Year: 2026
Type: article
Abstract: We conducted a long-term assessment of how natural free-water surface (FWS) wetlands respond to sustained loads of partially treated municipal effluent. We quantified the effects on vegetative cover, ammonium concentration, and fecal coliform bacteria densities and compared them to constructed wetlands with hydrologically defined flows. Variations in the area of open water and floating vegetation converted from emergent marsh, shrub or bottomland hardwood forest (0 to 124.6 ha) were directly proportional to the nitrogen loading at all eight sites (range 5.4 to 24.6 thousand Kg N yr−1). Trees exposed to effluent at five locations sometimes died in the first year, or they took decades to die. At the one location with fecal coliform data, their densities were directly related to ammonium concentrations, which were within the concentration range of untreated municipal sewage water. Ammonium levels exceeded US EPA chronic toxicity standards at three locations and aquatic toxicity levels developed by independent scientists at all eight locations. The loss of organic peat and habitat has multiple consequential effects that may be quick to happen or subtle, and be slow to restore, if at all. Compared to constructed wetland treatment systems, FWS systems are more difficult to constrain, have much reduced predictabilities and bring unwelcome consequences.
Source: Water
DOI: 10.3390/w18030418
Authors: R. Eugene Turner, James E. Bodker, Christopher Schulz
Institutions: Louisiana State University, Southeastern Louisiana University
Language: English
Subfield: Waste Management and Disposal
Field: Environmental Science
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $3,137
Funder: National Science Foundation
OpenAlex ID: W7127957665