Study Of The Effect And Mechanism Of Extracellular Polymers On Ozone Catalytic Oxidation In Petrochemical Secondary Effluent

Petrochemical wastewater is a type of toxic and refractory industrial wastewater with complex components,high pollutant concentration,and poor biodegradability.In actual engineering,due to the inhibitory and stress effects of toxic and harmful pollutants on the microorganisms in the biological treatment unit,the biochemical secondary effluent often carries a large number of microbial secondary metabolites,such as extracellular polymers(EPS)and others.After the effluent entering the advanced treatment unit,it consumes ozone and adsorbs on the surface of the catalyst to reduce the activity of the catalyst,causing problems such as deterioration of the effluent quality.In order to maintain the high activity of the catalyst and the stability of the effluent quality,it is an urgent problem to clarify the effects of the microbial products in the secondary effluent on the ozone catalytic oxidation.Based on this background,this article took the secondary effluent of a comprehensive petrochemical wastewater treatment plant in the north as the research object to investigate the degree and method of the effect of EPS on ozone catalytic oxidation treatment under different EPS concentration levels.Through the behavior characteristics of EPS in solution and on the surface of the catalyst,the impact mechanism of EPS on the ozone catalytic oxidation ozone was discussed.It provides a theoretical basis to a targeted pretreatment process in front of the ozone catalytic oxidation unit for improving the ozone utilization efficiency and maintaining the high activity of the catalyst.Firstly,a qualitative study was carried out on the secondary effluent of the petrochemical industry and the EPS solution extracted from the activated sludge.The results showed that the TOC value of the secondary effluent fluctuated between 16.7 and20.9 mg/L,mainly containing aromatic proteins and soluble microorganisms as well as some refractory humic acid-like substances.While,the TOC value of EPS solution was about 17.85 mg/L and the solution was mainly protein and polysaccharides.Secondly,the effect of EPS with different concentration levels on the ozone catalytic oxidation treatment was investigated.The results showed that EPS affected the removal of pollutants in the process of ozone catalytic oxidation,and the reaction sequence was protein in EPS>organic pollutants in water>polysaccharide in EPS.Besides,EPS competed with dissolved ozone for adsorption sites which was called the Lewis acid center on the catalyst surface.Finally,through the study of the adsorption and desorption characteristics of EPS on the catalyst,the influence mechanism of EPS on the ozone catalytic oxidation was summarized.The results showed that the adsorption of protein and polysaccharides in EPS on the catalyst surface tended to be chemical adsorption and physical adsorption,respectively,and EPS competed for adsorption sites with pollutants.In addition,compared with ultrasound,calcination can effectively desorb EPS on the catalyst surface and restore catalyst activity.