Eunsung Kan (right) and MS student Stuart Watson demonstrate
a system for neutralizing emerging contaminants.
Schoolchildren learn about the natural water cycle: clouds,
rain, streams, ocean, evaporation. In the municipal water cycle, water from the
tap is used for drinking/ cooking, bathing, washing, and irrigation; the
resulting “graywater” runs to the sewer, is taken to a wastewater treatment
plant, and is purified to be used again.
It’s in the purification process that things can get
problematic. Assistant Professor Eunsung Kan works with emerging contaminants,
adulterants of the water that appear in such small concentrations that they are
often ignored—and therefore not removed. But these contaminants, including
endocrine disrupters such as BPA, synthetic hormones, antibiotics and pain
relievers, and certain chemicals in makeup and sunscreen, can cause a host of
problems even in tiny amounts, including a higher incidence of breast, thyroid,
and prostate cancers and hormone disruptions. Other problems include drug resistance—and
not only in humans. Since the water is also used for irrigation, trace amounts
of antibiotic collect and concentrate in the tissues of the plants, leading to
pesticide resistance in the pests that eat them—and thus to the need for
Biochar made from locally grown greenwaste (left) is used as
a substrate for locally collected waterpurifying bacteria (right).
Dr. Kan looks at the entire municipal water cycle, but the
core of the research in his Bio/Green Engineering Lab in the Department of
Molecular Biosciences and Bioengineering is on removing emerging contaminants.
He explains that several processes in use pose problems of their own, such as
adding extra chemicals to neutralize those already present. His techniques,
both cheaper and “greener,” include a photocatalytic process and one using
specially selected and cultured bacteria.
In the first process, rods of biochar, or biologically
active charcoal, are impregnated with titanium oxide and placed in the water.
Sunlight excites the titanium oxide, which catalyzes, or breaks down, and
neutralizes the trace contaminants. In the second process, a particular strain
of bacteria that also breaks down the contaminants is isolated from the soils
surrounding UH Manoa and encouraged to grow in a thick biofilm on the surface
of biochar. The ideal system, Dr. Kan explains, combines the techniques: a
photocatalytic system can be fitted to any area where wastewater is outflowing,
after which the water is directed through a column treated with the bacteria,
emerging contaminant free. With their green and sustainable focus, his
techniques are contributing to detoxification and agricultural reuse of water.