WWTP Energy Audits Provide System-Wide View to Reducing Energy and Optimizing Processes

Transcription

1 WWTP Energy Audits Provide System-Wide View to Reducing Energy and Optimizing Processes Jane Atkinson, AECOM Anthony Fiore, NYC Mayor s Office of Sustainability Rob Pape, AECOM 2016 JOINT ENERGY CONFERENCE

2 NYC Department of Environmental Protection Supply 1 billion gallons of water per day to 9 million New Yorkers 19 storage reservoirs and 3 controlled lakes 550,000 water quality tests per year 7,000 miles of water mains 56 shaft sites; 500 pressure regulators; 3 pump stations 109,000 fire hydrants Treat 1.3 billion gallons of wastewater per day 14 In-city treatment plants ( MGD); 8 upstate 7,400 miles of sewer: 3,337 miles of combined, 2,271 separated 157,000 street segments of sewer 490 regulators (104 telemetered), 95 pump stations 144,000 catch basins $14 billion in active construction & design projects Air Quality, Hazmat, Emergency Response, & Noise

3 DEP Strategies for GHG Reduction Strategies: 1. Energy conservation and efficiency (Demand Side Initiatives) 2. On-site clean energy generation (Supply Side Initiatives) (e.g. beneficial use of anaerobic digester gas) 3. Traditional Renewable Energy (e.g. hydro, solar PV) Achieved through: Engineering/systems changes + organization cultural shift

4 DEP GHG Emissions Projected FY17 Business-As-Usual GHG Emissions 30% reduction 80% reduction ^FY15 Preliminary Data

5 WWTPs Energy Audits Goals Get better understanding of how energy is used at each WWTP Identify potential technically feasible energy saving opportunities Perform preliminary screening analysis of energy savings and economics Based on analysis, prepare a set of recommended projects for each WWTP that could be pursued further Methodology Benchmarking ASHRAE Level II audit protocols and NYC Local Law 87 requirements 1 or 2 days on-site, Tour of facility with Operations Staff

6 Benchmark Benchmarking is the normalized ranking of a particular performance marker of a system or subsystem in comparison to other similar functioning systems. Shows how the facility compares to others Shows the potential of room-for-energy reduction" Common Energy Benchmarks Energy Consumption/Plant Flow (kwh/mg) Energy Consumption/BOD (Btu/lb BOD removed) November 28, 2016 Page 6

7 Benchmarking Pitfalls Benchmarking based on plant flow or BOD has drawbacks, as it fails to factor in other significant plant aspects such as: Need for odor control Process technologies (trickling filter vs. conventional vs. BNR) Climate where a facility is located Onsite vs. offsite dewatering Onsite vs. offsite main sewage pumping November 28, 2016 Page 7

8 Building a Better Benchmark Water Research Foundation (WRF) and Energy Star have more sophisticated, multi-variable regression benchmarking tools which consider: Influent flow v Design flow Influent BOD loading Effluent BOD loading BNR v. non-bnr Fixed film v. non-fixed film November 28, 2016 Page 8

9 New York City Audit Example Facility Benchmarking WRF Note: Smaller scores indicate more potential for energy and GHG reductions Presentation Title November 28, 2016 Page 9

10 Process Mass Balance Historically, wastewater treatment plants were analyzed using only a mass balance. Influent mg TSS/L mg BOD/L Flow Primary Treatment Intermediate mg TSS/L mg BOD/L Flow Secondary Treatment Effluent mg TSS/L mg BOD/L Flow Digester Gas mg VSS/L mg TSS/L Waste Solids Treatment mg VSS/L mg TSS/L Solids Disposal Recycle Energy Neutrality 11/16/2016 Page 10

11 Process Energy Balance The comprehensive analysis incorporates an energy balance with a mass balance TYPICAL ENERGY BALANCE EXAMINES Primary Treatment Pumping Energy Solids Capture/Removal Secondary Treatment Pumping Energy Solids Production Aeration Energy Mixing Energy Solids Treatment Energy Neutrality November 28, 2016 Page 11 Pumping Energy Solids Thickening Heating Digester Gas Utilization

12 What Goes Into Baselines Global and Local Energy Data Global energy data (electric, natural gas, fuel oil, propane, etc.) Bills vs. meter/logs Costs Local energy data (rare) Anaerobic digester gas to flare, boiler, CHP, etc. Electric meters on major equipment Main pumps RAS pumps Blowers Centrifuges November 28, 2016 Page 12

13 What Goes Into Baselines cont. Local Operational Data Local operational data (influent, primary effluent, secondary, thickening, digestion, dewatering) includes: Flows BOD/COD (total, soluble) TSS VSS Permit and process control data November 28, 2016 Page 13

14 What Goes Into Baselines cont. Local Design and Equipment Data: Equipment specifications (hp, efficiencies, flow, tank dimensions, number of units, etc.) Equipment operating conditions (runtime, units in service, control, VFD, resistor banks) Pump/Blower curves Data period (a minimum of a year of data) Plant design parameters (total flow, loading, etc.) Plant flow schematic (units) Drawings (Record, shop) November 28, 2016 Page 14

15 New York City Audit Example Facility Benchmarking WRF Note: Smaller scores indicate more potential for energy and GHG reductions Presentation Title November 28, 2016 Page 15

16 Hunts Point North River 26 th Ward Newtown Creek Presentation Title November 28, 2016 Page 16

17 Energy End Use Analyses Results Aeration is largest energy user Digestion and heating needs are largest fuel consumer Main Sewage Pumps are consistently large consumers Ventilation and Odor Control needs varied considerably on location, but can be substantial

18 Specific Process ECM Areas Process area ECM Description Main Sewage Pumps (motors and control) Variable speed drive arrangement Replace resistor banks with VFD Installation or magnetic coupling drive Use of dual drives: use of engine driven drives in conjunction with the electric motors Primary treatment Equipment Efficiency Operate at higher wet well elevations Install/replace with energy efficient motors. Chemically Enhanced Primary Treatment (Coagulant dosing) Advanced primary treatment (High rate clarification) Improve solids removal Potentially reduce BOD to activated sludge, lower air requirements and increase digester gas production Improved solids removal, potentially reduce BOD, lower air requirements and increase digester gas production Secondary treatment Tank usage Reduce tanks in service Aerator upgrade Fine/ultrafine bubble diffuser, increased oxygen transfer, reduce air requirements DO Install DO monitoring and controls Possibly install anoxic zones for non-bnr plants Blowers Vastly improved high efficiency compressors are available. Flow distribution Reduce inefficiencies in aeration Equalization stabilize energy usage throughout the day Tank usage Operate tanks based on actual flows Efficiency Energy efficient mixers for anoxic zones Sludge blanket control Thicker RAS at lower pumping volumes Presentation Title November 28, 2016 Page 18

19 Specific Process ECM Areas Process area ECM Description Sludge pumping WAS/RAS pumps Replacement with energy efficient pumps. Use of VFD or other energy efficient control. Explore the use of magnetic drive couplings for variable flow application. Sludge Thickening Anaerobic digester Sludge thickening Feed parameters Install low energy thickening technologies Chemical addition Increase thickened solids concentrations (higher digester HRT) Lower waste sludge volume to heat Potentially reduce sludge disposal costs Heating Efficient Boilers Alternative heat sources (i.e. engine cooling/exhaust loops) Efficient heat exchangers and improved insulation. Type / Co-digestion Investigate meso/thermo/and acid phase digestion for best gas production Investigate decanting operations for increasing digester HRT/gas production Pre- or Post- treatment (lysing) [i.e. CAMBI] Co-digestion with FOG or Food Waste or CAFO waste Mixing Gas mixing and pump mixing for optimum digester operations and ADG production Maintenance Digester cleaning for improved gas production Solar HW Heating Utilize solar thermal collectors for process water heating. November 28, 2016 Page 19

20 Specific Process ECM Areas (continued) Process area ECM Description Sludge dewatering Dewatering efficiency Process improvements to reduce the sludge volume Energy efficient dewatering equipment Elutriation Elutriate sludge prior dewatering, reduce fine particles, reduce dewatering volumes and potentially improve dewatering operations Digester gas use Combined heat and power (CHP) Various configurations possible. Use of heat from engine generator for digester heating, building heating, etc. Could use chiller for cooling/air conditioning. ADG collection/storage Minimize fugitive emissions. Maximize gas collection and storage. Provide gas conditioning and boosting systems for beneficial use Use for boilers Modify boilers to dual-fuel or gas fuel type Engine driven Where dual drives could be installed, the use of engine driven equipment may equipment result in a more efficient use of digester gas Use of fuel cells Innovative technology Distribution Sell purified digester gas to grid Use of biosolids Incineration Incinerate solids Gasification Odor control Efficiency Energy-efficient blowers Control scheme Presentation Title November 28, 2016 Page 20

21 ECMs for Additional GHG Reduction Payback Period (years) Stop Fugitive ADG 118 ECMs have payback periods of less than 10 years and cost less than $2,000/MT MSP Improvements Clean Digesters Submetering Elutriation Operational Digester Heat Transfer Improvements Include in priority projects due to significant contribution to carbon goals Mix Digesters BWS ECMs Lighting Thickening Improvements Aeration Improvements Boiler Improvements ,000 1,500 2,000 2,500 3,000 3,500 4,000 $/MT GHG Avoided Controls Cogeneration Doesn t consider Resiliency benefits Misc Electrical HVAC

22 Recommended ECMs Operational changes Change temperature setpoints on heating and AC systems Adjustments to operation of main sewage pumps Control odor sources rather than use huge odor control systems Reroute centrate from head of plant to ATs Reduce recycle flows DO control

23 Economics of DO Control Could save $1.9 million per year Could save $1.4 million per year Would cost $6.8 million per year

24 Recommended ECMs (cont.) Metering Submetering and real-time energy information Sludge train improvements Increase concentration of influent sludge to gravity thickeners Elutriation Lighting Upgrade to LEDs Occupancy sensors Replace thickening centrifuges with low horsepower Rotary Drum or Gravity Belt thickeners

25 DON T FORGET: Programmatic and Institutional Controls Programmatic controls are in-plant actions that can be taken to reduce energy. Reduce recycle flows (washwater, draining tanks, ducking weirs, etc.) Automatic lighting controls Fan filter replacement Institutional Controls are those factors that are created on the management level that foster energy conservation, reduction and/or energy production. Energy usage/purchase reduction goals Source gathering (FOG program or a food waste program, etc.) SOPs for design specification Energy analysis/consideration during design Energy policies (i.e. LEED) November 28, 2016 Page 26

26 Thank You November 16, 2016