Benzene, toluene, ethylbenzene, xylenes.

Naturally occurring components of

petroleum end up largely in gasoline as a

result of the refining process.

volatile organic compound.

Used in the production of synthetic

materials and consumer products.

Such as synthetic rubber, plastics, nylon,

insecticides, paints, dyes, resins, and

cosmetics.

Toluene Occurs naturally as a component

of many petroleum products.

Used as a solvent for paints, coatings,

gums, oils, and resins.

Ethylbenzene is used mostly as a gasoline

and aviation fuel additive. It may also be

present in consumer products such as

paints, inks, plastics, and pesticides.

Three forms: ortho-, meta-, and para-.

Ortho-xylene is the only naturally occurring

form, the other two being man-made.

Xylenes are used in gasoline and as a

solvent in printing, rubber, and leather

industries.

With improper storage, chemicals leach into the groundwater and contaminate public and private water systems.

Large bulk facilities, surface spills, and pipeline leaks.

BTEX components may become attached to soil and rock particles

Find their way into groundwater. In groundwater, persist longer than if they were

exposed to air Therefore affecting water supplies for months or

even years

Associated with skin and sensory irritation,

central nervous system depression, and

effects on the respiratory system.

Affect organs like kidney, liver & also blood

systems.

Human carcinogen

Workers exposed to high levels of

benzene, found to have an increase in

leukemia.

Use of biological processes to degrade,

break down, change, and/or essentially remove

contaminants or impairments of quality from soil

and water.

a natural process which relies on bacteria, fungi,

and plants to alter contaminants

Metabolic processes of these organisms are

capable of using chemical contaminants as an

energy source,

rendering the contaminants harmless or less

toxic products in most cases.

Conventional methods include pump and

treat systems, soil vapour extraction,

incineration, and containment.

Suffers drawbacks and may involve some

level of risk.

Bioremediation offers an alternative

method to detoxify contaminants.

Nutrient availability

Moisture content

pH

Temperature

1) Bioremediation is a natural process.

2) It is cost effective.

3) Toxic chemicals are destroyed or

removed from environment and not just

merely separated.

4) Low capital expenditure.

5) Less energy is required as compared to

other technologies

6) Less manual supervision.

1) Slow. Time required is in day to months.2) Heavy metals are not removed.3) For insitu bioremediation site must have soil with high permeability.4) It does not remove all quantities of contaminants.5) Substantial gaps exist in the understanding of microbial ecology, physiology and genetic expression and site expression and site engineering. A stronger scientific base is required for rational designing of process and success.

In situ bioremediation involves a direct approach for the microbial

degradation of xenobiotics at the site of pollution

e.g. soil

nutrients is supplied at the site which promotes

the microbial growth at the site itself.

generally used for cleanup of oil spillages,

beaches etc.

In situ bioremediation Intrinsic bioremediation

Engineered in situ bioremediation

Intrinsic bioremediation The inherent metabolic ability of the

microorganisms to degrade certain pollutants.

Dependent on the type and concentration of

compounds, electron acceptor and the duration

of bacteria exposed to contamination.

Engineered in situ bioremediation bioremediation process is engineered to

increase the metabolic degradation efficiency.

done by supplying sufficient amount of nutrients

and oxygen supply, adding electron acceptors

and maintaining optimal temperature and pH.

done to overcome the slow and limited

bioremediation capability of microorganisms.

Advantages of in situ bioremediation

The method ensures minimal exposure to

public or site personnels.

There is limited or minimal disruption to the

site of bioremediation.

Due to these factors it is cost effective.

The simultaneous treatment of

contaminated soil and water is possible.

sites are directly exposed to environmental factors like temperature, oxygen supply etc.

The seasonal variation of microbial activity exists.

Problematic application of treatment additives like nutrients, surfactants, oxygen etc.

It is a very tedious and time consuming process.

Electron acceptors and electron tower

theory The rate of naturally occurring bioremediation of

BTEX compounds is often limited by either the

concentration of an electron acceptor or a

nutrient needed during degradation.

Typical electron acceptors utilized by

microorganisms are oxygen, nitrate, iron (III),

sulfate, and carbon dioxide

Depending on the mode of respiration,

microbes can be classified into three

categories:

Aerobic

Anaerobic

Facultative

Aerobic Aerobes thrive only in oxygenated environments.

Dissolved oxygen is used as an electron

acceptor.

AnaerobicStrict anaerobes grow only under highly reduced

conditions, where oxygen is effectively absent.

Strict anaerobes use electron acceptors such as

sulfate or carbon dioxide.

FacultativeMicroorganisms that are able to adapt to both

aerobic and anaerobic conditions, but are

typically more active in the presence of oxygen.

Most microbes utilizing nitrate as an electron

acceptor tend to be facultative.

The following figure adapted from Jorgensen

(1989) illustrates the sequence and products of

electron acceptor utilization for oxidation of

organic carbon.

Field evidence also seems to suggest that

natural in situ bioremediation may employ

different electron acceptors at various locations

throughout a given site.

Petroleum aromatic compounds have been

shown to degrade by cleavage of the

aromatic carbon ring as shown here for

benzene:

Figure courtesy of the Department of

Chemistry, VPI&SU.

Although natural or artificial recharge may

stimulate aerobic biodegradation by

reintroducing oxygen to anaerobic regions,

the low solubility of oxygen and the rapid

reaction rates typical of aerobic

environments can severely limit the

aerobic biodegradation of petroleum

hydrocarbons

Therefore for a more efficient degradation

we should either use all three types of

microbes or use enhanced in situ

bioremediation

Casestudy 1 Examples of Bioremediation Description 18: U.S. Army Contracting Command

Overseas Remediation.

An overseas U.S. Army Military Base. This base has been active since the Korean War. A Lieutenant with the Army Corps of Engineers contacted Alabaster Corp. about a bioremediation project he was conducting. For many years large volumes of military equipment had been utilized at the subject location. The location had many UST or underground fuel storage tanks as well as AST or above ground fuel storage tanks. The facility operates and maintains a large amount of equipment ranging from typical tractors, cranes, bulldozers, and other earth moving apparatus to heavy military items such as tanks and other combat designed vehicles. The concrete slab throughout most of the very large subject area was heavy and thick to withstand the tremendous weight of the equipment. Large amounts of hydrocarbons had accumulated around and underneath various large cemented areas as well as within soil or non-cemented areas.

Various Army Engineering experiments with bioremediation had showed only typical to minimal results. The current options being considered were destroying the concrete slab, excavating the contaminated earth and re-filling this with clean fill dirt before relaying the new concrete slab. This included several huge area around a large military base. The officers in charge were making a last attempt to keep this project within a budget. Many details must be left confidential.

Pollution: Hydrocarbons Accumulated From Years of Operation. Large volumes of hydrocarbon contamination. Total TPH ranged

from minimal detection levels to as high as well over 100,000 mg/kg. The concrete itself had a saturated amount of hydrocarbons accumulated within. The drinking water supply was effected. Ground water contamination had detectable amounts of BTEX components and other GRO or gasoline range organics. Many details must be left confidential.

Solution: Alabaster Corp. Bioremediation Products. Slab Injection, etc.

A very large volume of Alabaster Corp. Bioremediation products were supplied to the U.S. Army Contracting Command for this overseas base. These included products like our BCC#1 Concentrate (Sold as CS2 or Super Concentrate) and microbial blend AB with Booster.

• The Army engineers involved were well acquainted with the process of bioremediation and utilizing the products. They were more than typically equipped and knowledgeable about various techniques involved with applying the products. They had several flexible and creative solutions to contracting dilemmas which would have made this project difficult and more expensive for most. Many details must be left confidential. However, we were verbally assured that they remediated “the substances” they intended. Over the next few months they tripled the original order.