UV254 Go! Helps water treatment plant optimise its disinfection process
As part of an ongoing
process improvement
project, the water
treatment plant wanted
to optimise its
disinfection process.
It was known that the
presence of organics
caused instability in the
disinfection effectiveness,
by causing a shift in the
Total and Free Chlorine
residuals.
The only way to improve
the performance was to
thoroughly understand the
levels organic components,
which was difficult due to
their intermittent presence.
It is well known that
organics in the water can
cause harmful disinfection
by-products such as
Trihalomethanes (THMs)
and Halo-acetic Acids
(HAAs). The plant
measures these
parameters with samples
every 90 days, and
includes the running
averages in its annual
Water Quality Report.
Despite performing well, a
review was undertaken to
study the disinfection
process to see if any
improvements could be
made. The first step was
to identify the best means
of measuring the organic
presence.
For regulatory
compliance, samples are
taken periodically and
sent to a lab for analysis.
This is a straightforward
process, but limits the
level of testing that can be
done and has a cost with
each sample.
As the goal was process
improvement, it was
important to have a good
volume of data and to
have it quickly, so it was
decided to purchase a
measurement device,
however any such device
had to compare closely to
the results that a certified
laboratory would provide.
There are many stages in
water treatment and the
conditions can differ
considerably from stage
to stage, therefore it was
important to be able to
measure at various points
in the process, so having
a portable solution would
be a major benefit.
UV254 is an excellent
method of determining
Natural Organic Material
in the water. The
Ultraviolet Absorption
values (UVA) can also be
used as surrogate
measurements for COD,
BOD, TOC & DOC, as
long as they have been
correctly correlated.
The UV254Go!, from
Photonic Measurements,
was chosen because it
was “really, really simple”
to use, very user friendly
and portable.
The UV254Go!, not only
measures UVT/UVA but
also provides results for
the surrogate parameters.
In addition, all of the
collected data, including
surrogate values, is
stored on the unit and can
be transferred to a PC in
Excel-compatible format.
The unit was calibrated to
the lab results for the
COD effluent, and
maintained a strong
correlation against
subsequent lab samples.
This meant that the team
could have confidence in
the results and quickly
adapt the disinfection
process to live results.
As part of the project TOC
and DOC values were
also measured and
showed a strong
correlation to the UVA
values, meaning that
calibration curves for TOC
and DOC could be readily
created and entered
directly on to the Go!.
Following on from these
measurements the next
stage is to start
measuring BOD. BOD
measurement is a long
process, takes 5 days,
uses reagents and adds
additional cost.
The plant intends to
reduce its lab-based
measurement by more
than half, and use the Go!
for more data, saving both
time and money. A
further investment in
Photonic Measurements
UV254 continuous
measurement devices
will ensure that NOM data
is available throughout
the year for trend analysis
and process
improvement