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.