Source: USDA AGRICULTURAL RESEARCH SERVICE, 11/18/20 A model for an economical filter system that can remove
antibiotics from wastewater has been designed by Agricultural Research Service
(ARS) and University of California-Riverside (UCR) collaborators. Microbiologist Mark Ibekwe with
the ARS Agricultural Water Efficiency and Salinity Research Unit in Riverside,
California, and UCR soil chemist Daniel Ashworth constructed the prototype
system using four layers of natural materials: gravel, sand, soil, and biochar
in a column 50-cm tall and 12-cm diameter. They used the laboratory-scale
model to remove four antibiotics: amoxicillin, cefalexin, sulfadiazine, and
tetracycline at various levels of efficiency. These four antibiotics were
selected for testing in the scale model because they are among the most common
in wastewater treatment plant effluent. Conventional wastewater treatment plant
systems are relatively effective at removing nutrients and bacteria but can be
somewhat ineffective at removing antibiotics. The effectiveness of the
laboratory-scale system varied with the antibiotic being evaluated. It
successfully removed 98 percent of the tetracycline, followed by 91 percent of
cefalexin, 81 percent of amoxicillin and 51 percent of sulfadiazine. The
antibiotics had initial concentrations of 10 ppb, comparable to levels that
have been seen in municipal wastewater. Amoxicillin and cefalexin removal were largely controlled by chemical degradation in the gravel layer, while sulfadiazine was largely removed by a combination of chemical and microbial degradation in the soil mixed with biochar layer. Tetracycline was primarily removed by chemical reactions with water (hydrolysis) in the gravel layer. "These results show the
importance of using layers of different materials to target different
antibiotics rather than expecting one layer and material will be able to do the
job." said Ibekwe. Increasing the time it takes for
the water stream to pass through the column also improved removal efficiency,
especially for amoxicillin and cefalexin. In this design, the simulated
wastewater enters at the bottom of the column to saturate the bottom layer and
then is pumped up through the column to flow out through the top. A "full-size" scale-upped version of the researchers' filter system—one that might serve a small-town wastewater treatment plant—would be about 2 meters tall and 50 cm in diameter, according to Ashworth. Of course, you could use multiples of the columns to serve a larger need and the footprint would still be relatively small, which is one of the powerful features of this system, Ashworth added. There are
some existing systems that can remove antibiotics from wastewater, but these
tend to be very expensive or require much more space. This research was
published in the Journal of Environmental Chemical Engineering. The Agricultural Research Service is
the U.S. Department of Agriculture's chief scientific in-house research agency.
Daily, ARS focuses on solutions to agricultural problems affecting America.
Each dollar invested in agricultural research results in $20 of economic
impact.
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