8. Bioremediation Treatments Flashcards
Les grandes lignes of bioremediation (4 steps)
- Put bacteria on the contaminated site
- The bacteria secrete enzymes that attack fats, oil, grease, sugar, starch, breaking them down
- Bacteria can then eat the leftover smaller bits
- Bacteria excrete CO2 and water
BTEX
benzene, toluene, ethylbenzene, xylene
ppm
parts per million = mg pollutant / kg or L of sample
ppb
parts per billion = μm pollutant / kg or L of sample
TPH
Total Petroleum Hydrocarbons
What is TPH for?
It is a common chemical procudure used to quantify the amount of hydrocarbons in a contaminated sample
4 common modes of biodegradation of organic compounds
- Cellular metabolism
- Detoxifying enzymatic reactions
- Non-enzymatic reactions
- Cometabolism
Two types of cellular metabolism
- Catabolism
- Anabolism
What are we doing with carbon in catabolism
C used as a source of energy and CO2 released
What are we doing with carbon in anabolism
C converted to biomass
In cellular metabolsim, what are the pollutants converted to? (3)
- Cells (biomass)
- Residual organics
- Inorganics (CO2, etc.)
What are types of detoxifying enzymatic reactions? (2)
- Antibiotic degradation
- Metal transformations
- i.e. transforming heavy metals into there less toxic forms
- e.g. transforming methylmercury to Hg2+ to Hg 0 and transforming uranium 6+ to U4+)
Non-enzymatic reactions
When by-products of microbial metabolism change the environment
How do non-enzymatic reactions occur? (4)
- Depletion of O2
- Change in pH
- Production of reactive compounds like H2O2 → strong oxidant
- SO4 via SRB can be transformed to H2S which reacts with heavy metals (Zn, Cd, Pb) to create insoluble metal sulfides
Cometabolism
- Compound modified but NOT used for generation of energy or biomass
- Enzymes with low specifity
- Often via excreted enzymes i.e. extracellular enzymes
Is an integrated multi-disciplinary approach needed for bioremediation?
yes
Some fields involved in the successful use of bioremediation (5)
- Waste
- Optimal microbiology
- Remediation technology
- Analystical methods
- Statistical sampling
- Regulatory approval
Parameters involved in successful use of bioremediation (14)
- composition properties
- nutrients
- moisture
- aeration
- inoculum
- land treatment
- bioslurry
- composting
- bioventing
- correct method
- QA/QC (quality assurance/quality control)
- statistic procedures
- cleanup standards
- closure requiremetns
Remediation technologies in order of most expensive to least expensive:
* above ground bioremediation
* thermal desoprtion
* landfill
* incineration
* soil washing
- incineration
- landfill
- thermal incineration
- soil washing
- aboveground bioremedation
Conventional remediation technologies (5)
- Soil excavation
- Incineration
- Containement: landfill, land farming, solidification/stabilization (tar ponds example)
- Chemical additions
- Soil washing
Sydney Tar Ponds example
What were the contaminants? (4)
- hydrocarbons
- PAHs
- heavy metals
- PCBs
Sydney Tar Ponds example
Remediation strategy
Solidification / Stabilization (S/S) with cement
Sydney Tar Ponds example
What is Solidification / Stabilization (S/S) with cement?
- Contaminated sediments are mixed with cement powder
- This solidifies the contaminated soil and prevent pollutants from moving
* such as rain causing leaching of pollutants into the groundwater or being carried into streams by rain or snowmelt - So it’s just stabilizing the contaminants so they don’t go anywhere, not removing them
Sydney Tar Ponds example
What happens after the completion of the S/S process
- The solidified areas get covered with an engineered cap consiting of a high-density polyethylene liner or clay, folllowed by layers of gravel or soil.
- Then, the surface was planted with grass and other vegetation
Sydney Tar Ponds example
Weakenesses of S/S (2)
- high cost
- pollutant not necessarily destroyed, as they may be converted to another form which are still pollutants and/or moved to another environment
Sydney Tar Ponds example
Bioremediation is usually better than conventional technologies because … ? (2 pros + 1 con)
- The pollutants are usually totally destroyed
- The cost is generally lower
- But sometimes it is slower and with an unpredictable outcome
Types of bioremediaiton (2)
- Bioremediation following excavation
- In situ bioremediation
Types of In situ bioremediation (2)
- Intrinsic bioremediation
- Enhanced in situ bioremediation
What is intrinsic bioremediation? + characteristics (4)
- No intervention
- Rely on existing microbes, nutrients and other environmental parameters
- Inexpensive but destruction of pollutant could take a long time or never be completed
- Requires a comprehensive monitoring program to ensure contamination is not travelling off-site, limited toxicity, and contamination concentrations are being reduced
What is enhanced in situ bioremediation?
- Enhanced by additions but no excavation
- Can speed up degradation time and percent reduction in pollutant concentration
What are the two ways to do enhanced in situ bioremediation?
- Bioaugmentation
- Biostimulation
What is bioaugmentation?
Addition of microbes (natural or genetically engineered) known to break down the pollutant
Bioaugmentation isn’t as commonly used because it doesn’t work as well. Why is that?
- Problem is that these new microbes require other growth factors and so they will deplete other nutrients in the site
- Another problem is that there is a reason that the already present microbes are not doing their job currently, there is probably something missing, such that stimulation should work better
What is biostimulation
Addition of something to the contaminated site to stimulate the already present microbes in proceeding with bioremediation
Biostimulation
What can you add to stimulate? (4)
- Addition of O2 (air) or another electron acceptor
- Addition of fertilizers to optimize the C:N:P ratio, ensuring that growth is not limited by a nutrient and thus the growth rate of biodegrading microbes is maximized
- Addition of inducers (of gene expression) i.e. CH4 stimulates production of methane monooxygenase (MMO), known for ability to degrade some pollutants via cometabolism
- Alteration of any other important environmental parameter
How does one know what to add and in what proportions?
Need to preform a bioremediation assessment study to determine 4 elements… and then what do you do with those 4 elements
- Are the contaminants biodegradable
- Are biodegradive microbes present in the contaminated sites?
- Are the contaminated environement parameters (temp, pH) optimal for biodegradation to occur?
- Identify any paramaters that may be limiting biodegradive activity
Then, using the assessment, develop a bioremediation treatment strategy
* Optimize biostimulation parameters to maximise metabolize activity related to the biodegradation of the pollutant
* Apply optimized parameters to the field for in situ bioremediaiton strategy
Bioremediation assessment: Procedures for understanding the biodegradation processes: 2 PHASES
Phase 1
* Use of controls and methods for detection of pollutants or biodegradation end-products, detecting and quantifying pollutant-degrading microorganisms
* e.g. 14C labelling, analytical chemistry
* Lab test and determine optimal bioremediation treatments
Phase 2
* Overview examples of how biodegradation processes are worked out, understood
* Once basic processes are understood, they can be utilized in a bioremediation strategy
Bioremediation following excavation
Enhancing bioremediation with additions, as in in situ
Solid soils → Land farming (spread, toill to aerate), Biopiles
i dont understand this slide for real but at least u are seeing the info
Slurries via lagoons, vessel reactos (i.e. anaerobic sludge digesters)
What was the pollution problem in Eureka?
~37 000 L of diesel fuel in 1990
hydrocarbons
What was the best method to bioeremediate in Eureka?
Fertilizer + water
NWT Gold Mine Site - what was the pollutant?
Hydrocarbons!
NWT Gold Mine: What were the two bioremediation strategies used?
- Addition of fertilzier and air
- Covered biopile to maintain higher temperature
Are treating aquifers harder than soil?
Yes
Why is it harder to treat aquifers than soil? (3)
- Large area
- Flow is slow and unmoving
- Oxygen is the limiting element, and the system becomes anaerobic often
What are three ways to bioremediate contaminated aquifers?
- Bioventing of vadose zone soils
- Biosparging
- Permeable reactive barriers
How does bioventing of vardose zone soils work? (3)
- In situ
- Vacuum applied to bore hole, draws out volatile contaminants
- Promotes air flow in permeable soils
3 holes, 2 push air down the other is a vaccuum sucking up the fumes
How does biosparging work? (3)
- In situ
- Pumps air or O2 into the contaminates zones to increase aerobic biodegradive activity
- Requires a porous environment
How do permeable reactive barriers work? (4)
- A trench or engineered barrier is placed across ground water flow in a treatment zone
- The barrier passively captures a plume of contaminants and removes or breaks down the contaminants, releasing uncontaminated water
- Primary removal methods include
1. Sorption and precipitation
2. Chemical reaction
3. Biodegradation mechanisms - only for shallow aquifers
Pollution problem in Alberta Tar Sands
What are the issues with the tailing sands and tailing waters?
- Increased ion content, e.g. Na+
- Alkaline pH
- Nutrient depleted
- Residual hydrocarbons
Pollution problem in Alberta Tar Sands
What remediation can be used to solve this issue?
Phytoremediation
What is phytoremediation?
- Exploitation of plants and associated microbes that are capable of bioremediation
- Huge potential for treating large multi-contaminated sites
- Efficiency depends on plant-microbe interactions
Benefits of phytoremediation (8)
- Wide public acceptance (less so for transgenics)
- Inexpensive
- Energy efficient (solar-powered)
- Can occur in situ
- Sequester heavy metals and stimulate organic biodegradation
- Production of biomass for fuel (use of the plants for biofuel)
- Pioneer species
- Soil reconstruction
- Detoxifying the soil via the remediation
Pros of phytoremediation (5)
- One of the few methods for removing heavy metals from soil and shallow aquifers
- Inexpensive
- Can promote soil regeneration
- Additional uses for plant material (e.g. biofuels, C sequestration)
- In some cases, leads to effective stimulation of petroleum breakdown
Cons of phytoremediation (5)
- Can be slow remediation (15-100 years)
- Difficult to predict
- How to treat multi-contaminated sites? (plants thay can grow with one toxic contaminant, might not be able to grow with more than one, aka site too toxic for plant growth)
- Contaminant concentration thresholds can be hard to achieve
- May give a false image of site restoration
Phytoremediation summary (4 points)
- Plants contribute to phytoremediation both directly (e.g. accumulation of metals) and indirectly (e.g. stimulation of microbes that degrade organics).
- Optimizing phytoremediation means increasing plant growth and stimulating microbes that are efficient bioremediators.
- Phytoremediation can bring additional benefits (e.g. biomass production, habitat restoration) which will assist with its acceptance and utility in the future.
- A technology still under development!
