Carbon Redirection and its Role in Energy Optimization at Water Resource Recovery Facilities

Carbon Redirection and its Role in Energy Optimization at Water Resource Recovery Facilities Samuel Jeyanayagam, PhD, PE, BCEE, WEF Fellow Joint Energy Conference NYSAWWA & NYWEA Albany, NY 16 November 2016

Presentation Outline Energy & Wastewater Treatment Carbon Redirection Energy Savings in Liquid Stream Treatment Closing Thoughts 2 2

The Energy - Water Nexus Sankey Diagram, USDOE (2014) 3

Energy Content of Wastewater Wastewater contains about 5 times the energy needed to treat it (WE&RF). The wastewater sector has the potential to generate energy needed to heat approximately 13 million homes, nearly all the households in California (USEPA). Investing 25% of the $20.5 billion US spent on video games in 2015 in the 100 largest WRRFs would make them energy neutral (USEPA). 4

Energy Embedded in Wastewater USEPA 5

The Link Between Energy and Climate Change Recovering energy from wastewater: Eliminates 18 million tons of CO 2 emission Sequesters the same amount of carbon as 4 million acres of pine forest Mayor de Blasio s 80 by 50 Plan 6

Energy Use Scenario at WRRFs 7 7

Process Energy Requirements Power Consumption, kwh/mgal 3,000 2,500 2,000 1,500 1,000 500 1 10 100 Flow, mgd MOP8 8

Presentation Outline Energy & Wastewater Treatment Carbon Redirection Energy Savings in Liquid Stream Treatment Closing Thoughts 9 9

Anaerobic Digestion is a Major Route for Recovering Energy from Influent Carbon Mainstream Treatment Process Plant Influent Plant Effluent A D Primary Sludge (Influent Carbon) B WAS B C Anaerobic digestion To Dewatering & Disposal A Carbon Diversion B WAS Biodegradability C Advanced AD D External Carbon Source Chemically Enhanced Homogenization Acid Hydrolysis FOG Wastes A-B Process Pressure Release Thermophilic Digestion Food Wastes Sonication Phased Digestion Industrial Wastes Thermal Hydrolysis OFMSW Pulsed Electric Field 10

The Importance of Carbon Without carbon, life as we know it would not exist It has high propensity to combine with other elements to form stable, very large & complex compounds. Living forms have 10 Million C-based compounds that may be categorized as follows: Carbohydrates: starches & sugar (1g = 4cal) Lipids: fats & oils (1g = 9cal) Proteins: enzymes & antibodies (1g = 4cal) Nucleic acids: RNA & DNA Carbon is energy 11

Carbon is a Valuable Resource Traditional view: It is a pollutant (cbod or COD) get rid of it, energy-intensive process. Plant of the future view: Carbon is a valuable resource. Could potentially be diverted to: Produce energy (anaerobic digestion) Drive nutrient removal Recover carbon-based commodities WRRF of the future will face a competition for carbon Utilities need a roadmap for the optimum use of available carbon based on site-specific demands 12

What is Carbon Diversion or Redirection? The diversion of influent biodegradable material away from secondary treatment to energy recovery. The Good: Lower aeration demand More biogas for beneficial use Lower Biosolids Production Smaller Bioreactors/More Bioreactor capacity Sets plant up for future technologies like Mainstream Anammox The Bad: Less carbon available for EBPR & denitrification 13

Carbon Redirection Strategies Available approaches for redirecting influent carbon for energy production Conventional Primary Treatment Chemically Enhanced Primary Treatment (CEPT) High Rate Biological Contact A-B Process Captivator Anaerobic treatment Microscreens 14

Conventional Primary Treatment vs. CEPT Conventional Primary Treatment BOD 5 BOD 5 55% to 75% of Infl. BOD 5 to Secondary Treatment Chemically Enhanced Primary Treatment Ferric or Alum Polymer 25% to 45% of Infl. BOD 5 to Anaerobic Digestion BOD 5 BOD 5 20% to 60% of Infl. BOD 5 to Secondary Treatment 40% to 80% of Infl. BOD 5 to Anaerobic Digestion 15

Impact of Primary Clarification (1 MGD Facility) 16

Carbon Redirection Using High Rate Biological Contact Very short SRT system (0.25-0.5 days) BOD oxidation minimized; adsorption promoted Carbon (BOD) directed to anaerobic digestion BOD 5 Low DO, Short SRT BOD 5 40% to 70% of Influent BOD 5 to Secondary Treatment BOD 5 30% to 60% of Influent BOD 5 to Anaerobic Digestion 17

COD/BOD Removal Mechanisms in Conventional and High Rate Processes Conventional (SRT > 1-2 days) Truly Soluble COD Colloidal COD Particulate COD Uptake Oxygen ($$) (or nitrate) Growth Hydrolysis & Coagulatsion (solubilization) Waste Sludge scod ccod pcod High Rate (SRT < 0.5 day) Truly Soluble COD Colloidal COD Particulate COD Storage Some Coagulation Enmeshment Oxygen ($) Growth v Waste Sludge scod ccod pcod 18

The A-B Process Headworks High Rate Activated Sludge A-Stage Low Rate Activated Sludge B-Stage Effluent RAS RAS WAS with adsorbed BOD Biogas Dewatering Thickening Anaerobic Digestion Biosolids Disposal 19

Captivator System By Evoqua Vertical Loop Reactor (VLR) DAF Contact Tank Aeration Basins Final Clarifier Anaerobic Digestion Credit: Evoqua Water Technologies, 2015 20

Carbon Diversion Achieves Energy Use Optimization & Energy Recovery 1000 900 1000 used Energy Comparison 30 MGD Plant Aeration energy used Energy created from biogas 800 Kilowatts 700 600 500 400 500 created 600 used 700 created 300 200 100 0 Conventional Plant Credit: Evoqua Water Technologies; Captivator Systems, 2015 Plant with Carbon Diversion (Captivator ) 1 2 21

Strass WWTP (Austria) An Energy Neutral Facility 22

Energy Production & Consumption Profiles Strass WWTP 23 23

Why is Strass so Energy Efficient? Pumping Station/ Headworks High Rate Activated Sludge A-Stage Low Rate Activated Sludge B-Stage Effluent RAS RAS Co-generation Dewatering Sidestream Anammox Thickening Anaerobic Digestion Land Application 24

Presentation Outline Energy & Wastewater Treatment Carbon Redirection Energy Savings in Liquid Stream Treatment Closing Thoughts 25 25

In conventional treatment, significant energy (air) is used to keep the bugs happy & contented However, energy savings may be possible by: Using different bugs Conditioning the bugs Delivering air differently 26

Conventional Nitrogen Removal Autotrophs Aerobic Nitrate NO 3 Heterotrophs Anoxic Nitrite NO 2 O 2 Carbon 25% 40% Nitrite NO 2 Ammonium NH 4 O 2 75% Carbon 60% Nitrogen N 2 High carbon & high energy process 27

Short-cut Nitrogen Removal Nitrate NO 3 Nitrite NO 2 O 2 MeOH 25% 40% Nitrite NO 2 Ammonium NH 4 O 2 75% MeOH 60% Nitrogen N 2 28

Low-Carbon, Low-Energy TN Removal Anammox (Anaerobic Ammonium Oxidation) Nitrite NO 2 Ammonium NH 4 O 2 37% Nitrogen N 2 29 29

Mainstream Anaerobic Treatment Upflow Anaerobic Sludge Blanket (UASB) Reactor Track record: >30 years Methane production Elimination of aeration Reduced sludge production Nutrient rich effluent suitable for nutrient recovery Anaerobic MBR (AnMBR) represents an emerging technology 30

Membrane Aerated Biofilm Reactor (MABR) Air In O 2 Membrane Biofilm Air Out Substrate Mixing Bulk Liquid Scouring Hollow fiber gas transfer membrane Delivers oxygen by diffusion to a biofilm that grows on the surface of the membrane Diffusion due to concentration gradient across membrane bubbleless aeration Claimed to be 4 times more efficient than fine bubble diffusers. Testing at the O Brien WRP, Chicago GE ZeeLung 31

Concluding Thoughts Energy cost is only 2 nd to labor cost at WRRFs Wastewater contains 5 times the energy required to treat it Anaerobic digestion is a major route for recovering energy from influent carbon Gas production can also be enhanced by feed conditioning and codigestion Sidestream/Mainstream deammonification is a low C, low energy nitrogen removal process Low DO operation is a viable strategy that can be quickly implemented Anaerobic treatment & MABR are transformational technologies that can result in significant energy savings Roadmap for energy neutrality 32

Good Planning Always Avoids Unexpected Problems! 33

Wisdom Comes From Surprising Places: You ve got to be very careful if you don t know where you are going, because you might get there." Yogi Berra In theory there s no difference between theory and practice. In practice there is." Yogi Berra 34