Potential for Phytoremediation of Antibiotic-Contaminated Water
Phytoremediation shows promise in antibiotic removal.
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Contaminated soils and waters can pose major environmental and human health problems, which may be partially solved by emerging phytoremediation technology. Phytoremediation is a relatively new field in remediation technology, which uses plants’ ability to degrade, assimilate, metabolize, or detoxify metals, hydrocarbons, pesticides, and chlorinated solvents. Plants can be used to treat systems containing many different types of contaminants including petroleum hydrocarbons, chlorinated solvents, pesticides, metals, radionuclides, explosives, and excess nutrients. Phytoremediation of metals and metalloids involves plant uptake and accumulation of the pollutant metal at concentrations that might be several fold higher than that in the polluted environment around the plant. In the case of organic compounds, plants act by volatilizing, transforming or degrading the pollutant. Experiments in our laboratory have shown that plants can be used successfully to remove antibiotics from water.
Experiments in our laboratory have shown the phytoremediation capability of aquatic plants and plant hairy root cultures in removing antibiotic growth promoters like oxytetracycline (OTC) and tetracycline (TC) from water. Myriophyllum aquaticum (parrot feather) and Pistia stratiotes (water lettuce) were the aquatic species, while Helianthus annuus (sunflower) was the root culture studied for antibiotic remediation. The aquatic plants were grown in Mason jars, and the roots were cultured in 250-ml Erlenmeyer flasks containing 75 mL of microbe-free plant medium. During the course of the experiments, antibiotic concentrations in the aqueous medium were analyzed by using an HPLC-based method (high performance liquid chromatograph with UV detection). Control experiments, performed without plants to determine antibiotic degradation due to light or natural conditions, did not reveal any significant results in the time frame that the phytoremediation effects of the plants were studied (maximum of two weeks).
Parrot feather demonstrated antibiotic removal rates ranging from 60 to 100% in water containing OTC/TC at concentrations up to 10 mg/L in 2 weeks, with the maximum removal occurring in the first two days. Water lettuce gave complete antibiotic removal within 6 days, and hairy roots of sunflower gave complete antibiotic removal within 7 days, for the same concentration range. Filtered root exudates from these plant systems gave comparable antibiotic removal. The disappearance of the antibiotics on the exposure to root exudates, in the absence of live plants, may be due to the presence of some rhizospheric compounds (like enzymes) that may degrade/transform the antibiotics. Figure 5 shows the results obtained for water lettuce on exposure to 5 mg/L of TC. Similar disappearance curves were observed for both antibiotics with the other plant systems, as well.
Thus, aquatic species, as well as terrestrial plants (sunflower), have potential to remove antibiotics from water. For developing this potential into practical field applications, we have begun studies to evaluate water lettuce in greenhouse-scale wetlands. Although the potential for phytoremediation of antibiotic-contaminated water has been demonstrated, research and financial inputs are required to realize this potential in a practical situation.
