The objective of this research is to evaluate the possibility of enhanced metal precipitation inside algal biofilms. The pH environment surrounding microorganisms growing in biofilms is frequently different than the environment of the bulk liquid because products of metabolic reactions are limited in their ability to diffuse out of the biofilm. This occurs with algal biofilms, in which CO2 utilization during photosynthesis results in an increase in the pH. The pH inside algal biofilms can be several units higher than the pH of the surrounding liquid. This higher pH favors removal of metals by precipitation and possibly adsorption. Laboratory studies were conducted in which biofilms of Cladophora glomerata were grown in buffered nutrient media. Copper or nickel was added to the media to study short term metal removals. Experimental results were compared to predictions of solubility based on a theoretical model of pH inside algal biofilms. Results provide evidence to support the theory that higher internal pH can result in greater metal removal by the biofilms.

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