Microbial interference with the adsorption of target organic contaminants by granular activated carbon.

Microorganisms have been frequently observed to inhabit the exterior surfaces of granular activated carbon (GAC) particles in water and wastewater treatment applications of adsorption processes. Such microbial growth is often presumed to be generally beneficial to treatment operations employing GAC, chiefly because it is assumed that microorganisms will reduce the concentration of biodegradable compounds, leaving more sites available on the carbon for adsorption of recalcitrant compounds. Evidence has been found, however, that microorganisms and microbial products may themselves interfere with adsorption of specific nonbiodegradable compounds, in particular the adsorption of trace quantities of potentially hazardous compounds for which the GAC treatment is specifically targeted. These interference effects may be manifested in reductions in equilibrium adsorption capacities and /or in effective rates of mass transport of solute to adsorption sites on and within the carbon particles. Statistically significant reductions in one or more of the adsorption equilibrium and mass transport parameters for trichloroethylene (TCE), para-toluene sulfonate (PTS) and dodecylbenzene sulfonate (DBS) are observed in this research for adsorption on GAC containing previously adsorbed quantities of biological material. The statistical significance for reduction in mass transport parameters is determined based on a method developed for establishing conditional confidence limits for parameters in a non-linear system. The method entails the determination of selected points on a confidence region in the rate parameter mathematical plane. Reductions in parameters are observed on GAC that had been exposed either simultaneously or previously to: (a) a whole broth predominantly containing Pseudomonas putida, with microbial growth subsequently encouraged using a glucose-based medium; (b) a filtered broth containing only soluble microbial products from Pseudomonas putida; (c) primary, secondary, and tertiary effluent streams in the Ann Arbor, Michigan wastewater treatment plant; and (d) the protein bovine serum albumin. Implications for engineering design and operation are examined.Ph.D.Engineering, Sanitary and MunicipalUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/162237/1/8920598.pd