Biostimulation
Encyclopedia
Biostimulation involves the modification of the environment to stimulate existing bacteria
capable of bioremediation
. This can be done by addition of various forms of rate limiting nutrient
s and electron acceptors, such as phosphorus
, nitrogen
, oxygen
, or carbon
(e.g. in the form of molasses
). Additives are usually added to the subsurface through injection wells, although injection well technology for biostimulation purposes is still emerging. Removal of the contaminated material is also an option, albeit an expensive one. Biostimulation can be enhanced by bioaugmentation
. This process, overall, is referred to as bioremediation
and is an EPA
-approved method for reversing the presence of oil or gas spills.
The primary advantage of biostimulation is that bioremediation will be undertaken by already present native microorganisms that are well-suited to the subsurface environment, and are well distributed spatially within the subsurface. The primary disadvantage is that the delivery of additives in a manner that allows the additives to be readily available to subsurface microorganisms is based on the local geology of the subsurface. Tight, impermeable subsurface lithology
(tight clay
s or other fine-grained material) make it difficult to spread additives throughout the affected area. Fractures in the subsurface create preferential pathways in the subsurface which additives preferentially follow, preventing even distribution of additives.
Recently a number of products have been introduced which allow popular use of bioremediation using biostimulative methods. They may harness local bacteria using biostimulation by creating a hospitable environment for hydrocarbon-devouring microorganisms, or they may introduce foreign bacteria into the environment as a direct application to the hydrocarbon. While the jury is out as to whether either is particularly more effective than the other, prima fascie consideration suggests the introduction of foreign bacteria to any environment stands a chance of mutating organisms already present and affecting the biome.
Investigations to determine subsurface characteristics (such as natural groundwater
velocity during ambient conditions, hydraulic conductivity
of the subsurface, and lithology of the subsurface) are important in developing a successful biostimulation system. In addition, a pilot-scale study of the potential biostimulation system should be undertaken prior to full-scale design and implementation.
However, some biostimulative agents may be used in chaotic surfaces such as open water and sand so long as they are [oleophilic], meaning that they bond
exclusively to hydrocarbons, and basically sink in the water column, bonding to oil, where they then float to the water's surface, exposing the hydrocarbon to more abundant sunlight
and oxygen
where greater micro-organic aerobic
activity can be encouraged. Some consumer-targeted biostimulants bond possess this quality, others do not.
With the introduction of therapeutic lasers, biostimulation also refers to the application of photon energy to injured tissue, in order to achieve a stimulatory and regenerative effect at the molecular level.
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
capable of bioremediation
Bioremediation
Bioremediation is the use of microorganism metabolism to remove pollutants. Technologies can be generally classified as in situ or ex situ. In situ bioremediation involves treating the contaminated material at the site, while ex situ involves the removal of the contaminated material to be treated...
. This can be done by addition of various forms of rate limiting nutrient
Nutrient
A nutrient is a chemical that an organism needs to live and grow or a substance used in an organism's metabolism which must be taken in from its environment. They are used to build and repair tissues, regulate body processes and are converted to and used as energy...
s and electron acceptors, such as phosphorus
Phosphorus
Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks...
, nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...
, oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
, or carbon
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
(e.g. in the form of molasses
Molasses
Molasses is a viscous by-product of the processing of sugar cane, grapes or sugar beets into sugar. The word molasses comes from the Portuguese word melaço, which ultimately comes from mel, the Latin word for "honey". The quality of molasses depends on the maturity of the sugar cane or sugar beet,...
). Additives are usually added to the subsurface through injection wells, although injection well technology for biostimulation purposes is still emerging. Removal of the contaminated material is also an option, albeit an expensive one. Biostimulation can be enhanced by bioaugmentation
Bioaugmentation
Bioaugmentation is the introduction of a group of natural microbial strains or a genetically engineered variant to treat contaminated soil or water....
. This process, overall, is referred to as bioremediation
Bioremediation
Bioremediation is the use of microorganism metabolism to remove pollutants. Technologies can be generally classified as in situ or ex situ. In situ bioremediation involves treating the contaminated material at the site, while ex situ involves the removal of the contaminated material to be treated...
and is an EPA
United States Environmental Protection Agency
The U.S. Environmental Protection Agency is an agency of the federal government of the United States charged with protecting human health and the environment, by writing and enforcing regulations based on laws passed by Congress...
-approved method for reversing the presence of oil or gas spills.
The primary advantage of biostimulation is that bioremediation will be undertaken by already present native microorganisms that are well-suited to the subsurface environment, and are well distributed spatially within the subsurface. The primary disadvantage is that the delivery of additives in a manner that allows the additives to be readily available to subsurface microorganisms is based on the local geology of the subsurface. Tight, impermeable subsurface lithology
Lithology
The lithology of a rock unit is a description of its physical characteristics visible at outcrop, in hand or core samples or with low magnification microscopy, such as colour, texture, grain size, or composition. It may be either a detailed description of these characteristics or be a summary of...
(tight clay
Clay
Clay is a general term including many combinations of one or more clay minerals with traces of metal oxides and organic matter. Geologic clay deposits are mostly composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure.- Formation :Clay minerals...
s or other fine-grained material) make it difficult to spread additives throughout the affected area. Fractures in the subsurface create preferential pathways in the subsurface which additives preferentially follow, preventing even distribution of additives.
Recently a number of products have been introduced which allow popular use of bioremediation using biostimulative methods. They may harness local bacteria using biostimulation by creating a hospitable environment for hydrocarbon-devouring microorganisms, or they may introduce foreign bacteria into the environment as a direct application to the hydrocarbon. While the jury is out as to whether either is particularly more effective than the other, prima fascie consideration suggests the introduction of foreign bacteria to any environment stands a chance of mutating organisms already present and affecting the biome.
Investigations to determine subsurface characteristics (such as natural groundwater
Groundwater
Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of rock formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock...
velocity during ambient conditions, hydraulic conductivity
Hydraulic conductivity
Hydraulic conductivity, symbolically represented as K, is a property of vascular plants, soil or rock, that describes the ease with which water can move through pore spaces or fractures. It depends on the intrinsic permeability of the material and on the degree of saturation...
of the subsurface, and lithology of the subsurface) are important in developing a successful biostimulation system. In addition, a pilot-scale study of the potential biostimulation system should be undertaken prior to full-scale design and implementation.
However, some biostimulative agents may be used in chaotic surfaces such as open water and sand so long as they are [oleophilic], meaning that they bond
Chemical bond
A chemical bond is an attraction between atoms that allows the formation of chemical substances that contain two or more atoms. The bond is caused by the electromagnetic force attraction between opposite charges, either between electrons and nuclei, or as the result of a dipole attraction...
exclusively to hydrocarbons, and basically sink in the water column, bonding to oil, where they then float to the water's surface, exposing the hydrocarbon to more abundant sunlight
Sunlight
Sunlight, in the broad sense, is the total frequency spectrum of electromagnetic radiation given off by the Sun. On Earth, sunlight is filtered through the Earth's atmosphere, and solar radiation is obvious as daylight when the Sun is above the horizon.When the direct solar radiation is not blocked...
and oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
where greater micro-organic aerobic
Aerobic organism
An aerobic organism or aerobe is an organism that can survive and grow in an oxygenated environment.Faculitative anaerobes grow and survive in an oxygenated environment and so do aerotolerant anaerobes.-Glucose:...
activity can be encouraged. Some consumer-targeted biostimulants bond possess this quality, others do not.
With the introduction of therapeutic lasers, biostimulation also refers to the application of photon energy to injured tissue, in order to achieve a stimulatory and regenerative effect at the molecular level.