Water Resources Research Act Program

Details for Project ID 2017MT312B

Effects of floating treatment wetlands on the abundance and removal of dissolved and nanoparticulate contaminants in waste water lagoons

Institute: Montana
Year Established: 2017 Start Date: 2017-03-01 End Date: 2019-02-28
Total Federal Funds: $15,000 Total Non-Federal Funds: $40,463

Principal Investigators: Benjamin Colman

Project Summary: In the state of Montana, >84% of stream length that has been assessed is impaired, with metals and excess nutrients accounting for 40% and 32% of impaired stream miles, respectively. Typically measured as total metals, nitrogen, and phosphorous, these contaminants can have deleterious effects on aquatic life, which ultimately drives the sportfishing economy of Montana, estimated as a nearly $500 million industry in in 2011 alone. Municipal wastewater discharges serve as a substantive source of these contaminants in Montana surface waters. In particular, wastewater lagoons are used in many of the state’s small- to medium-sized municipalities, and nearly 40% of the these wastewater lagoon systems have had numerous violations of the Clean Water Act in the past three years for discharge of nutrients and metals at levels in excess of those permitted. While much of the regulatory emphasis is on total contaminant loads, the likelihood that a given contaminant will be removed or interact with organisms following discharge to surface waters likely depends on the form (particles > 0.45 μm; small colloids 1-450 nm; truly dissolved solutes, < 1 nm). A potentially cost effective way of adding to the capacity of existing infrastructure to remove nutrients and metals is through the use of floating treatment wetlands. These floating islands support hydroponic plant growth, with roots occupying a large fraction of the water column, thereby serving as biogeochemical hot spots that allow increased nutrient and metal removal rates compared to island-free lagoons. In this study, we propose to examine the distribution of contaminants within different size fractions in the water column in five wastewater lagoon systems. We further propose to examine how the concentrations and forms of these contaminants is altered in the presence or absence of floating treatment wetlands in outdoor simulated wastewater lagoons. This work will increase our understanding of how these contaminants move through wastewater lagoons systems, as well as highlight the mechanism and efficacy of a comparatively inexpensive ancillary treatment that could supplement existing wastewater infrastructure rather than fully replacing it.