Sustainable Wastewater Treatment Low Energy Alternatives to Energy-Intensive Aerated Activated Sludge Systems and Other Emerging Solutions to Your High-Energy Process Problems Erin Mackey, Ph.D., P.E.
There Are Already Many Ways to Save Energy at POTWs Enhanced primary treatment. Reduce headloss. Shorten SRTs for aeration basins. Use energy-efficient aeration diffusers. Use VFDs and higher-efficiency pumps. Dose-pace UV disinfection systems. Use trickling filters, not activated sludge. Use sand filtration, not membrane filtration. WateReuse and WERF funded Carollo to find the next big thing.
Not Just for Milk Anymore, Pasteurization of Reclaimed Water Andrew Salveson & Erin Mackey, Carollo Engineers
Acknowledgements WateReuse Research Foundation Water Environment Research Foundation Carollo Engineers, Inc. CH2MHill Kennedy/Jenks Consultants Perry McCarty, Consultant The Artemis Project O2 Environmental Hampton Roads Sanitation District United States Bureau of Reclamation Arizona State University
There are a lot of interesting ideas out there. Finding the great ones can be slow going.
Goals Phase I Identify and evaluate emerging low-energy wastewater treatment technologies. Recommend technologies with the greatest potential for large-scale implementation for further investigation. Phase II Test the recommended technologies at demonstration scale.
Phase I Results
To compare alternatives we first needed a basis of comparison.
WWTP Energy Use Is Dominated by Pumping, Aeration, and Disinfection UV Disinfection Pumping Aeration With denitrification
WWTP Energy Use Is Dominated by Pumping, Aeration, and Disinfection UV Disinfection Pumping Aeration Without denitrification
Energy Use for Hypo Generation Is Similar to UV Disinfection Utility 1 Utility 2 Utility 3
A More Energy-Efficient Secondary Process Would Give Us the Most Bang for Our Buck The largest energy use is the secondary process and thus dictates special attention. Capital cost vs. energy cost savings is important but not central at this stage. Disinfection energy is a secondary (yet important) concern. Other low energy processes are worth considering.
Technology Review What s out there? What do we know about it? Disclaimer: 1. The listing of technologies is not an endorsement of those technologies. 2. The omission of technologies is not a judgment against those technologies.
Enhanced Primary Treatment Examples M2 Renewables MicroScreen. Themes: Recover more energy (gas). Reduce need for downstream treatment. May conflict with biological nutrient removal. Simple-to-complex systems. Salsnes Filter fine screening. Chemically Enhanced Primary Treatment (CEPT). Veolia s Actiflo. Value of improved solids removal: 1. Reduces aeration demand (~5 to 35%). 2. Increases energy recovery in anaerobic digestion (~45%).
Enhanced Secondary Treatment Examples Anammox Value 40 to 60% reduction in nitrification energy. Themes: Shifting from aerobic treatment to anaerobic treatment. Use less oxygen (electricity). Recover more energy (gas). Reduce or eliminate nutrition Upflow Anaerobic Sludge Blanket (UASB) or Expanded Granular Sludge Bed (EGSB) needs. Value 50 to 80% reduction in aeration demand. More complex but not high-tech. Anaerobic MBR with and without Granular Activated Carbon (for membrane scouring). Value 50% reduction in energy use +75% increase in gas production.
More Enhanced Secondary Treatment Examples Grundfos Biobooster (Ceramic MBR). Emefcy s Spiral Aerobic Bioreactor (SABRE). Themes: Potential large reduction in oxygen use (electricity). Many options would be much more complex to operate. Value Potential energy savings, if proven. Value Estimated 95% energy reduction. American Water s NPXPress. Value 35% to 40% energy reduction.
More Enhanced Secondary Treatment Examples Emefcy s Electrogenic Bioreactor. Value Potential 30% energy savings if proven to work as designed. Themes: Potential improved oxygen transfer (less electricity). Better mouse traps. Increased complexity. APG-Neuros s Turbo Blowers. Noram Engineering s Vertreat Process. Value 10% to 40% reduction in aeration energy. Value 6X oxygen transfer efficiency.
Enhanced Tertiary Filtration Examples Water Tectonics Electrocoagulation and Filtration. Parkson DynaSand Ecowash. Themes: Increased process efficiency (less electricity). Less chemicals (embedded energy). More complexity. Schreiber s Fuzzy Filter. Value 50% or greater savings on energy use for filtration.
Enhanced Tertiary Disinfection Examples Carollo s PTG Pasteurization System. Themes: Increased efficiency of process (less electricity). Less chemicals (embedded energy). Value Free disinfection. Aquionics/Dot Metrics LED UV disinfection Light emitting diode (LED) UV disinfection. Value Future potential for low energy UV disinfection.
Energy Recovery Treatment Examples M2 Renewables Ultra High Temperature Gasification. Value Themes: Estimated 2X energy generation compared to anaerobic digestion and gas engines. Significant energy recovery. More complexity. OpenCel Focused-Pulsed Technology. Value 25% improvement in gas generation compared to baseline anaerobic digestion.
Energy Recovery Treatment Examples Fuel Cell Energy s Fuel Cell. Value 10% to 15% improvement in energy Themes: generation compared to engines and turbines. New ways to convert gas to electricity. More complexity.
Sorting Now that we have this great laundry list, what do we do with it?
Technologies Were Sorted Based on Market Readiness 1) Technologies that are that are proven and should be more widely used; 2) Technologies that are partially proven and need more evidence; and 3) Technologies that have substantial merit, but little to no track record.
Phase I Results Five Star Winner Anammox. Proven side-stream performance. Ready for full-stream demonstration. Themes: Targets high energy-demand process (high electricity savings). Ready for testing at full scale. Five Star Winner Anaerobic MBRs. Proven now at the laboratory scale in colder climates. The next step is demonstration-scale testing. Less complexity than many others.
Phase I Results Four Star Winner Pasteurization. Testing now underway at a demonstration scale. Long-term performance monitoring required. Themes: Still targets high energy-recovery Three Star Winner Gasification. Conflicting information exists on full-scale or demand installations. processes An independent (high energy audit is needed to prove performance. electricity savings). Ready for testing at full scale but Three Star Winner Aerobic Membrane Biofilm Reactor. Pilot testing less already proven. planned for North America. Independent energy audit recommended for this technology.
Phase I Results Two Star Winner Electrocoagulation. Low-cost benchscale work will be done to demonstrate energy efficiency of combined filtration and disinfection. Two Star Winner UASB. While operating Themes: internationally in warm climates, very little is know about true performance or energy use. Process and energy audit treatment of select international steps. systems is recommended. Targets less energy-intensive Further from market-ready or more of a gamble. More complex.
So what s most likely to soon be coming to a treatment plant near you? ANNAMOX NITROGEN REMOVAL ANAEROBIC MBR PRIMARY TREATMENT
What Does this All Mean to Me?
Take Home Points Major trends are moving us towards: Less oxygen use, More mechanical efficiency, More effective biochemistry. The cost of these benefits include: Increased complexity, More reliance on technology, Need for more sophisticated operator training and job performance. Cost:benefit will be site-specific.
Full Anaerobic Treatment When we can treat municipal wastewater anaerobically to achieve net energy production while meeting effluent quality standards, we will make our rate payers very happy.
Questions?