Bioremediation contaminants ch 14
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Bioremediation -contaminants (Ch. 14). Joonhong Park May 27, 2014. History of Hazardous Chemicals. Synthetic detergents (Germany during World War II): Poor Biodegradability of Branched Alkyl Benzene Sulfonate (ABS) [Figure 14.1] Pesticides: Silent Spring (Rachel Carson, 1962)

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Bioremediation -contaminants (Ch. 14)

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Bioremediation contaminants ch 14

Bioremediation-contaminants (Ch. 14)

Joonhong Park

May 27, 2014


Bioremediation contaminants ch 14

History of Hazardous Chemicals

Synthetic detergents (Germany during World War II): Poor Biodegradability of Branched Alkyl Benzene Sulfonate (ABS) [Figure 14.1]

Pesticides: Silent Spring (Rachel Carson, 1962)

Polychlorinated biphenyls (PCBs) and halogenated hydrocarbon: probably cause about half of the environmental problems attributable to organic pollution in the world (Tiedje et al., 1993)

Natural occurring pollutants: BTEX (benzene, toluene, ethlybenzene, xylene), polycyclic Aromatic Hydrocarbons (PAHs), dioxins, heavy metals, radioactive matters/rays, asbestos etc.

Recalcitrant to Microbial degradation of Chemicals


Bioremediation contaminants ch 14

Factors causing molecular recalcitrance

Martin Alexander (1965) described factors causing organic compounds to resist biodegradation in the environment, which he termed “molecular recalcitrance”:

  • A structural characteristic of the molecule prevents an enzyme from acting

  • The compound is inaccessible, or unavailable.

  • Some factor essential for growth is absent

  • The environment is toxic

  • Requisite enzymes are inactivated.

  • The community of microorganisms present is unable to metabolize the compound because of some physiological inadequacy.


Bioremediation contaminants ch 14

Molecular Structure

Relationship between enzyme activation site and the chemical structure of a pollutant (cf. Quantitative Structure-Activity Relationship)

Electronic, hydrophobic and steric effects

Henry’s constant, KH: volatilization

Octanol-water partitioning constant, Kow: hydrophobicity, sorption

Solubility, Cs: bioavailability


Bioremediation contaminants ch 14

Bioavailability

NAPL

Phase

Or

SOM

C-NAPL

C-SOM

water

Bacterium

C-water

What if the aqueous concentration is lower than “threshold” for

Microbial biodegradation ?


Contaminant availability for biodegradation

Contaminant availability for biodegradation

Two phenomena limiting substrate availability for biodegradation

  • Strong sorption to surfaces

  • Formation of a nonaqueous phase

    Limited substrate availability is bad for biodegradation of a contaminant while is good for biodegradation when the compound is toxic to microorganisms.


Bioremediation contaminants ch 14

Light NAPL (non-aqueous phase liquid) contamination

Tank

LNAPL

residual

Vapor from LNAPL

Capillary fringe

LNAPL

Free Phase

Water table

Dissolved LNAPL (plume)

Groundwater Flow


Bioremediation contaminants ch 14

Dense NAPL contamination

Vapor from NAPL

NAPL residual

Capillary fringe

Water table

Dissolved NAPL (plume)

Clay Layer

Groundwater Flow Direction

LNAPL

Free Phase

Groundwater Flow

Bedrock


Bioremediation contaminants ch 14

Relative ease of cleaning-up of contaminated aquifers as a function of contaminant chemistry and hydrogeology (1=easiest; 4 = the most difficult)

Contaminant chemistry

Strongly sorbed, dissolved

(degrades/volatilizes)

Strongly sorbed, dissolved

Separate

Phase

LNAPL

Separate

Phase

DNAPL

Mobile,

Dissolved

(degrades/

Volatilizes)

Mobile,

Dissolved

Hydrogeology

Homogeneous,

single layer 1 1-2 2 2-3 2-3 3

Homogeneous,

multiple layer 1 1-2 2 2-3 2-3 3

Heterogeneous,

single layer 2 2 3 3 3 4

Heterogeneous,

multiple layer 2 2 3 3 3 4

Fractured 3 3 3 3 4 4


Bioremediation contaminants ch 14

Microorganism presence

Even though a contaminant is known to be readily biodegradable, the absence of a suitable microbial population may be a limiting factor.

Bioaugmentation:

- addition of biodegradation populations into contaminated fields.

- The survival of foreign microbes in new environment is questionable.

  • Genetically modified organisms cannot be released into fields.

    (Genetically modified indigenous microbes? Digging contaminated soil into a field to be treated? Are they acceptable?)


Bioremediation contaminants ch 14

Categories of environmental contaminants

Hydrocarbons: BTEX (low FW), PAHs (high FW)

Oxygenated hydrocarbons: alchohols, ketones, ethers, MTBE

Halogenated aliphatics: chlorinated ethenes, chlorinated ethanes

(highly chlorinated vs. low chlorinated)

Halogenated aromatics: PCBs, chlorinated dioxins, chlorinated dibenzofurans (highly chlorinated) and other low chlorinated halogenated aromatics

Nitroaromatics: TNT, RDX, HMX

Metals: Cr. Cu, Ni, Pb, Hg, Cd, Zn etc.

Nonmetals: As, Se

Oxyanions: nitrate, (per)chlorate, phosphate

Radionuclides

See Table 14.1 and Table 14.2


Energy metabolism versus cometabolism

Energy Metabolism versusCometabolism

Energy Metabolism: Respiration and Catabolism of a Pollutant => Resulting in Microbial Growth => sustainable biodegradation

Cometabolism: Fortuitously biodegraded => Little Microbial Growth => May not be sustainable


Absence of physiologically significant compounds

Absence of physiologically significant compounds

Electron donor.

Electron acceptor (e.g. oxygen limitation is common).

Inducing agent (e.g. presence of toluene is needed to induce toluene oxygenase expression)

Carbon, nitrogen and phosphorus sources

Trace metals (e.g. Fe is needed for oxygenase)


Bioremediation contaminants ch 14

60

0.25CO2 + H+ + e- = (1/24)C6H12O6 + 0.25H2O (Glucose/CO2)

50

40

H+ + e- = 0.5H2 (Hydrogen/H+)

Electron

Donors

30

1/6CO2 + H+ + e- = (1/12)CH3CH2OH + 0.25H2O (Ethanol/CO2)

20

1/8CO2 + 1/8 HCO3- + H+ + e-

= 1/8 CH3OO- + 3/8H2O (Acetate/CO2)

10

0

∆Go’

(kJ/e- eq)

1/8 CO2 + H+ + e- = 1/8 CH4 + 0.25H2O (methane/CO2)

-10

-20

1/8 SO42- + 19/16H+ + e-

= 1/16 H2S + 1/16 HS-+0.5H2O (sulfide/sulfate)

-30

-40

Electron

Acceptors

½ CCl2CCl2 + ½ H+ + e- = ½ CHClCCl2 + ½ Cl- (PCE)

-50

-60

1/5 NO3- + 6/5H+ + e- = 1/10 N2 + 3/5H2O (N2/Nitrate)

-70

Fe3+ + e- = Fe2+ (Fe[II]/Fe[III])

-80

1/4O2 + H+ + e- = 0.5H2O (H2O/O2)


S min cstr and pfr

S-min, CSTR and PFR

PFR

CSTR

S(mg/L)

S-min

Travel Time through a Reactor


Scope and characteristics of contaminants

Scope and characteristics of contaminants

  • Category of Contaminants


Degree of halogenation vs biodegradation

Degree of Halogenation vs. Biodegradation

가장 산화됨

Cl

H

Cl

Cl

Cl

H

C

C

C

C

C

C

Cl

Cl

H

H

Cl

H

Tetrachloroethene

(Perchloroethene, PCE)

cis-Dichloroethene

(cDCE)

monochloroethene

(vinyl chloride, 발암물질)

Cl

H

H

H

Cl

C

C

H

C

C

C

C

Cl

Cl

Cl

H

H

H

Trichloroethene

(TCE, Cs = 1,100 mg/L)

ethene

trans-Dichloroethene

(tDCE)

가장 환원됨


Bioremediation contaminants ch 14

Aerobic degradation

Sorption

Reductive dechlorination

Sorption onto Subsurface Material

Degradation Rate

Monochlorinated

Polychlorinated

0.25

4

Degree of Chlorination


Biodegradability

Biodegradability

The apliphatic and aromatic hydrocarons are readily biodegradable by a range of aerobic bacteria and fungi. The key is that molecular O2 is needed to activate the molecules via initial oxygenation reactions.

Evidence of anaerobic biodegradation of aromatic hydrocarbons is growing. Anaerobic biodegradation rates are slower than aerobic rates, but they can be important when fast kinetics are not essential.

Most halogenated aliphatics can be reductively dehalogenated, although the rate appears to slow as the halogen substituens are removed.

Highly chlorinate aromatics, including PCBs, can be reductively dehalogenated to less halogenated species.

Lightly halogenated aromatics can be aerobically biodegraded via initial oxygenation reactions.

Many of the common organic contaminants show inhibitory effects on microorganism growth and metabolism. Due to their strongly hydrophobic nature, many of the inhibitory responses are caused by intereactions with the cell membrane. In some cases, intermediate products of metabolism can be more toxic than the original contaminant.


Scope and characteristics of contaminants1

Scope and characteristics of contaminants

  • Organic compounds

    - most often amenable to bioremediation

    - the most detected in groundwater

    - Many of them are hydrophobic (log Kow >1) and less soluble (solubility < 10,000 mg/l) Ex. PAH, PCB => Significance?

    - Some are volatile (KH > 10-3 atm-m3/mol)


Mixtures of organic compounds

Mixtures of organic compounds

- In many instances, the original contamination was a mixture of related components that co-exist normally in a commercial product

  • PCBs (Arochlor1242 has 42% chlorine overall but contains biphenyl congeners having 1 through 6 Cl substituents with 80% having 3, 4, or 5 Cl substituents)

  • PAHs (in tars, asphalts, and petroleum sludges)

  • Various petroleum distillation fractions


Hydrocarbon composition of gasoline components

Hydrocarbon composition of gasoline components

  • (Hill and Moxey, 1960)

4

4

4

4

2

1

2

1

1

1

5

3

3

5

3

3

5

Thermal-cracked

Catalytic reformed

Catalytic cracked

Straight-run

1: n-alkanes 2:alkenes 3: aromatics 4:isoalkanes 5:cycloalkanes

Troublesome BTEX: benzene (2-5% v/v), toluene(6-7% v/v), ethylbenzene(5% v/v), and xylenes (6-7% v/v) => their relatively high solubility causes them to be the prime water pollutants among the compounds in gasoline.

More complications – Additives: antiknock compds, antioxidants, metal deactivator,

Antirust agent, antipreignition agents, upper cylinder lubricants, alcohols, and oxygenates (MTBE => a big problem!)


Mixtures created by codisposal

Mixtures created by codisposal

- A common situation of codisposal: the mixture of organic and inorganic materials in sanitary landfills and in their leachates

Freeze and Cherry, 1979; Rittmann et al., 1994


Mixtures created by codisposal1

Mixtures created by codisposal

-Volatile and nonvolatile organic compounds and trace metals found in groundwater at an air force base (US, CA)

- Chemical-manufacturing facilities: long-term, mixture, very low solubility sludges, unacceptable products, other residues => “gumbo”

Pitra and McKenzie, 1990; Rittmann et al., 1994


Mixtures created by codisposal2

Mixtures created by codisposal

  • US Department of Energy (DOE) sites are unique in that the contamination of the subsurface often involves complex mixtures of organic and inorganic chemicals, including short- and long-lived radionuclides (USDOE, 1990)

  • The degree of complexation with the chelators controls the mobility of the radionuclides, while the biodegradation of the chelators is affected by their complexation to the heavy metals.


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