Biodegradation And Mineralization Of Dimethyl Phthalate

Phthalic acid esters(PAEs) have been detected recently from various environments and a considerable attention has been paid to their toxicity and the biodegradability, PAEs in low concentration can disrupt people and animals’ endocrinesystem.As a plasticizer widely used in plastic products,phthalates are not covalentbonded,but are connected by Van Der Waals force or hydrogen bonds.Thus they easily break away from the plastic and migrate to external environment, and can enter into human body through the food chain.Their potential harm has grabbed much attention recently. Now, Advanced oxidation processes(AOPs) and Biodegradation is a main process affecting the environmental fate of phthalate esters.In this research, by researching the degradation characteristic of dimethyl phthalate, the results can be used to assess the environmental risk and to adopt the relevant methods of PAEs bioremediation.In this research, in order to transform and degrade DMP effectively. Using intimately coupled UV/H2O2 with biodegradation for the treatment of wastewater containing DMP, which can accelerate the degradation rate of DMP largely.Analyze the intermediates in the process of UV/H2O2 and biodegradation, and exploring the mechanism how intermediates accelerate DMP biodegradation. Based on the research, an internal circulation baffled biofilm reactor used for DMP in the process biodegradation. In addition, the DMP under the condition of anaerobic degradation are also reasearched. Through the perseverance and consistent work, following achievements were obtained.(1) Using the device of UV/H2O2, which can degradate DMP effectively. Thedegradation of DMP was not obvious under UV alone, and it can not degradatewith H2O2 alone.In the system of UV/H2O2, the degradation of DMP affected byH2O2 quantity、the initial concentration of DMP、intensity of UV light.(2) In the system of UV/H2O2, the p H of DMP dropping throughout in the holeprocess, from the beginning of 6.7 to 3.3.The reason is that in the process ofDMP degradation, it can generate formic acid, acetic acid, oxalic acid, maleic acidand succinic acid,which made the p H dropped to acidity.(3) In the process of using ICBBR to degradate DMP, according to the principle ofcarbon and electronic balance, the biodegradation of DMP is in accordance withDMP ® MMP ® PA® CO2+H2O.(4) In the process of using ICBBR to degradate DMP, using three ways to comparethe degradation rate of DMP, that is: Direct biodegradable(B)、sequential couplingUV/H2O2 and biodegradable(UV+B) 、 intimately coupled UV/H2O2 withbiodegradation(UV&B). During sequential coupling, UV/H2O2 pretreatmentgenerated carboxylic acids that depressed the p H, and subsequent biodegradation generated phthalic acid; both factors inhibited DMP biodegradation. During intimately coupled UV/H2O2 with biodegradation, carboxylic acids and phthalic acid did not accumulate, and the biodegradation rate was 13% faster than with biodegradation alone and 78% faster than with biodegradation after UV/H2O2 pretreatment. Similarly, DMP mineralization with intimate coupling increased by5% and 39%, respectively, compared with biodegradation alone and sequential coupling. The enhancement effects during intimate coupling can be attributed to the rapid catabolism of carboxylic acids, which generated intracellular electron carriers that directly accelerated di-oxygenation of PA and relieved the inhibition effect of PA.(5) In the condition of Anaerobic, when the concentration of DMP was 80mg/L, DMP degradation rate is the fastest with C:N=10:1, and its mineralization degree is the highest accordingly.From the point of denitrification, when the C:N was 20:1, Denitrification rate is the fastest, The reason is because the carbon source is enough, and it can provide enough electron donor for the degradation of NO3-N.(6) Under the effect of anaerobic bacteria, DMP degradation was also follow the step, that is : DMP ® MMP ® PA® CO2+H2O.