Abstract
Pharmaceuticals and other micropollutants have been detected in drinking water, groundwater, surface water, and soil around the world. Even in locations where wastewater treatment is required, they can be found in drinking water wells, municipal water supplies, and agricultural soils. It is clear conventional wastewater treatment technologies are not meeting the challenge of the mounting pressures on global freshwater supplies. Cost-effective ecological wastewater treatment technologies have been developed in response. To determine whether the removal of micropollutants in ecological wastewater treatment plants (WWTPs) is promoted by the plant-microbe interactions, as has been reported for other recalcitrant xenobiotics, biofilm microbial communities growing on the surfaces of plant roots were profiled by whole metagenome sequencing and compared to the microbial communities residing in the wastewater. In this study, the concentrations of pharmaceuticals and personal care products (PPCPs) were quantified in each treatment tank of the ecological WWTP treating human wastewater at a highway rest stop and visitor center in Vermont. The concentrations of detected PPCPs were substantially greater than values reported for conventional WWTPs likely due to onsite recirculation of wastewater. The greatest reductions in PPCPs concentrations were observed in the anoxic treatment tank where Bacilli dominated the biofilm community. Benzoate degradation was the most abundant xenobiotic metabolic category identified throughout the system. Collectively, the microbial communities residing in the wastewater were taxonomically and metabolically more diverse than the immersed plant root biofilm. However, greater heterogeneity and higher relative abundances of xenobiotic metabolism genes was observed for the root biofilm.
Highlights
The treatment of human wastewater by ecological systems predates the advent of engineered wastewater treatment plants (WWTPs)
While exposure to human pathogens is greatly reduced in communities where modern wastewater treatment technologies have been implemented1, widespread detection of micropollutants in the environment2 raises serious concerns about the efficacy of modern WWTPs to treat this class of contaminants
Using whole metagenome sequencing (WMS) we have examined whether the microbial populations residing on the plant roots immersed in wastewater of an ecological WWTP showed evidence of the capacity for micropollutantant biodegradation
Summary
The treatment of human wastewater by ecological systems predates the advent of engineered wastewater treatment plants (WWTPs). The organizing principle of ecological wastewater treatment is the construction of “task oriented mesocosms” of eutrophic ecosystems that, like conventional systems, primarily rely on microbial metabolic processes to achieve water quality goals. A number of ecological systems have been operating around the world for decades including constructed wetlands, Eco-MachinesTM4, and biofilters for residential, industrial, and municipal wastewater. These systems perform reliably based on tertiary wastewater standards, while reducing operational costs and environmental and human health impacts of wastewater. The unique potential provided by ecologically engineered waste management is direct conversion of a liability (i.e. wastewater) to an asset (sequestered carbon, biomass, products, biodiversity, etc.)
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