The microbial ecology of metal-working fluids

Metal working fluids (MWF) have been employed in industry since the time of the Egyptians, for cooling and lubrication during cutting and grinding of metal. There are several types, which can be broadly categorized as oil-based, semisynthetic, and synthetic. It is estimated that in the region of 5 × 109 L−1 are in use in the European Union (EU) at any one time,where they represent in the region of 16% of manufacturing industries costs. The microbiology of MWF is of interest for two contrasting reasons namely: (1) they represent attractive nutrient sources for microorganisms, which lead to bio-deterioration, reducing metal working performance and potentially leading to invasion of human pathogens; (2) in contrast, the same biodegradation activities of potential microbial colonizers can be harnessed and exploited for biotreatment of waste fluids. These contrasting microbiological issues are discussed and details provided. The need for research to develop new MWF formulations that are unattractive to microbial colonization when in use, but with a few chemical modifications can be rendered susceptible to microbial biodegradation, when subsequent disposal of waste fluids is required, is discussed.