Roux Quick Facts

Engineered Natural Systems, Constructed Treatment Wetlands, Phytoremediation, and Natural Media Filtration


I. Quick Facts About Engineered Natural Systems

What are "Engineered Natural Systems"?
Engineered Natural Systems are a family of innovative sustainable technologies designed to passively reduce water discharges as well as the contaminant levels in these discharges. The term includes various natural technologies, including constructed treatment wetlands, phytotechnology, and natural media filters, to name a few.

What are the capabilities of Engineered Natural Systems?
Engineered Natural Systems are amenable for groundwater and surface water remediation, stormwater management (i.e., stormwater runoff and non-point source runoff), landfill capping, leachate treatment, and municipal and industrial wastewater treatment and discharge reduction.

What are the benefits of Engineered Natural Systems?
Under appropriate environmental conditions, Engineered Natural Systems can provide a highly effective, low cost alternative to conventional water treatment and contaminant remediation systems. Compared to conventional approaches, capital investment savings can be greater than 60%; O&M savings can be greater than 70%.

What contaminants can be remediated by Engineered Natural Systems?
Engineered Natural Systems have been successfully implemented to remove BTEX, PAHs, PCBs, metals, total suspended solids (TSS), biochemical oxygen demand (BOD), nutrients and pathogens from the environment.

What are the mechanisms of contaminant removal?
Engineered Natural Systems use a combination of physical, biological, and geochemical mechanisms, in both aerobic and anaerobic environments.
- Physical removal mechanisms include sedimentation, filtration, adsorption, and volatilization.
- Biological removal mechanisms include bacterial mediation, plant metabolism, absorption, and natural decay.
- Geochemical removal mechanisms include precipitation, adsorption, hydrolysis, and oxidation-reduction (redox) reactions.
- Aerobic mechanisms work on organic constituents such as biochemical oxygen demand (BOD), pathogens, ammonia nitrification, BTEX, and glycols.
- Anaerobic mechanisms work on metal constituents, halogenated volatile organic compounds (e.g., TCE, PCE), PCBs, and nitrate denitrification.

The sun serves as the energy source to drive and sustain Engineered Natural Systems. Electricity requirements are minimal or are not required at all.


II. Quick Facts About Constructed Treatment Wetlands (CTWs)

What is a constructed treatment wetlands?
A constructed treatment wetlands is a highly engineered 'natural' treatment system designed to emulate and optimize the physical, chemical, and biological removal mechanisms found in conventional treatment systems. Constructed treatment wetlands are comprised of a selected suite of plant and microbial life in conjunction with a specific substrate (i.e., soil type) to remove contaminants from water. Through evaporation and plant transpiration to the atmosphere, CTWs can substantially reduce the volume of water that needs to be discharged.

How effective are constructed treatment wetlands in removing contaminants?
Constructed treatment wetlands have very high contaminant removal efficiencies. Contaminant removal rates of 99% have been achieved for heavy metals, organics (BTEX, PAHs), BOD, nutrients, suspended solids, and pathogens.

What are the benefits of constructed treatment wetlands over conventional technologies?
Constructed treatment wetlands can be just as effective or even more effective than conventional technologies. However, as a passive technology, constructed treatment wetlands are much simpler and less expensive to operate. Importantly, the capital investment and O&M costs of constructed treatment wetlands are dramatically lower than conventional technologies. For wastewater treatment, capital and O&M costs can be 50-90% less than conventional systems. For surface water or groundwater remediation, capital costs can be 50-80% less than conventional technologies. O&M savings over conventional technologies typically range from 70-90%.

Are constructed treatment wetlands amenable for remediating surface water and groundwater?
The technology is amenable for treating water from both environments. For either application, the technology can be designed as open water marshes or subsurface flow type systems. The specific form of constructed treatment wetlands is selected and designed to meet a specific environmental and/or treatment need.



III. Quick Facts About Phytoremediation

What is phytoremediation?
Phytoremediation is an Engineered Natural System that uses a select variety of fast growing trees and plants to remove contaminants from soil, sludges, landfill leachate, groundwater, surface water, stormwater, and wastewater.

What contaminants are amenable for treatment by phytoremediation?
Phytoremediation is a sustainable technology for remediating metals, pesticides, chlorinated and non-chlorinated solvents, petroleum hydrocarbons, nutrients and PAHs.

Can phytoremediation be used instead of conventional remedial technologies?
Phytoremediation can be used instead of or along with conventional cleanup methods. The technology has been successfully used to replace long-term groundwater pump and treatment systems at remediation sites, as passive plume containment and treatment systems, and as alternative caps for closing municipal and industrial waste landfills.

How does phytoremediation work?
Phytoremediation is a passive technology that uses the natural features of plants to intercept, sequester, stabilize, uptake and/or degrade environmental contaminants. Selected tree species can also evaporate and transpire large quantities of rainwater, applied wastewater, and/or groundwater. The root zone (i.e., rhizosphere) of the plant also provides many of the remediation functions identified above. Collectively, they serve as a natural "pump and treat" system for contaminant mitigation.


IV. Quick Facts About Natural Media Filtration

What is natural media filtration?
Natural media filtration is an innovative, sustainable technology that uses high organic carbon natural media, such as leaf mulch, mushroom compost, and peat to filter contaminants in a variety of waters (i.e., stormwater, process water, and wastewater, landfill leachate, acid mine drainage, and agricultural runoff). The technology is also used in groundwater seeps, for the containment of contaminants in sediments, and to reduce the volume of water discharged downstream of a site or to a publicly owned treatment works (POTW).

What are the mechanisms of contaminant removal in natural media filtration?
Natural media filtration removes pollutants by filtration, adsorption, ion exchange, precipitation, and biodegradation. The high sorption capacity of the media effectively sequesters heavy metals, oils, grease, nutrients, and organics.

What conventional technologies can be replaced by natural media filtration?
Under appropriate conditions, natural media filtration can replace conventional gravel, sand, membrane, and even granular activated carbon (GAC) filtration systems.

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Additional Information

The Engineered Natural Systems Group of Roux Associates, headquartered in Roux's Long Island, NY Office, has researched, designed, and installed sustainable natural systems for clients such as Alcoa, BASF, BP, Norfolk Southern, Exxon Mobil, and the Town of Glen Cove (NY).

To view Roux's announcement to the media, "Alcoa Develops Sustainable 'Engineered Natural Systems' to Reduce Discharges and Contaminant Levels at its Aluminum Facilities; Roux Associates Provides Professional Expertise," click here.

For more information, please contact Walt Eifert, Principal Hydrologist and Director of Roux Associates' Engineered Natural Systems Group, at 304-274-0156 or weifert@rouxinc.com.