Study On The Mechanism Of Ultraviolet Photolysis-Biological Filtration For The Purification Of Toluene

Atmospheric pollution is becoming increasingly serious,and volatile organic compounds（VOCs）are one of the main causes of environmental pollution.Compared with traditional physical and chemical methods,biological methods for treating VOCs have the advantages of low operating costs and no secondary pollution,and are suitable for processing VOCs with large air volume,low and medium concentration,and good biodegradability,but are not ideal for the treatment of VOCs with poor water solubility and poor biodegradability.Therefore,in this paper,UV photolysis technology and biological trickle filtration technology are used to purify toluene waste water with poor water solubility.The effect of photolysis as a pretreatment device on the biodegradation effect is explored,and the degradation of intermediate products in the biological trickle filter tower is revealed.High-throughput sequencing and quantitative qualitative analysis were used to find out the distribution of dominant microbial flora and analyze its main degradation mechanism,in order to provide some theoretical support for subsequent research work.In this paper,the effects of parameters such as intake air concentration,intake air volume,and relative humidity on the removal efficiency of toluene and the characteristics of toluene degradation products during the photolysis process are mainly studied.Based on the qualitative analysis of gas chromatography-mass spectrometry,the pathway of photolysis degradation is deduced It was found that the main photolysis products were benzaldehyde,formic acid,acetic acid,etc.,and the water solubility of the products was greatly improved,and the biodegradability was improved,which provided the possibility for improving the biodegradation effect.Activated sludge was obtained from the aeration tank of Shanghai Bailonggang Sewage Treatment Plant and cultured for seven days.The activated sludge had an SV₃₀ of 25%,an MLSS of 3598 mg/L,and an SVI of 69.4830 ml/g.Domestication and membrane hanging were carried out in the biological drip filter tower.After 40 days,bioelectron microscopy and kinetic fit analysis revealed that the main bacterial groups were bacillus and sphaeroides and were evenly distributed.The removal efficiency of toluene was stable above 80%.The combined use of photolysis and biological method to treat toluene waste gas,when toluene inlet concentration is 200-300mg/m3,relative humidity is 30%-40%,and the inlet volume is 5L/min-7L/min,the toluene removal efficiency can be as high as 98%,using GC-MS analysis,the main degradation products are carbon dioxide and water,and a small amount of by-products such as formic acid and p-cresol.Using high-throughput sequencing analysis,a total of 508 Bacterial Operating Taxonomy Units（OTU）were detected.The main bacterial groups are Proteobacteria（71%）,Bacteroidetes（18%）,Verrucomicrobia（6%）,Actinobacteria（3%）,and other Mycobacteria（2%）,the dominant bacteria are Zoogloea,Acidovorax,Massilia.Experiments show that the efficiency of degradation of toluene by the UV photolysis-biological filtration unit purification device is higher than the sum of the degradation effects of UV photolysis and biological titration alone.This shows that there is a good synergy between the two,which provides a certain theoretical research and basis for the study of the combined technology to degrade VOCs.