Disinfection of Pipelines - Disinfection of Pipelines and Storage Facilities Field Guide - page 30

residual of the flush water exiting the chlorinated main should
be measured until the residual is no greater than the feed water.
Flush water containing high chlorine concentrations may
require treatment to avoid adverse environmental impact. Consult
appropriate regulatory agencies regarding requirements for the
disposal of heavily chlorinated water (Tikkanen, 2001). It may be
necessary to dechlorinate the water prior to disposal. Chapter 7
includes procedures for dechlorination. Some of these procedures
may not be approved by every regulatory agency. Follow regula-
tory agency directives regarding the approved treatment proce-
dures for your area.
Bacteriological Testing
Perform bacteriological tests on water in the new pipeline
after flushing but before it is connected to the distribution sys-
tem. The tests must satisfy all applicable regulatory require-
ments. A certified laboratory must perform the analyses. The
results must be negative (no coliform present) before connecting
the pipeline and releasing the water for use by customers. The
following testing protocol is listed in ANSI/AWWA Standard C651.
1. Collect two samples from the new pipeline taken at least
24 hr apart.
2. Collect a sample from at least every 1,200 ft (366 m) of
new main.
3. Collect a sample from the end of the line and at least one
from each branch.
4. Test samples for total coliform bacteria in accordance
with Standard Methods for the Examination of Water and
Wastewater . Additional tests may be required including:
chlorine residual, turbidity, pH, and heterotrophic plate
count (HPC).
5. Special Condition . Collect additional samples at intervals
of approximately 200 ft (61 m) if trench water has entered
the new main during construction or if excessive quanti-
ties of dirt or debris have entered the new main. Take
samples of water that has stood in the new main for at
least 16 hr after final flushing.