ranieri - university of tulsa cese professional ... · paul ranieri, and alan weston...

Presenters' Contact Information

Paul Ranieri

Conestoga-Rovers & Associates

2055 Niagara Falls Blvd. Suite Three,

Niagara Falls, New York 14304Niagara Falls, New York 14304

Phone: 716-297-2160

Email: [email protected]

CHEMICAL OXIDATION AT

OPERATING GAS STATIONS

Sophia Dore, Christa Nunn, Donald Pope,

Paul Ranieri, and Alan Weston

Conestoga-Rovers & Associates

1. Introduction

2. Application System Design

3. Case Studies

Section

4. Conclusion

ISCO Treatment Review

� Involves complex processes

� Requires expertise and suitable site conditions

� Can save $$$ and accelerate cleanup

� Can be used as a pretreatment for MNA� Can be used as a pretreatment for MNA

In Situ Chemical Oxidation

� An oxidizing agent breaks carbon bonds in organic contaminants and converts them into nonhazardous compounds, primarily carbon dioxide and water

� Commonly used oxidizing reagents include potassium/sodium permanganate, Fenton’s Reagent, ozone, and sodium persulfateozone, and sodium persulfate

� A laboratory treatability study is required to select the most effective oxidant, and oxidant dose

� Successful ISCO treatment depends on the effectiveness of the delivery system

1. Introduction


3. Case Study

Section

4. Conclusion

Active Gas Stations

� Source of contamination can be spills

during filling of tanks or leaky fuel

storage tanks

� Flammable substances - Gasoline and � Flammable substances - Gasoline and

diesel range petroleum hydrocarbons

and BTEX compounds in soil and

groundwater

� Remedial activities must accommodate

day to day workings of the gas station

Steps for Safe ISCO Application at an

Operating Gas Station

� Treatability Study

� Determination of most

efficient oxidant

Calculation of dose and � Calculation of dose and

application rate

� Design of application

system

� Design of monitoring

system

Treatability Study

� Initial Characterization

� Microcosm Tests

� Natural Oxidant Demand � Natural Oxidant Demand

(NOD) determination

� Metals Leaching Tests

Delivery Methods

� Injection wells

� Direct push

� Mixing into open excavation

� Perforated pipe infiltration system� Perforated pipe infiltration system

Removal of LNAPL is recommended prior to ISCO Application

Design of Application System

� Use of Injection Wells for Injection

� Advantages

• Permanent wells can be used multiple times

• Screened through the relevant depth interval

� Disadvantages � Disadvantages

• Expensive to install

• All applications must be made in the same locations

• May required well permits


� Use of Direct Push for Injection

� Advantages

• Can inject through the relevant depth interval

• Can offset injections during later events to cover

area more effectivelyarea more effectively

• Less costly than installing permanent wells

� Disadvantages

• Not appropriate for deep applications

• Not appropriate for bedrock applications

• Limited pumping rates


� Mixing of Oxidant into Open Excavation

� Advantages

• A large amount of oxidant can be applied therefore

the entire dose can be applied at once

• Can get good distribution of oxidant in tight soils• Can get good distribution of oxidant in tight soils

� Disadvantages

• Not appropriate for Fenton’s Reagent (H&S);

recommended for sodium persulfate

• Mixing equipment required

• Depth limitations


� Perforated Pipe Infiltration System In Excavation

� Advantages

• Multiple applications of oxidant can be made

• Inexpensive to install

• Gravity vs. pressure injection• Gravity vs. pressure injection

• Can be safer to apply oxidant after backfilling at an

active gas station

• Can locate injection ports away from traffic areas

� Disadvantages

• Difficult to get good distribution of oxidant in tight

soils

Design of Monitoring System

� Parameters to monitor:

� Chemicals of concern

• To determine whether reduction has taken place

� MetalsMetals

• To determine whether metals have been solubilized by the ISCO reagents; Fe and Mn levels show the oxidation state in the groundwater


� Parameters to monitor: (cont.)

� Sulfate

• If persulfate is used since sulfate can be a

breakdown productbreakdown product

� DO and ORP

• To verify that oxygen levels have been increased by

the oxidant


� Health and Safety Monitoring:

� Vapor monitoring for TPH and BTEX

• To determine whether chemistry has been volatilized

� Temperature

• To determine whether a vigorous reaction is taking • To determine whether a vigorous reaction is taking

place

� Pressure

• To determine whether the reaction is causing

pressure to rise

1. Introduction


3. Case Study

Section

4. Conclusion

Scenario

� Gasoline spill at an active gas station

� Gasoline has been detected in soil and groundwater samples

� No LNAPL is present

What to do?

� Consider In Situ Treatment

� Monitored natural attenuation (MNA)

� In situ chemical oxidation (ISCO)

� In situ enhanced biodegradation (ISEB)

� Permeable Reactive Barrier (PRB)

Treatment Assessment

� Permeable Reactive Barrier (PRB)

� Air Sparge Soil vapor extraction (AS/SVE)

Monitored Natural Attenuation

� Gasoline degrades readily under aerobic conditions however:

� Concentrations in soil and groundwater are high

� Site is paved therefore oxygen will be depleted quickly

� Potential for off-site migration if contamination is not addressed quickly

� Conclusion: This site is not a good candidate for MNA


� Conclusion: This site is not a good candidate for MNA

ISCO

� ISCO is effective for treatment of gasoline in soil and groundwater

� ISCO using sodium persulfate is safe for application at active gas stations

� ISCO using sodium persulfate is safe for application around underground utilities and around an AST


underground utilities and around an AST

� ISCO treatment would be complete in 1-2 years

� Conclusion: ISCO is retained for consideration

ISEB

� Gasoline biodegrades readily under aerobic conditions

� Oxygen injection would be safe at an active gas station

� Injection using a technology such as iSOC could be applied with most equipment below grade so the day to day activities of the gas station would not be affected

� ISEB treatment would be complete in 3-4 years


� ISEB treatment would be complete in 3-4 years

� Conclusion: ISEB is retained for consideration

PRB

� Could intercept and treat contaminated groundwater before it migrates off-Site

� Would not treat soil

� Would not address on-Site contamination

� Without source treatment PRB would need to be maintained for a long time


for a long time

� PRB alone not appropriate for this Site

� Could be considered in combination

with source treatment

AS/SVE

� Gasoline is volatile and could be removed by AS/SVE

� AS/SVE system would need to be installed

� May not be cost effective for such a small site

� Once concentrations are reduced to low levels AS/SVE is no longer efficient therefore another technology would be required for polishing


required for polishing

� Conclusion: AS/SVE is not a good technology for this site

Technologies Retained for Consideration

� ISCO

� ISEB

Next Step

� Conceptual designs and cost estimates


Conceptual Design

� 3 injection wells + MW-5 required for either ISCO or ISEB

� ISCO: reagent injection wells

� ISEB: air/nutrient injection wells


Proposed injection well

Cost estimates

� ISCO

� Assuming 1 year of treatment estimated cost: $75,250

� ISEB

� Assuming 3 years of treatment estimated cost:


� Assuming 3 years of treatment estimated cost: $96,550

� ISCO is more cost effective and faster

� Recommendation: ISCO

� A solution containing a mixture of 15 percent sodium persulfate solution and 25 percent sodium hydroxide solution was injected into MW-5 and each of the three newly installed injection wells

Oxidant Application

Well Volume Injected (gallons)

IW-1 650

MW-5 660

IW-2 1,330

IW-3 1,830

Post Injection Monitoring

� Monitoring was performed 1 month and 3 months after

the first ISCO injection

� Between 60 and 98 percent removal of petroleum

hydrocarbons was observed after treatment

� Concentrations in some areas remained above criteria� Concentrations in some areas remained above criteria

Post Injection Monitoring

Criteria not exceeded

Criteria exceeded

Second Injection Event

� A second injection event was performed focusing on the

area that still exceeded criteria

� After the second injection event, petroleum hydrocarbon

concentrations at all monitoring wells were below criteria

� No further treatment was required� No further treatment was required

Application of Sodium Persulfate at an

Operating Gas Station

� Soil and groundwater at an active gas station are impacted

by petroleum hydrocarbons

� GRO has been detected in Site groundwater at

concentrations of up to 100,000 µg/Lconcentrations of up to 100,000 µg/L

� Benzene has been detected at 2,000 µg/L

� An area 20 ft x 60 ft was excavated

� A perforated pipe infiltration system was installed into the

open excavation

Case Study Cont’d

� The injection consisted of 10% H2O2 mixed with 20%

sodium persulfate

� Mixing of the catalyst and oxidant occurred immediately

prior to injectionprior to injection

� The injection was performed by gravity

� A bromide tracer was included with the injection

Results

� Monitoring results showed that TPHg and BTEX

concentrations in groundwater were reduced below

criteria in all but one of the monitoring wells

� Mobilization of metals did not occur� Mobilization of metals did not occur

� Soil vapor monitoring did not show impacts to air quality

� A vigorous reaction did not occur

1. Introduction


3. Case Study

Section

4. Conclusion

CONCLUSIONS

� ISCO can be successfully implemented at

active gas station sites

� Correct dose, application rate, application � Correct dose, application rate, application

system design, and monitoring must be

carefully determined

Questions?Questions?

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