The duck floats in an aquarium holding two one-liter beakers and
marks the spot where Kristin Susens is conducting hot tub
research for the Environmental Protection Agency (EPA).
The duck is just for fun, but the tiny plastic bubbles that float
on the water keep the temperature at a steady 100.4 degrees. The
beakers simulate hot tubs and have miniature jets and the same
water chemistry as the real thing. Every so often, Susens adds a
liquid that imitates the sweat, oils and urine of weary users.
"It's been a lot of fun. ... It's been a really great
experience," said Susens, an undergraduate at Michigan
Technological University and one of eight students involved in
the Research Experience for Undergraduates program at the CBE
this summer.
"This is very relevant research. It's applicable for our
industrial associates who manufacture any of the disinfectants
that could be used in hot tubs," added Darla Goeres, a research
engineer overseeing Susens.
The EPA is funding a five-year project to develop a standard
method for testing the effectiveness of hot tub disinfectants.
The current method was developed in 1965 and has been modified
some, but it's aimed more at swimming pools than hot tubs, Goeres
said. The method gives no consideration to changes in water
chemistry and hot tub designs. It only looks at free-floating
bacteria and doesn't take into account the biofilms or slimy
communities of bacteria, that can accumulate in the pipes,
filters and seating areas of hot tubs that haven't been
disinfected properly.
Linda Loetterle, a CBE research assistant, found biofilms in 87
percent of the hot tubs she sampled around Gallatin County during
a four-week field study. The bacterial concentrations exceeded
state standards almost one-third of the time.
"In general, all bacterial concentrations increased over time,"
Loetterle said in a July 23 poster presentation to industrial
associates.
This is the third year MSU has been involved in the hot tub
project, and Susens will conduct a number of experiments before
she finishes her research program in August. In some, she tests
new filters. In others, she examines dirty filters and used
filters that have been cleaned. One beaker contains untreated
water. The other contains chlorine and is altered according to
the experiment.
"We are just looking at biofilms in the filters," commented
Susens who takes samples at the beginning of the experiment and
after 20 minutes, six hours and 24 hours. "There's obviously a
lot more to look at after this project."
The study has made Susens and Goeres nervous about hot tubs that
haven't been disinfected properly, but they predict continued
success for the hot tub industry.
"This study isn't going to result in people not sitting in hot
tubs," Goeres said. "... It's just going to help companies better
understand how their chemicals will perform."
"Chlorine does actually kill bacteria and does a pretty good
job," she added. "This will help confirm that."
The 10-week REU program is funded by the National Science
Foundation and gives college students an intensive research
experience. The hope is that they will be encouraged to go on to
graduate school, particularly at MSU, Goeres noted.
Posted by Evelyn Boswell for 7/29/02
