Changing the Face of Ultraviolet
Coiled Tubing Enables Longer Contact Time, Offers Greater Versatility
Innovations and advancements in technology in addition to
public awareness and media exposure are changing water treatment equipment and
marketing strategies. New ideas and the need for developing easier to use and
easier to service products are at the forefront of the industry's
manufacturers, suppliers and dealers worldwide. Producing water treatment
equipment that works in the background is easy to maintain and produces great
tasting, bacteria-free water, which is essential as we move through the new
millennium. A change that is going to revolutionize the UV light arena of water
treatment are coiled tubes that enable longer contact times and have excellent
UV light transmission, versatility in application and a compact system design.
This method of UV light transfer in applications such as drinking water,
icemakers, beverage dispensers, water coolers and aquaculture make the task of
changing the tube that protects the UV bulb safer and less costly to the
Test studies have shown excellent bacterial reduction, and
tests on scaling prove this method of bulb protection will work very
efficiently. Other uses include ozone contact chambers and aeration tubing for
ozonated pools and spas. A close look at this tubing has revealed greater than
expected results in bacterial reduction and scale issues associated with
different water sources. The outcome of a few simplistic experiments has
revealed enough positive information that more tests are warranted.
Efficacy and Scale Issues
Bacterial reduction tests and scale tests were performed on
the fluoropolymers. The first reaction when observing the coiled tubes would be
transmission levels of UV light into the water source. The opaque quality of
the tubes would make one wonder if high enough transmission levels for
bacterial reduction would be achieved. The tubes that were tested varied in
clarity and smoothness, and transmittance levels were wide-ranging. Figure 1
shows the differences in transmission levels of the four tubing materials
tested plus quartz. The FEP and MFA depict good transmission levels of UV light
at 254 nanometers, but the EFEP and THV demonstrate between 80 percent and 90
percent transmission of the UV source, which is slightly below the levels
achieved by quartz.
Increased contact time makes up for the loss of
transmittance to prove that fluoropolymers are a very good method of protecting
the bulb, while allowing excellent bacterial reduction. The dose rate is
calculated by multiplying the intensity of the bulb times the contact time
multiplied by the transmission rate. An example would be a bulb with an
intensity of 4 milliJoules per square centimeter (mJ/cm2) times a 20 second
contact time multiplied by 70 percent would render a 56 mJ/cm2 theoretical
dosage rate. The increased contact time and turbulence caused by the coiled
design allow very good reduction of bacteria.
A test was conducted on the MFA and FEP materials with
favorable results being obtained for the reduction of coliforms and E. coli.
This test was conducted to discover the efficacy of the tubing in UV light
transmission. The intensity of the bulb was not measured for this test; only the
bacterial reduction data was obtained. The initial tests were to observe
bacterial reduction and justify further research. Without getting into a lot of
detail as to how the tests were performed, there were significant reduction in
bacteria, both in total plate counts (TPC) and also coliforms and E. coli
The first test used a prototype that contained a 9-inch bulb
and then a second prototype using a 14-inch bulb. Both bulbs were
254-nanometers. The coiled tubing was used in the prototypes to protect the UV
bulb from water while providing exposure of the water stream near the UV light.
Water from a local lake was used, which tested positive for coliforms and E.
coli and high bacterial counts. The qualitative test (a presence or absence
test) was positive for both indicators of harmful bacteria. A quantitative test
(numerical data recorded) was conducted to determine possible log reductions.
Several methods of testing were conducted that revealed very
good results with filtration, UV light and coiled tubing to control bacteria.
There was enough positive information gathered to warrant more research and
development. With a three- to four-log reduction of coliforms, E. coli, and
TPC, the coils proved very effective in bacterial reduction.
Now that the efficacy of the bacterial reduction had been
examined, another issue of using coiled fluoropolymer tubes was to be analyzed,
and that was the issue of scaling. UV light applications in most cases require
the water to be pretreated to prevent excessive scale build-up caused by hard
water minerals or iron. The test was conducted without pretreated water to
compare scaling of four different types of fluoropolymers. MFA, EFEP, FEP and
THV were used to manufacture the coiled tubes. The water was high in iron (5
ppm), tannins (4 ppm), chlorides (400 ppm), hardness (25 gpg), total dissolved
solidas (TDS) (980 ppm) and alkalinity (280 ppm). The pH was tolerable at 7.4.
More than 10,000 gallons of this putrid water was passed at 2 gpm through the
tubes and each tube was equipped with a 14-inch, 254-nanometer UV bulb to
create heat and simulate a working model.
The coils were examined and the materials compared to find
out which fluoropolymers scaled the least. The MFA was the best material since
it scaled the least; the EFEP was the worst. The other two, FEP and THV, were
comparable in scaling. Figure 2 shows how the four compared and clearly reveals
a drastic difference on how well the coils performed using different types of
fluoropolymers. With proper pretreatment, these tubes would work very
efficiently in UV bulb protection, while providing an excellent UV dosage rate
to the water. The EFEP should have had less scaling, since it has a smooth
surface very similar to that of MFA. (See Figure 3.) The resin supplier has
revealed that a special grade of resin with a bonding enhancer was used in
manufacturing the coil for the test. Standard grade resin will be obtained and
the test will be repeated. Figure 3 also reveals the rougher texture of the FEP
as a comparison to the MFA and EFEP materials used in manufacturing the coils.
Efforts will continue to develop the optimum combination of qualities in coil
design. A picture of the prototype can be viewed in Figure 4.
The results in comparing the coiled fluoropolymers to quartz
in scaling were very similar. A quartz sleeve was tested using the same
unfiltered water source. A standard UV light filter housing without a filter in
place was used in this analysis and approximately 10,000 gallons of water were
passed through the UV chamber. The quartz sleeve scaled very comparably to the
coiled tubing. The sleeve was ruined, because it could not be cleaned and was
left with a permanent orange hue. The sleeve was also difficult to remove and
this reiterates the safety issue of the coiled tubing over the quartz sleeve,
since the coiled tubing will not break or shatter.
Information and Conclusions
When analyzing water treatment equipment and their
components, a wide spectrum of water supplies could be used on such equipment
and this variety of options must be considered in the analysis. Specifications
must be set on the components so that a standard is shown for each component
and they are accredited with NSF, the U.S. Environmental Protection Agency,
Water Quality Association and other accrediting organizations.
Every water supply could have different results, and
pretreatment generally is recommended with UV light systems to increase
efficiency and reduce maintenance costs. In each application, the pretreated
water provides a consistent source of feed so the UV system will operate
optimally. The coiled tubes offer a great alternative to using quartz, and the
jury is still out on many new applications. The availability, ease of use and
cost effectiveness of the coils make this component for UV light transmission
in water treatment a viable product for compact system design. The resistance
of UV light exposure and ozone exposure that these fluoropolymers depict
unveils many applications that
will implement coiled tubing in water treatment system designs because of their
versatility, cost and effectiveness.