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Bioremediation

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by

Robert Hope

on 6 May 2014

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Transcript of Bioremediation

Conclusion
Bioremediation
Inorganic
Organic
The Savannah River
Introduction
Contamination
Enhanced Bioremediation
Phytoremediation
Inorganic Compounds
Any compound that does not include carbon
Toxicity
Inorganic compound exist abundantly in nature, so they don't pose an inherent risk to humans
However, certain compounds containing Mercury, Lead, Cadmium, and Chromium can be dangerous to humans
Can cause damage to neurological and reproductive systems
Pollution
While toxic compound can exist naturally, the biggest threat comes from compounds that were introduced directly by human interaction
The Basics
Methods
Methods
Pros and Cons
Examples
Phytoremedition
: Remediation of contaminated soil and water through the use of plants

Types:
Phytoextraction
Phytostabilization
Phytovolatilization
Rhizofiltration
Phytoextraction
Plant absorbs the contaminated soil/water
Contaminant is moved throughout the plant

Rhizofiltration
Plant roots absorb the contaminated water
Keeps contaminant in roots until saturation
Phytostabilization
Plant absorbs the water from contaminated soil
Lack of water restricts movement of contaminant
Creates a "dead" zone of the immobilized contaminant

Phytovolatilization
Follows the process of phytoextraction
Plant volatilizes the contaminant into less harmful compounds
New compounds are expelled
Arsenic Contamination
Pteris Vittata
(fern) is an arsenic hypoaccumulator
Can't burn for disposal of arsenic
Marine systems have the potential to convert arsenic into nontoxic forms

Lead Contamination
Many plants are known to absorb lead
Chelators can be added to soil for plants that don't absorb lead
Chelators bond to lead, allowing for absorption
The Site
Remediation
Results
TCE Contamination
Site located in Aiken, SC on a nuclear power facility
Solvents and degreasers were dumped into an unlined basin
13 million pounds between 1952-1982
Solution: Microbes
Methanotrophic Bioremediation
Indigenous methanotrops were found to aid in the degradation of TCE
Enzyme methane monooxegenase (MMO) yields TCE epoxide
Degradation yields products eventually oxidized to CO2 biomass
SRS Success!
A study was done to pumped nutrients (N and P) as well as methane into the soil
Study showed a 10^3 - 10^5 increase in indigenous methanotroph populations during additions
TCE degradation not directly linked to methane concentrations in soils, but correlated with the increase in methanotroph populations
Pros and Cons
Immobilization
Reduction
Overview
Enhanced Bioremediation
involves the addition of organic amendments to contaminated soil to enhance naturally occurring processes

Two common types include:
Reduction
Immobilization
Organic material provides a source of electron donors and carbon substrates for mesophilic bacteria naturally present in soil
Enhances the bacterias ability to perform redox on contaminants
Microorganisms begin to break down the organic material to grow and reproduce, which changes the chemical properties of the soil
The bioavailability of the contaminants is changed
Induced retention is attributed to an increase in the surface charge of the contaminants and the presence of binding compounds
Advantages
Relatively cheap
Does not disrupt environment

Disadvantages
Constant application of organic amendments
Risk of N and P pollution
Does not completely remove contaminants
Pollution
Remediation
Organic Pollutants
Tend to be environmentally persistent, toxic, and even carcinogenic
Volatile organic carbons (TCE, toluene, benzene) can come from solvents, paints, cleaning agents, and dry cleaning agents
PCB's were originally components of electrical equipment, plastics, oil based paints, and insulation
Insecticides (DDT) accumulate in the environment
Can lead to cancer, kidney and liver problems, and nervous system damage
Bioremediation
Microbes are used to degrade organic contaminants to CO2, or metabolize them into smaller, less toxic compounds
Chlororespiration
Organisms use organochlorine as electron acceptors
Microbes classified as chemolithotrophs (Oxidizes hydrogen gas and reduces organochlorine)
Vinylchloride reductases carry out this reaction (Degrades vinyl chloride, TCE, and perchloroethylene)
Dehalococcoides are obligate anaerobes

Limitations: The organism must be placed in lower soil horizons lacking in oxygen in order to use organochlorine as the electron acceptor
Microbial Degradation Mechanisms
Dehydrochlorination removes a chlorine atom and a hydrogen atom simultaneously
DDT -> DDE

Oxidative Pathways
Hydrogenamonas sp
. is capable of opening the aromatic ring of DDT
Enzymes: oxidoreductes, oxygenases, and monooxygenases
Types
Bioremediation:
The use of organisms to treat environmental contaminants

Biostimulation:
Stimulation of microbes already present at a site

Bioaugmentation:
Addition of microbes to a site to help treat pollutants
Bioremediation has the potential to replace more intensive industrial methods

However, this does not make them the perfect solution. Applications are site specific and results are subject to time.
Questions?
Full transcript