Biodegradation And Kinetics Of The Diesel Blends Pollutants In Water

Many countries are seeking new and renewable substitute because of energy shortage,biodiesel as an alternative fuel is used extensive throughout the world. Biodiesel is oftenmixed with traditional fossil fuel to use currently, so it is inevitable to pollute theenvironment in the process of use. It is significant to research the degradation of hybriddiesel in water environment.In this thesis, the degradation of the hybrid diesel in the simulated natural conditionsand simulated enhanced biological conditions was studied firstly. The degradation of thehybrid diesel was researched under blank conditions and adding sludge and biofilm carrierconditions by shake flask experiments, and the effects of the different mixing ratio anddegradation time on the degradation of the hybrid diesel were discussed. Secondly, thesimulation of the hybrid diesel degradation by kinetics model was studied, then thedegradation kinetics model was obtained. Finally, the joint effects of the pH, degradationtemperature, degradation time and substrate concentration on the degradation of the hybriddiesel was studied by the Response Surface methodology (RSM), and the suitabledegradation conditions were discussed later. The conclusion is shown below:(1)Most hybrid diesel has been degraded in20d degradation time and the removal ratetends to be slow after20d. Moreover, the degradation rate of the hybrid diesel undersimulated enhanced biological conditions is significantly higher than that under simulatednatural conditions.(2)The higher rate of biodiesel in hybrid diesel means the faster rate of degradation. Forinstance, the degradation rate of the B100under simulated natural conditions andsimulated enhanced biological conditions is96.5%and89.5%respectively. Obviously, it ishigher than other samples. The degradation rates of the samples under different conditionsare as follows:96.5%,89.2%,86.9%,83%and89.5%,84.1%,82.5%,78%.(3)Pseudo first-order kinetic model could simulate the degradation of the hybrid dieselunder simulated natural conditions. The correlation coefficient of the regression equation is above0.9, which indicated that the simulation result is better. Pseudo second-order kineticmodel could simulate the degradation of the hybrid diesel under simulated enhancedbiological conditions. The correlation coefficient of the regression equation is above0.99,which suggests that the simulation result is better.(4)The joint effect of different factors could be simulated well by the Response Surfacemethodology and the simulation results gained from the three-dimensional responsesurface plot are shown below. As for degradation time, the removal rate accelerates as theextension of the degradation time. Temperature and pH have great influence on thedegradation. The degradation rate raises as the temperature increase in the range of0-25℃,and the degradation rate reduces as the temperature reduces when the temperature is above25℃. The degradation rate rises as the pH rises when pH is less than7, and thedegradation rate decreases as the pH increases when pH is above7. In comparison, thesubstrate concentration has little effect on the degradation of the hybrid diesel.(5)The suitable degradation conditions for the hybrid diesel are as follows, pH is6.61,the substrate concentration is4mg/l, the degradation temperature is22.8℃, and thedegradation time is30d.