Study of the Characteristics of Two Immobilized Microbial Materials in Degradation and Evolution of Petroleum Hydrocarbon

Abstract

To enhance the degradation efficiency of oily wastewater, polyacrylamide (PAM)-sodium alginate (SA) and poly(vinyl alcohol) (PVA)-sodium alginate (SA) were mixed and used as spherical supporting materials for the immobilization of microbials, which were employed as a platform to study the degradation of total petroleum hydrocarbons (TPHs) in the oily wastewater. The degradation and evolution of normal paraffin (n-paraffin) series have been studied by determining the crude oil group composition of the residual oils by the gas chromatography-mass spectrometry (GC-MS) analysis. The results show that the half-lives of the PAM-SA-immobilized microorganisms are 6.21 days, which is 2.11 days less than that of PVA-SA, indicating that more nutrients are provided by PAM-SA for microbial growth, which can accelerate the degradation of TPHs. As can be seen from the GC-MS analysis, the main peak carbons of the n-paraffin series are moved backward after 14 days of degradation, implying the degrading advantage of n-paraffin with low carbon numbers. The ∑C21-/∑C22+ value of PAM-SA was measured to be 0.749, which is greater than that of PVA-SA (0.051), indicating that PAM-SA has a superior ability to degrade normal paraffins with high carbon numbers. After 14 days of degradation, an odd-even predominance (OEP) (the mass ratio of normal alkanes of odd carbon/even carbon) value of 1.075 for PAM-SA was obtained, which is slightly larger than that of PVA-SA (0.967), indicating a better degradation performance of PAM-SA, especially for the degradation of the even-carbon normal paraffins with high carbon numbers. The Pr/Ph of PAM-SA is 0.938, which is also greater than that of PVA-SA (0.844), indicating that the ability of PAM-SA for the degradation of isoprenoids is superior to that of PVA-SA under the immobilized conditions. Based on these results, in terms of immobilization of microorganisms, PAM-SA, instead of PVA-SA, is more advantageous for the degradation of TPH in the oily wastewater.