Comparative study of microbiological monitoring of water-miscible metalworking fluids

• The ATP-measurement ASTM E2694 has a strong correlation to SPC, for that reason it will be suitable for condition monitoring of in use MWF.
• In use MWFs show a dynamic regarding their micobial diversity and populaton density over time.
• A MWF does not represent a uniform habitat witin the recirculation System.

Microbial activity is one of the primary causes of water-miscible metalworking fluid (MWF) deterioration in application. Although it is impractical to maintain MWF under microbe-free conditions, timely, accurate and easily interpreted microbial contamination condition can substantially reduce the risk of MWF biodeterioration. This paper compares different condition monitoring methods detecting the microbial contamination of MWF related to their speed and precision in laboratory and field samples. Two culture tests (plate count and dip-slides) and two adenosine triphosphate (ATP) test methods were compared. Additionally the matrix assisted laser desorption/ionization time of flight mass spectrometry (MALDI-ToF-MS) is introduced as a method for the identification of bacterial strains isolated from MWF. The results clearly indicate that MWF monitoring is in need of standardization concerning sampling, area of measurement, and analysis of determinable cell counts as well as species communities.