Comparison Between ATP Testing Systems
Used in Industrial Water Treatment
Original article for the Analyst publiscation by
Attila Relenyi, Ph.D. (AMSA, Inc.) &
Ken Davenport, Ph.D. (Biotrace, Inc.) and has
been edited for this website by AMSA, Inc.
AMSA, Inc.'s championed and introduced
ATP to the AWT, and due to the lack of developed methods, supplier support
and affordable test instruments, began in ATP manufacturing. Instrument prices
have dropped from the pre - AMSA entry from about $4,000 to about $2200. ATP
test method prices have dropped from two test pen method (total cost about
$5.40) to the one test pen method for about $2.50 - $3.00) (AMSA). the
method had been primarily used in the food & beverage market. There are two
methods are in use by AWT.
The two systems frequently produce different
Relative Light Unit (RLU) readings with the same water sample. The
two companies advocate a different approach to the interpretation of ATP test
results.
The ATP/luciferase
test method is complex. Several neutralizers and kinetic-altering substances that are added to the formulations
of each company’s enzyme mix in order to stabilize the signal and increase
reproducibility. All of these factors, including test instrument
design, conspire to produce different light
output from a reaction with identical amounts of ATP.
Luminometer settings will
also strongly effect the ultimate reporting of results. The AMSALite
allows AMSA to adjust these parameters so
it can read identical to any competitor unit or to guarantee that each AMSALite,
even from different models, will read the same.
Taken together these
factors contribute to the differing results found in ATP
testing systems. However,
a standard curve of RLU vs. ATP concentration will show
that systems will generally agree on the amount of
ATP within a system.
One key approach
advocates the establishment of pass/fail limits based on both general guidelines
we have developed and data generated from the individual tower. When a tower’s
ATP values rise above the limits established by the water
treater, this should
trigger a review of the biocide type, volume, and/or frequency of application.
AMSA’s approach to ATP
measurement interpretation tends to focus on the use of the values as a fouling
index – the higher the number, the greater the potential and rate of
bio-fouling. There is also an emphasis on following the trends in the data
– an upward trend indicates a loss of microbial control and the need to review
the current water treatment chemical program.
In most respects, the two
approaches produce similar results in practice. Both encourage increased
biocide dosage when ATP values rise over what is typical for the tower. Both
recognize that every tower is different and suggest that users develop a history
of ATP results with each tower.
ATP testing is a valuable
method in the hands of the water treatment professional and provides a
significant increase in speed and accuracy compared to plate counts and dip
slides.
For some more basic information about ATP, please
check out the following links: