解态,DON/溶解性总氮(soluble total nitrogen,STN)为21.88%~26.15%,DON平均质量浓度范围为2.7~3.4 mg/L.厌氧段DON质量浓度出现明显降低趋势,生物膜法(moving bed biofilm reactor,MBBR)工艺段中,分子质量高于30 ku的DON被降解为低于3 ku的DON.出水中低于1 ku的DON比例约为42%,79%的出水DON为亲水性化合物.荧光谱图显示进水DON以酪氨酸类蛋白质和溶解性微生物代谢产物为主要组分,总荧光响应百分比(P i,n,%)达76.5%,但是进出水中区域Ⅱ(酪氨酸类蛋白质)和区域Ⅳ(溶解性微生物代谢产物)的荧光区域标准体积去除率分别为77.0%和23.7%,进一步表明活性污泥工艺无法实现低分子有机氮的高效去除.

To investigate the pollution status and migration and transformation rules of dissolved organic nitrogen(DON)in urban wastewater treatment plants(WWTPs)of Taihu Basin,several typical WWTPs were selected.Through long-term wastewater quality monitoring of the DON pollution level and seasonal variation,DON molecular weight,hydrophobicity,and fluorescence spectrum characteristics were studied by multiple methods.Experimental results showed that 97.66%-99.22%of effluent nitrogen were dissolved nitrogen compound,and the proportion of DON to soluble total nitrogen(STN)was 21.88%-26.15%,and the average DON concentration ranged from 2.7 to 3.4 mg/L.A significant decrease of DON was observed in anaerobic tank,and the DON with molecular weight higher than 30 ku was degraded to lower than 3 ku after moving bed biofilm reactor(MBBR)process.In the study,42%of the DON with molecular weight lower than 1 ku was measured within effluent,and 79%of the effluent DON were hydrophilic compounds.Fluorescence spectrum showed that tyrosine-like proteins and soluble microbial metabolites were the main influent DON components,and the total fluorescence response percentage(P i,n,%)reached 76.5%.However,the removal rates of tyrosine protein and soluble microbial metabolite were 77.0%and 23.7%respectively,which further indicated that the activated sludge process was not suitable to the effective removal of low molecular weight organic nitrogen.