AWWA QTC98227

This study was undertaken to measure the effectiveness of a system-wide flushing program in removing unwanted microorganisms such as total coliforms and Aeromonas species in sediment deposits. This was accomplished by analyzing for these bacteria at the beginning of the program and then two years later to measure the removal of these bacteria from the sediments during the first flush and possible reintroduction back into the system before the second flush. A secondary reason for the program was to reduce the number of samples with chlorine residuals below 0.2 mg/L. The original 110 sediment samples flushed from the mains in pressure zones with previous coliform problems contained 42 (38.2%) coliform-positive samples. Aeromonas hydrophila was present in 31 (28.2%) of the other samples. The 110 sediment samples flushed 2 years later contained only 7 (6.4%) total coliform-positive samples and 7 (6.4%) samples containing Aeromonas hydrophila. This study did show that the flushing program was very successful in removing total coliforms from the distribution system. This study also showed that the Distribution Monitoring Plan that was put into effect at the same time as the flushing program, reduced the possibility of putting these microorganisms back into the system. Regrowth and sloughing of total coliforms was not observed. This reduced the number of coliform-positive samples in the distribution system.

Product Details

Published:

01/01/1998

ISBN(s):

0898679796

Number of Pages:

12

File Size:

1 file , 80 KB