| Soils and ground water at many industrial, commercial, and military facilities throughout the United States have been contaminated with petroleum based hydrocarbons, such as lubricants, hydraulic fluids, and fuels, often as a consequence of leakage, accidental spills, or equipment breakdown during active use or storage. To resolve this problem, significant efforts are being made to develop biodegradable lubricants and technologies fully compatible with the environment. This paper presents the results of investigation conducted on environmentally acceptable hydraulic fluids and lubricating greases found on the market. It discusses laboratory evaluation of these biodegradable materials formulated with synthetic esters or vegetable oils. Measured result reveal that the vegetable-based hydraulic fluids exhibit high biodegradability under an aerobic aquatic biotreatment condition. Synthetic ester-based lubricating greases also exhibited higher biodegradability than the conventional petroleum-based products. The general behavior of biodegradation rates was found to correlate closely to the growth rate of bacteria in batch reactors. The influence of water solubility, viscosity, and biodegradable additives on biodegradability of lubricants are also discussed. A new bio-kinetic model was developed to predict the half-life of biodegradation for lubricants. This bio-kinetic model did not correlate to oxidation-kinetic model due to its enzyme process. The performance characteristics of EA hydraulic fluids and greases were developed based on experimental data and existing EA lubricant technology. The additives used in biodegradable lubricants are also discussed in this paper. |
