Characterization of the planktonic and biofilm populations in an experimental pipe loop system fed with RO treated water

摘要

A PVC pipe loop system was constructed inline at the Water Authority-Cayman treatment and distribution location at Red Gate. The pipe loop consisted of two parallel wall-mounted systems fed by RO water and exposed to chlorinated or non-chlorinated conditions. Coupons of PVC, PE, mild steel, brass, copper and cement lined ductile iron were inserted into the pipe loop system for a period of 32 days and 90 days respectively to determine the quantity and type of bacteria present in the bulk water and biofilm. Bacterial ID was successful using a combination of fatty acid methyl ester (FAME) analysis and HPC culture analysis on R2A. Results show that in general chlorination reduced bacterial quantities in the bulk water but for surfaces such as mild steel the bacterial numbers increased due enhanced corrosion of the metal under chlorinated conditions. Bacterial types in the bulk fluid were similar to those isolated from other parts of the treated distribution system however a few morphologically different types of colonies were observed on the steel, copper and cement-lined ductile iron surfaces. In some cases the bacteria isolated from the chlorinated section of the loop were characteristically different from those isolated from the non-chlorinated section. As the industry moves to understand more about the quality of water within the distribution system, this paper will give unique and valuable information on the characterization of bacteria found in reverse osmosis systems served predominantly by a PVC piping system and an in-line distribution system temperature of 24oC or above.