By William E. Kirksey, P.E.
It’s an accepted practice to install on-site, decentralized water purification systems to supplement centralized drinking water treatment. Today, we see a similar, rapid movement in the wastewater industry toward advanced ecological, computer- controlled, decentralized systems that treat water for on-site reuse. This movement is providing on-site reuse opportunities for office buildings, educational institutions, industry, residential developments and other water users. These users can save significant fresh water by reusing treated water for a wide range of non-potable uses, such as irrigation, flushing toilets, air conditioning, etc.
For water companies and service providers, this presents a range of new opportunities to help commercial and industrial customers save substantial money and support corporate sustainability initiatives. Traditionally, wastewater treatment has been accomplished by extensive centralized infrastructure, using significant amounts of chemicals and energy to collect and treat water. Reuse of the water from centralized systems can also be expensive because of the energy and infrastructure cost of moving large quantities of water back upstream. Now a number of environmental and economic factors have made advanced, on-site technology an appealing alternative to expanding overtaxed centralized systems, and allow the implementation of a more decentralized, ecological wastewater treatment approach.
Wastewater infrastructure failing to keep up with demand
“Toxic Waters: A series about the worsening pollution in American Waters” by New York Times writer Charles Duhigg (August 2009–March 2010), shared some very alarming, but insightful information on the contamination in our drinking water, and documented that water and sewer systems are in need of repair and upgrading. According to the series, a significant water or sewer line bursts, on average, every two minutes somewhere in the country. The difficulty and cost of rebuilding and maintaining the centralized water infrastructure is compounded by the fact that treatment plants themselves are often overloaded and unable to adequately treat the concentrations of pollutants that are coming into them.
According to the US Department of Energy, the demand for energy and water resources worldwide is projected to grow at an alarming pace in 20 years, with demand for energy doubling and water tripling. This was made clear by Richard L. Stanley, Vice President, Engineering Division, GE Energy, who testified at a 2009 hearing of the House Science and Technology Subcommittee on Energy and Environment.
Figure 2. Diagram of the Living Machine
To meet this water demand through conventional methods will exact a huge cost when it comes to upgrading and building new water pipes. Those costs could be reduced significantly by coordinated strategies to provide on-site treatment where it makes sense to supplement central systems. In fact, a study by McKinsey & Company’s 2030 Water Resources Group indicates that globally, conventional means to increase supply and efficiency of use will meet only 40 percent of the total demand in the year 2030.
This is where decentralized systems of wastewater treatment and reuse come into play. More than 50-70 percent of water uses do not require potable-water quality, meaning that wastewater reuse should be a significant new resource. On-site septic systems do not produce water of sufficient quality for reuse, but new, advanced ecological, decentralized systems are being implemented that treat blackwater waste to tertiary standards. These advanced ecological systems, however, do provide a safe, natural and highly effective way to treat and produce reusable water locally, with resulting lower overall cost and energy requirements.
Decentralized systems can also help commercial and industrial companies facing difficult choices when it comes to their non-potable water needs. In addition, failing traditional septic systems, tighter regulations and high discharge fees based on pollutant loading can provide further economic justification for installing newer, advanced ecological, on-site systems that are geared to scale up to handle large commercial buildings, or even large residential communities.
Water treated and reused onsite will not need to be transported to a central system or back for reuse, a source of large cost savings. For example, a system installed at a school in North Carolina saved the school board $4.5 million (USD) in capital cost because they avoided connecting to a sewer over seven miles away. Advanced ecological treatment systems are at the leading edge of decentralized wastewater treatment and offer significant advantages in cost, operations, environmental sustainability, and simple beauty relative to other on-site systems.
A new decentralized, more natural architecture can be designed to evolve from the current model. The evolution to this new model is already underway, but can be accelerated and improved if we recognize the value of this direction and adapt policies, design standards, engineering models and monitoring technologies, funding programs and management structures to facilitate the transition (see Figure 1.)
Figure 1. A new decentralized, more natural architecture can be designed to evolve from the current model
Advanced ecological wastewater treatment defined
In the 1980s, a movement began to develop wetland wastewater treatment systems that could mimic nature more closely and reduce byproducts, such as sludge created by traditional centralized, activated-sludge treatment plants. First-generation wetlands reduced or eliminated sludge generation and demonstrated significant energy savings, but required a very large footprint and yielded variable performance. In just the past decade, new advances have taken place to make the technology more reliable and cost-effective. Cutting-edge environmental science and information technology have been applied to enhance the processes of natural tidal wetlands to improve performance and reduce system footprint by as much 90 percent, while retaining much of the energy efficiency of earlier wetlands. These systems have the added advantages of eliminating exposed wastewater surfaces and odors, thus improving site and architectural integration possibilities.
The most efficient of these tidal wetland approaches introduces wastewater to a dense, diverse micro-ecosystem contained in a series of cells. The cells fill with water allowing microorganisms to begin consuming the nutrients. When the cells drain by gravity, oxygen is passively brought to the wastewater at atmospheric concentration. This allows microorganisms that favor these conditions to complete the nutrient removal process. The alternating anaerobic (without oxygen) and aerobic (with oxygen) conditions make tidal wetlands Nature’s most productive ecosystem. The system adapts and enhances Nature’s own productivity (see Figure 2). This system is able to treat high-strength (blackwater) sewage in a safe, attractive and cost-effective manner. The systems are equipped with an Internet-connected computer system that automates operation of the wetland cells. The computer system controls water levels and cycling to optimize performance, sends text or email alerts to operators, and records system information for operators to view on the Web.
In the past, on-site, wetland-based wastewater treatment took up significant land that could be used for housing, commercial space, parking or other productive use. Now, advanced ecological, on-site wastewater treatment systems are much smaller (about 150 square feet for every 1,000 gallons per day of sewage treated), and attractive in their own right, becoming part of the aesthetics and landscaping around the facility, further adding to the positive image of the company (see Figures 3 and 4).
The key attributes of the newest generation of ecological wastewater treatment systems include:
- Lower operating costs than traditional activated sludge treatment
- High-quality, treated water suitable for reuse
- Sustainability, using completely natural processes andcreating no byproducts that must be hauled off and disposed of
- A small footprint, yet ready scalability for high volumes(hundreds of thousands of gallons per day)
- Low energy consumption and minimized greenhouse gas(GHG) emissions
- An aesthetic quality, integrating the beauty and complexity of nature into the structure of buildings and communities
- The move to decentralized, cost-saving wastewater treatment
Commercial and industrial companies have been transitioning to on-site, more sustainable wastewater treatment approaches that not only reduce operational costs, but create a source of much needed water for a variety of production and operational needs. Especially in water scarce areas, most municipalities enforce strict, aggressive water conservation measures and increased water charges to ensure that everyone has enough water. Expanded application of decentralized, ecological wastewater systems can offer a natural evolution, aided by collaboration among utilities, customers and water service providers. This evolution could create a cost-effective strategy combining existing, functional systems with proven innovations in ecological treatment. Key aspects of this transition include:
Figure 3. Esalen Institute, in Big Sur, CA
Figure 4. The Port of Portland building
Rehabilitating and extending the life of critical infrastructure. There is no question of the need to keep the existing systems working as well as possible for as long as economically feasible. The investment in these systems represents a huge store of value that provides a framework upon which to build 21st century infrastructure.
Decentralizing new construction. New ecological treatment systems make sense in a variety of applications, including areas of rapid growth, areas with failing existing treatment (e.g., small municipal systems, septic systems), regional networks as a means of avoiding expansion of a centralized plant and the interconnecting infrastructure, and as standalone applications to serve specific needs.
Enhancing local water cycles. The decentralized systems that are constructed will become part of a regional, natural and human ecosystem, so that the design of the wastewater treatment infrastructure can help integrate natural water cycles with human and environmental needs.
Enhancing the basis of the local economy. Water is the basis of economic activity, as well as the basis of ecosystems and human existence. The design of wastewater treatment can be coupled with the creation of business opportunities and new jobs by involving community interests in planning of water reuse opportunities to optimize the creation and maintenance of livelihoods and locally productive economic activity.
Adapting regulatory, funding and management structures. Public health and safety has to be foremost in any technological innovation or infrastructure strategy associated with wastewater reuse. Regulations, funding programs and management approaches need to evolve to encourage appropriate application of decentralized, ecological technologies, while maintaining high standards for quality and performance.
Ecological water reuse in retail and production
There are various ways on-site ecological wastewater treatment can help commercial and industrial facilities. The examples below include two scenarios that could be implemented by municipalities and developers, and two real-world examples that have been implemented by businesses.
Urban/suburban retrofits. Municipalities with aging infrastructure and strained budgets can apply decentralized, ecological treatment systems to ease the load on the central systems and postpone expensive upgrades. For example, mixed use retail and residential centers are being used for infill development or redevelopment in urban areas, often in areas with aging or insufficient infrastructure. Decentralized systems offer an effective strategy in which the municipality could work in partnership with developers to build self-sufficient systems with incremental expansion capability. In this approach, sewer conveyance systems can be built with smaller diameter pipes because large geographic areas do not need to be linked. The decentralized approach makes conveyance infrastructure for water reuse more cost-effective as well. The infrastructure required is much smaller in scale and is onsite—no connection to a central system is needed.
Urban infrastructure expansion. In a similar scenario, a municipality faced with insufficient capacity to serve existing development (such as where combined sewer overflows are a problem), could ease the load on the central sewer facilities by undertaking decentralized development. In this case, the municipality could construct multiple systems around the area to treat and reuse water locally, and maintain municipal management and control of the system operations and revenue. With ecological, on-site systems, the wastewater treatment could be located inside buildings or in plain view outside, using ornamental plants and other flora for visual appeal. Meanwhile, the water that is produced could be re-used onsite for landscape irrigation, water features (such as ponds or waterfalls) toilet flushing, air conditioning or other non-potable uses.
Discharge regulation. A food-production facility had to meet strict discharge requirements in Nevada, a water-short state. An ecological, on-site wastewater treatment system was installed to handle the treatment of 32,000 gpd (121,133 L/d) of high-strength confectionery production wastewater. The influent consisted of water that was used to wash the process area and equipment, along with water from the boilers and cooling towers. Following the treatment process, the resulting reclaimed water was reused for on-site landscape irrigation. Cities in the western US, such as San Jose, CA, are requiring that new construction include piping to accommodate reclaimed water for non-potable applications, such as irrigation and toilet flushing. The sewage water is treated and reused/disposed through sub-surface drip irrigation; there is no need to separate black and gray water.
Organic food processing. A cheese factory in Wisconsin needed an environmentally sound means of treating 6,500 gpd (24,605 L/d) of wastewater containing high concentrations of cheese whey. The factory chose an ecological wastewater treatment process that allows them to clean the water sufficiently for discharge into a local stream. The system also created an aesthetic asset for the factory and allowed them to maintain water quality in the surrounding environment.
A more natural, ecologically based water infrastructure can help resolve major, paralyzing water supply and regulation is- sues, especially in the most drought-stricken or rural areas. New design and technologies now make advanced ecological, on-site systems cost-effective to install inside or outside a facility, not only helping meet regulatory needs, but also saving companies money by reusing water and avoiding associated charges. Municipalities and water service businesses have opportunities to profit- ably provide solutions to commercial and industrial customers. Decentralized wastewater treatment and reuse technologies are widely penetrating the market. Advanced ecological systems are the cutting edge of decentralized technology and offer a proven track record. For companies that have an eye on sustainability, on-site, ecological wastewater treatment also helps support the local community and watershed by reducing downstream water treatment loads, offsetting potential water load growth, and creating a sustainable, renewable water resource cycle. That’s good for the local community—and good for business.
About the author
William E. Kirksey, P.E., Senior Vice President at Worrell Water Technologies, is an industry veteran with over three decades of experience in environmental engineering, technology and management with an emphasis in sustainable water and energy infrastructure. Kirksey’s prior experience includes senior management roles in the private sector, non-profit organizations and government, including Vice President and Senior Fellow with the American Society of Civil Engineers Research Foundation, Senior Policy Analyst in the Florida Governor’s Office and domestic and international consulting with Battelle, Price Waterhouse and SAIC. His background includes international work experience in over a dozen countries in Asia, Europe and Africa. Kirksey has written a wide variety of guidebooks, technical manuals and technology analyses. He is a frequent conference speaker, organizer and facilitator, and is the co-inventor of small-scale, decentralized water treatment technologies. Kirksey earned an MS Degree in environmental systems design from Southern Illinois University and a BS Degree in civil engineering from Tennessee Technological University. He is a registered Professional Engineer in the state of Florida.
About the system
The NextGen Living Machine® system is a patented product developed by Worrell Water Technologies, LLC (WWT). The Living Machine® technology is a new approach to wastewater treatment, employing the natural ecological process of a tidal wetland, enhanced by environmental science and information technology. The system applies state-of-the- art technology and advanced ecological engineering design to produce high-quality reuse water onsite. The patented process uses no chemicals, has very low energy consumption and minimal greenhouse gas (GHG) emissions.