CEE New Millennium Colloquium
March 20-21, 2000
Wong Auditorium, Tang Center, MIT Building E51
Research Needs to Optimize Wastewater as a Resource
JEFF C. MOELLER, DENNY S. PARKER, MARCK C. M. VAN LOOSDRECHT, MYRNA WATANABE
The word "wastewater" implies that the result of water use is a waste product. Wastewater derives from water use in households, commerce and industry, where water serves as a conveyance system for wastes, and from stormwater runoff. Scientists and engineers specializing in wastewater research and management increasingly are viewing wastewater as a source of products that have value. To retrieve that value, it must be determined how to convert existing systems to new, value-creating systems as well as how to design new systems from the ground up that will create products. Furthermore, specific products must be identified, and technologies must be developed that lead to their production.
On September 1214, 1998, an invited group of international scientists and engineers (see Attachment) - leaders in the field of wastewater research and management - from academia, industry, and government, met in Warrenton, Va. to consider means of harnessing new technologies to change wastewater from a waste product to a resource with value. The workshop, entitled "Biotechnology/Industrial Ecology: A Look Into the Future for Wastewater Treatment", was intended to take a fresh look at the wastewater field and consider research needed to develop products from wastewater, develop and implement new technologies and methods to deal with wastewater production, treatment and reuse, and define new paradigms for wastewater treatment in the future. The workshop was facilitated in a manner that encouraged a free exchange of ideas ensuring a cross pollination of concepts between the separate disciplines and backgrounds represented. A primary outcome of the workshop was the identification of research areas that represent good candidates for support from organizations such as the Water Environment Research Foundation (WERF) which sponsored this workshop, other not-for-profit organizations, corporations, and government entities. These research areas may help reduce treatment costs, improve performance/reliability of treatment, expand the scope of treatment controlled by biological processes, and better integrate treatment plants into the path of "green manufacturing".
PRODUCTS FROM WASTEWATER
To freely conceptualize resource utilization possibilities, perhaps wastewater treatment should be viewed as a manufacturing process with side-stream products (for example, energy, metals, and organic materials/compounds) reclaimed for marketing or reuse. Wastewater offers the promise of products to recycle, reuse, and resell. Some of these products have been realized to a small degree: energy production, biosolids as soil amendments, and water for reuse are among the most notable; but there is a long way to go before the vast range of products that can result from wastewater treatment is fully realized. Additional possible products to be derived from wastewater treatment include products from segregation of high-rate carbon conversion systems, those culled via the actions of genetically modified organisms that process organics, and nutrients such as phosphorus. In addition to creating usable products, other benefits such as a cleaner, safer wastewater effluent may result from the development and implementation of new technologies and methods for wastewater treatment.
NEW TECHNOLOGIES AND METHODS
Science and engineering discoveries are occurring at an increasingly rapid pace. Often the most significant advances that are made in a field come from ideas that are generated outside of the field. A critical element to moving wastewater treatment into the future may involve adapting advances in biotechnology, molecular genetics, information technology and other disciplines for use in wastewater treatment and management. Researchers in disciplines outside the traditional wastewater arena may not be locked into preconceived notions of how a problem is currently solved and might conceptualize how the problem could or should be solved. However, those with experience in today's wastewater processing technologies may be in the best position to successfully adapt and implement new technologies that could revolutionize current wastewater treatment practices
Along with adapting new technologies from other disciplines, conducting research across disciplines will play an increasingly important role in developing new solutions. Environmental research by its very nature involves a number of traditional scientific disciplines such as biology, chemistry, physics, and engineering as well as other disciplines such as economics, urban planning, and psychology. Cross-disciplinary research needs to be promoted and supported to find appropriate solutions to environmental problems. Additionally, synergisms that develop from a cross-disciplinary approach may lead to insightful solutions and treatment paradigms that may not otherwise have been found or discovered.
NEW PARADIGMS FOR TREATMENT
Today, wastewater treatment plants are generally large, centralized facilities that treat wastewater from numerous sources. Wastewater treatment plants have been developed for long-term use, and have been built in a centralized fashion. Unfortunately, such facilities have little flexibility. Everything comes in through a pipe and nothing is excluded including human and animal excrement, commercial and industrial effluents, and in many systems, storm runoff. The facilities also must cope with seasonal and temporal changes in flows. Rainfall event frequency and intensity may increase the amount of sewerage a plant is expected to treat. Exacerbating treatment concerns, stormwater runoff may be contaminated with chemicals.
Another important consideration is that the current practice of using water as a transport mechanism for wastes results in the pollution of clean water and the dilution and mixing of wastes that makes them more difficult to process at the plant. Additionally, the construction, operation and maintenance of large systems of sewers to transport wastes to centralized facilities is costly and represents a significant proportion of the expenses for treating wastewater.
Perhaps wastewater treatment plants should be rethought entirely. Wastewater treatment paradigms in the future may be radically different from those of the past incorporating design for adaptability and possibly with life spans shorter than the 30100 years of the current infrastructure. Multiple systems might handle various types of wastewater in different manners and locales.
New paradigms, however, do not mean that centralized treatment is no longer viable. Especially in urban areas, centralized treatment and large conveyance systems may be unavoidable; but systems need to be explored that differ significantly from those in existence now. These new systems may include separation of wastes at the beginning of the pipe; treatment within the pipe itself with advanced technologies; and use of anaerobic pretreatment or initial treatment. Stormwater may be treated differently from other wastewater components. In some areas and for some wastes, there could be small-scale, diverse treatment systems. These systems will have to be more robust and reliable than past technologies to equal the reliability of today's centralized systems.
Wastewater treatment should fit the locale. In setting up a system, the local situation must be evaluated. This includes evaluating the effects of the climate; topography; local availability of water; the political, legal, and social framework of the society; economics; and the needs of the community. For example, within the U.S., a system for Chicago would be different from one in the arid West. Chicago, which is located on the shore of a large freshwater lake, may have energy as a crucial need but not necessarily water; however, a city in the arid West has a need for water. Thus, a system in Chicago could produce energy as an end product, while one in the West could produce water for reuse as an end product.
Different solutions may be necessary for developing nations. Developing nations, for instance, may require low-tech solutions. It would, for example, be inappropriate to put a high-tech, centralized wastewater treatment facility in a city where rampant growth will likely outstrip the facility's ability to service the area before the facility is fully functional, and where the community may not financially support such a system.
To implement meaningful changes in wastewater treatment that may result from new treatment paradigms, the support and increased participation of the public must be obtained. Additionally, society must be willing and able to allocate funds or develop creative methods to pay for technologies that result in resource utilization. Otherwise, change will continue to be slow paced and incremental. Research findings and recommendations may be important factors in gaining public support and willingness to pay for any resulting changes to current systems.
The workshop participants selected twelve consensus research areas that they believed would be appropriate for funding to optimize utilization of wastewater as a resource for products, develop and implement new technologies to improve wastewater treatment, and promote new paradigms of wastewater treatment for the next generation. These areas include the following.
Process control. Technologies are needed to increase the performance of wastewater treatment plants and to allow them to tolerate fluctuating amounts and types of wastes. This may be especially important in producing a steady stream of product from the plant. This research area will include implementation of real-time monitoring, development of intelligent sensors, and investigation of flexible operational control.
Solids separation. Enhanced solids separation from raw wastewater has the potential to allow efficient recovery of organic matter for use in energy production and to reduce the size and number of downstream treatment facilities required. Among other topics, this research area will include the assessment of the broader use of membranes in wastewater treatment.
Anaerobic treatment. Although anaerobic biological treatment has been used in sludge management, anaerobic treatment of raw municipal wastewater is not widely practiced. Anaerobic processes consume less energy, produce potentially valuable byproducts (that is, organic acids and/or methane), result in production of less biosolids than aerobic biotreatment processes, and can result in more complete treatment of certain organics (for example, halogenated compounds).
Wetlands. Wetlands have the potential to play an important role in waste treatment for both point and non-point sources of pollution. Wetland plant and biogeochemical interactions should be studied and defined, the synergisms of microbial consortia need to be understood, system dynamics in sediments need to be characterized, and the fates of contaminants should be traced within the system. Development of plant species through selective genetic engineering will aid in optimizing system performance.
Microbial ecology of biological treatment systems. Microbes will continue to serve as a rich source of tools in wastewater management. Investigations in this area would include study of the enhancement of their function through bioaugmentation and controlled ecology.
Microbial ecology for aquatic ecosystem health. To understand the impact of specific environmental stressors, including toxicants from point and non-point discharges, on any microbial ecosystem, it is important to have the ability to measure and monitor changes within that ecosystem. Research in this area would identify microorganisms' physiological responses to environmental stressors, cover the use of indigenous microorganisms to monitor ecosystem health, and integrate new information technologies to monitor and control microbial activity and population dynamics.
Black water/gray water treatment technology. Separation of gray and black water at the source will result in more concentrated wastewater collected at central treatment facilities. Research projects under this topic would amass and evaluate existing research on end-product development from concentrated wastewater treatment; develop processes and technologies to study local recycling; develop recovery methods for phosphorus, methane, and hydrogen; and evaluate substituting membranes for clarifiers.
Local resource recovery demonstration. Reclaiming gray water and making it available for uses for which potable water is not necessary (for example, watering lawns, flushing toilets, or groundwater recharging) could have a number of benefits including saving valuable water and energy. The demonstration of resource recovery by contained communities such as apartment or office complexes requires the development of model systems. The goal is to establish a consortium of business, municipal government, and state or federal agencies to develop ongoing resource recovery businesses.
Molecular sensors. Molecular sensor technologies have been developed up to the proof-of-principle stage for use in wastewater treatment management and control. However, these technologies must be integrated for use in full-scale plant operation for problem solving and to yield information on the treatment process. The initial goal is to convene a sensor workshop to stimulate communication between sensor developers, scientists, and engineers in the wastewater treatment field. Next would be conduction of a field-scale demonstration of molecular sensors in wastewater treatment. Molecular sensors could even be used to aid in species identification and metabolic classification of organisms. A successful demonstration would lead to commercialization of such sensors.
Pathogens. The detection and fate of pathogens and the potential epidemiological risk they pose are vital considerations in resource utilization. This area will lead to development of molecular probe technologies to identify pathogens. It will require study of survival of pathogens and the ability to kill pathogens in different treatment systems and identify the situations where wastewater disinfection is required.
Material fluxes and flows. To better control wastewater treatment and the quality of effluent from wastewater treatment plants, it is essential that the wastewater industry be able to track chemicals and microorganisms to determine how their flows and fluxes affect key water quality issues. The goals are to determine how particular nutrients and contaminants enter the wastewater stream; to determine the fate of nutrients and contaminants; and to determine the effects of excess nutrients and contaminants on the wastewater system. These studies would also measure the endocrine disruption potential of waste constituents and would determine the relative contribution of point sources to non-point sources for these materials.
Unquantified risks. There have been several emerging national and worldwide scientific trends that seem to point to effects of environmental contaminants and have had a strong impact on the wastewater industry. The initial goal would be to convene a discovery and trends workshop to aid wastewater treatment officials with early recognition of major discoveries, trends, and risks that could have an impact on the field. An ultimate goal is the establishment of an information research clearinghouse to alert officials to new research findings.
Each of the twelve research areas above is presented in greater detail in a WERF report developed from the workshop entitled "Research Needs to Optimize Wastewater Resource Utilization". One of the research areas, black water/gray water treatment technology, is expanded upon below to provide a more detailed example of the types of research concepts that were developed for each of the twelve research areas listed. The full WERF report can be ordered via the internet at http://www.wef.org/applications/publications/index.cfm (order #D93015).
EXAMPLE: BLACK WATER/GRAY WATER TREATMENT TECHNOLOGY
This research area is based on the assumption that gray water recovery and local reuse become common. In the recovery of materials from wastewater, the concentration of materials is extremely influential on the process economics. The more concentrated the "waste", the easier and more economical the recovery process. In municipal wastewater, typical values for total phosphorus and nitrogen are 8 mgP/l and 40 mgN/l. With a good separation process, maximum values of 1 gP/l and 10 gN/l could be achieved. The flow to be treated would be an order of magnitude less and the ease of recovery or treatment of nutrients would be much improved. The more concentrated wastewaters can be collected and treated at central wastewater treatment plants. Significant public education may be required, however, to accept the separation of gray water from black water at the source.
In order for this research area to succeed, the goals for treating concentrated wastewaters must be developed to make use of a product or products produced from the waste. This means that treatment plants no longer solely meet the normal obligations of legal effluent requirements; plants will become production facilities as well, and perhaps even merchants of their specific products.
Once plants that treat concentrated wastewater have established commercial uses as product generation plants, some of the following products may be recovered for use by other industries:
The plant of the future must be able to sustain itself by forming a strong partnership with industry and utilities such as power plants and water companies. Thus, not only must products be developed from the treated wastes, but these products also must have a significant commercial market.
Although it would take development of breakthrough technology to make the energetics of ammonia recovery competitive to industrial production, breakthroughs in developing engineered bacteria may allow production of ammonia in fermentors from a wide variety of organics found in the wastewater stream. Also, if the nitrogen content in wastewater is high enough due to separate collection of black water, processes such as steam stripping may become competitive options for ammonium production.
Short-term Goals (Present to two years from now)
The goal is to amass and evaluate existing research on end-product development from concentrated wastewater treatment. This requires establishment of relationships with private industries and utilities that would most benefit from wastewater product use with the goal of creating partnerships for financing research and becoming initial purchasers of the products.
Medium-term Goals (Two years from now to 2005)
Using the framework established in short-term goals, developments in the wastewater recovery cycle need to be monitored, and partners and the public need to be updated when appropriate.
Long-term Goals (2005 and beyond)
A program needs to be organized to develop processes and technologies for research on the best methods of local recycling of gray water and treatment of concentrated wastewater streams for product development. Elements of this program include developing appropriate recovery methods for the following elements and compounds:
Phosphorus. To recover phosphorus in a usable state, the endpoints for recovery must be in a usable form. For example, calcium and magnesium compounds are available; iron compounds are not. Whether the phosphorous compound is recovered in a dry or wet condition will depend on its end use. Introduction of biophosphorus organisms into the bioreactor would be the first concentration step, and then a liquid, phosphorus-rich stream would be processed in a crystallizer or in a precipitation step. The technology exists and merely needs to be demonstrated and evaluated for North American application.
Methane. Recovery of methane is a demonstrated technology. The objective is to maximize waste carbon to the anaerobic step, while minimizing aerobic conversion. This method will maximize methane generation. To aid in methane generation, it will be necessary to evaluate enhanced solids recovery at the "primary" stage. This enhancement may require replacing sedimentation with filtration or adding flocculants to gravity separation steps.
A new "high rate" anaerobic process would generate methane directly while reducing the biochemical oxygen demand (BOD) that usually must be treated in a downstream aerobic process. This could be preceded by conventional sewer design to serve as prefermentors along with their typical function as conveyances.
Alternatively, methane recovery may be increased by either mechanical or heat disruption of the macromolecules, cell walls, etc., breaking down these molecules to simple fatty acids prior to digestion. This will increase methane production and will reduce the quantity of volatile matter, potentially producing Class A solids.
Hydrogen. Evaluation of procedures to recover hydrogen gas, rather than methane, directly from a microbial fermentation process is proposed. This requires engineering of an appropriate microbial population and of methods to recover hydrogen formed at low partial pressures.
PHA. PHA is a bioplastic with characteristics similar to polypropylene which can be produced from fatty acids. These acids can, in a fermentation stage, be produced from organics in wastewater. Several researchers in Europe and Japan have shown that it is possible to produce PHA from wastewater in a process similar to the activated sludge process. Due to the free supply of substrate and the simplified production conditions, the costs of PHA production from wastewater are estimated to be less than 50% of the present industrial production costs.
Finally, as part of the research program of methods for local recycling of gray water and treatment of concentrated wastewater streams for product development, substitution of membranes for clarifiers should be considered. Membranes may provide better preparation of the wastewater for subsequent processing for reuses. The reason for this exchange is that membranes provide particle size discrimination, allowing easier and more effective disinfection.
While numerous areas require study, only a dozen were targeted at the workshop. The general public and those involved in the wastewater industry must begin to see wastewater as a resource that offers the promise of products to recycle, reuse, and resell. While some of these products have been realized to a small degree, there is a long way to go before the vast range of products that can be derived from wastewater treatment is fully exploited. Funding of work in the twelve research areas suggested in this paper is a starting point. The research areas are broader in scope than any one organization has the resources to undertake, but the goal of designing the wastewater systems of the future is a grand one that should involve many individuals and organizations.
WERF gratefully acknowledges the time and efforts of the Steering Committee and all of the other workshop participants in contributing their time and energies to making the workshop "Biotechnology/Industrial Ecology: A Look Into the Future for Wastewater Treatment" a success.
Rita R. Colwell, Ph.D., D.Sc., Committee Chair , National Science Foundation*
Bruce E. Rittmann, Ph.D., Committee Vice-Chair, Northwestern University*
Paul L. Busch, Ph.D., P.E., DEE, Malcolm Pirnie, Inc.*
Roger J. Dolan, P.E., DEE, Central Contra Costa Sanitary District*
Michael A. Heitkamp, Ph.D., Monsanto Life Science*
James M. Kelly, Central Contra Costa Sanitary District*
Robert M. Kelly, Ph.D., North Carolina State University*
Denny S. Parker, Ph.D., P.E., DEE, Brown and Caldwell*
Lily Young, Ph.D., Rutgers University*
M. Bruce Beck, Ph.D., University of Georgia
Douglas L. Britt, Dynamac Corp.
Donald S. Brown, U.S. Environmental Protection Agency
Glen T. Daigger, Ph.D., P.E., DEE, CH2M Hill
Jay L. Garland, Ph.D., Dynamac Corp
Willi Gujer, Ph.D., Swiss Federal Institute of Environmental Science and Technology
Peter R. Jaffe, Ph.D., Princeton University
David Jenkins, Ph.D., University of California at Berkeley
Jay D. Keasling, Ph.D., University of California at Berkeley
Perry L. McCarty, Sc.D., Stanford University
Mark C. Meckes, U.S. Environmental Protection Agency
David F. Ollis, Ph.D., North Carolina State University
Lutgarde Raskin, Ph.D., University of Illinois at Urbana-Champaign
Mike Roco, Ph.D., National Science Foundation
Gary Sayler, Ph.D., University of Tennessee
Barth F. Smets, Ph.D., University of Connecticut, Storrs
Paul M. Sutton, Ph.D., Paul M. Sutton and Associates, Inc.
Kenneth M. Timmis, Ph.D., GBF - National Research Centre for Biotechnology
Mark van Loosdrecht, Ph.D., Delft University of Technology
Workshop Report Editor:
Myrna Watanabe, Ph.D.
WERF Project Manager:
Jeff C. Moeller, P.E.
* Denotes Workshop Steering Committee member.
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