MIC 303 INDUSTRIAL AND ENVIRONMENTAL MICROBIOLOGY CHAPTER 11

MIC 303 INDUSTRIAL AND ENVIRONMENTAL MICROBIOLOGY CHAPTER 11 PRINCIPLES OF BIOREMEDIATION

Bioremediation • is any process that uses microorganisms or their enzymes to detoxify or degrade pollutants. • offers the possibility to destroy or render harmless contaminants using natural biological activity. • can be classified as in situ or ex situ. ü In situ bioremediation involves treating the contaminated material at the site (Bioventing, Biosparging, In situ biodegradation, Bioaugmentation). ü Ex situ involves the removal of the contaminated material to be treated elsewhere (Landfarming, Biocomposting, Biopiles, Bioreactors).

In situ Bioremediation Bioventing • Lower cost, less disturbance of the environmental. • Examples of in situ strategies on land treatments: • Bioventing: ü supply air and nutrients through wells to contaminated soil to stimulate indigenous microorganisms. ü It works for simple hydrocarbons. ü Can be used for the contamination site deep under the surface.

Bioventing schematic systems

Biosparging • Involves the injection of air under pressure below the water table to increase groundwater O 2 concentrations → enhance the rate of biological degradation of contaminants by naturally occuring bacteria. • Increases the mixing in in the saturated zone → increases the contact between soil and groundwater.

Biosparging schematic systems

In situ Biodegradation • Supplying O 2 and nutrients by circulating aqueous solutions through contaminated soils to stimulate naturally occuring bacteria to degrade organic contaminants. • It can be used for soil and groundwater.

Bioaugmentation • Addition of specific microbes to degrade of pollutant. • Bioaugmentation involves the introduction of microorganisms into contaminated media to promote the degradation of contaminants. • Bioaugmentation has become particularly popular for increasing the rate and extent of reductive dechlorination of chlorinated solvents.

Oil spill Bioremediation clean up of oiled beach Workers outfitted in safety attire spray benign nutrients for Bioremediation Project on the Exxon Valdez oil spill in Prince William Sound, Alaska. The portion of beach on the left is uncleaned, the beach on the right has been treated with applications of carbon free nutrients (fertilizer).

Ex situ Bioremediation Biocomposting • Compost is a common name for humus, which is the result of the decomposition of organic matter. • Decomposition is performed primarily by microbes, although larger creatures such as worms and ants contribute to the process. • Biocomposting: technique in combining contaminated soil with nonhazardous organic amendants such as manure or agricultural wastes. • The presence of organic materials → supports the development of a rich microbial population.

Biocomposting

Landfarming • A simple techniques which contaminated soil is excavated and spread over a prepared bed and periodically tilled until pollutants are degraded. → to stimulate indigenous biodegradative microorganisms and facilitate their aerobic degradation of contaminants. • The practice is limited to the treatment of 10 -35 cm of soil.

Landfarming schematic systems

Biopiles • A hybrid of landfarming and biocomposting. • Biopiles are designed to optimize the conditions for aerobic bacteria to biodegrade organic contaminants. • used to reduce concentrations of petroleum constituents in excavated soils through the use of biodegradation. • This technology involves heaping contaminated soils into piles (or "cells") and stimulating aerobic microbial activity within the soils through the aeration and/or addition of minerals, nutrients, and moisture. • The enhanced microbial activity results in degradation of adsorbed petroleum-product constituents through microbial respiration.

Biopiles schematic systems

Bioreactors • Slurry reactors/ aqueos reactors used for ex situ treatment of contaminated soil and water pumped up from a contaminated site. • A slurry bioreactor is a vessel used to create a three phase (solid, liquid and gases) mixing condition to increase the bioremediation rate of soil bound and water soluble pollutants. • Rate of biodegradation are greater than in situ techniques → more manageable, controllable and predictable.

Xenobiotics The Degradation of Synthetic Chemicals • Natural organic matter is easily degraded by microbes • Xenobiotics are resistant to degradation. • Examples of xenobiotics compound: Herbicides 2, 4, 5 -T (used to kill shrubs)

Microbial Decomposition of Herbicides