Biodegradability Research Of Phthalic Acid Esters

Financially supported by the fund of visiting scholarship of State Key Laboratory of Pollution Control and Resources Reuse, Tongji University, China, this project was carried out to investigate the aerobic biodegradability, anaerobic biodegradability, quantitative structure biodegradability relationships of phthalic acid esters (PAEs), and to deepen the understanding of biodegradation mechanism and to promote the application for the prediction and risk assessment of the effect of the PAEs congeners on ecosystem. Through three years' hard work, the following achievements were obtained.(1) The results showed that the biodegradation rates of PAEs could be described by first-order kinetics. The primary biodegradation percentage under the aerobic conditions was between 99.9%~30.0%, respectively. All compounds of the PAEs tested with the acclimated inoculum had been degraded hi different degree, the biodegradation equations for PAEs were showed as follows:Compounds Biodegradation kinetics equations R2DMP InC = 5.689 -3.6984t 0.964DEP InC = 5.749 - 3.446t 0.927DnPP InC = 5.299 -1.529t 0.948DnBP InC = 5.292 -1.092t 0.995DiAP InC = 5.345 - 0.322t 0.977DiHP InC = 5.399 - 0.325t 0.972DnOP InC = 5.375 - 0.2911 0.973DINP lnC = 5.339-0.155t 0.964DUP InC = 5.343-0.1301 0.958The biodegradation rates of low molecular weight PAEs were obviously different from those of high molecular weight PAEs. The rate constants (kj,) decreased and the half-life time (ti/2) of PAEs biodegradation incresed with an increase in alkyl chain length (n). The correlations of alkyl chain length of PAEs to biodegradation rate constants (2-1) and half-life time (2-3) were established.lnkb = 0.0266n2 - 0.672n + 2.157......................................................................(2 -1)(r = 0.975)t1/2 = 0.0391n2 + 0.0959n + 0.0246....................................................................(2 - 3)(r = 0.972)(2) Biodegradation of DMP was affected by high concentration ofdimethylphthalate (DMP). It was found that biodegradation rate constants appeared a peak at concentration of 60mg/L.(3) While the concentration of phthalate sodium was less than 500 mg/L, there was little effect on rate constants of DEP biodegradation, but once the concentration was more than 500 mg/L, the rate constant declined.(4) The higher temperature, the larger the rate constants during DnOP biodegradation. After cultivated for 40 hours, DnOP (in terms of concentration) was degradaed by 41% at 10癈, 93% at 40C.(5) Net biogas production (NBP) was investigated for 10 PAEs under the same conditions, nonlinear equations for the correlationship of each PAE's NBP to time (d) were established and they were showed as follows:Compounds Nonlinear equations R2DMP G = 0.0033 t2+0.05721-3.709 0.961DEP G = 0.0015 t2+ 0.7741-4.686 0.971DnPP G = - 0.005 t2 + 1.2471 - 9.970 0.960DnBP G = - 0.004712 + 1.0851 - 7.891 0.962DnAP G = 0.0025 t2+ 0.0518t + 0.644 0.985DiHP G = -0.0025 t2 + 0.3291 - 1.418 0.96...