Study On Optimization Of Simulation Photocatalysis Floating Bed For The Treatment Of Secondary Effluent

The seeondary effluent is a good potential water source due to its large quantity and stable quality. However, the organics of secondary effluent were biochemical non-degradable which are difficultly removed by traditional biochemical treatment. TiO2 has been developedand used as a photocatalyst for air and water purifications becauseof its excellent photocatalytic activity, physical and chemical stability, and nontoxicity. Photocatalysis technique has emerged as a promising technology for organic wastewater treatment due to its advantages over the traditional advanced treatment techniques. If we can set the photocatalysis fioting bed in the secondary sedimentation tank of traditional biological treatment for advanced treatment of textile wastewater by solar energy, operating costs and capital costs will be greatly reduced. It can provide strong support for wastewater reuse and ease the shortage of water resources in China. A Simulation photocatalysis floating bed reactor was assembled by short quartz tube loaded TiO2 film, showing a good catalytic activity. SEM and XRD were used to characterize the structure of the TiO2 films. Used for the advanced treatment of secondary effluent aiming at water reuse.The SEM results indicated that the TiO2 films of 1μm were loaded on short quartz tube in the photocatalysis floating bed reactor. The degradation experiments of methyl orange indicated that the three layers TiO2 films annealed at 600℃exhibited a good repeatability for photocatalytic activity.The secondary effluent from a municipal sewage treatment plant was fractionated into three parts:the suspended, the near-colloidal and the dissolved. The variation of each composition was investigated individually during winter, spring and summer. The fractionation study revealed that the TOC of the dissolved accounted for 76.63%～82.45%. The molecular weight distribution (MWD) of the secondary effluent indicated that the organics with molecular weight (MW)<3000 accounted for more than 70% of total organics.The effluents of different molecular weight were also treated by this reactor. The results indicated that the TOC reduction rate of the organic pollutants molecular weight exceeding 100k Dalton in secondary effluent was 45.8%, the TOC reduction rate of the organic pollutants molecular weight between10k and 100k was 31.84%, the TOC reduction rate of the organic pollutants molecular weight betweenlk and 10k was 34.76%, and the TOC reduction rate of the organic pollutants molecular weight less than 1k was 39.18%. By comparing the water sample before photocatalysed to after with FT-IR technique, the functional groups of organic pollutants in secondary effluent have been effectively broken down by photocatalysis floating bed.GC-MS was used to analyze the degradation mechanism of the organic pollutants in secondary effluent by this photocatalysis floating bed. The results showed that lots of refractory organic matters are not detected after treated, the reduction rates of some environmental hormones such as DBP, DMP exceed 60%, and the reduction rates of aromatic and phenolic compounds surpass 50%. By comparing the water sample before photocatalysed to after, the macromolecular compounds in secondary effluent have been effectively broken down into small molecular matters by this photocatalysis floating bed.