Bioremediation of Terrestrial Oil Spills

Kerry L. SubletteUniversity of Tulsa

Integrated Petroleum Environmental Consortium (IPEC)

What is bioremediation?

Using microorganisms that live in thesoil to eat hydrocarbons from a spill

When you do bioremediation your job isto make it possible for the bugs to eat asmuch of the hydrocarbon as they can as fastas they can

Bioremediation is not your firstresponse to a fresh oil spill

If it’s a fresh spill it is important to:Recover free fluids (recycle back to the stock tank if possible)Use an absorbent to get fluids that can’t be recovered (dispose of properly)

It is to your benefit to bioremediate only those fluids that soak into the ground

Bioremediation is not the first responseto this problem!

Bioremediation can be used to treat theoil-stained soil after fluids have been

properly disposed of.

Bioremediation begins with two questions

1. Is the contamination deeper than 8 inches?

Why? The bugs need oxygen and it’s hard to get good penetration of air into the soil any deeper that 8 inches

The second question:

2. Is there shallow groundwater under the contamination?

Why? We must have enough of a soil column between the oil and groundwater to prevent groundwater contamination. Rule of thumb – 6 ft of soil

Must answer NO to both questions to use the most basic form of bioremediation –in situ landfarming

Basic landfarming- It’s just gardening!

The microorganisms that eat hydrocarbons need the same things as crops to thrive:

FertilizerMoisture

Good soil structureWarm temperatures

It’s a bioremediation garden!

What’s good for your tomatoes isgood for the bugs!

IPEC has developed simplified guidelines for bioremediation of crude oil

spills by landfarming

Step 1Add fertilizer

13-13-13 (cheap, readily available)1/2 lb per square yard for a recent spill1/4 lb per square yard for an old spill

One-half pound of 13-13-13

Don’t use too much fertilizer

You know what that does to your lawnIt will do the same thing to the microorganisms that eat the oilAnd, it wastes money!This is the inherent danger in EPA’s 100:10:1:1

Resist the temptation to use manure if you have an alkaline soil – can cause nitrite to accumulate.

Toxic to bugs

Nitrogen from manure

Step 2

Add organic matterBuilds soil structure and allows the soil to breatheHay, straw, etc. (but not wood!)Hay: 5 small square bales per 1000 square feet

One round bale is about 8-10 small square bales

An example of the desired soil structure in a landfarm

Step 3

Till the fertilizer and organic matter into the soil to a depth of 6-8 inches

Step 3, continued

Soil wet with hydrocarbon?Blend in uncontaminated soil from the edges or under contaminationA good mixture should crumble in your hands

Step 4

Repeat the addition of fertilizer with tilling after about 30 days and again after about 60 days if the weather is warm (March-November)

After this initial three-month start up period add fertilizer only every othermonth as long as the weather is warm.

Don’t add fertilizer during the cold months (December-February)

Around 40 - 45 oCin temperate climates

Step 4, continued

Try to till every month whether you fertilize or not, even when it’s cold

Continue fertilizer additions and tilling on this schedule until you no longer smell hydrocarbon in the soil

Revegetate to prevent erosion

Example 1. Bioremediation started March 22, 2004Fertilize and till Till only

Example 1. Bioremediation started March 22, 2004Fertilize and till Till only

Example 2. Bioremediation started January 22, 2004Fertilize and till Till only

Example 2. Bioremediation started January 22, 2004Fertilize and till Till only

These guidelines apply equally well to small jobs and……

Fertilizer

Organic matter

Tilling

…….. big jobs!

ChevronTexaco landfarm in Rangeley, CO

What about moisture?

We can speed the process up by keeping the soil moist or we depend on rain.

If you do water don’t saturate the soil.

Here’s a large project in a dry climate usingirrigation equipment to supply moisture

One way to supply moisture to a small project

Be careful – what was hauled in that truck before it was filled with fresh water?

What about pH?

Just like your plants microorganisms require certain pH ranges for optimum growthFor most soil environments this is in the range of 6-8.

How do you adjust pH in soil?

Acidifying amendments (to lower pH) include:

Aluminum sulfate [Al2(SO4)3]Ferrous sulfate (FeSO4)Sulfur (slow acting, requires microbial activity to generate acid)

Neutralizing acidity (to raise pH):Lime [CaO/Ca(OH)2]

What is the best time to start a bioremediation project?

If you have a spill in December – February go ahead and till in organic matter to keep hydrocarbons from moving offsite until warm weather returns.Rule of thumb: It takes a hydrocarbon concentration in the soil of less than 5% to prevent a sheen in runoff!

If the impacted area is sloped it may be necessary to construct a low earthen dike at the bottom to prevent runoff.If the spill occurs at any other time of the year go ahead and get started.

How long does it take to bioremediate a site?

It depends:Tilling and fertilizer scheduleOrganic matter (soil structure)RainAge of the spill

Should see results in 1-2 growing seasons

What hydrocarbon removal rates canbe expected?

Hydrocarbon removal rates are proportional to the initial hydrocarbon concentrationThe average half-life considering all hydrocarbons types is 56 days (range 35 -72 days)Considering diesel only, the average half-life is 41 days (range of 22 - 57 days)

Soil B is an old spill and Soil A is a fresh spillThe Take Home Lesson?

Don’t wait, remediate!

Remember those two questions?

1. Is the contamination deeper than 8 inches?

2. Is there shallow groundwater under the contamination?

What if you can’t answer no to both of those two questions?

Treatment in place will remediate the top 6-8 inches. In order to remediate the deeper contamination you must:

Excavate the soil and spread 6-8 inches deep at a location where there is no shallow groundwater Landfarm the excavated soil as usualTransfer treated soil back to the source

Buying Bugs

Notice we didn’t say anything about adding bugs!

Why?

Because you don’t need to, they’re already there in the soil!

Don’t buy bugs!

Other “bioremediation products”

What about other products that are supposed to enhance bioremediation?

EnzymesSurfactants

Ionized waterMagic pixie dust

A waste of money!

How to recognize snake oil

Claims of bioremediation in hours or daysClaims that the product is useful for a wide range of applications (you can even put it down your well and increase oil production!) No independent test data

Watch out for fertilizer disguised as a miracle product!

In conclusion

Bioremediation of crude oil spills on soil is not rocket science – it’s gardening!

All you need is fertilizer, organic matter, and a little know-how!

Want To Learn More About IPEC and IPEC Products?

Visit the IPEC BoothGet on our mailing listVisit the IPEC web site:http://ipec.utulsa.edu

Contact me at (918)631-3085 or kerry-sublette@utulsa.eduContact IPEC’s Outreach Manager (Sheila Kumpe) at (918)631-3284 or sheila-kumpe@utulsa.edu