ARPA-E held a workshop on the topic of “Energy from Wastewater” on January 27, 2010 in Arlington, VA. The goal of the workshop was to gain a deeper understanding of those areas and technologies that have the highest potential to meet DOE’s goal of developing the technical foundations necessary to achieve net energy output and clean usable water from municipal and industrial wastewaters. ARPA-E sought to target high-risk R&D technologies that have been historically overlooked or are considered too risky for typical government-supported R&D funding. Specifically, ARPA-E was interested in methods to produce energy while simultaneously producing clean usable water via:

• Thermal methods for energy generation from wastewater, including ideas related to incineration, high temperature thermal oxidation of volatiles, pyrolysis gasification of solids, plasma processing, and others.
• Biological methods for energy generation from wastewater, including ideas related to algae use, anaerobic digestion, enzymatic hydrolysis, and others.
• Chemical/electrical methods for energy generation from wastewater including ideas related to chemical hydrolysis, microbial fuel cells, and others.
• System components that can enable the production of energy and/or clean water from wastewater, such as new materials (non-fouling membranes, functionalized dendritic materials for binding nutrients, blue light active photocatalysts), new biological microbes, and others.
• Hybrid systems that combine various methods (thermal/biological/ chemical/electrical) and components for energy generation from wastewater, including ideas related to chemical hydrolysis, anaerobic digestion, and/or enzymatic hydrolysis, combined with heat; combined enzymatic hydrolysis and digestion; anaerobic digestion with membrane bioreactors; or others.

The workshop served as an opportunity for ARPA-E leadership to engage with thought-leaders from diverse technical communities to collectively develop new directions in methods, components, and systems related to the production of energy and clean water from wastewater. ARPA-E will use this information to shape the scope and focus of potential future programs in net energy output and clean usable water from municipal and industrial wastewaters.

The meeting proceedings are summarized below. 

Speakers and Presentations:

1. Shane Kosinski, Deputy Director for Operations, ARPA-E: “Introduction to ARPA-E” (pdf) 2. Mark Shannon, Director, WaterCAMPWS: "Net Energy from Wastewater" (pdf) "Net Energy and Clean Water from Wastewater" (pdf) 3. Michael Hightower, Distinguished Member Technical Staff, Sandia National Laboratories: “Embedded Energy in Water/Wastewater Systems” (pdf) 4. Lauren Fillmore, P.E., Energy Program Director, Water Environment Research Foundation: “State of the Science in Energy Generation from Wastewater” (pdf)   Breakout Sessions:   During the workshop, participants broke into two sets of breakout sessions comprised of four topical group discussions per breakout session. The eight topical areas were:

• Clean Water from Wastewater: Science and technological challenges to obtaining clean water from wastewater with more than an order of magnitude better performance than current technologies
• Clean Water from Wastewater: Emerging methods of deriving clean water from wastewater with associated metrics
• Energy and Clean Water from Wastewater: Quality and costs needed for water to be reused from wastewater
• Energy and Clean Water from Wastewater: Barriers (infrastructure, codes, permits, and requirements) and incentives needed
• Net Energy from Wastewater: Science and Technology Needed, with Associated Metrics - Science and technological challenges to obtaining energy from wastewater with more than an order of magnitude better performance than current technologies
• Net Energy from Wastewater: Science and Technology Needed, with Associated Metrics - Emerging methods of deriving energy from wastewater with associated metrics
• Translation into Practice: Metrics, Outcomes, Piloting, Barriers and Solutions - Metrics and outcomes needed for pilot demonstrations and implementation of technologies developed in program
• Translation into Practice: Metrics, Outcomes, Piloting, Barriers and Solutions - Barriers to adoption and solutions needed for translation of technologies into practice

The goal was to gain a deeper understanding of those areas and technologies that have the highest potential to meet DOE’s goal of developing the technical foundations necessary to enable massive reductions in energy consumption in buildings. Each group responded to the respective breakout questions below with summary slides of their responses. These summary slides are also included below.

Questions or Discussion Topics:

Clean Water from Wastewater: Science and technological challenges to obtaining clean water from wastewater with more than an order of magnitude better performance than current technologies

Chair: Jim Smith, US EPA NRML (pdf)

• How could we achieve the following goals: zero-pathogens (including viruses), sub-parts per trillion in disinfection by-products, and clean water <250 ppm potable TDS in water derived from wastewater? If it is not possible, why? What are the biggest challenges? How close can we get to these goals?
• What technology/combination of technologies demonstrates the greatest potential to minimize the many energy intensive steps of the current water treatment process (contaminant removal, nutrient extraction, hydrogen peroxide treatment, and UV radiation, etc.) across the entire spectrum of wastewater sources (agricultural, municipal, industrial)? How could the energy (all forms including chemical) to clean water from wastewater be less than 1 kW.hr/m3 (3.6 MJ/ m3) for clean water of less than 250 ppm of potable TDS?
• What scientific/technical breakthroughs are required to enable anti-fouling membranes for a recovery process with these characteristics: 1) < 250 ppm total dissolved solids, 2) maximum two-step process, 3) use of sustainable materials only? If this optimized membrane was engineered, what are expected obstacles to widespread deployment (in addition to cost)?
• Are there any other non-energy intensive (heat, mechanical) options for anti-fouling (reversible fouling, forward osmosis, etc.), or for the separation of wastewater into water/biomass in general?
• To what extent could advanced photocatalysis alone deal with degrading complex hydrocarbons, eliminating pathogens, and degrading toxic compounds? What technological breakthroughs would be required to achieve this? What are expected obstacles to widespread deployment (in addition to cost)?

Clean Water from Wastewater: Emerging methods of deriving clean water from wastewater with associated metrics

Chair: Benito Mariñas, University of Illinois (pdf)

• How viable and promising are bio-energy producing processes (including hydrogen production, bio-electricity and methane gas) in a short-term and long-term perspective?
• How might anaerobic biological processes provide more robust and efficient treatment than conventional aerobic biological processes (e.g., activated sludge) with positive net energy production?
• Could anaerobic biological technologies and hybrid technologies, such as anaerobic membrane bioreactors (AnMBRs), be better suited than aerobic processes for treating concentrated wastewater resulting from distributed wastewater management (e.g., no dilution of black or black + grey water by storm water)?
• What breakthroughs would be required in advanced membranes, catalysts, adsorbents and/or oxidants made with novel ceramic, polymeric and biomimetic materials for significantly more robust hybrid wastewater treatment technologies that are inert to (bio)chemical attack and irreversible fouling? Could any of these membrane, catalysis, adsorption and oxidation processes be developed such that chemical pre-/post-treatment steps could be eliminated?
• Can treatment efficiency and bio-energy production be maximized through optimizing microbial populations that are responsible for those energy producing steps?
• What types of integrated or hybrid systems can be used to maximize treatment efficiency and energy production as well as resource (i.e. nutrient) recovery?
• Could the production of toxic by-products/residues be avoided with novel membrane, catalysis, adsorption and oxidation processes?
• Could new membrane materials with order of magnitude higher water permeability and tunable water/contaminant selectivity be developed for optimal treatment of wastewater-specific complex mixtures of microbial and chemical contaminants? Could any of these membranes, catalysis, adsorption and/or oxidation processes be developed such that chemical pre/post treatment steps could be eliminated?

Energy and Clean Water from Wastewater: Quality and costs needed for water to be reused from wastewater

Chair: Eugenio Giraldo, American Water (pdf)

• What are the appropriate/critical constituents to measure? Do we have the appropriate analytical methods? What analytical methods would be required from any newly developed/implemented systems?
• For you to consider replacing current clean water/energy generating technologies/systems what specific level of performance would be required (purity of clean water, amount of clean water, life of system, etc)? What are the key metrics you are interested in?
• What are acceptable costs (start-up, sustainment - $/m3)?
• What is acceptable energy usage? Are there different levels for treatment at the industrial, municipal, and agricultural levels?
• What CECs are relevant for different reuse applications?
• What are possible surrogate parameters that represent a suite of CECs?
• To facilitate the use of microbial systems, what could be some new methods for detecting microorganisms in reclaimed water, e.g. microarrays, free living amoeba, PCR for viruses?
• What would be the optimal methods to deal with the fate and risk of respiratory pathogens (e.g. legionella, mycobacterium, fungi), control of algae and algae-related toxins, and control of bacterial regrowth in reclaimed water systems?

Energy and Clean Water from Wastewater: Barriers (Infrastructure, codes, permits, and requirements) and incentives needed

Chair: Sudhir Murthy, DC WASA (pdf)

• What are some challenges with implementing new technologies into the current wastewater treatment infrastructure?
• What codes/permits/requirements apply to the treatment of wastewater?
• Could new codes/permits/requirements be written to accommodate new transformational technologies? Which cannot change under any circumstances? Where is the “gray area”?

Net Energy from Wastewater: Science and Technology Needed, with Associated Metrics - Science and technological challenges to obtaining energy from wastewater with more than an order of magnitude better performance than current technologies

Chair: Mohamed Dahab - University of Nebraska (pdf)

• Studies have shown that there is ~10x as much energy in wastewater as what is required to treat it. How far can we realistically expect science/technology to take us along that that gap?
• What are the roadblocks that are preventing current systems from maximizing the energy extracted from the biomass produced from wastewater treatment?
• What technologies/combination of technologies have the greatest potential to overcome these roadblocks?
• What are some possible sustainable methods/technologies to remove nutrients from water with net energy?

Net Energy from Wastewater: Science and Technology Needed, with Associated Metrics - Emerging methods of deriving energy from wastewater with associated metrics

Chair: William Horak, Brookhaven National Laboratory (pdf)

• How much do the kinetics of reactions (such as in microbial fuel cells, anaerobic digestion, enzymatic hydrolysis) need to be increased for widespread deployment? What breakthroughs in the development of new microbes could satisfy this gap?
• How could these new microbes be cost-effectively developed and scaled up for widespread deployment?
• What are promising strategies to increase the robustness of these microbes?
• What breakthroughs and systems would be required to enable the conversion of biomass from wastewater into CO2 + nutriments to grow algae? What species are the most promising?
• How would the resulting algae be efficiently broken up for processing into liquid fuels? How much energy could actually be generated from this entire process?
• What are the largest costs of such systems? Can things be done to make them cost effective for widespread use?

Translation into Practice: Metrics, Outcomes, Piloting, Barriers and Solutions - Metrics and outcomes needed for pilot demonstrations and implementation of technologies developed in program 

Chair 1: Cat Shrier, Watercat Consulting (pdf) Chair 2: Shahid Chaudhry, California Energy Commission, Water-Energy Efficiency Programs (pdf)

• If you could envision the ideal technology to meet your challenges, what attributes would it have?
• What demonstrations would be required for you to be convinced that ARPA-E developed technologies that have achieved acceptable performance levels?
• What smaller scale demonstrations could be done in the prototype/development process that would allow you to assess/prepare for the eventual full scale technologies?
• Who should likely pilot participants be?
• What kind of arrangements might facilitate an agreement on a pilot or demonstration?

Translation into Practice: Metrics, Outcomes, Piloting, Barriers and Solutions - Barriers to adoption and solutions needed for translation of technologies into practice

Chair: Joe Zuback, Global Water Advisors (pdf)

• What are the institutional, commercial, and legal risk barriers for adoption of new water technology (for the user, technology provider, design engineering firms)
• What actions are possible that could remove risk barriers to adoption of new water technology with minimal expense?
• What role can the U.S. and state governments play in mitigating new technology risk? Ideas for discussion are: a.) Funding support specifically targeted for beta site early adopters; b.) Provide access to liability insurance fund for new technology providers; c.) Peer review and validation process prior to approval of new technologies for participation in government beta site funding and insurance programs
• What factors must be considered for the implementation of any new wastewater treatment/energy generation technologies?
• Consider systems of different form factors, sizes, etc. What would be ideal, and why? Are there any know constraints on these considerations?
• What would be the advantages to having the technologies be decentralized or all together at a central plant?