真空紫外活化过硫酸盐去除藻类胞外有机物

Removal of algal extracellular organic matter by vacuum ultraviolet activated persulfate

摘要:

在水华爆发期间,藻类胞外有机物（EOM）在水体中累积,对水处理工艺和出水水质带来不容忽视的风险。EOM难以被常规净水工艺去除,且次生消毒副产物会显著影响供水水质,亟需开发高效的水处理技术来降解EOM。真空紫外（VUV）能够原位产生活性氧化物种（ROS）去除有机污染物,具有去除EOM的潜力。为此,采用真空紫外（VUV）活化过硫酸盐（PS）去除EOM,探究其处理效能、影响因素、反应机制和对消毒副产物（DBPs）生成的影响,并将其应用于天然含藻水处理。结果表明:VUV/PS体系能快速降解和矿化EOM,UV₂₅₄和DOC去除率分别为93.7%和74.1%；随PS投加量的增加,EOM的降解率显著增大,酸性条件可促进EOM的降解和矿化效率；水中共存的HCO-₃和Cl-会明显抑制VUV/PS体系对EOM矿化的效能,而NO-₃的影响相对较小；由于VUV辐照促进了ROS的生成,VUV/PS体系中羟基自由基（HO^·）和硫酸根自由基（SO^·-₄）浓度高于UV/PS体系；EOM在VUV/PS体系中的高效矿化主要归因于HO^·和硫酸根自由基 SO^·-₄,溶解氧通过促进以HO^·和SO^·-₄为主的ROS生成,可有效促进EOM的降解；经VUV/PS处理后,后续氯消毒过程中DBPs的生成量显著下降。VUV/PS体系在处理天然含藻水时能够明显降低水中的UV₂₅₄、DOC质量浓度以及DBPs生成量。

Abstract:

During the outbreak of water blooms, extracellular organic matters (EOM) of algae accumulates in water bodies, causing great risks to water treatment processes and effluent quality. EOM is different to remove using conventional water treatment technologies, and secondary disinfection by-products may significantly affect the quality of the water supply. Therefore, it is urgent to develop efficient water treatment technologies to degrade EOM. Vacuum ultraviolet (VUV) can generate reactive oxidative species (ROS) in situ to remove organic pollutants, so it has the potential to remove EOM. In this study, vacuum ultraviolet (VUV)-activated persulfate (PS) was used to remove EOM, and its treatment efficiency, influencing factors, reaction mechanism, and impact on the formation of disinfection by-products (DBPs) were investigated, aiming to apply it to the treatment of natural algae-containing water. The results revealed that the VUV/PS system can rapidly degrade and mineralize EOM, with a removal rate of 93.7% for UV₂₅₄ and 74.1% for DOC respectively. The degradation rate of EOM significantly increases as the dosage of PS increases, and acidic conditions promote the degradation and mineralization efficiency of EOM. The coexisting HCO-₃ and Cl- in water significantly inhibit the mineralization efficiency of the VUV/PS system for EOM, while the influence of NO-₃ is relatively small. As VUV irradiation promotes the generation of ROS, the concentrations of hydroxyl radicals (HO^·) and sulfate radicals (SO^·-₄) in the VUV/PS system are higher than those in the UV/PS system. The efficient mineralization of EOM in the VUV/PS system is mainly attributed to HO^· and sulfate radical SO^·-₄. Dissolved oxygen effectively promote the degradation of EOM by facilitating the generation of ROS, primarily HO^· and SO^·-₄. After treatment with VUV/PS, the generation amount of DBPs in the subsequent chlorination disinfection process decrease significantly. The VUV/PS system demonstrates the ability to significantly reduce the mass concentrations of UV_254, DOC in water and the generation amount of DBPs when treating natural algae-containing water.