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Conventional methods of remediation : 

Conventional methods of remediation Dig up and remove it to a landfill Cap and contain Risk of excavation, handling and transport of hazardous material Very expensive to find another land to finally dispose these materials Maintain it in the same land but isolate it Only an interim solution Requires monitoring and maintenance of isolation barriers for a long time Is there a better approach? Products are not converted into harmless products. Stay as a threat!

Better approaches : 

Better approaches Destroy them completely, if possible Transform them in to harmless substances High temperature incineration Chemical decomposition like dechlorination, UV oxidation Methods already in use But, are they effective?

Yes : 

Yes But only to some extent Drawbacks Technological complexity The cost for small scale application – expensive Lack of public acceptance – especially in incineration Incineration generates more toxic compounds Materials released from imperfect incineration – cause undesirable imbalance in the atmosphere. Ex. Ozone depletion Fall back on earth and pollute some other environment Dioxin production due to burning of plastics – leads to cancer May increase the exposure to contaminants, for both workers and nearby residents

Slide 5: 

Bioremediation makes effective better approach possible. Either by destroying or render them harmless using natural biological activity.

Slide 6: 

Relatively low cost Low technology techniques Generally has general public acceptance Can often be carried out on site – no excavation, no transport Drawbacks May not be effective on all contaminants Time duration – relatively long Expertise required to design and implement – although not technically complex What is Bioremediation?

Biodegradation : 

Biodegradation is a general term referring to the microbially mediated decomposition of paper, paint, textiles, concrete, hydrocarbons Superior technique over using chemicals – why? Microorganisms – easy to handle Easy to clear – using antibiotics

Types of Biodegradation : 

Types of Biodegradation Minor change in a molecule Fragmentation Complete mineralization One example to describe all 3 types

Minor change in a molecule (dehalogenation) : 

Minor change in a molecule (dehalogenation) HOH Cl Cl is replaced with OH

Fragmentation : 

Fragmentation HOH HOCH2-COOH Original structure can still be recognized in these two types. But…

Mineralization : 

Mineralization CO2 2Cl HOH Completely converted into inorganic forms

Slide 12: 


Bioremediation : 

Bioremediation is defined as the process whereby organic wastes are biologically degraded under controlled conditions to an innocuous state, or to levels below concentration limits established by regulatory authorities

Types of Bioremediation : 

Types of Bioremediation Engineered Bioremediation Intrinsic Bioremediation 2 types Intentional changes Simply allow biodegradation to occur under natural conditions

Slide 15: 

Engineered Bioremediation Factors affecting Engineered Bioremediation Qualities of microorganism & environment Sources of microorganisms Disadvantages of GEMs

Factors affectingEngineered Bioremediation : 

Factors affectingEngineered Bioremediation Contact between the microbes and the substrate Proper physical environment Nutrients Oxygen Absence of toxic compounds

Qualities of : 

Qualities of Microorganisms Environment Able to degrade hydrocarbons Able to fix nitrogen No secondary/side effects Presence of accessory nutrients (N P K Fe) Absence of heavy metals Adequate O2, Temperature, pH

Sources of microorganisms : 

From contaminated field sites (with varying environmental conditions - subzero temperatures or extreme heat, desert conditions or in water, with excess of oxygen or in anaerobic conditions, with presence of hazardous compounds or on any waste stream) From culture collections Genetically Engineered Microorganisms (GEMs) Sources of microorganisms

Disadvantages of GEMs : 


Mainly 3 reasons… : 

Mainly 3 reasons… Lab strains become food source for soil protozoa Inability of GEMs to contact the compounds to be degraded Failure of GEMs to survive/compete indigenous microorganisms. Mostly due to lack / decreased activity of House Keeping Genes.

Intrinsic Bioremediation : 

Intrinsic Bioremediation is a natural attenuation process that leads to the decrease in contaminant levels in a particular environment due to unmanaged physical, chemical and biological processes. Is it advantageous over engineered bioremed.? May give unexpected results - a bioremediation under natural conditions

Example - Intrinsic Bioremed. : 

Example - Intrinsic Bioremed. Microbes in Hudson river mud developed an ability to partially degrade PCB (Poly Chlorinated Biphenyls) Partial dehalogenation of PCBs occurs naturally under anaerobic conditions Then mud is aerated to promote the complete degradation of these less chlorinated residues Process occurs in 2 steps Less chlorinated residues

Application of Technology : 

Application of Technology Bioremediation in ALASKA OIL SPILL

South Central Alaska : 

South Central Alaska South Central Alaska is beautiful and unique. Prince William Sound, surrounded by land from the Chugach National Forest Has many islands, bays, and fjords, giving it more than 2,000 miles of shoreline and making it one of the nation’s largest relatively undeveloped marine ecosystems Entire region also has many national Wildlife Refuges.

Slide 25: 

People also live in this region. Valdez, population about 4,000 is about 110 miles from Anchorage, Alaska’s largest city and home to half of the state’s population The state of Alaska is heavily dependent on its natural resources, with 80% of the state treasury connected to oil. It is here … a few minutes after midnight March 24, 1989 video

Decisions had to be made! : 

Decisions had to be made! The oil was spreading and contaminating more and more beaches every day. Clean-up methods had to be decided upon to prevent further spreading of the oil. Try Bioremediation?

Proceedings : 

Proceedings Panel of experts in this field was assembled on April 17-18, 1989, to discuss the feasibility of using bioremediation in Alaska Recommended EPA to apply fertilizer (the addition of nutrients) on small scale plots

Questions raised : 

Questions raised Could the technology be applied to an environment so cold? Were there favorable conditions for degradation of petroleum hydrocarbons? Is Prudehoe Bay Oil of sufficient quality for biodegradation?

Slide 29: 

Scientists knew that this type of oil was degradable from past studies Now they needed to know the concentrations of native hydrocarbons degraders. Proceedings (Contd.) Is there anything called native hydrocarbon degrader? If so, How?

Slide 30: 

Naturally Hydrocarbons have been added to the environment by pine tree droppings and natural seeps for millions of years Carbon-hydrogen bonds of hydrocarbons yield very high energy This became an excellent energy source that allowed a complex community to evolve over millions of years to degrade these hydrocarbons Also, isolated in Prince William Sound that degrade petroleum and it’s products

Slide 31: 

So, they expected accumulation of these organisms in the oil spilled areas Found 10,000-fold increase of oil-eating microbes in contaminated areas Acinetobacter Calcoaceticus Arthrobacter/Brevibacterium sp. Oceanospirillum sp. Pseudomonas putida Pseudomonas sp. Trichosporon sp. Alcaligenes sp. Flavobacter/Cytophaga sp. Pseudomonas fluorescens Pseudomonas stutzeri Pseudomonas vesicularis Vibro sp. What were the organisms found? This large community of microorganisms made it unnecessary to introduce microbes. Then type of Bioremediation?

Any other limiting factors? : 

Any other limiting factors? Scientists knew that biodegradation was occurring. But to speed up the process… Wanted to know the limiting factors Nitrogen and Phosphorous in seawater are severely limiting to microbial hydrocarbon degradation (had already been published) Is Oxygen a limiting factor? – No Is Temperature a limiting factor? - Yes (ranging from 32oF in the winter to as high as 68oF in the summer) – slows down the process

Alaskan Bioremediation Project : 

Alaskan Bioremediation Project Started on May of 1989 on Knight Island This project was designed to determine the feasibility of biodegradation enhancement by adding fertilizers Nutrient applications began on June 8, 1989 at Snug Harbor, located on the southeastern side of the island Selected as the first test site because it had a long length of shoreline with several beach materials

Positive Results? : 

Positive Results? Approximately after 10 to 14 days visual reductions in the amount of oil covering the rocks were apparent also a visual reduction in the oil-covered sand and gravel beach Further tests proved that this reduction is due to BIOREMEDIATION and to prove that this is not due to chemical cleaning.

Application : 

Application Based on the promising results of the initial field test at Snug Harbor and the absence of any adverse effects on the area’s ecosystem, EPA recommended in July that the bioremediation efforts be scaled up during summer. By the end of the summer of 1989, 74 miles of shoreline were treated with nutrient applications

Bioremediation Strategies : 

Bioremediation Strategies In situ Bioremediation (at the site) Ex situ Bioremediation (away from the site)

In situ bioremediation types : 

In situ bioremediation types Bioventing involves supplying air and nutrients through wells to contaminated soil to stimulate the indigenous bacteria. Biosparging involves the injection of air under pressure below the water table to increase groundwater oxygen concentrations and enhance the rate of biological degradation of contaminants by naturally occurring bacteria.

Slide 38: 

Bioaugmentation involves practice of adding specialized microbes or their enzyme preparation to polluted matrices to accumulate transformation or stabilization of specific pollutants

Ex situ bioremediation types : 

Ex situ bioremediation types Landfarming involves a simple technique in which contaminated soil is excavated and spread over a prepared bed and periodically tilled until pollutants are degraded.

Slide 40: 

Composting Traditional method to convert waste into household usable materials involves combining contaminated soil with nonhazardous organic amendants such as manure or agricultural wastes. The presence of these organic materials supports the development of a rich microbial population and elevated temperature characteristic of composting.

Slide 41: 

Phytoremediation Where did they get the concept from? Evolutionary some plants have evolved the capacity to take up and accumulate selected metals in their shoots in levels that are toxic to ordinary plants Some plants have developed symbiotic association with microbes that can degrade certain pollutants to compounds which are non-hazardous to the environment

Slide 42: 

Introduction Although the application of microbe biotechnology has been successful with petroleum-based constituents, microbial digestion has met limited success for widespread residual organic and metals pollutants. Vegetation- based remediation shows potential for accumulating, immobilizing, and transforming a low level of persistent contaminants. In natural ecosystems, plants act as filters and metabolize substances generated by nature. Phytoremediation is an emerging technology that uses plants to remove contaminants from soil and water .

Phytoremediation : 

Phytoremediation Phytoextraction 1 Phytotransformation 2 Phytostabilization 3 Phytodegradation Rhizofiltration 4 5 Term coined in 1991 5 types based on the fate of contaminants

Phytoextraction : 

Phytoextraction Also called Phytoaccumulation A process used by the plants to accumulate contaminants into the roots and shoots or leaves. Technique saves tremendous remediation cost by accumulating low levels of contaminants from a widespread area (usually metals)

Phytotransformation : 

Phytotransformation Also called Phytodegradation refers to the uptake of organic contaminants from soil, sediments, or water and, subsequently, their transformation to more stable, less toxic, or less mobile form. Metal chromium can be reduced from hexavalent to trivalent chromium, which is a less mobile and non-carcinogenic form.

Phytostabilization : 

Phytostabilization Leachable (permeate gradually) constituents are adsorbed and bound into the plant structure so that they form a stable mass of plant from which the contaminants will not reenter the environment

Phytodegradation : 

Phytodegradation Also called rhizodegradation is the breakdown of contaminants through the activity existing in the rhizosphere. Due to the presence of proteins and enzymes produced by the plants or by soil organisms such as bacteria, yeast, and fungi. a symbiotic relationship that has evolved between plants and microbes Plants provide nutrients necessary for the microbes to thrive, while microbes provide a healthier soil environment.

Rhizofiltration : 

Rhizofiltration is a water remediation technique that involves the uptake of contaminants by plant roots used to reduce contamination in natural wetlands and estuary areas The wide part of a river where it nears the sea; fresh and salt water mix

Phytoremediation is well suited for : 

Phytoremediation is well suited for use at very large field sites where other methods of remediation are not cost effective or practicable use at sites with a low concentration of contaminants where only polish treatment is required over long periods of time in conjunction with other technologies where vegetation is used as a final cap and closure of the site

Limitations : 


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