'Direct' Monitoring of Bacteria in Metalworking Fluids

With the HSE now requiring a defined ‘COSHH Risk Assessment’ for dealing with bacteria found within water-mix system, set testing procedures with subsequent remedial protocols have to be put in place.

Dipslides pic


A dipslide consists of a plastic carrier coated with a sterile culture medium, which is dipped into the liquid to be tested. It is then incubated to allow microbial growth and the resulting colonies are estimated by reference to a chart on which the density of the resulting colonies is compared to a reference chart to indicate the level of bacterial contamination. Results are expressed in terms of colony-forming units per millilitre (CFU/ml) of fluid.

  • One of the key points of the COSHH risk assessment is that ‘direct’ bacteria monitoring is essential for water based coolants and wash chemicals.

  • Weekly bacteria dipslide tests of every machine using MWF and wash chemicals are stipulated by the HSE.


  • If a history of good control can be demonstrated the HSE will allow the testing period to be varied.

  • The cost of each bacteria dipslides (typically market cost of £1.50).

  • The associated manpower of retrieving the samples.

  • Incubating the test samples for up to 48 hours with final collating of the results and recording.

  • Disposal of the dipslides.

  • The following values indicate what can be regarded as good, reasonable and poor standards of fluid management, and what action should be taken. Monitoring should be used to confirm your high standard of control, as well as indicating increased levels of bacteria at an early stage.

  • <103 CFU/ml Good control – Bacteria are being maintained at low levels. No further action is required;

    103 to <106 CFU/ml Reasonable control – Review control measures to ensure levels of bacteria remain under control.  Risk assessment should specify action to be taken.  Biocides and or cleaning may be indicated.  If biocides are used, professional advice should be obtained, and the concentration of biocides should be monitored;

    > 106 CFU/ml Poor control – Immediate action should be taken in line with the risk assessment.  Normally at very high levels draining and cleaning, should take place.

Our Services

Conduct onsite 'Bacteria Dipslide' testing / sampling

Our engineers undertake onsite sample retrieval of all fluid systems onsite. These dipslide samples are then forwarded onto out technicians for culturing and final analysis.

Technical 'Bacteria Dipslide' incubating and culturing

All retrieved samples are forwarded to our in-house technician team where the incubation period is monitored for up-to 36 hours.  Upon completion, the samples are recorded, with all data being uploaded to the client specific online database.

'Bacteria Dipslide' recording and final analysis via the 'MWFdirect' portal

Upon completion of the incubation and culturing process, the recorded data is then analysed, with recommendations made in accordance with the required HSE bacteria risk assessment.  The data is uploaded to the client specific web-based database, ‘MWFdirect’ which is fully accessible 24 hours a day.  ‘MWFdirect’ has the additional functionality of generating customer specific ‘reports’ from the data inputted, highlighting the specific recommended remedial actions required for your individual systems, all in accordance with the protocols of the client ‘Risk Assessment’.

Metalworking fluid efficiency, bacteria control and 'Fixed Annual Budgeting'

The long-term efficiency of metalworking fluids to prevent bacterial growth is of the utmost importance in preventing increased cost implications to fluid users. MWF Consultants specialise in delivering ‘Fixed Annual Budgeting’ to clients, providing budgetary certainty with a focus on ‘Wet Waste Disposal Reductions’ and ‘Metalworking Fluid Consumption Reductions’.  These programs work in unison with our clients own ‘Waste Reduction’ policies, particularly those with an onus placed under ISO 14001.


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