Treatment Of PAEs Wastewater By Immobilized Microbial Cells

In this study, dominant bacterial colony Burkhorderia P (shortened as BP)as experiment bacteria ,was immobilized using embedment technique. Bio-degradation characteristics of four kinds of phthalic acid esters DMP,DEP,DBP and DEHP (mainly DBP)by immobilized cells were studied. Appropriate embedding material was chosen and the best immobilization operating condition was fixed on. Then, effects of several environmental factors on the degradation of DBP by immobilized cells were studied. Immobilized BP bacteria was used to treat simulated DBP wastewater. In the end, treatment progress of PAEs wastewater was brought on in allusion to water quality of PAEs wastewater.The results of this paper were shown as follows:1 BP strain was immobilized by sodium alginate and PVA. Bio-degradation characteristics of four kinds of phthalic acid esters DMP,DEP,DBP and DEHP by two kinds of immobilized cells and free cells were studied. It was demonstrated that in the same concentration level, the order of the degradation velocities of the four kinds of PAEs was DMP>DEP>DBP>DEHP, and the order of degradation abilities of the three kinds of cells was sodium alginate immobilized cells> PVA immobilized cells> free cells. As a whole, PAEs degradation by immobilized cells was more quickly than by free cells; The adaption range of pH and temperature was by immobilized cells wider than by free cells. Kinetic study showed that PAEs biodegradation by two kinds of immobilized cells conformed to first-order reaction model.2 BP strain was immobilized sodium alginate and PVA complex carrier. The activity of immobilized cells was denoted by the DBP degradation percentage. The optimization operating condition of immobilization was fixed on: proportions between sodium alginate and PVA was 1% sodium alginate and 8% PVA; crosslinking time with saturated boric acid+ 2% CaCl₂ was 20 hours; granule diameter of immobilized cells was 2-3 millimeters; the bacteria concentration was 3%; bacteria quantity was around 3000mg/L (wet bacteria weight / wastewater volume). It was shown that immobilized cells embedded with complex carrier has favorable mechanical intensity and penetration capability, in the basis of the test results.3 Effects of environmental factors (pH, temperature and oxygen quantity) on the degradation of DBP by immobilized cells and free cells were studied. DBP degradation percentage by PVA - sodium alginate immobilized cells was higher than by free cells; the adaption range of pH by PVA - sodium alginate immobilized cells was wider than by free cells; the immobilized cells had ability to balance acid and alkali in the water.The immobilized cells had ability to adjust the temperature variety. In the range of 20 to 40℃, DBP degradation percentage by immobilized cells was above 75% . the optimum temperature was 30℃.When the rotate speed of the shaking bed was below 90r/min, DBP degradation percentage by PVA - sodium alginate immobilized cells was much lower than by free cells. However, when the rotate speed of the shaking bed was below 90r/min, the state was the reverse. Therefore, the aeration condition in the taper flasks had a huge influence in the immobilized cells' degradation activity.4 Immobilized BP strain was used to treat simulated waster water and the COD in wastewater could be removed quickly when the COD was below 3000mg/L. PVA - sodium alginate immobilized cells were used to treat simulated wastewater made by domestic sewage water, which was compared with wastewater without immobilized cells. It was demonstrated that immobilized BP strain had perfect performance in degrading DBP. In the second day, the DBP degradation percentage had come to 70% .Natural bacteria had hardly any DBP degradation ability. COD elimination effect in reactor with immobilized cells was a little better than in reactor without immobilized cells. At the forth or the fifth day in two reactor, COD was degraded to 100mg/L.