Integrated Resource Recovery and

the “Carbon Positive” Wastewater

Treatment Plant

1

Steve Krugel

Pacific Northwest Clean Water Association

PRE-CONFERENCE WORKSHOP

The Future of Wastewater Treatment:

Sustainable Solutions

Boise, ID Sept. 13, 2009

Discussion Topics

�Definition of Sustainability

�Achieving Sustainable Vision

�Role of Resource Recovery

�Examples - Adding Metrics �Digester Gas

�Heat Recovery

�“Carbon Positive” WW Treatment

Webster

• sus·tain·able

• Pronunciation: \sə-’stā-nə-bəl\

• Function: adjective

• Date: circa 1727

• 1 : capable of being sustained2 a : of, relating to, or being a method of harvesting or using a resource so that the resource is not depleted or permanently damaged <sustainable techniques><sustainable agriculture> b : of or relating to a lifestyle involving the use of sustainable methods <sustainable society>

Sustainable Vision

“Act to sustain our livelihoods and that of future generations by acting in a socially and fiscally responsible manner to reduce the use of non-renewable resources and to prevent irreparable degradation of our environment that supports our wellbeing”

Achieving a Sustainable Vision

• Use a combined Philosophical / Technological approach in decision making

• Expanding the boundaries of traditional thinking

▫ Expansion to a global perspective

▫ Expansion of utility perspective

▫ A resource based approach

What We in WW Industry

Need to Do – Think Big

How we design the whole system

�Household segregation (supply and wastes)

�Sewer design

�Treatment selection (low energy, high removals)

�Discharge criteria impacts (impact of removal)

�Impact balances (LCA)

�Resource recovery (energy, nutrients)

�Other…

Sustainability in WW Treatment:

Current Issues

MAJOR WW SUSTAINABILITY ISSUES

�Energy use/recovery linked to GHG emissions

�Other GHG and toxic emissions from sewers, treatment

processes, odor control - methane, N2O, VOCs, others

�Effluent quality – BOD, EPOCs, nutrients

�Resource recovery – reclaimed water, nutrients, energy

MINOR WW SUSTAINABILITY ISSUES

�LEED ratings

�Construction Materials

�Land

�Social issues

WWTPs can produce 100% of their power

needs – energy self sufficient

• Grevesmühlen, Germany: ~4mgd WWTP

• Grease and trucked wastes added to anaerobic digesters �biogas �power

BUT WE CAN DO EVEN BETTER!

Schwarzenbeck et al, 2008 – WS&T

8

Integrated Resource Recovery Opportunities

9

Typical Energy Profile of Wastewater

Treatment and Disposal Options

Typical Wastewater Treatment Energy Profiles

Biosolids/Biogas Process kW-hr per

MG

MBtu per

MG MJ per ML

CO2 emissions

from hydro

power

generation, kg

per ML

treated

CO2 emissions,

kg per MJ.

(From power

generation for

gas-fuelled

power plant)

Liquid Stream Treatment

Conventional Activated Sludge 600 2.0 570 5.2 95

Nitrifying Activated Sludge 1200 4.1 1140 10.5 190

MBR 1700 5.8 1620 14.8 270

MBBR/IFAS 800 2.7 760 7.0 125

BAF (assuming equivalent BOD concentration) 700 2.4 670 6.1 110

TF/SC 400 1.4 380 3.5 65

Ultra Membrane Filtration following Secondary Treatment 500 1.7 480 4.4 80

Reverse Osmosis following UF 1300 4.4 1240 11.3 205

Typical Conventional Water Treatment 300 1.0 290 2.6 50

Desalinization of Seawater 16,000 54.6 15,200 140 2535

Solid Stream Treatment

Anaerobic Digester Heating

Required - 1.1 320 - -

Supplied by gas boiler - 1.3 380 - 18.2

Supplied by heat pump 90 0.3 80 0.8 14.2

Digester Gas Value

Biogenic CO2 emission from combustion - - - - 99

As commercial fuel (offset natural gas) - (7.2) (2010) - (101)

Boiler production of heat - (6.1) (1710) - (85)

Electricity production (740) (2.5) (700) (6.4) (116)

Potential recovered heat from cogeneration - (3.2) (900) - (45)

CO2 removal with pressure swing adsorption 160 0.5 150 1.3 25.2

Gas compression to 3000 psi useable as vehicle fuel 60 0.2 60 0.5 9.5

Sludge Hauling (digested/dewatered per 200 km one way) - 0.3 80

Nutrient Value of Biosolids - (1.1) (290)

Sludge Drying

Raw - 6.0 1670 -

Digested - 3.1 860 -

Thermal Value of Dried Biosolids

Raw

As commercial fuel (offset coal) - (14.1) (3930) - (363)

Electricity production (1440) (4.9) (1380) (12.5) (227)

Potential recovered heat from power generation - (6.3) (1770) - (89)

Digested

As commercial fuel - (5.3) (1470) - (136)

Electricity production (560) (1.9) (520) (4.9) (88)

Potential recovered heat from power generation - (2.4) (670) - (34)

Extractable Heat from Wastewater Effluent (offset nat. gas) - (80) (20,000) - (1005)

Power to mine extractable heat (3.5 COP) 6860 (22.9) 5710 56 1080

Digester gas sold as commercial

fuel � 2000 MJ/ML

Raw sludge sold as commercial

fuel � 3900 MJ/ML - 1700

MJ/ML for drying

Extractable effluent heat �

20,000 MJ/ML

CAS with nitrification �

1140 MJ/ML

CAS �

570 MJ/ML

Enhanced Options for Use of Gas

-Cogeneration

-Scrubbing and Sale

-Vehicle Fuel

11

Cogeneration – Combined Heat and

Power� Cogeneration can provide about 40 to 60% of power needs for a plant

� Recovered heat from cogeneration typically can provide all process and building heat needs

Biogas Scrubbing and Sale - Cleaning to

Utility Pipeline Quality

• Renton, WA - CO2 scrubbing system

• Sacramento – moisture, sulfide and siloxane removal

�Sustained demand

�100% available for sale

�100% fossil fuel carbon offset

Biogas Potential as

Vehicle Fuel

�Biogas now powers a train in Sweden

The train can run for 600km before it needs to refuel and can reach 130km/h

�Biogas has the potential for use in fleet vehicles

C02 Emission Rates for Power Generation

• Hydro � 0 lbs/kWh*

• Gas � 1.3 lbs/kWh*

• Coal � 2.1 lbs/kWh*

• Pacific Contiguous � 0.42 lbs/kWh*

• British Columbia � 0.16 lbs/kWh

• North Central � 1.77 lbs/kWh*

• Oregon, Washington, and Idaho � <0.3 lbs/kWh

* Source Carbon Dioxide Emissions from the Generation of Electric power in the united States, US Department of Energy, July 2000

Carbon Profile for Digester GasNorthwest

�Cogeneration – 20 kg CO2/ML saved + 45 kg/ML potential recovered heat (65 Net Saved)

� Sale as Natural Gas – 101 kg CO2/ML saved – 5 for scrubbing (96 Net Saved)

� Sale as Vehicle Fuel - 135 kg CO2/ML saved – 7 for scrubbing and compression (128 Net Saved)

Northeast

�Cogeneration – 155 kg CO2/ML saved, 45 kg/ML potential recovered heat (200 Net Saved)

� Sale as Natural Gas – 101 kg CO2/ML saved – 30 for scrubbing (71 Net Saved)

� Sale as Vehicle Fuel - 135 kg CO2/ML saved – 7 for scrubbing and compression (128 Net Saved)

Generating More Gas

-Enhanced Digestion

-Co-Digestion

17

80

70

60

50

40

30

Volatile Solids Reduction, %

0 10 20 30 40 50 60 70

Total SRT, days

1

5

2

3

4

7

6

0

WLSSD , Duluth

King County Renton (Pilot)

Neenah - Menasha

Madison (Pilot)

City of Los Angeles (Pilot)

Cologne, Germany

Sturgeon Bay

1

2

3

4

5

6

7

Performance Change - Mesophilic

to Temperature Phased Digestion

Boosting Digester Biogas Production

Advanced Digestion

Food Processing Wastes

Wastewater Solids

- Meso

Grease - FOG

Source-Separated Food

Wastes

Average

Biogas

Production

(scfm)

2005 2015 2025

Advanced Digestion

Food Processing Wastes

Advanced Digestion

Food Processing Wastes

Wastewater Solids

- Meso

Grease - FOG

Source-Separated Food

Wastes

Average

Biogas

Production

(scfm)

2005 2015 2025

Wastewater Solids

- Meso

Grease - FOG

Source-Separated Food

Wastes

Average

Biogas

Production

(scfm)

2005 2015 2025

19

Example with Standard Assumptions (add 25 % grease solids load)

Sludge Sludge %only + grease increase

Gallons fed 23,500 gpd 26,500 gpd 12.5

TS fed 10,000 lbs/d 12,500 lbs/d 25

VS fed 7,800 lbs/d 10,175 lbs/d 30

VS destroyed 4,290 lbs/d 6,310 lbs/d 47

Biogas 68,600 ft3/d 109,000 ft3/d 59

Methane 43,900 ft3/d 72,500 ft3/d 65

Example with Symbiotic Assumptions(same 25 % grease solids load)

Sludge Sludge %only + grease increase

Gallons fed 23,500 gpd 26,500 gpd 12.5

TS fed 10,000 lbs/d 12,500 lbs/d 25

VS fed 7,800 lbs/d 10,175 lbs/d 30

VS destroyed 4,290 lbs/d 6,310 lbs/d 47

Biogas 68,600 ft3/d 109,000 ft3/d 59

Methane 43,900 ft3/d 72,500 ft3/d 65

Sludge VSR 55 → 65% Grease VSR 85 → 90%

7,210 lbs/d 68

123,900 ft3/d 81

82,400 ft3/d 88

Effluent Heat Extraction

-In-Plant Process and Space Heating

-District Heating

22

Energy Opportunities of Wastewater

Resources

• Digester Gas Cogeneration

• Digester Gas Scrub and Sale

• Effluent Heat Extraction

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

20000

Cogen Gas

Sale

Heat

Extract

MJ/ML

South Plant’s 1980’s Innovative Heat Pump

System Provided Heat for Digestion and Building

Heat at the Plant

� Nearly inexhaustible source of heat in the plant effluent (10 times the energy from digester gas)

� Allows greater sale or use of biogas

� Opens options for sale of heat (hot water) for District Heating

� Recent major advances in heat pump technology

� Freon replaced

� COP 2.5 » 4 » 7 (New units transfer up to 7x the amount of heat as required to run heat pumps)

� Product Temperatures 125o » 1650 » 200o

24

District Heating and Cooling from

Plant Effluent

• Taking hold in Scandinavia and Northern Europe, facilitated by integrated utility and resource planning

• The same energy supply stream can serve heating and cooling functions – plant effluent as a heat sink for cooling and as a heat source for heating

South Plant District Heating Feasibility Check

1 Mile

Hypothetical South Plant District

Heating Profile

Hypothetical Customer Annual Average Total Annual Heat Extraction CO2 Emmission CO2 Emmission

Heating Load Heating Load Power for Heat Extraction for Natural Gas

(Btuh) (Million Btus) (million kw-hrs) metric tons CO2/yr metric tons CO2/yr

Boeing 5,828,663 51,000 4.98 810 2805

South Center 20,332,049 178,000 17.38 2830 9790

Airport 11,322,321 99,000 9.67 1580 5,445

No action STP Heat Extract No action STP Heat Extract No action STP Heat Extract

Capital cost 2,606,800 10,768,800 22,401,400

Annual costs1,2

Heating energy cost at STP 274,270 956,732 532,776

Cooling energy cost at STP 12,000 24,000 18,000

Pumping cost at STP 12,000 24,000 18,000

O&M cost at STP 24,000 48,000 36,000

Heating energy cost at facility 420,487 1,466,778 816,806

Cooling energy cost at facility 148,007 486,584 284,757

O&M cost at facility3 100,000 200,000 150,000

Total 668,494 322,270 2,153,362 1,052,732 1,251,562 604,776

Simple payback, yr 7.5 9.8 34.6

Boeing South Center Airport

The Carbon “Positive” Plant

28

Biosolids nutrients offset

Cogeneration - recovered heat

- 1000

Cogeneration power

Secondary treatment

Primary and solids treatment

Plant heat

MJ / ML

+ 1000

Net energy use

Energy use

Energy production

29

Modern Low Energy Plant

- 1000

Nutrient recovery (Ostara)

Digester gas as commercial fuel

Secondary treatment (TF/SC)

Primary and solids treatment

MJ / ML

+ 1000

Net energy production

Plant heat

Gas scrubbing, organic waste heating, biosolids drying, heat pumping

Organic digester amendment - gas increase

Sale of heat/chilled water to local industry

Biosolids use for cement kiln

Energy production

Energy use

+ 1000

Heat pump - digester and plant heating, biosolids drying

30

Highly Sustainable “Carbon Positive” Plant

Discussion

31