Bioremediation of Organochlorine Solvents in Groundwater

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Bioremediation of Organochlorine Solvents in
Groundwater

• Institute of Technology, Sligo
• Department of Environmental Science and
  Technology
• By
• Leif Barry
• Edel Kilgallon
• Breda King
• Subject Waste Management
• Lecturer Dr. Michael Broaders

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INTRODUCTIONOrganochlorine Compounds

• Toxaphene
• Endrin
• Dieldrin
• Aldrin
• Endosulfan
• Chlordane
• Heptachlor
• Dichlodiphenyltrichloroethane (DDT)
• All have been manufactured since the 1940s for
  use as pesticides. They are not safe for
  household application. They persist in the
  environment long after initial use.

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What are Chlorinated Solvents

• Chlorinated solvents and their natural
  transformation products are the most prevalent
  organic groundwater contaminants.
• Consisting of chlorinated alphatic hydrocarbons
  (CAHs) have been used for
• Degreasing aircraft engines
• Automoible parts
• Electronic components
• Dry cleaning clothes

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Examples of Organochlorine Solvents

• trichloroethylene (TCE)
• 1,1,1 trichloroethane (TCA)
• Perchloroethylene (PERC)
• tetrachloroethane is a manufactured chemical that
  is widely used in the dry cleaning of
  fabrics,including clothes. tetrachloroethane is
  found in consumer products including some paints
  and spot removers, water repellents, brake and
  wood cleaners, glues and suede protectors.

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• Other names for tetrachloroethane include
  perchloroethylene (PERC) and tetrachloroethylene.
• In the USA, EPA studies showed that people who
  wear freshly dry cleaned clothes, such as a
  jacket and shirt, every week over a 40 year
  period could inhale enough PERC to measurably
  increase their risk of cancer by as much as 150
  times.

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The major sources of pollution by organochlorine
solvents to groundwater

• Landfills
• Leaking tanks/pipes
• Spillages
• Soakaway drainage
• Lagoons
• Well injection
• Sewage landspreading/infiltration and leakage
  from other aquifers

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Minor sources of pollution by organochlorine
solvent to groundwater

• Surface water
• Irrigation
• rainfall

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• Organochlorine solvents discharged in sufficient
  quantities may form an immiscible layer separate
  from the main body of water.
• This is because of the
• Low solubility of the solvents
• And their different characteristics they are
• Denser and
• Less viscous
• Than water
• An aquifer may remain contaminated for hundreds
  or thousands of years.
• Due to low guideline values it may only take a
  few litres of solvent to contaminat millions of
  gallons of groundwater.

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WHO Guidelines for chlorinated solvents in
drinking water

• Contaminant Guideline value (mg/l)
• 1,2- dichloroethane 10
• 1,1- dichloroethane 0.3
• Chloroform 30

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Goundwater Supply of Drinking Water

• Ireland 11
• Germany 25
• USA 50

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Limits for Drinking Water

• WHO guidelines for chlorinated solvents in
  drinking waterContaminant.
• Guideline value (ug/l)1,2-
• dichloroethane 101,1-
• dichloroethene 0.3
• chloroform 30
• Tentative guideline values
• Carbon tetrachloride 3.0
• tetrachlorethene 10.0
• trichlorethene 30.0

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Pathway of Exposure

• Inhalation
• Swallowing
• through the skin.

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Health Effects

• Acute
• Generally last only minutes, hours or days
• Are reversible once the exposure is over.
• They are more easily identified.
• Common acute effects from solvent exposure
  include

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• Respiratory Irritation
• Eye Irritation.
• Dermatitis.
• CNS Depression.
• Heart Arrhythmia

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Chronic Effects

• occur after repeated exposures
• are often long-lasting
• irreversible.
• Symptoms may appear gradually, so they may be
  initially ignored. This can make it hard to
  identify the chronic health problems related to
  solvent exposure.

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Chronic health effects include

• Respiratory Effects.
• Dermatitis
• Nervous System.
• Liver Damage
• Blood
• Reproductive Effects
• Cancer

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Effects depends on serval factor

• how easily the solvent evaporates at the ambient
  temperature? 
• what are the characteristics of that solvent is
  it water soluble or able to dissolve fats? 
• what is the concentration of the solvent in the
  air at the place of work? 
• what type of work is involved, light or heavy?
  (Panting increases the amount inhaled.)
• how long does the exposure last? 

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Prevention Control

• SOLVENT SELECTION
• TRAINING
• CONTAINERS
• GLOVES, GOGGLES
• AIR CONTAMINATION
• DOCUMENTATION

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Case study
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What is Bioremediation?

• The term bioremediation is applied to any system
  or process in which biological methods are used
  to transform or immobilize contaminants in soil
  or groundwater.

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How does it work?

• The right temperature, nutrients, and amount of
  oxygen must be present in the soil and
  groundwater.
• These conditions allow the microbes to grow and
  multiply and eat more chemicals.
• Drill wells and pump some of the groundwater into
  tanks. Here, the water is mixed with nutrients
  and air before it is pumped back.
• Groundwater can also be mixed underground by
  pumping nutrients and air into the wells.

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There are two types of Bioremediation.

• Ex-Situ Bioremediation
• In-Situ Bioremediation

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Ex-situ Bioremediation

• Pump and Treat
• This is the most commonly used technology for
  contaminated groundwater.
• Now used to contain contaminated material rather
  than to remediate it.

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In-situ Bioremediation

• Percolation
• Pump, treat and reinject
• Injection wells
• Hydrogen peroxide injection
• Air sparging

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Cometabolism

• Most studies on biodegradation of chlorinated
  solvents have focused on using aerobic microbial
  metabolism
• An exception
• Cometabolism with another substance

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Synergism

• Many biodegradations require the cooperation of
  more than a single species of microbe
• Two or more species of microbes carry out a
  transformation that one alone could not
• Some reactions take place in mixtures of species
  but not in pure culture or take place more
  readily in multi-species associations
• Pseudomonas spp.

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Treatment Walls

• Involves installing a permeable wall
• It consists of an excavated ditch

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Disadvantages of In-Situ treatment

• Ineffective at contaminated sites where
  conditions are unfavourable
• Longer treatment times
• Nature of contaminant distribution

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Advantages of In-Situ Treatment

• More cost effective
• Little disruption to site processes
• No need for large treatment areas
• It minimises exposure to humans and the
  environment to contaminants

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Conclusion

• Bioremediation is by far one of the most
  innovative technologies to be employed by
  man/woman for remediation of contaminated
  groundwater
• There is a lot yet to be learned and understood
  about bioremediation of contaminated groundwater
• This is a remarkable and true story of a David
  and Goliath battle