AWWA QTC98284

Two separate laboratory model systems fed by potable water were established to compare the rate of biofilm formation on three distribution pipe materials and the effect of the bacteria on the materials. The three distribution pipe materials used were cast iron, MDPE and uPVC. The numbers of heterotrophic bacteria increased exponentially in the first experiment between 0 and 11 days on each of the materials before reaching a steady state population. The mean viable count was 99% higher on cast iron than on MDPE and uPVC. The free chlorine residual, temperature and the number of bacteria in the water all influenced the rate of biofilm formation. In the second experiment the three materials were exposed to a high density bacterial suspension and the surface and the substratum properties were observed over a period of 15 months. The biofilm formation on cast iron was on average two log units lower than on MDPE or uPVC at every sample time. The substratum properties of the cast iron changed over time but the properties of the MDPE and uPVC did not change. The strength of the cast iron decreased considerably over the experimental period but again no change was noted for MDPE or uPVC. In conclusion, the use of MDPE and uPVC in United Kingdom distribution systems is supported by the data presented, because the bacterial biofilm numbers were 99% lower when compared to cast iron and the bacteria did not cause biodeterioration of MDPE or uPVC over the period investigated.

Product Details

Published:

01/01/1998

ISBN(s):

0898679796

Number of Pages:

10

File Size:

1 file , 74 KB