EXXON CHEMICAL COMPANY February 24, 1993 Hasmukh C. Shah, Ph.D. Chemical Manufacturers Association 2501 M Street, NW Washington, DC 20037 Dear Has: Enclosed are materials I was able to gather for possible inclusion in the oilfield microbiocides education package for the EPA. I hope some of them may be useful. Sincerely yours, Oliver Bourgeois Material Safety Chemis Enclosure cc: Gary Bond 8230 Stedman, Houston, Texas 77029-3999 A Division of Exxon Corporation
IDENTIFICATION OF MICROORGANISMS FOUND IN INDUSTRIAL AND OILFIELD WATERS Many microscopic organisms exist in the world in which we live. Bacteria are just one of the groups of microorganisms that surround Bacteria are us. found on our skin, in our mouths, stomachs, intestines, and in the water we drink and the air we breathe. When the word bacteria is used, most people think of "germs", disease, or some other unpleasant association. While it is true that many bacteria are harmful to man, they are vastly out-numbered by the bacteria that are beneficial to man, and required in our daily life processes. Bacteria are microscopic, unicellular organisms that are capable of carrying out all functions necessary for life and reproduction when they are placed in a favorable environment. Most bacteria measure less than 8 microns in length and 1 micron in width. In order to place bacteria in the proper perspective in oil and gas production, one must have an understanding of: (1) the classifi- cations of microorganisms (2) their requirements for sustaining life and reproduction (3) how they can be identified (4) the problems associated with bacteria in the petroleum industry. CLASSIFICATION OF MICROORGANISMS The simplest form of microorganisms can be grouped into three classifi- cations: 1. Algae - contains chlorophyll - require sunlight 2. Fungi - do not contain chlorophyll 3. Bacteria - have some properties common to both algae and fungi Bacteria comprise the broad class of microorganisms of greatest interest in the petroleum industry, and are normally classified as belonging to one of two groups. Group I aerobic bacteria - bacteria which require free oxygen for growth. Growth II are anaerobic bacteria - bacteria that require the absence of free oxygen for growth.
-2- aerobic. forming bacteria and iron bacteria are They cannot Slime reproduce in an oxygen free environment. grow or reducing bacteria are anaerobic. They require an oxygen Sulfate for growth and reproduction. Sulfate environment reducing free can and do exist in systems that contain free oxygen, bacteria but are scale, bacteria located under deposits such as mud, the corrosion by-products, or some other sheath which shields them from the oxygen bearing water. PHYSICAL REQUIREMENTS OF MICROORGANISMS Bacteria have been found in many different types of environments. sulphur They have been found on the ocean floors, in hot springs, and the arctic seas. Each of these environments however met in certain requirements which were necessary for the growth and of encountered. A particular reproduction the bacteria species of requires a particular environment, and the bacteria environment must specific needs of the bacteria. meet the Temperature is one of the controlling factors that is most important for all to all forms of life. The limiting temperatures forms of can be effectively utilized life is the temperature at which enzymes life processes. are protein complexes to promote the Enzymes which catalyze the chemical reactions necessary for sustaining life. Bacteria temperature range. flourish under an extremely broad Depending on the can g6ow at temperatures as low as O°F(-17.8°C) and species, they as (82.2 C). high as 180°F species of bacteria will grow at temperatures within a certain Each The temperature which allows the most rapid growth is called range. the optimum - growth temperature . The extremes of the growth range called the minimum and maximum growth temperatures are temperatures. influences Gaseous constituents are another factor which the growth are oxygen and of microorganisms. The two most important gases carbon dioxide. Bacteria display a variety of patterns of response to free oxygen, which results in their being classified into one of four groups: I are the Group aerobic microorganisms - they grow in presence of free oxygen. Group II are anaerobic microorganisms they grow in the absence of - free oxygen.
are Group III facultative microorganisms - they grow in either the absence presence or of free oxygen. Group IV are microaerophilic microorganisms - they grow in the presence of minute quantities of free oxygen. increase of An carbon dioxide content facilitates the growth of some microorganisms, and has no effect on others. pH of the environment greatly affects the growth rate . of micro- organisms . The optimum pH range for most microorganisms is 6.0- 8.0, but they can grow in an environment with a pH as low as 4.0 or as high as 9.0. Microbial enzymes are as sensitive to pH change as they are to temperature change . In addition to affecting the enzyme action, pH also affects the state of colloidal suspension of protoplasm and the permeability of the cellular membrane. Osmotic pressure is the driving force behind the passage of fluid through the cellular membrane , as in the process of osmosis. Osmosis tends to equalize the concentration of dissolved substances surrounding the cell and the fluid within the cell . Sodium chloride is generally the most common dissolved substance which affects osmotic pressure . Microorganisms receive their nutritional requirements by the process of osmosis , thus if the osmotic pressure is altered in some manner the microorganisms cannot continue to grow and reproduce. Many fresh-water species cannot grow in an environment with salinities in excess of one percent . However, organisms from either fresh- water or salt - water environments can adapt to the environment of the other. Thus , microorganisms exist in almost every environment, regardless of osmotic pressure. Radiant energy ( sunlight ) is required by algae and a few species of bacteria . Sunlight is required by algae in order that the metabolic process can be carried out for their life functions . The majority of bacteria do not require radiant energy for their life processes, and in fact , high concentrations of X-Rays and ultraviolet light can be lethal to them. Sublethal doses of radiant energy can cause microorganisms to form mutations and give rise to new species of microcrganisms. Hydrostatic pressure changes can be detrimental to some species of microorganisms. Death can occur to many species when they are subjected to pressures of 9,000 pounds per square inch, while many other species are injured when subjected to pressures of 5,000 pounds per square inch.
-4- is a relationship between pressure There and temperature . Unduly temperatures may be high thought of as causing deleterious expansion the enzymes within the cellular structure of of the microorganism. Increased pressure tends to lessen the expansion of the enzymes and thus prevents or offsets the unfavorable effect caused by increased temperatures . Some deep sea bacteria and others found in producing oil and gas wells appear to be favorably influenced by high pressures . Some bacteria are not injured by pressures up to 150,000 pounds per square inch, and these are said to be barophilic ( pressure - loving). NUTRITIONAL REQUIREMENTS OF MICROORGANISMS All living organisms require nutrition to sustain life. While the requirements vary from species to species , they are shared by all living organisms. An energy source is required by all forms of life. Green plants radiant energy and are utilize designated as phototrophs. Forms of life which are not capable of using radiant energy must rely on chemical reactions to provide energy and are designated as chemotrophs. Chemotrophs are broken down into two other classifications and are to be either autotrophs said or heterotrophs . Autotrophs utilize inorganic compounds as their sole source of energy , while heterotrophs require organic compounds as a source of energy. A carbon source is required by all organisms . Most microorganisms require organic carbon. Algae and a few other bacteria require inorganic carbon in the form of carbon dioxide and carbonates. Some forms require the more complex form such as carbohydrates. Nitrogen is required by all living organisms. Algae and a few other microorganisms use nitrogen in the form of inorganic salts. Other forms utilize nitrogen from the atmosphere . Most organisms however require nitrogen in the organic form of protein. Metallic ions such as sodium potassium , calcium, magnesium, iron, copper, and phosphorus are needed by all organisms . While the amounts required are mere trace amounts, life cannot be sustained without them. The metallic elements are present in most natural environments. Vitamins and vitamin - like compounds are utilized by all living organisms . Microorganisms present a unique pattern in this aspect of nutrition. While many microorganisms will not grow unless vitamins are present in the environment, there are others that are capable of
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