Biological Activated Carbon: Understanding the Role of Cometabolism in Extending Service Life and Improving Process PerformanceEPA Grant Number: U916014
Title: Biological Activated Carbon: Understanding the Role of Cometabolism in Extending Service Life and Improving Process Performance
Investigators: Putz, Andrea R.H.
Institution: The University of Texas at Austin
EPA Project Officer: Packard, Benjamin H
Project Period: January 1, 2001 through January 1, 2003
Project Amount: $76,242
RFA: STAR Graduate Fellowships (2001) RFA Text | Recipients Lists
Research Category: Academic Fellowships , Fellowship - Water Treatment , Water and Watersheds
The objective of this research project is to explore the effect of cometabolism of synthetic organic chemical (SOC) mixtures on the performance of biologically active granular activated carbon (GAC) columns. GAC often is used in drinking water and groundwater treatment to adsorb SOCs. SOCs in the environment may result from such things as gasoline spills or improper disposal of dry-cleaning solvents. Much research has been conducted on the adsorption of mixtures of SOCs and on the biodegradation and adsorption of mixtures of biodegradable SOCs. Very little work has been conducted, however, on the biodegradation and adsorption of mixtures of biodegradable and nonbiodegradable SOCs. In addition, almost no work has been conducted on simultaneous metabolism and cometabolism of such mixtures. The absence of such research is particularly problematic because many practical applications involve mixtures of biodegradable and nonbiodegradable SOCs (as a result of their widespread occurrence in the environment).
Once a GAC column is exhausted, the GAC must be replaced and disposed of or recycled in some way (i.e., landfilling, incineration, thermal reactivation). Replacement and disposal of exhausted GAC is quite expensive. Encouragement of biodegradation (in the form of metabolism and cometabolism) where one or more of the SOCs are biodegradable should lengthen the GAC service life for some SOC mixtures. The GAC service life increases because a biofilm that forms on the GAC can metabolize or cometabolize SOCs, reducing competition for GAC adsorption sites and allowing any nonbiodegradable or uncometabolized SOCs to adsorb onto the GAC to a greater extent than in the absence of biodegradation. SOCs present both in the aqueous phase and adsorbed on the GAC are available to the microorganisms. Biodegradation of adsorbed SOCs (termed bioregeneration) renews the GAC's capacity for SOC adsorption, while biodegradation of SOCs in the aqueous phase slows the rate of GAC exhaustion. Biodegradation of SOCs present in either phase can lengthen the GAC service life, decreasing operation and maintenance costs. In addition, if biodegradation of the SOC is complete, the SOC is broken down into harmless byproducts, removing any health threat. The research approach will consist of several continuous-flow, biologically active GAC columns fed different concentration ratios of toluene (primary substrate) and trichloroethylene (cometabolite). Preliminary isotherm and kinetic studies will be performed before the continuous-flow studies, and mathematical modeling work will occur during and after the continuous-flow studies.