eBook: TOC and Microbial Detection Monitoring - 39

200

Sanitization

32000
30000

180

28000
160

26000

AFU (cells/100mL)

140

22000
20000

120

18000
100

16000
14000

CFU/mL

Case Study

24000

12000
10000

8000
40

6000
4000

2000
0

7
AFU Cell Cnt

8
Average

9
Week Number
Alert Limit

Action Limit

Breach Limit

Plate Count

Figure 1: Comparison of 7000RMS continuous Auto Fluorescent Unit (AFU-the 7000RMS' unit of measurement) data and intermittent
plate count results.

processes and improve control, the
customer identified three major
causes of added costs and delays:
* Delay in microbial growth results
due to retrospective testing.
Using data from a plate count test
started five days ago, the customer
could not proactively engage in
process control at the time of a
contamination event.
* Low data granularity for microbial reporting. With plate counts
being snapshots of the water quality, the customer did not have a full
picture of the health of their water
system or the water quality, leading to delays during investigations
into events.
* Potential for non-representative
results. With the possibility of
false positive or false negative
results from plate counts, effective
control of a process is not possible.
Repeated plate counts are necessary to confirm validity of the
contamination indication.
Continuous on-line monitoring
addresses key requirements
As the customer explored ways to
address these major causes of

added costs and delays, they approached METTLER TOLEDO to discuss using the 7000RMS real-time
microbial detection analyzer to
meets their needs. With the
7000RMS analyzer, the customer
could continuously monitor their
water quality, leading to better decision making and process control.
Moreover, the customer could immediately determine whether an
actual contamination event occurred when plate count results
were positive, thus providing a
confirmation of the validity of the
plate count results. In addition,
using the 7000RMS analyzer could
lead to reduced plate counting by
providing continuous monitoring.
Thus reducing labor and material
costs as well as product release
delays.
Convinced of the benefits of the
7000RMS, the customer installed the
analyzer on their ambient WFI loop
and continuously monitored the
water quality. After a baseline and
associated alert, alarm and breach
limits had been established, the
analyzer continuously measured the

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METTLER TOLEDO

microbial levels in the WFI loop
providing the customer with full
transparency of the water quality.
As seen in Figure 1, results exceeded
the alert limit a few times early on.
The gradual increase and subsequent drop in microbial counts corresponded to water usage and refill
of the WFI storage tank. This information helped the customer to optimize
their processes, regain control and
keep the water quality within specification going forward.
The customer continued to use their
validated method of plate counts to
release the water while using the
7000RMS analyzer for process
control. Using this approach, the
customer plotted and compared the
plate count results with the 7000RMS
data, as observed in Figure 1, to
identify false positive plate count
results immediately. This helped
them to confirm that the water quality was under control and reduced
the need for repeated plate counts to
validate the results.

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