Wetlands Remove Pathogens from Water
6/1/98
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Title: Wetlands Remove Pathogens from Water
Source: CNN
Status: Copyrighted, contact source to reprint
Date: 6/1/98
ATLANTA (CNN) - Vegetative wetlands can serve as an alternative method for
reducing bacterial paathogens such as salmonella in wastewater, according
to researchers.
The research was presented Wednesday by Mohammad R. Karim at a meeting of
the American Society for Microbiology in Atlanta. A vegetative wetland is
a natural system with no added chemicals.
Because more than 30,000 cases of salmonella poisoning are reported each
year, it is a major health concern in the United States. Conventional
wastewater-treatment technologies depend on disinfection to reduce
pathogen populations. The researchers believe wetlands could be an
improvement over traditional methods.
Karim and colleagues who conducted the research at the University of
Arizona in Tucson examined the survival of E. coli and salmonella
typhimurium in six different wetland systems receiving either potable
water or secondary sewage.
"Our results suggest that the presence of aquatic plants significantly
increases die-off of both bacteria in potable water and secondary sewage,
indicating that vegetative wetlands could provide an alternative method
for reduction of bacterial pathogens in wastewater," Karim said.
The researchers added E. coli and salmonella typhimurium at a
concentration of 1 million cfu/ml to each wetlandd system. Four wetland
system receiving potable water contained a combination of cattail, iris
lily, taro, duckweed and elodea. Two other wetland systems receiving
secondary unchlorinated sewage contained water hyacinth and duckweed.
Potable water and secondary sewage without the presence of aquatic plants
were used as controls.
"Bacterial die-off in potable water and secondary sewage was significantly
higher when aquatic plants were present in these systems. We examined
whether any antibiotic-like substance or inhibitory substances were
released by the plants in the studied wetlands, which could enhance
bacterial die-off," Karim said.
No antibiotic or inhibitory substances were found in these wetland waters.
"Further work on the survival of E. coli in nonsterile, filter sterilized
and autoclaved wetland water indicated that the plausible mechanism of
bacterial die-off in constructed wetlands is through microbial competition
or predation," Karim said.
The results of the University of Arizona research, along with other
literature, show promise for improving water quality.