APPLIED RESEARCH:WILLIAMSON COUNTY

AERATED BIOREACTOR LANDFILLPresented by

Civil & Environmental Consultants

for the

Intercontinental Landfill Research Symposium

Asheville, NC

PROJECT TEAM

Williamson County, Tennessee GovernmentWilliamson County, Tennessee Government

Civil & Environmental Consultants, Inc.Civil & Environmental Consultants, Inc.

Tennessee Technological UniversityTennessee Technological University

University of GeorgiaUniversity of Georgia

Environmental Control Systems, Inc.Environmental Control Systems, Inc.

WILLIAMSON COUNTY DEPARTMENT OF SOLID WASTE MANAGEMENTØDepartment is managed by Mr. Lewis Bumpus, former county-assistance consultant for the University of Tennessee on solid waste management issues

Ø 100% funding for the bioreactor research is provided by Williamson County government

ØBioreactor research site is currently operated and maintained by Williamson County and CEC personnel

OTHER PROJECT TEAM MEMBERSØ Tennessee Tech Department of Civil and

Environmental Engineering and the University of Georgia Bioconversion Research and Education Center are involved in providing services for solids processing and analysis

Ø Environmental Control Systems provided the original design and installation services for the air and leachate delivery system (vertical injection wells and header pipes, pumps, blowers, thermocouples)

Ø ALL FIELD AND REMOTE DATA FOR THIS PROJECT HAS BEEN COLLECTED BY CEC. ALL STATISTICAL ANALYSES AND DATA INTERPRETATION HAS BEEN PERFORMED BY CEC.

WILLIAMSON COUNTY LANDFILL

Bioreactor Area

WILLIAMSON COUNTY BIOREACTOR FACT SHEET

ØWaste footprint = 6 acres (2.43 hectares) at base

Ø Maximum waste depth is approximately 40 feet (12.2 meters)

Ø Total original waste tonnage = 69,880 short tons or 63,394 Mg (currently closed; received wastes from 1995 to 1998; – stopped receiving MSW in early 1998)

ØShape of subject area resembles a truncated pyramid with steep sideslopes (Avg 1.5:1)

ØRetrofit operation only. No pre-processing of wastes occurred before placement. No new waste placement is taking place.

WILLIAMSON COUNTY BIOREACTOR FACT SHEETØ Site has been operating continuously as a

forced-aeration bioreactor landfill since October 17, 2000

Ø Compressed air is injected into the waste via vertical screened wells. Three 1000 acfm (28.3 m3/min) blowers are utilized on-site

Ø Leachate, and occasionally storm water, is pumped into the mass via vertical screened wells

Ø This is a “temperature-feedback” operation. Subsurface temperatures are monitored by over approximately 170 type “T” thermocouple locations within the waste mass

SYSTEM LAYOUT

Storm Water Pond

Blowers

N

Mix Tank For Leachate Injection

Data Collection Trailer

Leachate

Air

LCS Manhole

TYPICAL VERTICAL INJECTION WELL ARRANGEMENT

50 ft x 50 ft (15.2 m x 15.2 m)

INJECTION PIPE GRID

POSITIVE DISPLACEMENT BLOWERS

AIR HEADER SYSTEM BACKPRESSURE MONITORING

CLUSTER WELLS

WILLIAMSON COUNTY BIOREACTOR FACT SHEET (CONTINUED)ØØ The site is composite lined with a granularThe site is composite lined with a granular--

material underdrain leachate collection material underdrain leachate collection system. All leachate flow drains towards the system. All leachate flow drains towards the southeast corner of the footprintsoutheast corner of the footprint

ØØ Injected volume of leachate/storm water to Injected volume of leachate/storm water to date is approximately 4.3 million gallons (16.3 date is approximately 4.3 million gallons (16.3 million liters)million liters)

ØØ Leachate injection rate has varied from 0.01 Leachate injection rate has varied from 0.01 to 0.07 gallon/cy waste/day (0.05 to 0.35 to 0.07 gallon/cy waste/day (0.05 to 0.35 liters/mliters/m3 3 waste/day)waste/day)

ØØMaximum head on the liner to date has not Maximum head on the liner to date has not exceeded 4 inches (10 cm) per data exceeded 4 inches (10 cm) per data collected from riserscollected from risers

MIX TANK AND LCS MANHOLE

Manhole Connected To Bioreactor LCS

Mix Tank

Influent Flow To Mix Tank

MONITORING WELLS

There are a total of 11 monitoring wells randomly dispersed throughout the footprint of the bioreactor. The wells are used for gas and leachate sampling/analysis. Temperatures are logged at various depth intervals at each monitoring well.

SUBSURFACE TEMPERATURE HISTORY

20.00

25.00

30.00

35.00

40.002/

23/0

1

4/23

/01

6/23

/01

8/23

/01

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3/01

12/2

3/01

2/23

/02

4/23

/02

6/23

/02

8/23

/02

Time

Deg

rees

C

AVERAGE TEMPERATURE DISTRIBUTION OVER ALL DEPTHS (MARCH 2001)

Temperature Range: 10.29o to 50.47o C

Mean = 22.64 o C

0.0

30.0

60.0

90.0

120.0

10.0 22.5 35.0 47.5 60.0

Histogram of Temps__degrees_C__March_20__2001

Temps__degrees_C__March_20__2001

Cou

nt

AVERAGE TEMPERATURE DISTRIBUTION OVER ALL DEPTHS (September 30 2002)Temperature Range: 16.3o to 57o C

Mean =40.8o C

0.0

13.3

26.7

40.0

10.0 26.7 43.3 60.0

Sept_30_2002

Per

cent

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9/1/

02

Time

Deg

rees

CAVERAGE WELL TEMPERATURES FOR 2002 WITHOUT THE EFFECTS FROM AIR INJECTION

AVERAGE OF ALL MONITORING WELL TEMPERATURES RELATIVE TO DEPTH

1

2

3

4

5

6

7

8

9

15.00 20.00 25.00 30.00 35.00 40.00Temperature °C

Dep

th

(Met

ers

belo

w s

urfa

ce)

3/21/01 9/21/01 1/8/02 3/21/02 9/21/02

INJECTION AIR TEMERATURE VARIATIONS

-30

-20

-10

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Tem

pera

ture

(de

gree

s C

)

Upper Air Line

Terminal Air Line

Inlet Air Temperatures vs. MW-11 Temperatures at 5 to 10 ft Depth (1.5 to 3 meters)

-1.5

-1

-0.5

0

0.5

1

1.5

Time

Avg

. Tem

pera

ture

C

hang

e E

very

4 H

ours

MW-11B

Air Line Temps

ØAssessing air injection influence on MWs based on comparison of injection air temp changes with internal MW temp changes.

OPERATIONAL ZONES

N

Zone AZone BZone C

OVERALL AVERAGE TEMPERATURES BY ZONE

25

27

29

31

33

357/

19/0

27/

26/0

28/

2/02

8/9/

028/

16/0

28/

23/0

28/

30/0

29/

6/02

9/13

/02

9/20

/02

9/27

/02

T

empe

ratu

re (

degr

ees

C)

Zone AZone BZone C

Zone B Leachate Wells Turned Off

Zone A Leachate Wells Off From 8/28/02 To 9/16/02 Heavy

Rainfall From “Isadore”

GAS DATA

LANDTEC GEM 500 GAS ANALYZER

MONITORING WELL WITH GAS CONNECT PORT

BIOREACTOR GAS EMISSION DATAMW-1 Gas Monitoring

0

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Date

Per

cen

t

0.0

20.0

40.0

60.0

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100.0

120.0

140.0

160.0

Inch

es W

ater

Co

lum

n

CH4 CO2 O2 Backpressure

BIOREACTOR GAS EMISSION DATAMW-10 Gas Monitoring

0

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cen

t

0.0

20.0

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100.0

120.0

140.0

160.0

Inch

es W

ater

Co

lum

n

CH4 CO2 O2 Backpressure

BIOREACTOR GAS EMISSION DATA - OVERALL AVERAGE FOR ALL MONITORING WELLS COMBINED

0.0

10.0

20.0

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cen

t G

as

0

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40

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120

140

160

Pre

ssu

re (

Inch

es o

f H

2O)

Methane Carbon Dioxide Oxygen Balance Back Pressure

QUALITATIVE GAS CHARACTERIZATION

Ø Most of the monitoring wells respond to and are influenced by air injection points when air header system static backpressure is greater than 4.5 to 5 psig (best response is when system BP is over 6 psig)

ØOverall, the gas characterization from each monitoring well has been influenced by the air injection. The degree of influence varies with the spatial location of the MWs.

ØTypically, the lowered CH4 values are seen when the air system header has elevated backpressures indicating minimal leakage from the header piping system

QUALITATIVE GAS CHARACTERIZATION

Ø Typically, the decrease in CH4 % is correspondingly followed by an increase in balance gas (i.e., primarily nitrogen gas) indicating that the gas overall in the area of the monitoring well is being diluted by the adjacent air injection wells

Ø There is some variability in how certain MWs respond to air injection. Variability is possibly due to fluctuations in moisture distribution and the limitations on Free Air Space (FAS)

Ø Certain wells (including MW 5) have exhibited “breakthrough” effects of air injection on gas character.

% CH4 AND O2 CHANGES RELATIVE TO AIR INJECTION - 2002 DATA

Monitoring Well

Number

% CH4 and Header Static Pressure At

Initial Measurement At Time = 0

% CH4 and Header Static Pressure At

Final Measurement At Time = t

Change In % CH4 Relative To Value At Initial Measurement

(Initial %-Final% ) x 100 Initial %

Change In Residual %

O2 (Initial % –

Final %)

Change In Air Header Static Back

Pressure (Initial psig – Final

psig)

Elapsed Time Between Readings (time, t)

1 53% 28.5% -46% -0.9% +1.4 psig (4.1 to 5.5)

2 weeks

2 42.2% 1.1% -97% +8.5% +3.5 psig (1 to 4.5)

2 weeks

3 55% 12.1% -78% +2.4% +1.4 psig (4.1 to 5.5)

2 weeks

4 55.6% 15.1% -73% +7.7% +2.7 psig (1.8 to 4.5)

1 week

5 43% 10.6% -75% -0.9 %

+1.3 psig (4.2 to 5.5)

2 weeks

6 54.2% 27.2% -50% +1.8% +1.3 psig (4.2 to 5.5)

2 weeks

7 53% 15.1% -71.5% negligible No change 1 month

8 65.5% 11% -83% +1.6% +2.5 psig (2.5 to 5 psig)

1 day

9 50.2% 9.3% -81% +7.6% +4.0 psig (0.0 to 4 psig)

2 weeks

10 51.6% 1.1% -98% +8.9% +2.4 psig (1.8 to 4.2 psig)

1 week

11 54.5% 5.4% -90% +16.4% +4.8 psig (0.0 to 4.8 psig)

2 weeks

CHANGES IN INTERNAL LEACHATE ORP RELATIVE TO RADIAL DISTANCE FROM AIR INJECTION WELL

Air Injection Well 855C

(ORP: -147 mV)

Conditions When Air Header Backpressure At 3.5 psig

25 ft

MW 10(ORP: -230 mV)

Air Injection Well 856

(ORP: -180 mV)

Conditions When Air Header Backpressure At 4.5 psig

25 ft

Air Injection Well 855C

(dry-no pooled water within well)

25 ft

MW 10(ORP: -150 mV)

Air Injection Well 856

(dry)25 ft

SOLIDS DATA

ØSamples are taken approximately every 6 months via auger drilling. Frequency of sample events is dependant on how system operations have progressed

ØSample locations are chosen based on a grid system overlay of the reactor with designated x,y,z coordinates. Random number generator (based on uniform distribution) is utilized to chose sample locations for each event

Ø9 to 10 sample events will be ultimately performed. A set of 9 to 12 samples are taken per event, depending on the success of the drilling activity (i.e., adequate return of sample volume)