In 2010, while innocently sitting in my office in the Department of Sustainable Technology and the Built Environment at Appalachian State University in the small mountain town of Boone, North Carolina, a diminutive and unassuming Appropriate Technology undergraduate student entered, wanting to discuss a research project. Bobbie Jo Swinson worked at a local salon as a hair stylist and wondered if I would be interested in helping her design a graywater treatment system for her workplace, Haircut 101. Our Department has a strong tradition of supporting undergraduate research, and our research agendas are most often driven by the passion of our students. So I was not about to say no, but I must admit that I thought it to be a fairly off-the-wall concept that was unlikely to bear much fruit. Yet the more Ms. Swinson explained her idea, the more impressed I became with both the concept, her level of expertise, and her firm grasp of the big picture. As Swinson later told the Winston-Salem Journal, “I love making people feel better about themselves and giving them a fresh look, which sometimes gives them a whole new world, [but] as I was shampooing people and reading these bottles and the chemicals in them, it seemed we needed to find a better way of treating water.” From this moment of revelation grew the brilliant and challenging idea of designing a functional yet attractive plant-based graywater treatment system that could be incorporated into the business space.
There is a popular meme on the internet that depicts a young blonde woman from a technologically developed country speaking with a small child from a less technologically developed country. “You mean you have so much clean water that you poop in it?” asks the child incredulously. Strangely enough, the answer to this child’s question is, “Yes!” This resounding yes rings true in reality and is absurd in a world where safe drinking water is so hard to find. Every day, 6,000 children die of water-related diseases, and more than half of the developing world’s population is suffering from one or more of the main diseases associated with unsafe water and poor sanitation.1 Nevertheless, humans continue to contaminate large quantities of relatively benign graywater with small quantities of sewage. Graywater treatment and reuse in toilets is one way to start addressing the absurdity of pooping in drinking water; however, the ultimate goal is to have graywater and sewage wholly separate, with graywater being treated, reused, and disposed of on-site through irrigation. Such a system would get full use out of water, a precious and increasingly scarce resource, and would greatly reduce flows to overburdened wastewater treatment plants. Due to the passion of one concerned student who happened to support herself as a hair stylist, our research team at Appalachian State University, supported by funds from the US EPA P3 program, has spent the past six years investigating the first step towards that ultimate goal. The EPA P3 (People, Planet, and Prosperity) research grants are written by students under the guidance of faculty mentors. Swinson’s initial EPA P3 Phase I grant was funded, allowing us to do proof-of-concept research that led to a much larger Phase II grant. As a result, on-site graywater treatment systems have become one of the major areas of research in the Department of Sustainable Technology and the Built Environment, helping to support numerous graduate and undergraduate researchers in in both this department, as well as the Departments of Chemistry and Biology.
The thrust of our research effort has been to design a small, simple, energy-efficient, low-maintenance, and affordable system using plants and biofilters to treat graywater from hair treatment sinks for reuse in the toilet facilities of Haircut 101. Toilet reuse resolves any regulatory issues that may be associated with on-site graywater disposal, as graywater reused in toilets ultimately enters the normal sewer system. Nevertheless, graywater treatment regulations in North Carolina require specific standards to meet public health concerns. For instance, none of the graywater can be exposed while being treated, it must be dyed blue to make clear it is treated graywater, and it must be disinfected before reuse in toilets. Even though the treated graywater returns to the normal sewer system, the reuse of graywater helps to conserve water and may even slightly reduce water bills.
Based on the water consumption records of Haircut 101 from November 15, 2007 to November 10, 2011, the salon used an average of 7,190 gallons of water per month from the city water supply.2 If the salon is assumed to have around 20 open days per month, this means that the average daily water use is about 360 gallons, only a part of which is graywater. We determined through flow rate and shampoo timing tests that the salon uses an average of 165 gallons of water per day for shampooing and other sink services. Based on 20 open days per month, this translates into 3,300 gallons per month, or 39,600 gallons per year, of available graywater from the shampoo sinks alone. Based on use estimates by the owner, there are about 18 bathroom visits and four loads of laundry each day. Assuming five gallons per flush and an average laundry load of 25 gallons, toilet flushing accounts for about 1,800 gallons per month, or 21,600 gallons per year, while laundry accounts for 2,000 gallons per month, or 24,000 gallons per year. Currently, graywater reuse in North Carolina is only permitted for toilet flushing, and, according to a survey conducted with Haircut 101 patrons, over 75 percent were comfortable with graywater reuse in toilets, but much less were comfortable with reuse in laundry. Our system is designed to handle all of the graywater from shampoo bowls, therefore it could conceivably meet the needs of both laundry and lavatory services. Until that time when regulations and perceptions allow water reuse for laundry, however, we will be treating more than enough water to meet the needs of toilet flushing. Any excess graywater will overflow into the sewer system.
Based on current water utility rates in Boone, Haircut 101 spends about US$60 per month on water (not counting sewer rates), of which about US$15 goes to toilet flushing (25 percent of the water bill). Over the course of one year, this system could save Haircut 101 approximately US$180 in water costs. This figure alone is not necessarily significant, but it would also prevent the consumption of over 21,000 gallons of potable water each year, conserving a precious resource that much of the world is literally dying for lack of. Based on these utility rates, operation of the graywater system could also conceivably pay for itself. The energy needs of the system are low, utilizing an eight watt ultraviolet light and a 187 watt sump pump. Assuming 20 days of operation per month, and that the ultraviolet light and pump are always running (though in reality the sump pump does not run constantly, as it cycles on and off based on the water level in the holding tank), the total energy usage of the system would be about 96 kWh per month. The current commercial utility rate in Boone is US$0.0871/kWh, so the cost of running the system would be about US$8 per month, while potentially saving the business about US$15 dollars in water costs. While there may be some inaccuracies in these estimates, it does give a strong indication that the system could pay for itself operationally, though initial capital costs may not justify the system on a purely economic basis. As these systems are further developed, the hope is that capital and installation costs will decrease.
John Mena, the proprietor of Haircut 101, is a forward-thinking business owner who incorporates the concepts of sustainability and community into his business. Most of his conservation efforts have been in the area of lighting, using highly efficient LED bulbs and sun tubes to deliver natural light into the salon. This is his first foray into addressing water conservation for his business, and we have discussed with him other water conservation options such as low-flush toilets and low-flow faucets. Throughout the course of our research, he has been a willing partner in the effort to bringing a groundbreaking on-site graywater system to Boone. Our research team has worked with Mena each step of the way in order to ensure that the system we were developing would meet his aesthetic and functional requirements. But first, we had to prove that plants could survive in, let alone remediate, salon graywater. As such, the first phase of our EPA grant was “proof-of-concept,” establishing that plants could indeed live in and remediate Haircut 101 graywater.
It has long been recognized that plants degrade and remove chemicals from wastewater, making constructed wetlands a common wastewater treatment option. Terrestrial species such as Lolium multiflorum (Italian ryegrass), Medicago sativa (alfalfa), Typha angustifolia (narrowleaf cattail), Juncus effusus (common rush), Pontederia cordata (pickerelweed), and many more have been shown to have significant phytoremediation potential as well as the aquatic plants Lemna sp. (duckweed), Pistia stratiotes (water lettuce), and Eichhornia crassipes (water hyacinth).
Such plant-based treatment systems are known as “living systems,” a concept pioneered by the ecologist Dr. John Todd, founder of the New Alchemy Institute, who explored the application of biological principles to the development of appropriate technology for sustainable systems. Since that time, there has been substantial research and application of these biological systems. The Nutrient Film Technique of William Jewell at Cornell University is used in the Cornell EatMe Wall (as a Cornell graduate I am not surprised by this unfortunate name choice). The EatMe Wall is an esthetically pleasing panelized-facade system that serves as a graywater filtration medium. The Living Machine® at Oberlin College, designed by the same John Todd, now of Living Machines, Inc., treats up to 2,000 gallons of wastewater daily from the Adam Joseph Lewis Center for Environmental Studies using a system of engineered ecologies that include microbes, plants, snails, and insects in a beautiful, garden-like setting.
At Appalachian State University, we recreated such a structure in an already existing graywater system used at our Sustainable Biodiesel production facility on campus. Meanwhile, Mena made plumbing alterations to his business, allowing us to collect actual salon graywater from the shampoo bowls in five-gallon containers. Using this collected water, various plant species were batch tested by immersing their root systems in graywater resulting from different classes of salon services: shampoo/conditioner, hair dye, and chemical permanents. Plant health during these tests was monitored using qualitative criteria (e.g., plant color, size, and robustness) and chlorophyll fluorescence measurements. The removal of contaminants in the salon graywater was determined with a gas chromatograph mass spectrometer. Removal efficiencies from these batch tests were between 30 to 85 percent over three days and 60 to 100 percent over eight days. The plants themselves thrived in the salon graywater samples, becoming greener and more vigorous. Chlorophyll fluorescence readings quantitatively confirmed this qualitative observation.
The actual pilot-scale “living system” was a series of gravity-flow fed tanks and ponds with a recirculating pump. The plants used in the system were Lemna sp. (duckweed), Pontederia cordata (pickerelweed), Juncus effusus (common rush), Typha angustifolia (narrowleaf cattail), Lolium multiflorum (Italian ryegrass), Pistia stratiotes (water lettuce), Eichhornia crassipes (water hyacinth), and Medicago sativa (alfalfa). Removal of contaminants from 325 gallons of salon graywater by the system was between 50 to 70 percent for many constituents of concern within 24 hours (the retention time of the system).
Using these results, and considering Mena’s preferences, students designed a number of potential systems that became the basis for our first small-scale prototype: a two-trough system with a 20-gallon storage reservoir. Water was pumped from the storage reservoir to the top trough, where water flowed by gravity through the top trough to the lower trough and back to the storage reservoir. Three Matala® filters in series (low, medium, and high density) were used in the storage reservoir. The open flow configuration of these filters allowed high volumes of dirty water with very high biological oxygen demand to pass through without clogging.
A number of different pumps were tested for reliability, noise level, and affordability. Ultimately, a TACO 008-SF6 cartridge circulator pump was determined to be the best fit for the prototype and, perhaps, the final installed system. The TACO pump is completely silent and is routinely used in systems that require long-term continuous operation. Trial runs were performed to check the hydraulic performance of the system and to determine an equilibrium flow rate. Ultimately, using inline control valves, a final flow rate of 0.7 gallons/minute was found to be the optimum flow rate to balance the hydraulics of the system, which was similar to the flow rate of the Phase I living system (0.5 gallons/minute). The entire system held about 34 gallons, so at a flow rate of 0.7 gallons/min, water passed through the system about 30 times per day. As building codes for graywater systems in North Carolina require that there be no exposed open water, the prototype had covered troughs with holes cut in them, allowing the roots of the potted plants to sit in the graywater.
Tests for remediation of unique salon graywater contaminants (e.g., soaps, oils, and waxes) were performed by chemistry students under the guidance of Dr. Mike Hambourger, who incorporated the necessary lab procedures into his curriculum. Thanks to the work of Hambourger and his students, our research won the American Institute of Chemical Engineers/ Youth Council on Sustainable Science and Technology Award at the EPA P3 expo. However, during the Phase II funding period, the decision was made to transition to alternative methods for water analysis. This change better aligned our measurements with the recent NSF/ANSI 350-2011 standard for “On-site residential and commercial water reuse treatment systems.”3 Following this standard, the following parameters were chosen for analysis: temperature, pH, turbidity, total suspended solids, and chemical oxygen demand (a measure of organic contamination). These tests were considered a reasonable subset of the specifications listed in the NSF/ANSI 350-2011 standard. Sample results are shown in the graphs above demonstrating turbidity reduction and pH. Dissolved oxygen (DO) measurements were also taken from graywater in the system and were found to be low, at about 50 percent of saturation. Aerators were added to increase DO saturation, but this motivated us to reincorporate water cascades into our final design.
A second prototype, based on the design wishes of Mena, was developed for display at the P3 Sustainable Design Expo in April 2014. This second prototype was based on a very simple, three-trough system with one trough on top of a free-standing wall in the hair salon, and the other two troughs on opposite sides of the wall. Shade and graywater-tolerant plants were tested. Ferns and begonias (Begonia sp.) were most tolerant of the graywater conditions. The begonia has a particularly beautiful flower, and grew well even in stagnant, low DO water with no signs of disease. As potted plants can be easily removed and replaced, the final system is designed to allow the owner to use whatever type of plants he desires and to quickly remove any compromised plants to prevent disease or pest transmission.
A final prototype design was developed through consultation with Mena, plumbing professionals, and modifications based on hydraulic testing of Prototype 2. The final design is a three-trough system that will require no modification of the wall or existing space, making it easy to remove the system if the owner desires. A specialized saddle-like frame was constructed to go over the wall unit in the salon so that the system troughs can sit on this frame. This facilitates both installation and removal of the system. Transparent Plexiglas troughs were built and piped for testing Prototype 3 to allow for complete transparency of the system.
Other key modifications have been made to the latest prototype to address concerns that had come up in the testing of previous iterations. One is the pump. Rather than having a pump that is continually running, we are using a sump pump that will automatically switch on when water levels reach a certain height in the graywater storage tank, and then automatically switch off once the tank has been emptied. We also added a turbidity sensor that will automatically open a switch valve to send acceptably treated graywater to tanks for toilet water storage.
In order to ensure that plant roots are always in water, even if the system is shut down for extended periods, there is a trough within each trough where the plants are placed. Water fills those troughs first, and then overflows into the larger trough that is drained. Hence, there is always water in the plant troughs. A large problem we had with the initial prototypes was lack of DO in the graywater. We believe we have resolved that issue through the use of an inlet pipe that uses the power of the pump to diffuse large amounts of air into the pipe discharge. An ultraviolet light limits algae and fungus growth in the system, while a biofilter captures sediment and hosts microbial activity that metabolizes excess nutrients, chemicals, and other organic compounds. Plants feed on the nutrients and uptake or degrade organic compounds. The system still incorporates easily replaceable potted plants.
As the water will be reused in toilets, a primary concern is water turbidity and color. Since regulations require that the water is dyed blue before being sent to the toilets, we need to be sure that the water is clear and colorless prior to this stage. Otherwise, adding blue dye to murky water might result in cloudy brown water—the last thing one hopes to see when opening a toilet lid. The final prototype performed remarkably well in reduction of turbidity and dye color while maintaining pH and adequate DO levels.
At this point, the research team feels that we have a technologically viable system design. However, we will not know what the total capital costs of fabrication and installation will be until final design specifications are submitted to contractors. Nevertheless, due to the small amount of monetary savings (if any) the system creates, the energy payback period will undoubtedly be what conventional wisdom would call unacceptably long. However, as E.F. Schumacher, the father of appropriate technology, pointed out in his book Small is Beautiful: Economics as if People Mattered, fossil fuels are actually capital, or what he called Natural Capital. Once they are used, they are lost forever and cannot be replaced. From that perspective, one could make the argument that the payback period for a fossil-fuel power plant is essentially infinite and cannot be calculated. For renewable energy systems that by definition generate income energy, it is at least possible to calculate some kind of payback scenario. The true currency of payback should not be some fleeting valuation of a monetary unit that might change tomorrow, but rather conservation of Natural Capital. Any project that conserves Natural Capital is a step towards resource sustainability.
With that, now comes the hard part: turning the prototype into an actual working system at Haircut 101. This will involve coordinating with plumbing and fabrication professionals, local planning and regulatory agencies, and contractors to create the final, building-inspected installation; in other words, the full gamut of real-life implementation of system installation. Successful implementation of the system in an actual working business will be a true challenge and a groundbreaking installation for the town of Boone. Maintenance and monitoring of that system, as well as studying the effect of the system on the business, public and professional perceptions, and local graywater reclamation efforts will be a source of ongoing and long-term studies and project development both in the physical and social sciences. This will also provide service-learning opportunities for university students, with the research project embedded in the community to meet an important local need. Such an interdisciplinary, community approach led to our research being awarded an Annual Sustainability Research Forum Award from the Appalachian State University Office of Sustainability and Hubbard Programs for Faculty Excellence in 2014. In 2016, our research went on to win the Boone Discovery Forum competition, hosted by the North Carolina State University Institute for Emerging Issues, BB&T Student Leadership Center, and Transportation Insight Center for Entrepreneurship.
As you may now realize, it is painfully obvious that my initial impression of the legitimacy of this research direction was a bit off, to say the least. Thank goodness for the wisdom of my students, and a local business owner dedicated to the principle of sustainability.
References
- United Nation’s Children Fund (UNICEF). Child survival fact sheet: Water and sanitation [online] (2004). http://www.unicef.org/media/media_21423.html.
- Boone, NC Public Utilities (2011).
- NFS International. NSF International Standard/American National Standard for Wastewater Technology 350: Onsite residential and commercial water reuse treatment systems [online] (2011). http://www.nsf.org/services/by-industry/water-wastewater/onsite-wastewater/onsite-reuse-water-treatment-systems.
