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)

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

Factors causing molecular recalcitrance

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

1. A structural characteristic of the molecule prevents an enzyme from acting2. The compound is inaccessible, or unavailable.3. Some factor essential for growth is absent4. The environment is toxic5. Requisite enzymes are inactivated.6. The community of microorganisms present is unable to metabolize the

compound because of some physiological inadequacy.

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

Bioavailability

NAPLPhase

Or

SOM

water

Bacterium

C-water

C-NAPL

C-SOM

What if the aqueous concentration is lower than “threshold” forMicrobial 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.

Light NAPL (non-aqueous phase liquid) contamination

Capillary fringe

Water table

Groundwater Flow

Tank LNAPL

residual

LNAPLFree Phase

Dissolved LNAPL (plume)

Vapor from LNAPL

Dense NAPL contamination

Capillary fringe

Water table

Groundwater Flow

NAPL residual

LNAPLFree Phase

Vapor from NAPL

Dissolved NAPL (plume)

Groundwater Flow Direction

Bedrock

Clay Layer

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

Contaminant chemistry

Mobile,

Dissolved

(degrades/

Volatilizes)

Mobile,

Dissolved

Strongly sorbed, dissolved

(degrades/volatilizes)

Strongly sorbed, dissolved

Separate

Phase

LNAPL

Separate

Phase

DNAPL

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

Hydrogeology

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?)

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 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

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)

60

50

40

30

20

10

0

-10

-20

-30

-40

-50

-60

-70

-80

∆Go’

(kJ/e- eq)

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

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

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

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

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

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

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

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

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

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

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

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

ElectronDonors

ElectronAcceptors

S-min, CSTR and PFR

Travel Time through a Reactor

S(m

g/

L)

CSTR

PFR

S-min

Scope and characteristics of contaminants

• Category of Contaminants

Category of compounds Examples Prevalent uses

Aromatic hydrocarbons

Oxygenated hydrocarbons

Hydrocarbons with specific elements

Other hydrocarbons

Metals and cations

Nonmetals and anions

Microorganisms

Radionuclides

Benzene,

toluene etc.

Phenol

acetone etc.

TCE

1,1,1 TCA

2,4-D

Kerosen, gasoline, lignin…

Iron

Chromium

arsenic

Chloride, sulfate, ammonia

Bacteria, viruses

Uranium238, tritium, radium226

Dyestuffs

solvents

Paints

Solvents

Solvents

Munitions

pesticides

Fuels

Alloys

Electrical and electronics

Fertilizers, Foodadditives

Medical applications

Degree of Halogenation vs. Biodegradation

C C

Cl

Cl

Cl

Cl

C C

Cl

Cl

H

Cl C C

H

Cl

Cl

H

C C

Cl

Cl

H

H

C C

H

H

Cl

H

C C

H

H

H

H

Tetrachloroethene(Perchloroethene, PCE)

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

cis-Dichloroethene(cDCE)

trans-Dichloroethene(tDCE)

monochloroethene(vinyl chloride, 발암물질 )

ethene

가장 산화됨

가장 환원됨

Monochlorinated Polychlorinated0.25 4

Degree of Chlorination

So

rpti

on

on

to S

ub

surf

ace

Mat

eria

l

Deg

rad

atio

n R

ateSorption

Reductive dechlorination

Aerobic degradation

BiodegradabilityThe 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 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)

Synthetic organic contaminants reported to be most frequently found in drinking-water wells (Council on Environmental Quality, 1981)trichloroethene (TCE), toluene, 1,1,1-trichloroethane, acetone, methylene chloride, dioxane, ethyl benzene, tetrachloroethene, cyclohexane, chloroform,

di-n-butyl-phthalate, carbon tetrachloride, benzene, 1,2-dichloroethene,

ethylene dibromide, xylene, isopropyl benzene, 1,1-dichloroethene, 1,2-dichloroethane, bis phthalate, dibromochloropropane, trifluorotrichloroethane, dibromochloromethane, vinly chloride, chloromethane, butyl benzly-phthalate, gamma-BHC (lindane),

1,1,2-trichloroethane, bromoform, 1,1-dichloroethane, alpha-BHC, parthion, delta-BHC

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

Boiling range of fraction(oC) # of C per molecule Use

<20

20-60

60-100

40-200

175-325

250-400

Nonvolatile liquids

Nonvolatile solids

C1-C4

C5-C6

C6-C7

C5-C10

C12-C18

C12 and higher

C20 and higher

C20 and higher

Natural gas

Pet. Ether, solvents

Solvents

Gasoline

Kerosene and jet fuel

Diesel oil

Grease

Parffin was, asphalt

Hydrocarbon composition of gasoline components

• (Hill and Moxey, 1960)

1 1 1 1

3 3 3 3 52 2

4444

55

Straight-run Thermal-cracked Catalytic reformed Catalytic cracked

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- A common situation of codisposal: the mixture of organic and

inorganic materials in sanitary landfills and in their leachates

Compound

/Parameter

Representative range (mg/L)

Compound

/Parameter

Representative range (mg/L)

K+

Na +

Ca 2+

Mg 2+

Cl-

SO42-

Alkalinity

Fe(total)

Mn

Cu

Ni

200-1200

200-1200

100-3000

100-1500

300-3000

10-1000

500-10000

1-1000

0.01-100

<10

0.01-1

Zn

Pb

Hg

NO3-

NH4+

P as PO4

Organic nitrogen

Total Diss. Org. C

COD

Total Diss. Solids

pH

1-100

<5

<0.2

0.1-10

10-1000

1-100

10-1000

10-1000

1000-90000

5000-40000

4.8

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

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”

Compound Representative range (mg/L)

Compound Representative range (mg/L)

1,1-dichloroethene

Acetone

Methyl ethyl ketone

1,1,1-TCA

TCE

Methyl isobutyl ketone

Vinyl chloride

Dichlorobenzene

Benzene

60

35

25

12

11

5

3.7

2.5

0.17

0.68

Phenols

Tetrachloroethane

t-1,2-dichloroethene

Chromium

Nickel

Zinc

Lead (Pb)

Selenium

Cadmium

0.5

0.07

0.2

0.12

0.10

0.073

0.093

0.049

0.012

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

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.

Inorganic species Organic species

Radionuclides (plutonium, americium, thorium, uranium, technetium, strontium, cesium-134,137, cobalt-60, europium-152, 154, nickel-63, iodine-129, neptunium-237, radium)

Metals (lead, nickel, chromium, copper, mercury, silver, bismuth, palladium, aluminum)

Others (carbon-nitrogen compounds, nitrite, nitrate)

Organic contaminants (chlorinated hydrocarbons, methyl ethyl ketone, cyclohexanone, tetraphenyl boron, PCBs, PAHs, tributyl phosphate, toluene, benzene, kerosen)

Facilitators (aliphatic organic acids, chelating agents, aromatic acids, solvent, diluent, and chelate radiolysis fragments)