urban gasoline stations: new techniques for early leak detection

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NATO/CCMS Pilot Study Meeting – Athens – June 4-7, 2006

Urban gasoline stations: new techniques for early leak detectionfrom USTs and removal of low concentration pollutants from

groundwater

Renzo Boni, Rosario Pappa and Salvatore Contarini

Environmental Technology Research Centre (CEAMB)EniTecnologie SpA, Via Ramarini 32, 00016 MONTEROTONDO (Roma), Italy

e-mail: [email protected]

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OUTLINEOUTLINE

• Activities in support to Eni Refining & Marketing Division o Environmental monitoring at Service Stations

• Hydrocarbon leak detection in soils (SOIL ALERT) o Principles and main characteristics o Application to USTs (Underground Storage Tanks)

• Groundwater remediation by Pump & Treat (EN-Z-LITE)o Laboratory tests o Pilot plant o Full scale application

• Future activities and developments

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Eni Refining & Marketing DivisionEni Refining & Marketing Division

Fuel retail leader in Italy with ~ 5,000 Agip service stations.Reorganization of the distribution network, ~ 1000 small size urban area service stations ceded or removed. Enitecnologie involved in subsoil quality assessment and, where necessary, in remediation and environmental restoration actions.

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Scope of the workScope of the work

Development of a combined monitoring – remediation system capable to provide early warning for hydrocarbon leaking and effective groundwater treatment

Two Enitecnologie patents:

1. SOIL ALERT: a leak detector based on a resistive gas sensor

2. EN-Z-LITE: an adsorbent for effective groundwater removal of hydrocarbons, including BTEX and MtBE, associated to Pump & Treat technology

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SOIL ALERTSOIL ALERT

• SOIL ALERT is an alarm system for tank leakage control.

• It consists of a probe for interstitial gas detection in subsoil.

• The probe contains two sensors, one at the micro-holed bottom tip

and one at the top for aboveground air referencing.

• Can take continuous measurements, without use of extraction

systems and chemical analysis.

• ATEX explosion proof certification (EEX d II B T5) allows for use in

hazardous zones.

• Applications:

• Service stations and aboveground storage tank fields (AST)

• Remediation monitoring

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SOIL ALERT:SOIL ALERT: LeakLeak detection ofdetection of USTsUSTs

S1

S2

S3

S4S5

Volt meter

Data logger

Solar panel

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SOIL ALERT: Leak detection of USTsSOIL ALERT: Leak detection of USTs

External part of probe

-5,5

-5

-4,5

-4

-3,5

-3

101

102

103

104

105

106

107

108

109

110

111

112

113

115

116

117

118

119

201

202

203

204

205

206

207

209

210

211

212

213

214

215

216

217

218

219

220

Log

(1/R

s)

-6,5

-6

-5,5

-5

-4,5

-4

-3,5

-3

-2,5

-2

Log

(con

c. P

ID)

Log(1/Rs) Log(conc.PID)

Comparison of SOIL ALERT Probe and PID signals

Same day measurements on 37 probes

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Calibration of gas sensorsCalibration of gas sensors

y = 0,3887Ln(x) - 0,6743

0,0

0,5

1,0

1,5

2,0

2,5

3,0

10 100 1000 10000 n-octane concentration (ppmV)

Out

put

(V)

Volts ppmV0,6 251,1 1001,7 4002,2 1600

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• Monitoring campaign at an Agip service station in central Italy

15 days monitoring

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

25/7

/00

13.0

1

26/7

/00

13.1

8

27/7

/00

13.1

4

28/7

/00

13.1

1

29/7

/00

13.0

7

30/7

/00

13.0

3

31/7

/00

12.5

9

1/8/

00 1

2.55

2/8/

00 1

2.57

3/8/

00 1

3.12

4/8/

00 1

3.08

5/8/

00 1

3.04

6/8/

00 1

3.00

7/8/

00 1

2.57

8/8/

00 1

2.53

Vout

(V)

0

5

10

15

20

25

30

35

Tem

p. (°

C)

Sonda 1 Sonda 2 Sonda 3 Sonda 4 Sonda 5 T aria T suolo

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• A field simulation was carried out by spilling small amounts of gasoline and diesel

0

0,05

0,1

0,15

0,2

0,25

0,3

0,35

0,4

0,45

23/7

25

/7

27/7

29

/7

31/7 2/8

4/8

6/8

8/8

10/8

12

/8

14/8

16

/8

18/8

20

/8

22/8

24

/8

26/8

Vout

(V) Sonda 1

Sonda 2

Sonda 3

Sonda 4

Sonda 5

Gasoline leak simulation

Gasoline spill start

30 days monitoring

Simulazione perdita di gasolio

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80 days monitoring

Diesel leak simulation 1.00E+00

Diesel leak detection

Diesel spill start

9.00E-01

8.00E-01 0.8 V 7.00E-01

sonda1 sonda2 sonda3 sonda4 sonda5

Vout

(V) 6.00E-01

5.00E-01

4.00E-01

3.00E-01

2.00E-01

1.00E-01

0.00E+00

10/3

/01

0.00

15/3

/01

0.00

20/3

/01

0.00

25/3

/01

0.00

30/3

/01

0.00

4/4/

01 0

.00

9/4/

01 0

.00

14/4

/01

0.00

19/4

/01

0.00

24/4

/01

0.00

29/4

/01

0.00

4/5/

01 0

.00

9/5/

01 0

.00

14/5

/01

0.00

19/5

/01

0.00

24/5

/01

0.00

29/5

/01

0.00

3/6/

01 0

.00

8/6/

01 0

.00

Genova Pegli dal 28/11/2004 al 9/12/2004

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11 day monitoring at a dismissed service stationMisure (t=30 min) Media Mobile (t=24 h) Soglia di Preallarme Soglia di Allarme

1600

1550

1.5 V 1500

1450

1400

1350

V out 1300

1250

1200

1150

1100

1050

10001.0 V

19.4

0

2.10

8.40

15.1

0

21.4

0

4.10

10.4

0

17.1

0

23.4

0

6.10

12.4

0

19.1

0

1.40

8.10

14.4

0

21.1

0 950

3.40

900

10.1

0

16.4

0 850

23.1

0 800

5.40

750

12.1

0

18.4

0 700

1.10

650

7.40

60014

.10

20.4

0

3.10

9.40

16.1

0

22.4

0

5.10

11.4

0

18.1

0

0.40

7.10

13.4

0

20.1

0

2.40

9.10

Time

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0.5 V

1 year monitoring1 year monitoring

3 months

6 months

12 months

0.5 V

0.5 V

• Sensor output is an electrical signal, easily manageable for automatic and continuous remote control

• Large HC concentration range (10 - 5000 ppmV)

• Leak detection is fast compared to normal monitoring systems

• Low selectivity: these sensors respond, although to a different extent, to many reducing gases

• Signal fluctuates with changes in water table level

• Signal saturates in severely contaminated soils

• Require soil perforation for positioning

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• Sensor output is an electrical signal, easily manageable for automatic and continuous remote control

• Large HC concentration range (10 - 5000 ppmV)

• Leak detection is fast compared to normal monitoring systems

• Low selectivity: these sensors respond, although to a different extent, to many reducing gases

• Signal fluctuates with changes in water table level

• Signal saturates in severely contaminated soils

• Require soil perforation for positioning

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SOIL ALERT: Advantages and limitationsSOIL ALERT: Advantages and limitations

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Groundwater remediationGroundwater remediation

Pump & Treat is the most common form of groundwater remediation. It is often associated with treatment technologies such as Air Stripping or Adsorption.

In adsorption systems, granular activated carbon (GAC) is mainly used as sorbent material

Extraction well Tank Recovered

Pump & treat Groundwater

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Adsorption: Granular Activated Carbon (GAC)Adsorption: Granular Activated Carbon (GAC)

With GAC, organic molecules as well as certain metal and inorganic ions are attracted and adsorbed in the porosity of the sorbent

Limitations and Concerns

GAC not efficient with small organic molecules and water soluble contaminants like MtBE

If humic acids are present GAC adsorption capacity is rapidly decreased

If treated water has high salinity (eg. marine coastal sites), GAC regeneration and recycling becomes very difficult or not applicable

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EniTecnologieEniTecnologie ENEN--ZZ--LITE approachLITE approach

EN-Z-LITE (Enitecnologie US Patent 20040206705) for the removal of groundwater contaminants based on synthetic zeolites

Advantages of zeolites used for water treatment:

1. selectivity (based on physical-chemical affinities of

adsorbate and adsorbent)

2. good adsorption capacity (up to 15%)

3. higher efficacy towards MtBE

4. easy regeneration by thermal desorption

5. no effects of salts and interfering compounds such as humic

acids and inorganic ions

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PumpPump && TreatTreat: EN: EN--ZZ--LITELITE

Successfully proven applications

Simulation apparatus operating with sampled groundwater:• different hydrocarbon contaminants: chlorinated,

aromatic hydrocarbons (BTEX), MtBE, etc. at high concentration

Mobile pilot scale plant: • Field tested for various kinds of contaminants

Full scale plant at an Agip Service Station • Automotive fuels (gasoline, diesel) and MtBE

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Laboratory Simulation ApparatusLaboratory Simulation Apparatus

200 mL columns 2 L column

20 ENEN--ZZ--LITE application: highLITE application: highconcentration of MtBE and BTEXconcentration of MtBE and BTEX

GCGC--MS inlet of simulation apparatusMS inlet of simulation apparatus

1.3o-xylene

1.5ethylbenzene

2.9p-xylene

>15 g/Lsalt as NaCl

mg/LCompound

17.9MtBE

0.5toluene

2.8benzene

21 ENEN--ZZ--LITE application: highLITE application: highconcentration of MtBE and BTEXconcentration of MtBE and BTEX

GCGC--MS outlet of simulation apparatusMS outlet of simulation apparatus

MtBE and aromatics (BTEX) outlet concentrations < 1 ppbMtBE and aromatics (BTEX) outlet concentrations < 1 ppb

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ENEN--ZZ--LITE pilot plantLITE pilot plant

Mobile unit with 4 x 75 kg, water flux of ~ 1m3/h,trucked to field sites for differently contaminated waters

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Full scale application: Agip service stationFull scale application: Agip service station

Pump and Treat system using GAC and EN-Z-LITE to reduce outlet TPH, BTEX and MtBE concentration below the limit imposed by controlling authority

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Full scale application: operating conditionsFull scale application: operating conditions

Remediation plant dimensions

GAC pretreatment vessels: 4 x 1300 kg EN-Z-LITE vessels: 4 x 350 kg Water flow: 17 m3/h (max)

GAC replacement: ~ 2 tons/month

Zeolite replacement: ~ 100 kg/month

Costs

Water treatment total 0.85 Euro/m3 of treated water

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Full scale application: resultsFull scale application: results

Groundwater decontamination figures (ppb)

Inlet EN-Z-LITE outlet

Controlling authority

TPH 500 – 9000 < 1 ≤ 10

MtBE 500 - 3000 < 10 ≤ 10

BTEX 0 - 900 < 1

Benzene ≤ 1 Ethyl-benzene ≤ 50 Toluene ≤ 15 p-Xylene ≤ 10

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Full scale application: resultsFull scale application: results

Groundwater decontamination Removed hydrocarbons vs. time

TPH MtBE Benzene K

g/da

y

1,8

1,6

1,4

1,2

1,0

0,8

0,6

0,4

0,2

0,0

0 50 100 150 200 250 300 350 days

EN-Z-LITE provides a technological improvement since it allows

more effective removal of contaminants

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SOIL ALERT and ENSOIL ALERT and EN--ZZ--LITE: Future developmentLITE: Future development

SOIL ALERT can be used in water media also

Upgrade by means of a protective polymeric membrane in the probe micro-holed section, selectively permeable to contaminant vapors

Benefits:

1. Measurements in water

2. Measurements in saturated zone

Future development:

SOIL ALERT sensor switches for the EN-Z-LITE groundwater remediation system

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SOIL ALERT: tests in waterSOIL ALERT: tests in water

Laboratory tests in water containing toluene from 25 to 100 ppb

Volt

(Vou

t)

0,20

0,16

0,12

0,08

0,04

0,00 0 20 40 60 80 100

Time (min)

25 ppb

50 ppb 75 ppb

100 ppb

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SOIL ALERT: field tests in saturated soilSOIL ALERT: field tests in saturated soil

continuous measurements for 80 days

0,00

0,20

0,40

0,60

0,80

1,00

1,20

0 10 20 30 40 50 60 70 80

days

Volt(

Vout

) ~ 400 ppb TPH

30 Development of the combined SOIL ALERTDevelopment of the combined SOIL ALERT and ENand EN--ZZ--LITE remediation systemLITE remediation system

SOIL ALERT will be applied to continuous monitoring of groundwater remediation plants. Placed on vessels outlets, it can provide better timing for exhaust adsorbent replacement

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AcknowledgementsAcknowledgements

This presentation was made possible thanks to the dedicated work of:

Adriano Bernardi Lucio De Angelis

Umberto Cova Vincenzo Mancini

Fabio Fabiani Raffaello Sisto

Gianni Grillo Rodolfo Vignola

Vittorio Vittori

urban gasoline stations: new techniques for early leak detection

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