LIUBing,CHENYan-min,LUXin,et al.Coagulation Mechanism of Dissolved Organic Nitrogen Based on 3DEEM-FRI[J].China Water & Wastewater,2025,41(1):85-92.
基于3DEEM-FRI的溶解性有机氮混凝机制研究
- Title:
- Coagulation Mechanism of Dissolved Organic Nitrogen Based on 3DEEM-FRI
- Keywords:
- effluent from the secondary treatment process; dissolved organic nitrogen; coagulation; excitation-emission matrix spectroscopy; fluorescence regional integration
- 摘要:
- 考察了硫酸铝、氯化羟铝和氯化铁对溶解性有机氮（DON）的去除效果，分析DON分级组分和极性之间的关系，并利用三维荧光光谱（3DEEM）和荧光区域积分法（FRI）分析DON组分和转化特征。结果表明，硫酸铝（27 mg/L）、氯化羟铝（40 mg/L）和氯化铁（70 mg/L）对DON的平均去除率分别为25.7%、45.3%和48.6%。当阳离子型聚丙烯酰胺投加量为0~4 mg/L时，铝盐对DON的去除率呈先增加后降低的趋势，氯化铁对DON的去除率逐渐下降。当pH为4~10时，硫酸铝和氯化铁对DON的去除率变化幅度较大（分别为17.6%和27.1%），氯化羟铝对DON的去除率变化幅度最小（≤3.2%）。经砂滤处理后，DON混凝去除率均有一定增加。氯化羟铝和氯化铁对DON的去除量与DON初始浓度具有一定的相关性（R2分别为0.64和0.57）。氯化铁对溶解性有机碳（DOC）和正磷酸盐的去除率最高，分别约为42%和96%。采用氯化羟铝和氯化铁进行混凝可将浊度降低到0.1 NTU以下，经硫酸铝混凝后浊度为（0.8±0.3） NTU。水样中<0.45 μm的DON平均浓度为（1.88±0.12） mg/L，<3 ku的DON平均浓度为（0.89±0.09） mg/L，小分子质量DON（<3 ku）约占总DON的47.3%。<0.45 μm、<0.1 μm、<10 ku和<3 ku水样中区域Ⅰ和区域Ⅱ的FRI分别占28%和30%，区域Ⅳ和区域Ⅴ的FRI所占比例均为12%。经过混凝后，0.1~0.45 μm和10 ku~0.1 μm水样中DON去除率均大于80%，3~10 ku和<3 ku水样中DON去除率均低于20%；相对于亲水性DON，疏水性DON去除率更高；<0.45 μm、<0.1 μm、<10 ku和<3 ku水样中区域Ⅰ和区域Ⅱ的FRI去除率均小于15%，表明二级出水中酪氨酸类和色氨酸类有机物是强化混凝、提高DON去除率的关键组分。
- Abstract:
- The removal characteristics of dissolved organic nitrogen (DON) by aluminum sulfate, aluminum chlorohydrate, and ferric chloride were examined. The relationship between the DON components and polarity was analyzed. The DON components and transformation characteristics were investigated through excitation-emission matrix spectroscopy (3DEEM) and fluorescence regional integration (FRI). Aluminum sulfate (27 mg/L), aluminum chlorohydrate (40 mg/L) and ferric chloride (70 mg/L) demonstrated the average removal efficiencies of 25.7%, 45.3% and 48.6% respectively for DON. When the dosage of cationic?type polyacrylamide ranged from 0 to 4 mg/L, the DON removal efficiency of aluminum salt initially increased and then decreased, while the DON removal efficiency of ferric chloride decreased gradually. When pH was within the range of 4 to 10, it significantly influenced the DON removal efficiency by aluminum sulfate and ferric chloride (with the removal efficiencies varying by 17.6% and 27.1% respectively), and the DON removal efficiency of aluminum chlorohydrate showed the smallest change (≤3.2%). After undergoing sand filtration treatment, the coagulation removal efficiency of DON rose to a certain degree. The removal of DON by aluminum chlorohydrate and ferric chloride showed certain correlation with the initial concentration of DON (R2 was 0.64 and 0.57, respectively). Ferric chloride achieved the highest removal efficiencies for dissolved organic carbon (DOC) and orthophosphate, approximately 42% and 96% respectively. The turbidity could be reduced to less than 0.1 NTU through coagulation with aluminum chloride and ferric chloride, and to (0.8±0.3) NTU by means of coagulation with aluminum sulfate. The average concentration of DON with particle size less than 0.45 μm was (1.88±0.12) mg/L, the average concentration of DON with molecular weight less than 3 ku was (0.89±0.09) mg/L, and the low molecular weight of DON (<3 ku) accounted for 47.3% of the total DON. In the water samples with DON particle size less than 0.45 μm, DON particle size less than 0.1 μm, DON molecular weight less than 10 ku and DON molecular weight less than 3 ku, the FRI of region Ⅰ and region Ⅱ accounted for 28% and 30% respectively, while that of region Ⅳ and region Ⅴ accounted for 12%. After coagulation, the DON removal efficiency in water samples within the range of 0.1-0.45 μm and 10 ku-0.1 μm exceeded 80%, while the DON removal efficiency in water samples within the range of 3-10 ku and less than 3 ku was less than 20%. The removal efficiency of hydrophobic DON was higher compared to that of hydrophilic DON. The removal efficiencies of FRI in water samples with particle sizes less than 0.45 μm and 0.1 μm, and molecular weight less than 10 ku and 3 ku were all less than 15%, suggesting that tyrosine and tryptophan organics in the effluent from the secondary treatment process were the key components for enhancing coagulation and increasing the DON removal efficiency.
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