Ultraviolet Photodegradation Enhances The Biodegradability Of Organic Matter

With fast development of industrial production, many contaminated waste waters were discharged into natural environment, which leads pollution of surface, even ground water. Especially, some wastewater with recalcitrant organic compounds was discharged into the environment. For the common contaminated compounds, biological methods were superior to be accepted for the treatment because it is economic cost, and easy to be used for real application. But for treatment of wastewater containing recalcitrant compounds, superiority of biological methods is hard to show, if it was alone employed, as most recalcitrant compounds have their inhibition, even toxicity to microorganism.In this work, we focused on common organic compounds, phenol, 2,4,6-trichlorophenol and pyridine, as they have the similar structure of benzene ring. The experimental results documented that phenol, TCP and pyridine were photosensitive compounds, and some intermediates and some carboxylic acids were generated during UV photolysis, among them, carboxylic acid can supply electrons for recalcitrant compounds biodegradation to accelerate their biodegradation.Firstly, phenol was treated with UV photolysis, and catechol and hydroquinone were generated with phenol loss, and some carboxylic acids, oxalate, maleate, formate, which formed a basis to build a mass balance and support phenol photolysis pathway. During phenol biodegradation, photolyzed phenol removal rate was higher by 39 % than the direct biodegradation of phenol.Secondly, 2,4,6-trichlorophenol(TCP) was photolyzed with UV light to yield that ortho Cl ion was lost and 2,4-dichlorophenol(DCP) generated, which further converted TCP into dichlorocatechol(DCC), monochlorophenol(MCP), and dichlorophenol(DCP), and this relieved inhibition by TCP. Following mass balance was made based on Cl and C ions to support TCP photolytic pathway. Following biodegradation document TCP biodegradability was enhanced after photolysis, as photolysis relieved TCP inhibition to microorganism.Finally, pyridine was treated by UV light to show that some intermediates formed, such as hydroxyl pyridine, as well as carboxylic acids, such as succinate and formate. The pyridine photolytic pathway was supported with pyridine intermediates balanced. Pyridine biodegradation show that photolyzed pyridine was superior to that of pyridine with direct biodegradation, and the biodegradation rate was incrased by 20 % to 40 %.In summary, for phenol, TCP and pyridine, their biodegradation rates incrased obviously when photolysis was used as pretreatment. The experimental results can give theoretic and application basis for real industrial wastewater treatment.