Development of Bio-Kinetic Model for Lubricants

Biodegradation is a natural process caused by the action of microorganisms, in the presence of oxygen, nitrogen, phosphorous, and trace minerals. Organic pollutants can support microbial growth and are converted into a series of oxidation products that generally conclude with carbon dioxide and water. Modern lubricants are formulated with petroleum based oils or ester oils derived from renewable resources, or chemical synthetic sources. Their biodegradation process is somewhat similar to the fermentation process wherein hydrocarbons are converted into carbon dioxide by the action of metabolism of microorganisms. This biodegradation technology is currently used to remove hazardous materials contaminated in soil, sludge and ground water. Wastewater treatment process is one of its application areas. Recently, the ASTM D-2 Subcommittee 12 on Environmental Standard of Lubricants has developed the ASTM D 5864, Standard Test Method for Determining Aerobic Biodegradation of Lubricants and Their Components. This test method is a version of the Organization for Economic Co-Operation and Development (OECD) Sturn test that closely simulates the wastewater biodegradation conditions and was designed to determine the degree of aerobic aquatic biodegradation of lubricants on exposure to an inoculum under laboratory conditions. In this test, the biodegradability of a lubricant is expressed as the percentage of maximum carbon conversion under well -controlled conditions for a period of 28 days. This test method has been widely used to determine the biodegradability of lubricants in the laboratory. The advantages of this test method are to provide a meaningful data and its low cost of the test apparatus. But the test method requires a long testing time, the knowledge of microorganisms, and manpower. In addition, it has very poor precision due to the various and multiple inoculums sources.