城市污水有机磷在以臭氧为主体的高级氧化中的迁移转化特性

Migration and Transformation Characteristics of Organic Phosphorus in Municipal Sewage During Ozone-Based Advanced Oxidation

针对目前对城市污水处理厂中有机磷(OP)组成结构、迁移转化规律认识欠缺,且出水OP占总磷比例较高等问题,开展了以臭氧为主体的高级氧化技术中磷迁移转化特性研究,对比分析了单独臭氧氧化体系及O_(3)/H_(2)O_(2)体系中OP的降解效能,采用31P NMR和FT-IR协同分析方法,全面解析不同磷组分转化机制,明确单独臭氧氧化体系中残留难降解OP组分.结果表明,在单独臭氧氧化体系中,随着臭氧投加量的增加,UV_(254)去除的反应速率常数(kobs)提升速率为COD的11.2倍,为OP的21.0倍,表明臭氧对含有不饱和键的有机物氧化作用较强,对于难降解的OP氧化能力仍较弱.残留OP组分为难降解磷酸单酯和膦酸酯.磷酸二酯在臭氧氧化中易被分解为磷酸单酯、其他中间产物及磷酸盐(PO_(4)^(3-)).O_(3)/H_(2)O_(2)体系能够实现OP的高效降解,O_(3)投加量为2.20 mg(O_(3))/mg(COD)时,H_(2)O_(2)最佳浓度为2.45 mmol/L,OP去除率大于80%,OP逐渐向PO_(4)^(3-)转化.然而当H_(2)O_(2)投加量小于0.33 mmol/L时,与单独臭氧氧化体系相比,对OP去除无增强作用,是由于氯离子及碳酸盐等对产生的·OH具有较强捕获作用所致.本文研究成果能够为城市污水深度除磷或再生水安全利用技术领域提供新思路和新方法.此外,全面揭示以臭氧为主体的高级氧化技术中磷迁移转化特性,对深度除磷工艺的选取有重要的指导意义.

At present,the structural composition,migration,and transformation of organic phosphorus(OP)in municipal sewage treatment plants are not fully clear.In addition,the proportion of OP in effluents is high.In this study,the migration and transformation characteristics of phosphorus composition in an advanced oxidation technology based on ozonation were evaluated.Further,the degradation efficiencies of OP in sole ozonation and the O_(3)/H_(2)O_(2) process were compared.The conversion mechanism of different components of phosphorus and the residual refractory OP components in ozonation were analyzed comprehensively through 31P NMR and Fourier-transform infrared(FT-IR)spectroscopy.In sole ozonation,with an increase in the ozone dosage,the observed rate constant(kobs)of UV_(254) removal was 11.2 times that of the COD removal and 21.0 times that of the OP removal,indicating that ozone has a strong oxidation effect on organic matter that contains unsaturated bonds;however,the effect was weak for the refractory OP.The residual OP components were phosphomonoesters and phosphonates.Phosphodiester was easily decomposed into phosphomonoesters,other intermediates,and PO_(4)^(3-) by ozonation.The residual OP was degraded effectively by the O_(3)/H_(2)O_(2) process.When the ozone dosage was 2.20 mg(O_(3))/mg(COD),the optimal concentration of H_(2)O_(2) was 2.45 mmol/L,and the OP removal rate was higher than 80%;the OP gradually converted to PO_(4)^(3-).However,there was no enhancement effect on OP removal when the H_(2)O_(2) dosage was lower than 0.33 mmol/L because of the strong trapping effect of chloride ions and carbonate on the produced·OH.These findings may motivate the development of new,advanced approaches and methods for phosphorus removal from municipal sewage and safe utilization of water technology.Further,it is important to study the migration and transformation characteristics of phosphor components in the advanced oxidation technology based on ozone as they are critical for selecting an advanced phosphorus removal process.