es500351e_si_001.pdf (3.73 MB)
Biotransformation of Trace Organic Contaminants in Open-Water Unit Process Treatment Wetlands
journal contribution
posted on 2014-05-06, 00:00 authored by Justin
T. Jasper, Zackary L. Jones, Jonathan O. Sharp, David L. SedlakThe
bottoms of shallow, open-water wetland cells are rapidly colonized
by a biomat consisting of an assemblage of photosynthetic and heterotrophic
microorganisms. To assess the contribution of biotransformation in
this biomat to the overall attenuation of trace organic contaminants,
transformation rates of test compounds measured in microcosms were
compared with attenuation rates measured in a pilot-scale system.
The biomat in the pilot-scale system was composed of diatoms (Staurosira construens) and a bacterial community dominated
by β- and γ-Proteobacteria. Biotransformation was the
dominant removal mechanism in the pilot-scale system for atenolol,
metoprolol, and trimethoprim, while sulfamethoxazole and propranolol
were attenuated mainly via photolysis. In microcosm experiments, biotransformation
rates increased for metoprolol and propranolol when algal photosynthesis
was supported by irradiation with visible light. Biotransformation
rates increased for trimethoprim and sulfamethoxazole in the dark,
when microbial respiration depleted dissolved oxygen concentrations
within the biomat. During summer, atenolol, metoprolol, and propranolol
were rapidly attenuated in the pilot-scale system (t1/2 < 0.5 d), trimethoprim and sulfamethoxazole were
transformed more slowly (t1/2 ≈
1.5–2 d), and carbamazepine was recalcitrant. The combination
of biotransformation and photolysis resulted in overall transformation
rates that were 10 to 100 times faster than those previously measured
in vegetated wetlands, allowing for over 90% attenuation of all compounds
studied except carbamazepine within an area similar to that typical
of existing full-scale vegetated treatment wetlands.