Algae, Tree, Herbs, Bush, Shrub, Grasses, Vines, Fern, Moss, Spermatophyta, Bryophyta, Fern Ally, Flower, Photosynthesis, Eukaryote, Prokaryote, carbohydrate, vitamins, amino acids, botany, lipids, proteins, cell, cell wall, biotechnology, metabolities, enzymes, agriculture, horticulture, agronomy, bryology, plaleobotany, phytochemistry, enthnobotany, anatomy, ecology, plant breeding, ecology, genetics, chlorophyll, chloroplast, gymnosperms, sporophytes, spores, seed, pollination, pollen, agriculture, horticulture, taxanomy, fungi, molecular biology, biochemistry, bioinfomatics, microbiology, fertilizers, insecticides, pesticides, herbicides, plant growth regulators, medicinal plants, herbal medicines, chemistry, cytogenetics, bryology, ethnobotany, plant pathology, methodolgy, research institutes, scientific journals, companies, farmer, scientists, plant nutrition
Select Language:
 
 
 
 
Main Menu
Please click the main subject to get the list of sub-categories
 
Services offered
 
 
 
 
  Section: General Biotechnology / Biotechnology & Environment
 
 
Please share with your friends:  
 
 

Environmental Biotechnology

 
     
 

In situ Bioremediation
In situ bioremediation is the clean up approach which directly involves the contact between microorganisms and the dissolved and sorbed contaminants for biotransformation (Bouwer and Zehnder, 1993). Biotransformation in the surface environment is a very complex process. Potential advantages of in situ bioremediation methods include minimal site disruption, simultaneous treatment of contaminated soil and ground water, minimal exposure of public and site personnel, and low costs. But the disadvantages are (i) time consuming method as compared to other remedial methods, (ii) seasonal vatiation of microbial activity resulting from direct exposure to prevailing environmental factors, and lack of control of these factors, and (iii) problematic application of treatment additives (nutrients, surfactants and oxygen) (Christodoultos and Kontsospyros, 1998). The microorganisms act well only when the waste materials help them to generate energy and nutrients to build up more cells. When the native microorganisms lack biodegradation capacity, genetically engineered microorganisms (GEMs) may be added to the surface during in situ bioremediation. But stimulation of indigenous microorganisms is preferred over addition of GEMs. There are two types of in situ bioremediation: intrinsic and engineered in situ bioremediation.

Intrinsic Bioremediation
Conversion of environmental pollutants into the harmless forms through the innate capabilities of naturally occurring microbial population is called intrinsic bioremediation. However, there is increasing interest on intrinsic bioremediation for control of all or some of the contamination at waste sites. The intrinsic i.e. inherent capacity of microorganisms to metabolize the contaminants should be tested at laboratory and field levels before use for intrinsic bioremediation. Through site monitoring programmes progress of intrinsic bioremediation should be recorded time to time. The conditions of site that favor intrinsic bioremediation are ground water flow throughout the year, carbonate minerals to buffer acidity produced during biodegradation, supply of electron acceptors and nutrients for microbial growth and absence of toxic compounds. The other environmental factors such as pH, concentration, temperature and nutrient availability determine whether or not biotransformation takes place. Bioremediation of waste mixtures containing metals such as Hg, Pb, As and cyanide at toxic concentration can create problem (Madsen, 1991).

The ability of surface bacteria to degrade a given mixture of pollutants in ground water is dependent on the type and concentration of compounds, electron acceptor and duration of bacteria exposed to contamination. Therefore, ability of indigenous bacteria degrading contaminants can be determined in laboratory by plate count and microcosm studies.

Engineered in situ Bioremediation
Intrinsic bioremediation is satisfactory at some places, but it is slow process due to poorly adapted microorganisms, limited ability of electron acceptor and nutrients, cold temperature and high concentration of contaminants. When site conditions are not suitable, bioremediation requires construction of engineered systems to supply materials that stimulate microorganisms. Engineered in situ bioremediation accelerates the desired biodegradation reactions by encouraging growth of more microorganisms via optimizing physico-chemical conditions (Bouwer et al, 1998). Oxygen and electron acceptors (e.g. NO31- and SO42-) and nutrients (e.g. nitrogen and phosphorus) promote microbial growth in surface.

  Surface treatment using above-ground reactor, injection of oxygen, acid nutrient and extraction walls.  
 

Fig. 21.1. Surface treatment using above-ground reactor, injection of oxygen, acid nutrient and extraction walls.

 
 

 Content

Bioremediation

 

In situ bioremediation

 

 

Intrinsic bioremediation

 

 

Engineered in situ bioremediation

 

Ex situ bioremediation

 

 

Solid phase system (composting, composting process)

 

 

Slurry phase system (aerated laggons, low shear airlift reactor)

 

 

Factors affecting slurry phase bioremediation

 

Bioremediation of hydrocarbon

 

 

Use of mixture of bacteria

 

 

Use of genetically engineered bacterial strains 

 

Bioremediation of Industrial wastes

 

 

Bioremediation of dyes

 

 

Bioremediation of heavy metals

 

 

Bioremediation of coal waste through VAM fungi

 

Bioremediation of xenobiotics

 

 

Microbial degradation of xenobiotics

 

 

Gene manipulation of pesticide-degrading microorganisms

Utilization of sewage, and agro-wastes

 

Production of single cell protein

 

Biogas from sewage

 

Mushroom production on agro-wastes

 

Vermicomposting

Microbial leaching (bioleaching)   

 

Microorganisms used in leaching

 

Chemistry of leaching

 

 

Direct leaching

 

 

Indirect leaching

 

Leaching process (slope leaching heap leaching in situ leaching)

 

Examples of bioleaching

 

 

Copper leaching

 

 

Uranium leaching

 

 

Gold and silver leaching

 

 

Silica leaching

Hazards of environmental engineering

 

Survival of released GMMs in the environment

 

 

Adaptive mutagenesis in GMMs

 

 

Gene transfer from GMMs into other microorganisms

 

 

Gene transfer via conjugative transposons

 

 

Effect of environmental factors on gene transfer

 

Ecological impact of GMMs released into the environment

 

 

Growth inhibition of natural strains

 

 

Growth stimulation of indigenous strains

 

 

Replacement of natural strains

 

Monitoring of GEMs in the environment

 

 

Risk assessment of the GEMs released into the environment

When contamination is deeper, amended water is injected through wells. But in some in situ bioremediation systems both extraction and injection wells are used in combination to control the flow of contaminated ground water combined with above-ground bioreactor treatment and subsequent reinjection of nutrients spiked effluent are done (Fig. 21.1).

 
     
 
 
     



     
 
Copyrights 2012 © Biocyclopedia.com | Disclaimer