Metalworking Fluids Disinfection by the Ozone - Kristína Ger...

During the cutting process, the metalworking fluid is changed due
to chemical reactions between its substances; tool surfaces and
workpieces; the presence of particles and high temperatures on
contact surfaces. Except changes in chemical composition is the
biggest problem with the bacterial contamination. Changes in the
composition and contaminants such as bacteria pose risks to workers
and influence the quality and economy of the whole machining
process. To eliminate bacteria mostly biocides are added to the
tank side however biocides also pose some health risks for the
workers. Tightening legislation creates pressure on the minimizing
of the hazardous substances and therefore the utilization of ozone
instead of biocides for the sterilization of MWFs was studied. The
main aim was to investigate ozone appropriateness for bacteria
elimination for in-use metalworking fluid samples while three
different kinds (semi-synthetic, synthetic and emulsion type) were
tested. It was find out that ozone is able to eliminate bacteria in
all tested samples and types of MWFs. When taken into account ozone
concentration, with increased amount of ozone, shorter treating
time was needed for total bacteria elimination. With decreased
initial bacterial load (from 107 to 104 CFU/ml) treating time
drastically decreased from 20 to only 2 minutes when 15 g/hour of
ozone was applied (in the case of semi-synthetic sample). However
ozone application caused on the other hand also small decrease in
pH value. The pH decrease might be the critical point in the ozone
utilization as a sterilizing agent however the protection function
of the fluid against corrosivity was not harmfully affected during
the experiment in semi-synthetic or synthetic type of fluid.