BIOTECHNOLOGY AND ENVIRONMENT

Chapter Contents What Is Bioremediation? Bioremediation Basics Cleanup Sites and Strategies Applying Genetically Engineered Strains to Clean Up the Environment Environmental Disasters: Case Studies in Bioremediation Future Strategies and Challenges for Bioremediation

What Is Bioremediation? Biodegradation - the use of living organisms such as bacteria, fungi, and plants to degrade chemical compounds Bioremediation – process of cleaning up environmental sites contaminated with chemical pollutants by using living organisms to degrade hazardous materials into less toxic substances

Why is bioremediation important?? The quality of life directly related to the cleanliness and health of environment. Environmental chemicals can influence our genetics: some chemicals can act as mutagens- leading to disease conditions- reason to concern on the consequences of environmental chemicals on human and animals. Bioremediation is Way to clean up the environment thru cheaper and cleaner approach. To convert harmful pollutants into relatively harmless materials such as carbon dioxide, chloride, water, and simple organic molecules Bioremediation can be conducted at the site of contamination- complete clean up is possible.

What Is Bioremediation? Biotechnological approaches are essential for; Detecting pollutants Restoring ecosystems Learning about conditions that can result in human diseases Converting waste products into valuable energy

Bioremediation Basics What needs to be cleaned up? Soil, water, air, and sediment Pollutants enter environment in many different ways Tanker spill, truck accident, ruptured chemical tank at industrial site, release of pollutants into air

Eg: leaking of chemical tanker Eg: leaking of chemical tanker. Initially, only contaminate surface and subsurface soils; however, if large amounts of chemicals released and undetected, chemicals may move deeper into the soils. Following heavy rains, these chemicals may create runoff that can contaminate the adjacent surface water supplies; ponds, river Chemicals may leak into the ground creating leachate. Leachate can cause contamination of subsurface water- common source of drinking water.

Bioremediation Basics Chemicals in the Environment Carcinogens – Compounds that cause cancer Mutagens Cause skin rashes, birth defects Poison plant and animal life

Bioremediation Basics

Bioremediation Basics Fundamentals of Cleanup Reactions Microbes convert chemicals into harmless substances by either Aerobic metabolism (require oxygen) or anaerobic metabolism (do not require oxygen) Both processes involve oxidation and reduction reactions Oxidation – removal of one or more electrons from an atom or molecule Reduction –addition of one or more electrons to an atom or molecule During redox reaction, oxidizing agents (electron acceptor) accept electrons and become reduced.

Bioremediation Basics

Aerobic biodegradation In environments such as surface water and soil, O2 is readily available Aerobic bacteria degrade pollutants by oxidizing chemical compounds. O2 can oxidized variety of chemicals including organic molecules such as petroleum products. In the process, O2 is oxidized into water. Microbes can further degrade the compounds into simpler molecules; CO2 and methane. Bacteria derived energy from the process, producing more bacterial cells.

Anaerobic degradation In some environments where O2 is lacking, biodegradation may take place thru anaerobic biodegradation. Also requires redox reaction but using other molecules as electron acceptors. Fe3+ , SO42+ , NO3- are common electron acceptors.

Metabolizing microbes Ability of microbes to degrade different chemicals effectively depends on many conditions Types of chemical, temp, zone of contamination, nutrients influence the effectiveness and rates of biodegradation/ The search for useful microbes for bioremediation is often carried out at the site of contamination. Anything living in a polluted sites will have developed the resistance to the polluting chemicals. Indigenous microbes- found naturally in the contaminated area.

The most common and effective microbes for bioremediation Indigenous microbes The most common and effective microbes for bioremediation Indigenous microbes found naturally in the contaminated site Isolated, grown and studied in the lab Released back into the cleanup environments in large scale

Bioremediation Basics Stimulating Bioremediation Many indigenous microbes are very effective in biodegradation There are a few strategies used to enhance the effectiveness of the microbes. Nutrient enrichment (fertilization) – fertilizers are added to a contaminated environment to stimulate the growth of indigenous microorganisms that can degrade pollutants. - Adding more nutrients, more microbes and grow rapidly, therefore, increases the rate of reaction. Bioaugmentation (seeding) –bacteria are added to the contaminated environment to assist indigenous microbes with biodegradative processes

Phytoremediation: using plants to clean up the contaminated soils. Chemical pollutants are taken up by roots of the plants as they absorb water from the contaminated soil. The contaminated plants are disposed off or burned. It can be low-cost, effective and low-maintainance approach. Disadvantages: only surface layers can be cleaned up and may take several years to clean up.

Cleanup sites and strategies Soil cleanup Ex situ bioremediation (removing of contaminated soil to other locations for treatments) In situ bioremediation (cleaning up at the contamination site without removal of soil to other location)

In situ bioremediation Preferred method; Less expensive- soil and water does not have to excavated or pump out of the site and larger area can be treated. Rely on stimulating microbes in the contaminated soil or water Those that require aerobic degradation: involve bioventing Bioventing: pumping air/H2O2 into the contaminated soil. H2O2 is used because it can be degraded into water and O2 easily to provide microbes with source of o2. Fertilizers may also be added to stimulate the growth of bacteria and degrading activities

Disadvantages of in situ bioremediation: not suitable for solid clay and dense rocky soils. Soils that have been contaminated with chemicals persist for long periods of time can take years to clean up this way

Ex situ bioremediation Slurry-phase bioremediation Moving contaminated soil to another site, mixing with fertilizer and water in bioreactors in which conditions can be controlled and monitored. Solid phase bioremediation (Composting, landfarming and biopiles) More time consuming and requires a large amount of space.

Solid phase bioremediation composting Degrade household wastes, degrade chemical pollutant in contaminated soils. Hay, strawa added to soil to provide bacteria with nutrients that help bacteria to degrade chemicals. landfarming Spreading contaminated soils on a pad so that water and leachates can leak out of the soil. Primary goal: to collect leachate so that polluted water cannot further contaminate the environment biopiles When chemical in the soil can evaporate easily and when microbes in the soil pile degrade the pollutant rapidly A few bulking agents are added and fans and piping systems are used to pump air into or over the pile. As chemicals in the pile evaporate, the vacuum airflow pull the chemical vapors away from pile and released into the air/filter.

9.3 Cleanup Sites and Strategies

Cleanup Sites and Strategies Bioremediation of water Wastewater treatment Groundwater cleanup

Wastewater treatment It is a well known application of bioremediation The purpose is to remove; Human sewage fecal material paper wastes Soaps Detergents Other household chemicals

Wastewater treatment: in typical septic system Human sewage and wastewater from a household move thru plumbing system out to septic tank Feces and paper wastes are ground and filtered into small particle. Settle out into a tanks to create mud like material- sludge Water flow out of the tank called effluent and sent to aerating tanks- aerobic bacteria oxidize organic materials in the effluent Effluent is passed into activated sludge system –tank containing microbes. Effluent then disinfected with chlorine and released to lake/river Sludge is pumped into anaerobic digester tanks. Anaerobe microbes degrade the sludge producing methane gas. Resulting sludge can be used as fertilizers

Cleanup Sites and Strategies

Groundwater cleanup Groundwater- source of drinking water may be contaminated with pollutants. Polluted groundwater can be difficult to clean up because it get trapped in soil and rocks. Ex situ and in situ approaches are used in combination. For eg: groundwater contaminated by gasoline/oil These pollutants rise onto the surface of the aquifer, It can be directly pumped out but the portion mixed with groundwater must be pumped to the surface and passed thru bioreactors Inside bioreactor: bacteria in biofilms growing over a screen degrade the pollutants The clean water containing fertilizer, bacteria pumped back into the aquifer for in-situ hybridization.

Cleanup Sites and Strategies

Cleanup Sites and Strategies Turning Wastes into Energy Wastes from landfills are used to produce energy Scientists are working to produce bioreactors that contain anaerobic bacteria that can convert food wastes into soil nutrients and methane gas. Methane gas used to produce electricity Soil nutrients can be sold commercially as fertilizers Anaerobes in sediment that use organic molecules to generate energy Electicigens – electricity-generating microbes

Applying Genetically Engineered Strains to Clean Up the Environment Many indigenous microbes cannot degrade certain types chemicals: highly toxic compounds. Radioactive compounds- kill microbes thus preventing biodegradation. The development of genetic engineering- enable scientists to create genetically engineered microbes that capable of improving bioremediation process.

Petroleum eating bacteria Created in 1970s Isolated strains of pseudomonas from contaminated soils Contained plasmids that encoded genes for breaking down the pollutants

9.4 Applying Genetically Engineered Strains to Clean Up the Environment E. coli to clean up heavy metals Copper, lead, cadmium, chromium, and mercury Genetically modified strain of E. coli that can degrade heavy metals. Biosensors – bacteria capable of detecting a variety of environmental pollutants Genetically Modified Plants and Phytoremediation Plants that can remove RDX and TNT

Environmental Disasters: Case Studies in Bioremediation jet fuel and Hanahan, south carolina 80,000 gallons kerosene leaked. After series of clean up- spill could not contained from soaking thru the sandy soil and contaminating the water after 10 years, reached residential areas- removing contaminated soil was impractical- large area Scientists found that indigenous microbes were degrading the fuel and adding fertilizers increasing the rate of biodegradation

Future Strategies and Challenges for Bioremediation Recovering Valuable Metals Metals such as copper, nickel, boron and gold. Many microbes can convert metal products into insoluble substances called metal oxides that will accumulate in their cells/cell surface. For eg: many manufacturing processes using silver and gold plating techniques that create waste solutions with suspended gold/silver particles. Microbes can be used to recover this metals.

Future Strategies and Challenges for Bioremediation Bioremediation of radioactive wastes Removing radioactive wastes from environment. Although radioactive kill materials kill a majority of microbes, some strains of bacteria have demonstrated a potential for degrading radioactive chemicals. For eg: Geobacter can reduce soluble uranium in groundwater into insoluble uranium effectively, immobilizing the radioactivity.