WaterHub at Emory University: Atlanta
From Waste to Resource
Appears in the Summer 2016 issue.
As water resources grow increasingly taxed and scarce in communities across the U.S., an Atlanta university is turning to an unlikely resource to reduce its drinking water demand: the local sewer. The WaterHub at Emory University turns waste into a resource, recycling wastewater via an ecological treatment facility–the first of its kind in the U.S. Its sustainable treatment process sets an example of how adaptive technology can be used to meet water needs while reducing water costs.
Water reclamation and reuse helps minimize potable water consumption, reduces strain on sewer lines and reduces potential for wastewater discharge from the combined sewer system. Since wastewater is treated closer to the source and reused on campus, water reclamation reduces energy use and the carbon footprint associated with the treatment and distribution of water. Additionally, this project minimizes risk by limiting exposure to drought with backup storage capable of serving Emory's critical operations.
Emory’s WaterHub is designed to supply nearly 40% of campus water needs by replacing potable water with reclaimed water. Wastewater circulated through the WaterHub is cleaned and used as process makeup water in Emory’s steam and chiller plants and for toilet flushing in select residence halls. Previously, drinking-quality water was being used for these purposes.
At full capacity the system can recycle up to 400,000 gallons per day, reducing Emory’s draw of potable water from Atlanta’s municipal water supply by up to 146 million gallons of water annually. More than 43 million gallons have been processed since May 2015, when the WaterHub began operating, through mid-April 2016.
The WaterHub includes a 50,000 gallon underground storage tank. This reserve will allow Emory’s heating and cooling systems to function for an average of seven hours if water availability is interrupted.
Using a small footprint of undeveloped land on the densely developed Emory campus, the WaterHub features a greenhouse-like structure and outdoor planting areas. The project was designed by Sustainable Water, a Virginia-based provider of water reclamation and reuse solutions that supplies the WaterHub’s biomimetic technology. Atlanta-based Reeves Young served as general contractor, while McKim and Creed provided the mechanical engineering services for the project.
The WaterHub’s technology is housed on two nearby sites on Emory's campus. To the north is the greenhouse, a nearly 2,000 square foot concrete and glass structure. To the south is a series of largely underground concrete processing tanks. The portion of the tanks that extends above ground by a few feet appears as ornamental landscaping planters; in reality the seven tanks are up to 25 ft deep.
Building the WaterHub involved coordinating technology that had never been assembled together before. While hydroponic systems and wetland systems have been used successfully before, this is the first location that uses them together.
The two technologies are parallel treatment systems, purposefully kept separate to provide operational redundancy and research opportunities for students.
The treatment times differ for each (hydroponic is more efficient for larger quantities), so careful evaluation was needed to make sure the right amounts of wastewater were being sent to the appropriate technology to process the desired amount of recycled water.
Constructing the WaterHub on two tight footprints on a highly developed campus also presented logistical challenges. Construction and materials delivery required close coordination to avoid impacting the functions of the university. Another challenge involved installing purple reclaimed water distribution piping throughout the campus.
Workers hang purple piping to transport the reclaimed water from the WaterHub to where it will be reused in campus chiller plants, the steam plant and residence halls for toilet flushing. This pipe serves the largest chiller plant on campus.
A water purchase agreement with Sustainable Water made the project possible and, over time, will provide water at a lower cost than the municipal supply—and at a long-term stable rate. This agreement is expected to save Emory millions of dollars in water utility costs over 20 years. The economics of the facility were based on current and projected sewer pricing, ability to displace potable water with recycled water, and desired technology and aesthetics. While this is not a “one size fits all” application, decentralized treatment such as this system can be replicated in a variety of physical settings and should be considered if all of the above factors align.
The WaterHub treats local wastewater through biomimicry technology (Figure 1). Harnessing the power of biological processes found in nature, the WaterHub intensively grows beneficial bacteria and microorganisms in natural ecosystems. The ecosystems treat large quantities of water in small spaces in short periods of time.
The WaterHub uses two technologies to develop large colonies of hungry microorganisms:
• Hydroponic technology, which contains plants and specially engineered submerged fixed film textile media; and
• Reciprocating wetland technology, which involves filling and draining wetlands to mimic the ebb and flow of tidal marshes.
Wastewater is drawn from an on-campus sewer pipe and then pumped into the greenhouse portion of the WaterHub. . There it travels through a series of interconnected, sequentially operated cascading hydroponic biohabitats.
Water is circulated through aerobic, anoxic and anaerobic chambers and . These bioreactors contain specially engineered free moving plastic pellets or engineered fixed-in-place textile in addition to suspended plant roots. The pellets, textile and plant roots serve as a natural habitat for 2,000 to 3,000 different microorganisms and form a unique ecosystem that breaks down waste.
From the greenhouse, the water travels to the outdoor hydroponic treatment tanks (on the south site) for further processing .
The microorganisms consume the nutrients in the wastewater and ultimately convert it to high-quality reclaimed water.
Additionally, on the south site, a demonstration treatment system uses an alternative ecological treatment technology. The demonstration reciprocating wetland mimics the ebb and flow of tidal marshes and creates an alternate habitat for waste-eating microorganisms. The reciprocating wetland technology is well-suited for rural areas and developing world communities that have adequate land resources and seek an ultra-energy–efficient process and simplified construction.
After biological treatment the wastewater is filtered and and disinfected with ultraviolet (UV) light . The biological processes remove all of the nutrients and color, but disinfection and filtration is required to ensure all pathogens are also removed. After treatment and disinfection, a portion of the water is stored in the reuse tank , while the remainder is distributed to select campus locations .
The WaterHub minimizes resources needed to treat wastewater in terms of energy, land and chemical use. Unlike traditional systems, which use enormous pumps to move water through progressive treatment areas, the WaterHub’s ecological treatment processes contain simpler mechanical components and rely on gravity to move water from one level of treatment to another. Additionally, with its close proximity to the source of the wastewater, the WaterHub requires relatively minimal energy to transport waste for processing.
In contrast, centralized municipal treatment systems require miles of infrastructure and multiple pumping stations to move wastewater long distances for treatment and then for redistribution.
Ultra-efficient and compact, the WaterHub is much smaller than municipal systems and requires significantly less land, so it’s ideal for highly developed urban spaces that have a smaller and isolated nonpotable water demand.
The WaterHub used over 400,000 kWh of electricity in its first 10 months of operation with 6,500 kWh displaced by on-site solar generated power. A majority of the energy is used to distribute recycled water across campus.
Designed to be aesthetically pleasing with lush plantings, no wastewater is exposed in the treatment process. The WaterHub’s odor-free, natural aesthetic allows it to be located in densely populated urban areas. Traditional wastewater treatment systems are typically large open basins with exposed wastewater located on outlying, low-value land.
The WaterHub’s ecological approaches to wastewater treatment mimic natural methods of water treatment found in wetlands, tidal marshes and rivers. Traditional wastewater systems often rely on more mechanical and chemical approaches. Further, the WaterHub’s ecological treatment system breaks down organic materials in water more completely than traditional activated sludge treatment systems.
The WaterHub serves as a living, learning laboratory for research and teaching from environmental, legal, ethical, human health, and other perspectives. This research will help determine the applicability and functionality of water reclamation beyond Emory’s campus.
The Center for Global Safe Water (CGSW) at Rollins School of Public Health at Emory has already conducted applied research, training, and evaluation in water, sanitation, hygiene and health implications. Students seeped in theory and program administration have gained practical exposure and real-world experience in sampling and analysis methods.
Going forward, CGSW researchers will use the WaterHub as a field learning resource and will monitor the removal of enteric microbes and pathogens by testing the influent and effluent for fecal coliforms, E. coli, coli phage, and selected enteric pathogens (norovirus, adenovirus, and enterovirus).
CGSW will also monitor the parameters required by the State of Georgia for reclaimed water. The sampling data will aid in analyzing overall treatment efficacy and microbiological quality of the reclaimed water.
The data on the pathogens could be used to estimate the human health risk associated with reuse as drinking water (not allowed under U.S. regulations) and help determine if similar facilities can be effectively used in developing countries.
Through collaboration with Emory’s facilities management, professors are invited and encouraged to incorporate the WaterHub in their curriculum. The facility will provide research and teaching opportunities for those in environmental sciences, chemistry, biology, etc. Undergraduate students pursuing a minor in Sustainability can explore and research the environmental, social, and economic aspects of the WaterHub. In particular, these opportunities also provide students with an option for their required capstone project that integrates classroom work with experiential learning through research, internship, or sustainability-related activity.
Tropical plants in these hydroponic treatment chambers were selected for this controlled environment; outdoor hydroponic chambers use more native plants.
Know what’s going down your drains, and when. Emory has a lot of lab space tied to the sewer shed from which it is pulling, so invest the time up front to interview the researchers and understand what types of chemicals and other materials they may be putting into the sewer and roughly at what time of day. Sometimes it’s smart to let a high-level discharge of a chemical bypass and continue along in the existing sewer, if that timing can be determined.
Collaborate early and often with the local jurisdiction having authority. In Emory's case, it was seeking approval from the local county to mine its sewer system. Engineering and economic impacts resulted from this project, such as the impact that lesser wastewater in the county’s pipe has on the existing system hydraulics and a potential loss of revenue for the county.
Have patience during start-up. This facility is the first of its kind in the U.S., so a longer learning curve was anticipated and is being realized. Water chemistry consistency can be erratic and not always compatible with end-use needs; a partnership is necessary between the operator and owner to thoughtfully and patiently work through such issues.
The WaterHub at Emory University has had multiple noteworthy results: providing relatively inexpensive water for utility purposes through sustainable means; meeting the university’s educational and research mission; and expanding community outreach and education around water conservation.
The financial benefits gained from the WaterHub stem from purchasing water at a lower and long-term stable rate than possible with municipal drinking water. •
About the Author
Brent Zern, P.E., LEED AP, is the assistant director for environmental, safety, and maintenance programs for Emory University in Atlanta.