1. Steven A. Gabriel, Christopher Peot and Mark Ramirez
Identification of optimal strategies for energy management and reducing carbon dioxide emission at the Blue Plains Advanced Wastewater Treatment Plant (AWTP)
Chalida U-tapao
Steven A. Gabriel, Christopher Peot and Mark Ramirez
Dept. of Civil & Env. Engineering, University of Maryland, College Park, Maryland
District of Columbia Water and Sewer Authority, Washington DC
13 November 2009

2. Outline
Overview of energy, wastewater treatment
process and objective of this research
Flowchart of modeling decisions/processes
(the Blue Plains AWTP is case study)
Ongoing work

3. U.S. Primary Energy Overview
Imports fill the gap between U.S. energy use and production
Petroleum is the major imported fuel
(Source: EIA, Energy perspective , June 2009)

4. U.S. Energy Consumption by Energy Source, 2008
More renewable energy will decrease imported petroleum, coal and natural gas
Many renewable energy sources can be selected
(Source: EIA, Renewable Energy Consumption and Electricity 2008 Statistics)

5. Wastewater Treatment Process
Contaminated substances are separated in solid form
Almost all solids are biomass
(Source: DC Water and Sewer Authority)

6. Biosolids is a Significant Renewable Energy Source
Biosolids is biomass that is renewable energy source
(Source: DC Water and Sewer Authority)

7. A Huge Plant Such as The Blue Plains AWTP Has Great Potential to Produce Renewable Energy
(Source: DC Water and Sewer Authority)

8. Objectives of this research
Find optimal strategies for energy management
Use energy sources that can reduce the carbon footprint at the Blue Plains AWTP

9. Flowchart SEWAGE Investment $ Operations/Investments WASA Operations
PB=% of sewage to be converted to biosolids $ $
PE,W=% of power from methane to be used at WASA
WASA
Operations
IWASA $
Iwind
Isolar
Idigester
PG,W=% of methane to be used at WASA PB
1-PB
1-PG,W
Biosolids
Methane
Outside sales
transp.
indust.
Biogas
Other clean energy
wind, solar, etc
PG,W
Use at
WASA
Electricity
Land
application
natural gas grid/market
1- PE,W
PE,W
Outside sales
carbon allowance market
Use at
WASA
electric power grid/market

10. The Blue Plains AWTP operating process
330 MGD
736,087 kWH/day
GHG (CO2)
GHG
(CO2 CH4 ,N2O)
GHG (CO2)
Odor
Biosolids
1,163 tons/day
(Source: Gabriel, S.A., et al., Statistical Modeling to Forecast Odor Levels of Biosolids Applied to Reuse Sites. Journal of Environmental Engineering, 2006).

11. Average 1,163 tons per day

12. Average 239 tons per day

13. The Anaerobic Biodegradation Production Process
Active biomass + C-substance CH4 + CO2 + stabilized biomass + H2O
Biogas composition
Methane gas %
Carbon dioxide %
Water vapor, traces of H2S and H2 0-5%
(Source: Appels, L., et al., Principles and potential of the anaerobic digestion of waste-activated sludge).

14. ODS : organic dry solids of the sludge (wt%)
The Relation Between Biogas Production and Retention Time
ODS : organic dry solids of the sludge (wt%)
(Source: Appels, L., et al., Principles and potential of the anaerobic digestion of waste-activated sludge).
Biogas is 0.4 x 239 x = 95.6 x 103 cubic meters per day
Methane is 60 % = 57.3 x 103 cubic meters per day
Carbon dioxide is 35% = 33.5 x 103 cubic meters per day

15. Historic Daily Power Consumption Data for The Blue Plains AWTP
Average 2008 = 736 x 103 kilowatt hours per day

16. From Methane Gas to Electricity
Methane 1 ft3 = 1,028 BTU
3,412 BTU methane = 1 kWH
Blue Plains AWTP will have almost 534 x kilowatt hours per day from methane gas
( Source:
Plant needs 736 x 103 kilowatt hours per day (not enough)

17. Other Renewable Options are at Blue Plains
Methane from biosolids generate electricity that is not enough for the Blue Plains AWTP operations
(Need 736 x 103 kilowatt hours per day but it is able to generate only 534 x kilowatt hours per day )
Other options more than methane or electricity is to invest in renewable energy source (e.g., wind, solar, hydropower and geothermal)

18. Prediction of Carbon Dioxide (CO2) Credits
0.8 tons CO2 credits per dry ton biosolids
(Brown, S., H. Gough, and et al., Green Aspects of Biosolids Processing and Use 2009)
0.8 x 1,163 tons biosolids per day
CO2 credits are 930 tons per day

19. Financial Benefit from CO2 Credits
Transaction Volume and Value, Global Carbon Market, 2008
Market
Volume (MtCO2)
Value( US$ million)
RGGI
27.4
108.9
108.9/27.4 = $ 3.94 per ton CO2
Source: Ecosystem Marketplace, New Carbon Finance
The Blue Plains AWTP
$3.94 x 930 tons per day = $ 3,692 per day
= $ 1.3 million per year

20. Summary
Biosolids from the Blue Plains AWTP is a significant renewable energy source. It has a high efficiency to generate methane and electricity
Methane is x103 cubic meters per day
Electricity is 534.5x103 kilowatt hours per day
CO2 credits is 930 tons CO2 per day
Financial benefit from CO2 credits is about $ 3,692 per day
Methane for transportation grid
Selling Electricity to Grid Electric Power

21. Will consider both investment decisions as well as operational ones
Ongoing Work
Build a multiobjective optimization model in order to make best decisions to:
minimize DCWASA’s CO2 footprint
minimize energy usage
minimize costs
other considerations (as appropriate)
Will consider both investment decisions as well as operational ones