Effect of acetate on biofilms utilized in PAH bioremediation

Supplemental acetate was used to alter biofilm characteristics for the improved capture and biodegradation of polycyclic aromatic hydrocarbons (PAHs) in laboratory sand columns. Acetate was provided at a dose of 48% of the carbon mass of PAHs (naphthalene, phenanthrene, and pyrene) in the feed solution. A companion study indicated that acetate increased the rate at which PAH biodegradation was established along the sand column profile. An integrated biofilm characterization approach was performed in this study using chemical (viable biomass, exopolymers), physical (confocal laser microscopy), and Biolog microbial community analysis (carbon substrate utilization patterns). Overall sand medium viable biomass content increased by 91%, or more with pulsed acetate addition, and extracellular polysaccharide content increased by 55 to 106% with acetate amendment. Confocal laser scanning microscopy (CSLM) indicated the presence of both thin surface biofilms on sand grain surfaces and protrusion structures extending, from the surface biofilm. The occurrence of loosely attached protrusion structures increased by 1.7 to four times with pulsed acetate amendment, as indicated by quantitative viable biomass measurements. Biolog results indicated that a shift occurred in the PAH-degrading microbial community composition with either pulsed or continuous acetate addition.