Potential exoproteolytic activity assay for the determination of fixed bacterial biomass on distribution system materials

The application of the potential of exoproteolytic activity (PEPA) assay described in this paper concerns the determination of fixed bacterial biomass densities on drinking water pipe material coupons at pilot scale. The coupons were cut from actual distribution networks (the member governments) in Florida (USA) and were incubated in pilot distribution systems whose pipe sections were from the same networks. Four different common types of materials have been used as substratum for biofilm development namely polyvinyl chloride (PVC), lined cast iron, unlined cast iron, and galvanized steel. A significant linear relationship between biomass measurements was made from heterotrophic plate counts on R2A medium and this enzyme assay was shown. Pristine material coupons were also incubated simultaneously with aged coupons, and similar biofilm levels were observed between aged and pristine coupon results for both quantification techniques. Therefore, the age of the material did not significantly affect biofilm formation. Earlier work also demonstrated a correlation between biomass measurements and this enzyme assay. However, the conditions of biofilm development described in this article were much more similar to the conditions met in a real distribution system. Therefore, the protocol and the results presented here may be more useful for application of this assay at full scale.