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Materials Used - Material Safety Data Sheet
Aqueous Film Forming Foams
Background
Aqueous Film Forming Foams known by the acronym AFFF are used commonly world wide. Nevertheless, there are strong environmental pressures in many countries to satisfy regulatory authorities and users about the safe use of these foams. It should be noted that when foams are used in actual fire emergencies, they do in effect work to prevent other adverse environmental impacts caused by the accidental release into the environment of chemicals and products of combustion caused by fires.
Foams are sometimes also exposed to the environment when released during testing or training. Environmental impact of foams in the environment may be considered to have four key areas of interest.
1) Toxicity
2) Biodegradability
3) Disposal
4) Nutrient Loading
These are valid areas of concern, however ETI foam is pre-mixed in 6% concentration and therefore is already substantially diluted when used. It is also used in small quantities compared to other applications for fire fighting foams. If it is released into the environment it will tend to become infinitely more diluted as it is exposed to various eco systems. Nevertheless, we should look at data relating to these four issues.
Toxicity
Toxicity tests are performed using two species of fresh water fish. The most common species used are the the Rainbow Trout (Salmogairdneri) and the Killifish, (Fundulus heteroclitus). Basically the rainbow trout is sensitive to toxicity whilst the Killfish is much more tolerant. In this way we gain an indication to the likely impact at both ends of the scale. Tests are done to establish at what concentration chemical is evident to be lethal to 50% of the test population over a 96 hour period known as (LC50) and measured in parts per million (ppm). So milligrams per liter of water also equates to ppm. The higher the value, the better as it indicates higher tolerance. For the foam used by ETI the figures are 2000 to 6500 PPM for the Rainbow Trout and 26,000 – 36,000 PPM for the Killfish. To give a practical indication to the impact; if ETI foam were mixed with water at the prescribed mix rate for say an 85 liter pre-mix, the concentration would already be down to 58,900 Mg/Liter, which is about double the 96 hour 50% lethal rate for the Killfish. So if say this was completely discharged into a small body of water say 20 metres by 20 metres with an average depth of 2 metres; the average dilution would now be less than 7 PPM. This not meant to justify chemical impact of such chemicals however it helps us to understand practically the impacts of such exposures.
The ETI fire system uses relatively small quantities of pre-mixed foam which in turn limits potential exposures. Consider a fire monitor delivering the same produced foam at its rate of discharge. Recognised standards indicate that such a device might deliver 4000 litres per minute for 50 minutes in a fire fighting situation. If this were discharged into the same body of water above, the dilution would be 12 tonnes of concentrate giving 15,000 PPM which is well above the 50% lethal range of the Rainbow Trout. Devices like these are typically prevalent at oil refineries and oil storage tank farms which in turn tend to be located at ports and river systems. These water bodies nevertheless are correspondingly vast which dilute the exposures. Marine environments are used for toxicity tests because they are considered the most sensitive to chemical impact and a release into such an environment can travel over vast distances.
Biodegradeability
This is a measurement of how quickly; bacteria in the environment are likely to break down the AFFF. The chemicals used in AFFF in effect become foods for such bacteria in the form of an oxidisable carbon source in their metabolic process. This also uses up dissolved oxygen in the water. Two measurements are done to determine this. The chemical Oxygen Demand Test known as (COD) which measures how much oxygen is needed to completely break down the AFFF. The second is the Biological Oxygen demand test known as (BOD) which measures how much oxygen the bacteria will use over a given time period. Normal testing allows a 5 day test period, however AFFF experiences a lag phase before bacteria populations become effective and so a twenty day period is used. A laboratory test is performed which compares the oxygen demand biologically compared to the absolute potential oxygen demand. Above 50% is considered biodegradable while below 15% is regarded as non-biodegradable. The Foam used by ETI is well above the 50% level and may be regarded as biodegradeable.
Disposal
Sewerage treatment plants are considered the most responsible method of safely disposing of foam mixes. The ETI foam is behaves typically like other foams in this regard. They are not particularly harmful to micro-biological populations. Large volumes of foam mixes can present problems to sewage processing plants, however, given the extremely small quantities involved in the ETI fire System, this is very unlikely to occur as dilutions of 250 ppm are normally considered acceptable without adverse effects to the sewage disposal system. This can be checked with the local authority controlling sewage treatment if there is any concern.
Nutrient Loading
Sudden releases of chemicals which are high in nutrients can unbalance the natural ecology, particularly in marine environments. For example an algae bloom may occur. Of particular concern for marine environments are phosphates and nitrates which are common in rural fertilizers. As the foam used by ETI contains none of these chemicals it may be regarded as having negligible impact for nutrient loading.
It contains very small amounts of organic carbon which are of far less concern than phosphates and nitrates.
Disclaimer
This information is formulated for use by ETI Customers in countries with an approved distributor. ETI in no manner whatsoever, expressly or implied, warrants this information to be accurate and disclaims all liability for its use. Any person utilizing this document should seek competent professional advice to verify and assume responsibility for the suitability of this information to their particular situation.
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