Treatment plant management shall continuously monitor
disinfectant residuals and report the following to the Division within ten days
after the end of each month that the system serves water to the public, except
as otherwise noted:
(1) For each day,
the lowest measurement of residual disinfectant concentration in mg/L in water
entering the distribution system, except that if there is a failure in the
continuous monitoring equipment, grab sampling every 4 hours may be conducted
in lieu of continuous monitoring, but for no more than 5 working days following
the failure of the equipment. Systems serving 3,300 or fewer persons may take
grab samples in lieu of providing continuous monitoring on an ongoing basis at
the frequencies listed in Table 215.2 below:
TABLE 215-2
RESIDUAL GRAB SAMPLE
FREQUENCY
|
System size by population
|
Samples/day
|
Less than 500
|
1
|
501 to 1,000
|
2
|
1,001 to 2,500
|
3
|
2,501 to 3,300
|
4
|
Note: The day's samples cannot be taken at the same
time. The sampling intervals are subject to Director's review and
approval.
|
Note: The day's samples cannot be taken at the same time. The
sampling intervals are subject to Director's review and approval.
(2) The date and duration of each
period when the residual disinfectant concentration in water entering the
distribution system fell below 0.2 mg/L and when the Division was notified of
the occurrence. The system shall notify the Division as soon as possible, but
no later than by the end of the next business day. The system also shall notify
the Division by the end of the next business day whether or not the residual
was restored to at least 0.2 mg/L within four hours.
(3) The following information on the samples
taken in the distribution system in conjunction with total coliform monitoring
pursuant to R309-211 and
R309-210-8(3)(a)(i):
(a) number of instances where the residual
disinfectant concentration is measured;
(b) number of instances where the residual
disinfectant concentration is not measured but heterotrophic bacteria plate
count (HPC) is measured;
(c) number
of instances where the residual disinfectant concentration is measured but not
detected and no HPC is measured;
(d) number of instances where no residual
disinfectant concentration is detected and where HPC is greater than
500/ml;
(e) number of instances
where the residual disinfectant concentration is not measured and HPC is
greater than 500/ml;
(f) for the
current and previous month the system serves water to the public, the value of
"V" in the formula, V = ((c+d+e)/ (a+b)) x 100, where a = the value in
sub-section (a) above, b = the value in sub-section (b) above, c = the value in
sub-section (c) above, d = the value in sub-section (d) above, and e = the
value in sub-section (e) above.
(4) The residual disinfectant concentration
must be measured at least at the same points in the distribution system and at
the same time as the total coliforms are sampled as specified in R309-211. The
State may allow a public water system which uses both a surface water source or
a ground water source under direct influence of surface water, and a ground
water source, to take disinfectant residual samples at points other than the
total coliform sampling points if the Director determines that such points are
more representative of treated (disinfected) water quality within the
distributions system. Heterotrophic bacteria, measured as heterotrophic plate
count (HPC) as specified in paragraph
R309-200-4(3),
may be measured in lieu of residual disinfectant concentration.