The Role Of Electron Donors For Accelerating Pyridine And Dimethyl Phthalate Biodegradation

With the rapid development of social economy, various organic compounds are widely used in production and daily life. Among them, most organic compounds are difficult to be biodegraded, and also toxic to the eco-environment. These compounds will cause environmental problem, and harm to health of human beings if they are discharged to the natural environment. In this study, we selected the representative toxic and recalcitrant organic pollutants, nitrogen heterocyclic compounds: pyridine and phthalic acid esters: dimethyl phthalate(DMP) as the research object. Pyridine is a kind of typical nitrogenous heterocyclic compounds with stable structure, which is found in coking wastewater; while DMP has the shortest chain in phthalic acid esters and it is widely used in plastic production as plasticizer. Both pyridine and DMP are hard to be biodegraded and their biodegradations are concerned to electron requiring reactions. Therefore, it has important theorical and practical significant to investigate the effect of electrons on their biodegradation.In this study, an internal circulation baffled biofilm reactor(ICBBR) was employed for pyridine and DMP biodegradation, during which the role of electrons for accelerating the biodegradation were studied. Especially, how endogenous and exogenous electron donors accelerating the biodegradation were respectively investigated, and their intermediates were also investigated quantitatively. The experimental results documented that extra electron donors did not only accelerate original pyridine biodegradation through mono-oxygenation, but also accelerated the intermediate through di-oxygenation to accelerate original DMP biodegradation by means of reducing its accumulation. Main experimental results are shown in following:1. Original pyridine biodegradation was initialized with two mono-oxygenation reactions. With 2.94 m M and 4.34 m M electron donors added, pyridine biodegradation rates increased by 23% and 54% than no electron donors added.2. Pyridine biodegradation rates were obviously increased, after it was pretreated with UV photolysis, which suggested that succinate as main interemediate was generated during the photolysis, and succinate as electron donor could accelerate pyridine biodegradation, and longer the photolysis time was, the more succinate generated.3. Pyridine biodegradation rates were proportional to electron equivalents, which were verified by using the same equivalent of formate and acetate.4. Both extrogenous and endogenous electron donors could accelerate pyridine biodegradation, and succinate did not accelerate original pyridine, but also accelerated its intermediate, hydroxyl pyridine biodegradation.5. The first two steps of DMP biodegradation are hydrolysis to generate its intermediate phthalatic acid(PA), and following PA biodegradation is di-oxygenation, which is also electron requiring reaction, and PA existing can inhibit DMP biodegradation.6. Addition of succinate as exogenous electrons accelerated PA di-oxygenation, and promoted DMP hydrolysis, and PA biodegradation rates were proportional to quantity of exogenous electron added.