Fire fighting foams and the environment.
Turekova, Ivana ; Balog, Karol ; Rusko, Miroslav 等
Abstract: Extinguishing foams are commonly used for extinguishing
the fire of flammable liquids, whereby their insulating, choking and
quenching effects are exploited. The purpose of this paper is to
consider and compare foams currently used in fire departments, with
respect mainly to their high extinguishing effect (capability of faster
aborted burning on a large surface at low foam consumption), but also
their impact on the environment in each stage of their life cycle.
Key words: foams, fire extinguisher, fire, extinguishing
properties, biodegradability
1. INTRODUCTION
Extinguishing agents are various substances and materials used to
stop (slow down) the combustion process. Basic requirements for
extinguishing agents are as follows:
* they must have high fire effects (the ability to quickly stop the
burning of large areas at low consumption),
* they must not be harmful to human (living) organisms, when used
or stored,
* they must be available at a reasonable price, etc.
Solution of used biodegradability fire-fighting foams has been the
subject of the projects VEGA and with application in fire units.
Fire-fighting foam is an extinguishing agent composed of numerous
bubbles formed mechanically or chemically from liquid. Chemical foam is
formed by the reaction of alkaline solution with acidic solution in the
presence of a foam stabilizer. Mechanical foam is formed after
introducing air and/or inert gas into a foaming solution.
Foams belong to two-phase disperse systems consisting of dispersive
media (liquid) with a dispersed phase--three-dimensional lamellae of
permanent structure containing enclosed gas. Plate thickness ranges from
0.001 to 0.01 mm.
Foam fire effects consist of the following physical principles
(Fig. 1.):
* Isolation--separate flammable substance from flame,
* Choky--prevents access of air oxygen to the flammable substance,
prevents the evaporation of flammable liquids,
* Refrigerating--reduces the temperature of the burning substance
and consequently slows down burning, which is directly proportional to
the water content of the foam.
[FIGURE 1 OMITTED]
2. EXPERIMENTAL
The aim of the experiment was to assess the extinguishing
properties of foamers in the laboratory, and subsequently verify their
impact on the environment in an experimental way. The following
measurements were therefore made:
* monitoring the numbers of frothing and foaming time,
* determining the half-life,
* determining viscosity,
* determining the biochemical and chemical oxygen consumption,
* carrying out ecotoxicological tests on higher plants.
The following foamers were used in the experiment (Tab. 1):
The limitations of the research were used fire test methods
available and used by the existing foams.The choice extinguishing
foamers, procedures and tests was based not only on the fire
characteristics, but also in relation to biodegradation. Their selection
was based on the research findings available in HZZ. Foamers were
prepared in five different concentrations (1%, 3%, 6%,9% and 12%).
2.1 Number of foaming
The number of foaming (E) was determined in accordance with STN EN
1568-3:2002 standard Technical conditions of foamers for heavy foam on
the surface use with the liquid immiscible with water. The determination
comprised the number of frothing of selected foamers of different
concentrations, and the time of foam formation (Tab. 2).
Number of frothing ranged around the value 4.9 [+ or -] 0.1 for all
foamers, allowing a fair comparison of foaming time. The fastest foamed
foamers Sthamex AFFF 1%, AFFF Sthamex F-15, then Pyronil and the longest
foaming time had Moussol APS F-15, in which time foaming at 1%
concentration significantly extended.
2.2 Half-life
As regards the manufacturer recommendations in the safety data
sheets, half-life was tested by using 3% solutions, while monitoring the
time at which 50% of the foaming solution were released from the foam.
The results of the measured values for each foamer are given in Tab. 3.
The most favorable results were achieved with the use of foamers
Pyronil and Moussol APS F-15 foamers, where the half-life was 187
seconds.
2.3 Determination of biochemical oxygen demand
The basic part of the test is treatment and dilution of water
sample to be analyzed by different amounts of diluent water with a high
amount of dissolved oxygen and vaccinic aerobic microorganisms with
prevention of nitrification. Incubation was conducted at 20[degrees]C
within a defined time of 5 days in the dark in a full closed flask. The
dissolved oxygen concentration was determined before and after
incubation according to STN EN 1899-1 Water quality--Determination of
biochemical oxygen consumption after n days (BSKn): Part 1: Dilution and
inoculation method with the addition of allylurea. Use was made of
vaccinated diluting water, and dissolved oxygen was electrochemically
determined (Tab. 4.).
2.4 Determination of chemical oxygen demand
The oxidizable substances in the test sample volume are oxidized by
a known quantity of potassium dichromate in the presence of mercuric
sulfate and silver catalyst in an environment of concentrated sulfuric
acid in a defined time interval. The COD value was calculated on the
basis of the amount of reduced dichromate.
The indicator COD shows the total content of organic substances in
water--organic water pollution (Tab. 4.).
The results of foamer biodegradability suggest that foamers have
little ability to biological degradation due to a very small proportion
of degradable substances.
3. CONCLUSION
Currently many types of fire-fighting foams different physical and
extinguishing properties are known. Each of them has its own pros and
cons, as was shown by our testing. It is necessary to know their
physical characteristics, e.g. their stability at low and high
temperatures defined by half-life; the number of foaming specifying
whether it is heavy, medium or light foam, and also their viscosity,
resistance of fluid to internal friction and other properties to be
appropriately selected and used in fire-fighting practice.
Modern fire-fighting foams can be considered to be very good in
terms of physical characteristics, but in recent years, the REACH
legislation draws attention to their ecotoxicological properties. If
fire-fighting foams are used to extinguish large fires, their products
(such as decomposed water from the formed foam) are very likely to get
into the soil and water flow, concurrently affecting the possibility of
wastewater purification. All types of foam have different ecological
characteristics since their components determine the rate of
biodegradation. The ecotoxicological tests of Sinapis alba also showed
that even a low concentration of foamer exhibits significant toxicity.
The research highlighted the need for an additional test. The aim
of further research will be looking for fast and safe testing methods,
not only physical and chemical properties of foamers but ekotoxical
properties, too.
4. ACKNOWLEDGEMENTS
This contribution/ is the result of the project implementation:
Centre of Excellence for the development and application of diagnostic
methods in the processing of metallic and non-metallic materials,
ITMS:26220120048, supported by the Research & Development
Operational Programme funded by the ERDF.
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STN-EN 1568: 2002, Fire extinguishing media--Foam concentrates 1-4
Tab. 1 Used foamers and their characteristics
Name of
foamer Producer for fires Concentration Notes
Sthamex Fabrik chemischer A a B 1%. specially
AFFF Praparate von Dr. designed for
1% Richard Sthamer hydrocarbon
GmbH & CoXG, fires,
Hamburg, Germany plastics
and mineral
oil products
Sthamex Fabrik chemischer A a B 3%. Specially
AFFF Praparate von Dr. designed for
F-15 Richard Sthamer fires of oil
GmbH & CoXG, products and
Hamburg, plastics
Pyronil Chemtura A a B 3% Synthetic
Corporation, USA multipurpose
foamer, also
light foam
Moussol Fabrik chemischer A a B 3% Fire fighting
APS F-15 Praparate von Dr. of liquid of
Richard Sthamer non-polar
GmbH & CoXG, hydrocarbons
Hamburg, Germany
6% Fire fighting
of liquid of
polar,
hydrocarbons
Tab. 2 Number of frothing and time of foaming tested foamers
Concentration of
foamers 12 9 6 3 1
Number of frothing E
Sthamex 4,886 4,894 4,890 4,906 4,827
AFFF
1%
Sthamex 4,909 4,891 4,827 4,826 4,883
AFFF F-15
Pyronil 4,901 4,908 4,878 4,839 4,820
Moussol 4,822 4,854 4,887 4,837 4,807
APS F-15
Time of foaming [s]
Sthamex 6,61 11,69 13,35 14,7 27,35
AFFF
1%
Sthamex 16,58 19,2 19,25 25,28 35,04
AFFF F-15
Pyronil 17,71 20,34 25,63 30,55 34,44
Moussol 19,23 23,38 26,2 30,24 57,81
APS F-15
Tab. 3 Half-life of tested foamers (3% solutions)
No Name of foamer Half-life [s]
1. Sthamex AFFF 1 % 62
2. Sthamex AFFF F-15 166
3. Pyronil 187
4. Moussol APS F-15 187
Tab. 4. Results of COD and BOD5 values tested foamers (3%
foreign solutions)
COD BOD5 BOD5/COD
Name of foamer [mg.[1.sup.-1] [mg.[1.sup.-1] [%]
Sthamex AFFF 1 % 76.23 22790 0.33
Sthamex AFFF F-15 73.68 21370 0.34
Pyronil 79.20 33530 0.23
Moussol APS F-15 83.46 17470 0.47
