Biodegradability & International Standards
At the time of writing (January 2017), there are no internationally recognised European or US standards on biodegradability testing of foams. This means that there is no systematic methodology defining test type, testing time and acceptable limits on biodegradability for fire fighting foam concentrates.
The one exception is US Military Standard MIL-F 24385 which requires a result of 50% or greater for a BOD/COD ratio.
How is biodegradability measured?
The most commonly used method of indicating the biodegradability of chemicals is by BOD (Biological Oxygen Demand) and COD (Chemical Oxygen Demand) testing. These tests measure the mass of oxygen a chemical removes from water over a set period of time and are generally accepted indicators of biodegradability.
Once both BOD and COD measurements have been taken, the results are combined and are usually ratioed to give a BOD/COD percentage result.
A BOD/COD result giving a percentage greater than or equal to 50% is generally accepted as indicating that the chemical is readily biodegradable.
So what's the problem?
As there is no internationally recognised standard for biodegradability performance, there can be conflicting information regarding published results.
Most fire fighting manufacturer’s test the concentrate of the Fire Fighting Foam for biodegradability, rather than the actual foam inducted into the environment (typically 1-3% as opposed to 100%). Furthermore, a combination of BOD results - 5 day, 20 day, 28 day, undefined duration and measured by Total Organic Carbon (TOC) - are often quoted.
The European Foam testing standard BS EN 1568: 2008 Parts 1-3 is currently being revised to address this issue. It is hoped that this revision will lead to changes to ensure that all fire fighting foam concentrates can be compared equally on environmental performance.
Oil Technics (Fire Fighting Products) Ltd have made the decision to commission testing for both the foam concentrate and inducted/produced foam solutions for 5 day and 25-day BOD. This will allow a better view of the actual environmental impact when the foam is discharged into the environment.
For further information please contact Oil Technics (Fire Fighting Products) Ltd’s Technical Department.