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An American University Constructed Wetland

An American University Constructed Wetland. Achieving the Green Dream By: Sara Schwartz. What is a Constructed Wetland?. Wastewater treatment system based on ecological systems found in natural wetlands Able to control the wetland to meet certain treatment standards

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An American University Constructed Wetland

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  1. An American University Constructed Wetland Achieving the Green Dream By: Sara Schwartz

  2. What is a Constructed Wetland? • Wastewater treatment system based on ecological systems found in natural wetlands • Able to control the wetland to meet certain treatment standards • Vegetated submerged bed: water flows through media (gravel) instead of being exposed to the air

  3. Basic Components • Pre-treatment tank: solids settle here • Cells containing plants and media • Plants: roots act as substrate for bacteria which digest organic matter ex. Bulrush, Cattail • Media: usually gravel, acts as filter for suspended solids • Liner: type of plastic or rubber • Inlet and outlet drains: help regulate water flow • Indoor filters: increase clarity, decrease particulate • Storage tank

  4. Water Flow Storage tank trickle filter (cylindrical tank with plastic media and air, different bacteria hosted and treats different contaminants), one of two top cells, sand filter, third cell, 1/3 to sand filter and 2/3 back to trickle filter to repeat process Inside: 2 different sized micron filters UV filter sock filterpressuretankstoilets

  5. Commonly Asked Questions • Are they reliable? What do they treat? Performs many of same functions as conventional wastewater treatment, acts as filter and a sink for sediment and precipitates, recycles and transforms nutrients, treats total suspended solids, biochemical oxygen demand, nitrogen, metals, toxic organics • Does it smell? May have odors by inlet pipes, but overall not a problem because water remains below the surface of the media • What about bugs? No pools of standing water exposed to air, so not a problem

  6. Nitrogen Removal

  7. Commonly Asked Questions • How long do they take to become fully operational? Sidwell took about 1.5 years, need more than one growing season to reach proper plant density, and 3 to 6 months for microbial biomass to establish in media • How much effort is needed for operation and maintenance? About one day a week for labor, monthly or weekly inspection of weirs, weekly sampling of water, control panel provides constant feedback for technicians • How long do they last? Estimated to last 15 years but systems vary • What happens in the winter? System still works but transformation and removal of nitrogen may occur at slower rate

  8. Our Wetland • Location: front lawn Beeghly-unused, natural slope, visible to visitors, proximity to science classes • Capacity: treat about 300 gallons a day from bathrooms (small system), requires about 300 square feet, lawn is 14,700 square feet • Would wait for extension to be built

  9. Costs • Upfront: EPA estimates $20 per ft2, AU wetland=$6000, lots of factors including aesthetics • but with other filters and piping NSI says $64,540.88 • Maintenance: about 6% of total cost, paid annually, $360, NSI says a couple thousand a year, energy costs minimal • Funding options: DDOE $986,000 in grants for LID/green infrastructure, Chesapeake Bay Trust grants, EPA grants for green infrastructure

  10. Benefits • slow the flow of storm water and decrease sewage overflows into D.C. rivers • reduce our use of the D.C. water supply, reduced Sidwell Friends Middle School’s use of the water supply by 93% • decrease the university’s water bill by reusing treated water for toilet flushing, take in less water and put out less water, thus decreasing those charges on our water bill • could help us gain up to 9 LEED credits, also give us more points for our STARS report and contribute to our status as a leading green school

  11. Benefits • educational outreach possibilities for Chemistry, Biology, Water Resources, Ecohydrology, Sustainable Cities, and more (checking nitrogen, pH, dissolved oxygen, etc.). • research opportunities for professors such as Dr. MacAvoy studying movement of nutrients, and the new professor specializing in water. • noticeable feature on campus tours and therefore a good example of how AU is working to be sustainable • the construction of a wetland would not impact the extension of the Beeghly building

  12. Next Steps • Receive quote from Natural Systems International -said water from lab sinks would be okay, cleaning supplies down drain more of a concern, look for mop sinks in maintenance closets -could design it to get nitrogen out so can use for irrigation - Not easy to re-plumb toilets, maybe just use for extension • More research: better estimate of wastewater (see number of students in classes, faculty profile, how much will come from extension), effect of reduction of students in summer, see how much space available for indoor filters • Submit to Facilities Management, Office of the Architect, District Department of Health

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