Characterizing the microbial biofilm growth on pipes made of pvc as compared to steel pipes.

Overview

• Municipal drinking water facility wanted to compare the microbial communities of biofilms which develop on the inside of pvc and steel pipes.

• Coupons made of pvc or steel were employed at various locations along a municipal water system. After incubation, the coupons were analyzed to characterize the microbial community on the biofilms. The assumption was that the microbial growth on the coupon was representative of what would grow inside pipes made of pvc or steel.

Question

Is there any difference in biomass or community structure of the microbial communities which grow on pvc versus steel coupons?

 
Analyses Requested:
           
            PLFA

Results:

• PLFA analysis showed that at most locations and sampling events, there was little difference in total biomass between the steel or pvc coupons. Whenever a difference in biomass was observed, the highest biomass was on the steel coupon. Ft. DeSoto showed the largest difference in total biomass, particularly at the 2 month sampling event.

• PLFA profiles showed that there were notable differences in the microbial communities found on the steel and pvc coupons.

• At all locations, the steel coupons had higher proportions of Gram negative Proteobacteria, than the corresponding pvc coupon. Steel samples also contained Firmicutes, which were not seen in the pvc samples.

• The microbial communities growing on the pvc coupons had greater proportions of oxiranes, which are a type of fatty acid produced by microbes experiencing stress from chlorination. PVC samples also tended to have lower proportions of eukaryotes, and slightly higher proporitons of SRB sulfate-reducing bacteria).

Answer:

Results from the PLFA analysis showed that there were differences in both biomass and microbial community structure on steel versus pvc coupons. PVC had lower biomass, lower proportions of Proteobacteria and eukaryotes. PVC samples also had higher levels of oxiranes.

This data suggests that the microbial community growing on the pvc surface was experiencing more stress response to chlorination, particularly in members of the Gram negative Proteobacteria population.