AWWA ACE56347

Control of biofilm growth is essential in maintaining the health of the distribution system and ultimately the public. Providing a chlorine residual alone, is not effective in eliminating biofilm growth in iron pipe systems and periodic removal of the biofilms is required. Biofilms can be removed either by mechanical cleaning (pigging) or flushing. Pigging is effective in removing the biofilm; however, it is expensive and can cause leaks and damage to older, deteriorated systems. Especially for small systems, flushing can also be effective in biofilm removal. However, two critical factors will govern the effectiveness. First, the flow velocity in the pipes must be 2 m/sec (6 ft/sec) or greater to effectively remove the biofilm, and second, the system must be flushed in a systematic manner to ensure all pipe sections are completely flushed and that biofilm residue is not simply moved from one part of the system to another. The paper discusses several important issues that have become apparent through past experience, along with the Code of Practice that was developed to provide for effective control of the water quality within a distribution system and to enable the implementation of an effective flushing plan. The elements of this distribution system water quality management program include: unidirectional flushing; tank exercise; tank cleaning; line repair/replacement disinfection; corrosion control; valve exercise; and, monitoring. The paper continues with a discussion of flushing techniques and the benefits of flushing.

Product Details

Edition:

Vol. - No.

Published:

06/16/2002

Number of Pages:

8

File Size:

1 file , 260 KB