It is important to note that wetland systems are generally part of a multi-part treatment system and for wastewater, typically serve as secondary or tertiary treatment technologies.
Benefits of Wetland Technologies for Wastewater Treatment:
- Non-proprietary (constructed wetlands): Allows for capacity building and technology transfer
- Stimulates the local economy by using most if not all locally sourced materials.
- Treatment does not require external energy or chemicals to operate (Considerably lower O&M costs vs. conventional packaged treatment plants)
- Wetlands polish excess nutrients, preventing pollution downstream
- Educaitonal value and opportunities
- Provide LEED credits
- Aesthetically pleasing
- Convert Wastes to Resources. Produce valuabel byproducts such as flowers, fodder, and water ready for reuse.
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The U.S. Environmental Protection Agency (EPA) has acknowledged constructed wetlands as an ideal wastewater treatment system due to their affordability, passive design, natural appearance, and lack of odors. Constructed wetlands are inherently engineered to be mechanically simple, yet ecologically complex. The system is a passive, lined reactor following primary treatment in an anaerobic digester or septic tank (for smaller systems). The wetlands provide high quality secondary treatment that do not require external energy for treatment (thus little to no maintenance and low operating costs) while also being an aesthetic addition to the landscape.
In subsurface flow (SSF) wetlands all water flows below the surface and the plant roots and gravel provide substrates for microorganism attachment. The two media provide different habitats that allow for both aerobic and anoxic bacteria to reside in the same ecosystem which allows for an efficient breakdown of a range of pollutants. In doing so it converts waste into resources via the complex food web. Another significant advantage to a SSF wetland is lack of odor since the all the water flows beneath the surface of the wetland. Furthermore, the wetland treatment system can showcase native and local tropical plants that promote the local culture, regional biodiversity and can provide opportunities for commercial harvest. The wetland technology will naturally provide Hawaii Department of Health R-3 quality reuse water without the need of external energy or chemicals and can meet R-2 and R-1 with disinfection. In addition the systems are excellent in removing nutrients such as ammonia and nitrates, which protects fragile ecosystems and groundwater supplies where disposal/water reuse occurs.
Eco-Machines are essentially tank-based wetland technologies serving as secondary and tertiary treatment systems.
The driving engine for treatment is the wetland ecology occurring within the various substrates.
What makes these systems different than constructed wetlands is that they are designed for placement in urban settings or where land cost is at a premium. In effect, the tank-based strategy allows for treatment to occur vertically where wastewater is recycled multiple times within the wetland treatment cells before discharge to maximize the treatment process within each tank.
This process does require external energy, although typically still considerably less than conventional treatment systems, but the trade off is a smaller land footprint. Often Eco-Machines are coupled with constructed wetland treatment systems to achieve the benefits of both systems and can be operated on renewable energy sources.
Eco-machines maintain all the other benefits of constructed wetland in that they are aesthetically pleasing, minimize odor, can produce commercially viable byproducts and have educational and outreach potential
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Roth Ecological Design International
