Concerns arise when excessive irrigation of the container crops grown in soilless media leads to leaching and loss of nutrients and chemicals in runoff. The resulting runoff can escape from production areas and have a negative impact on surface and ground water.
The presence of nutrients in runoff and concerns of their impact on surface and groundwater quality has undergone increasing interest and scrutiny from the public, environmental groups, governmental agencies, and elected officials. Since its enactment, the U.S. Environmental Protection Agency (EPA) has enforced provisions of the Clean Water Act related to point-source pollution. In 1999, the EPA began enforcing nonpoint source pollution controls, mandating that all states implement a Total Maximum Daily Load (TMDL) program for all watersheds and bodies of water.
Constructed wetlands (CWs) have been promoted as inexpensive, low-technology approaches to treating agricultural, industrial, and municipal wastewater to comply with increasingly stringent environmental regulations. CWs, or marshes built to treat contaminated water, incorporate soil and drainage materials, water, plants, and microorganisms. "Surface-flow" constructed wetlands resemble shallow freshwater marshes and generally require a large land area for wastewater treatment. More effective for greenhouse and nursery operations with limited production space and expensive land are a type of constructed wetland called "subsurface flow". Subsurface flow wetlands consist of a lined or impermeable basin filled with a coarse medium, typically gravel, and wetland plants. Wastewater flows horizontally or vertically below the surface of the media to prevent exposure to humans or wildlife.
Robert Polomski and his colleagues at Clemson University published a study in the June 2008 issue of HortScience that investigated the nitrogen and phosphorus removal potential by a vegetated, laboratory-scale subsurface flow system. "In this study, we investigated a cost-effective approach of reducing water treatment costs. Instead of traditional wetland plants, we found that commercially available aquatic garden plants can be used in a production/remediation system."
Over an eight-week period, five commercially available aquatic garden plants received a range of nitrogen and phosphorus that spanned the rates detected in nursery runoff. According to Polomski, "the results support the use of aquatic garden plants as aesthetic and economically viable alternatives to traditional wetland plants in constructed wetlands. Although more research is necessary to address other variables, the study concluded that the use of commercially produced plants in constructed wetlands has the potential to generate revenue for producers.
Michael W. Neff | EurekAlert!
Waste in the water – New purification techniques for healthier aquatic ecosystems
24.07.2018 | Eberhard Karls Universität Tübingen
Plenty of habitat for bears in Europe
24.07.2018 | Deutsches Zentrum für integrative Biodiversitätsforschung (iDiv) Halle-Jena-Leipzig
There are currently great hopes for solid-state batteries. They contain no liquid parts that could leak or catch fire. For this reason, they do not require cooling and are considered to be much safer, more reliable, and longer lasting than traditional lithium-ion batteries. Jülich scientists have now introduced a new concept that allows currents up to ten times greater during charging and discharging than previously described in the literature. The improvement was achieved by a “clever” choice of materials with a focus on consistently good compatibility. All components were made from phosphate compounds, which are well matched both chemically and mechanically.
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New design tool automatically creates nanostructure 3D-print templates for user-given colors
Scientists present work at prestigious SIGGRAPH conference
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Scientists at the University of California, Los Angeles present new research on a curious cosmic phenomenon known as "whistlers" -- very low frequency packets...
Scientists develop first tool to use machine learning methods to compute flow around interactively designable 3D objects. Tool will be presented at this year’s prestigious SIGGRAPH conference.
When engineers or designers want to test the aerodynamic properties of the newly designed shape of a car, airplane, or other object, they would normally model...
Researchers from TU Graz and their industry partners have unveiled a world first: the prototype of a robot-controlled, high-speed combined charging system (CCS) for electric vehicles that enables series charging of cars in various parking positions.
Global demand for electric vehicles is forecast to rise sharply: by 2025, the number of new vehicle registrations is expected to reach 25 million per year....
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