ISO 4240-4

© ISO/NP 4240-4 – All rights reserved
ISO/NPFDIS 4240-4:####(X)
ISO/TC 281/WG 3
Secretariat: JISC
Date: 2026-06-12
Fine bubble technology — Environmental applications —
Part 4:
Test method for the removal of oil from soil by washing using fine
bubbles
DISTechnologie des fines bulles — Applications environnementales —
Partie 4: Procédé d'essai pour l'élimination de l'huile du sol par lavage à l'aide de fines bulles
FDIS stage
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© ISO/NP 4240-4 – All rights reserved
ISO/FDIS 4240-4:2026(en)
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iv
ISO/FDIS 4240-4:2026(en)
Contents
Foreword . vi
Introduction . vii
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Test equipment . 3
6 Test-bed preparation . 4
7 Procedure . 4
7.1 Environmental conditions for soil washing test . 4
7.2 Procedure of the test . 5
8 Test report . 6
Annex A (informative) Mechanism of oil-contaminated soil washing process using fine bubbles 8
Annex B (informative) The example of oil-contaminated soil washing setting with fine bubbles
operation . 17
Annex C (informative) Example of integrated soil washing system including wastewater
treatment options . 24
Bibliography . 28

Bibliography . 22
v
ISO/FDIS 4240-4:2026(en)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
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The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types of
ISO documentsdocument should be noted. This document was drafted in accordance with the editorial rules
of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawnISO draws attention to the possibility that some of the elementsimplementation of this
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This second/third/… edition cancels and replaces the first/second/… edition (ISO #####:####), which has
been technically revised.
The main changes compared to the previous edition are as follows:
— xxx xxxxxxx xxx xxxx
A list of all parts in the ISO ##### series can be found on the ISO website281, Fine bubble technology.
Any feedback or questions on this document should be directed to the user’s national standards body. A
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vi
ISO/FDIS 4240-4:2026(en)
Introduction
0.1 0.1 General
Soil contamination with petroleum-based oils poses significant environmental challenges. Oil pollutants can
severely impact soil quality, degrade water resources, and harm overall ecosystem health. Effective treatment
of oil-contaminated soil is therefore essential to enable land reuse and prevent further ecological damage.
0.2 0.2 Definition of Oil
In this document, the term oil refers specifically to petroleum-based oils commonly found in contaminated
soils. These include crude oil, fuel oils, lubricating oils (e.g., machine oil), and other hydrocarbon-based oils
originating from industrial processes. This definition excludes non-petroleum oils such as cooking oil or
vegetable oil, which fall outside the scope of the soil washing procedures described herein.
0.3 0.3 TPH Characterization and Analysis
Petroleum contamination in soil typically consists of both volatile and non-volatile hydrocarbon fractions.
Volatile fractions (C6-C10) include lighter petroleum products such as gasoline components, while non-
volatile fractions (C10-C40) include heavier petroleum products such as diesel, heating oil, and lubricating
oils. Complete assessment of soil remediation effectiveness requires separate analysis of both fractions using
appropriate analytical methods. This approach ensures accurate evaluation of fine bubble technology
performance across the full spectrum of petroleum contaminants commonly found in contaminated soils.
0.4 0.4 Limitations of Traditional Soil Washing Methods
Conventional soil washing techniques often rely on the use of harsh chemicals and intensive mechanical
operations. These methods may be costly, environmentally disruptive, and less effective when treating certain
types of soils or oil contaminants. Alternative remediation approaches—such as excavation and disposal,
chemical washing, and thermal desorption—are widely employed but also present limitations. Excavation and
disposal typically require off-site treatment or landfill disposal, incurring high transportation and
environmental costs. Chemical washing maycan introduce secondary contamination risks, while thermal
desorption, though effective, is energy-intensive and expensive, making it impractical for large-scale
applications.
0.5 0.5 Market Outlook for Soil Remediation
The global market for soil remediation was valued at approximately USD 50 billion in 2023. This figure is
projected to grow substantially, driven by tightening environmental regulations and increasing demand for
land restoration. Key factors contributing to this trend include industrial expansion, accidental spills, and
improper disposal of hazardous materials—all of which necessitate efficient and sustainable soil treatment
solutions.
0.6 0.6 Fine Bubble Technology as a Sustainable Alternative
Fine bubble technology has emerged as a promising alternative for oil-contaminated soil remediation. This
technique enhances the interaction between microscopic gas bubbles and oil particles in the soil matrix,
resulting in more efficient contaminant removal. Compared to traditional methods, fine bubble technology is
less invasive, requires fewer chemicals, and preserves the natural structure of the soil. These attributes make
it particularly suitable for remediation projects in ecologically sensitive areas.
0.7 0.7 Benefits of Using Fine Bubbles in Soil Washing
The effectiveness of fine bubble technology lies in the physicochemical properties of the bubbles themselves.
Their small size and large surface area significantly improve contact efficiency with hydrophobic
vii
ISO/FDIS 4240-4:2026(en)
contaminants. This leads to enhanced oil removal performance while reducing the degree of soil disruption.
The method also offers economic advantages by lowering energy consumption and chemical use.
0.8 0.8 Challenges and Future Development
Despite its benefits, fine bubble technology faces challenges such as variability in performance across soil
types and the need for specialized generation equipment. These factors can increase initial implementation
costs. Future research is expected to focus on improving bubble generation methods, optimizing system
scalability, and enhancing adaptability to various soil conditions. Automation and real-time control of bubble
injection systems may further improve operational consistency and expand potential applications.
0.9 0.9 Conclusion and Outlook
Fine bubble technology presents a viable and environmentally sustainable solution for oil-contaminated soil
remediation. As technological developments continue, it is anticipated that this method will play an
increasingly important role in environmental protection and land rehabilitation. The advancement of fine
bubble systems could establish a new standard in soil washing, promoting long-term ecological restoration
and sustainable land use.
viii
ISO/FDIS 4240-4:2026(en)
Fine bubble technology — Environmental application —
applications —
Part 4:
Test method for the removal of oil from soil by washing using fine
bubbles
1 Scope
This document specifies a test method for evaluating the performance of soil washing using fine bubble
technology for the removal of oil (petroleum hydrocarbons) from contaminated soil.
The test method is based on determining the concentration of oil in soil samples before and after washing with
fine bubbles under defined test conditions, in order to quantify the efficiency of oil removal.
This document is applicable to pilot-scale and full-scale soil-washing systems and is independent of specific
equipment configurations or system designs. The test method maycan be conducted in controlled
environments, such as indoor or outdoor test facilities, provided that the test conditions are appropriately
managed.
This document does not address site remediation design, soil excavation, soil transport, or the execution of
full-scale remediation projects. Treatment of wastewater generated during the soil washing process is outside
the scope of this document; however, informative guidance on potential treatment options is provided in
Annex BAnnex B and Annex CAnnex C.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 16703, Soil quality -— Determination of content of hydrocarbon in the range C10 to C40 by gas
chromatography, which specifies a method to determine non-volatile petroleum hydrocarbon content;
ISO 15009, Soil quality - Determination— Gas chromatographic determination of the content of volatile
aromatic hydrocarbons, selected ethers,naphthalene and volatile halogenated hydrocarbons by gas
chromatography ---— Purge-and-trap method with thermal desorption, which specifies a method for volatile
petroleum compounds;
ISO 22155, Soil quality - Determination— Gas chromatographic determination of selected volatile organic
compounds in wateraromatic and soil by headspace gas chromatography ---halogenated hydrocarbons and
selected ethers — Static headspace method, which provides an alternative method for volatile petroleum
compounds.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
ISO Online browsing platform: available at https://www.iso.org/obp3.1
—
ISO/FDIS 4240-4:2026(en)
— IEC Electropedia: available at https://www.electropedia.org/
3.1
oil-contaminated soil
presence of petroleum-based substances in soil
Note 1 to entry: This contamination often results from industrial activities, leaks, spills, or improper disposal of oil and
oil products.
3.2 3.2
soil washing
remediation technique involving the use of liquids, usually water and sometimes combined with chemical
additives, to remove contaminants from soil
3.3 3.3
total petroleum hydrocarbons
(TPH)
broad family of several hundred chemical compounds originally derived from crude oil, comprising both
volatile and non-volatile petroleum fractions
Note 1 to entry: TPH includes volatile petroleum compounds (typically C6-C10) and non-volatile petroleum compounds
(typically C10-C40).
Note 2 to entry: For soil remediation assessment, volatile petroleum hydrocarbons are determined in accordance with
ISO 15009 or ISO 22155, or both as applicable. Non-volatile petroleum hydrocarbons are determined in accordance with
ISO 16703.
3.4 3.4
soil washing setting with fine bubbles
facility designed for the remediation of oil-contaminated soil using fine bubble technology
3.5 3.5
inflow rate
volumetric flow rate of the washing liquid supplied to the soil washing system during operation
Note 1 to entry: The inflow rate is a controlled operating parameter that can influence contact conditions between soil,
washing liquid, and fine bubbles.
4 Principle
The principle underlying this document is to evaluate the performance of soil washing plants that use fine
bubble technology for reclaiming soil consistency by oil. The evaluation is conducted by measuring the
concentration of TPH in the soil both before and after the treatment process.
Fine bubble technology enhances oil removal from soil based on physical and physicochemical principles. Fine
bubbles provide a large specific interfacial area, which facilitates the attachment of oil to bubble surfaces and
promotes the detachment of oil from soil particles during the washing process. In addition, the buoyancy and
movement of fine bubbles contribute to the transport and separation of oil from the solid phase. These
interactions promote the mobilization and removal of oil contaminants while maintaining the intrinsic
properties of the soil matrix.
The concentration of oil in soil shall be determined using established analytical methods to ensure
comparability and reliability of the test results. The determination of volatile petroleum hydrocarbons shall
be conducted in accordance with ISO 15009 or ISO 22155, or both, as applicable. The determination of non-
volatile petroleum hydrocarbons shall be conducted in accordance with ISO 16703.
ISO/FDIS 4240-4:2026(en)
Further explanatory and illustrative information on the mechanisms of oil removal using fine bubble
technology is provided in Annex AAnnex A for supplementary purposes.
5 Test equipment
The following equipment shall be used for conducting soil washing using fine bubbles:
a) a) Soil Washing Plant Structure
Outline: The soil washing plant shall consist of a system capable of washing oil-contaminated soil using fine
bubbles under controlled operating conditions. The system shall allow continuous or batch processing and
shall include components for soil feeding, soil washing, and collection of treated soil and separated
contaminants.
Functional requirements: The soil washing plant shall be capable of:
— - introducing contaminated soil into the washing system;
— - supplying washing liquid and fine bubbles to the soil;
— - controlling and maintaining a defined treatment (residence) time;
— - discharging treated soil for subsequent sampling and analysis.
Size: No specific plant dimensions are required. The size and layout of the soil washing plant may vary,
provided that the functional requirements of the test method are satisfied.
Materials: The structure shall be made of materials resistant to corrosion from water, soil, and petroleum
hydrocarbons. Materials such as stainless steel or equivalent corrosion-resistant materials may be used.
b) b) Fine Bubble generation and injection system
1) - Injection Location: Fine bubbles shall be supplied to the soil washing system at locations that enable
effective contact between fine bubbles, soil particles, and washing liquid.
2) - Generation Method: Any fine bubble generation system may be used, provided that it produces fine
bubbles suitable for the test and meets the performance requirements specified in this document. The
generation method shall not be restricted to a specific technology and may include any equivalent
system in accordance with ISO 20480-3.
c) c) Flow Meter: a device used to measure the inflow rate or the flow velocity of the washing liquid or fine
bubble supply, so that the operating conditions are monitored and recorded during the soil washing test.
d) d) Timer: an instrument used to measure and control the treatment time (or residence time) of soil within
the soil washing system, ensuring accurate and reproducible operation of the test.
e) e) Soil Sampler: a tool designed for obtaining soil samples from the site without altering the soil's
composition or injection of contaminants.
f) f) Sampling Bottle: a 2 L (litre) airtight container, such as a glass bottle with a chemically resistant lined
lid, used to collect and store soil samples. The container shall prevent contamination and preserve the
sample condition for accurate analysis.
ISO/FDIS 4240-4:2026(en)
6 Test-bed preparation
When evaluating the efficiency of soil washing in a soil washing setting with fine bubbles, the evaluation shall
be conducted at a pilot-plant scale, since laboratory-scale batch tests can exhibit a high margin of error. The
test conditions shall be established to ensure representative sampling, stable operation, and reproducible
results.
The preparation and configuration of the test bed are independent of the physical dimensions or layout of the
soil washing plant and shall be determined based on functional performance requirements rather than
geometric constraints.
a) a) TPH concentration
The TPH concentration of the test bed shall be representative of oil-contaminated soils to be evaluated. A
concentration range of 500 mg/kg to 2 000 mg/kg may be used as an example to ensure measurable
removal efficiency; however, lower concentrations may also be applied, provided that sufficient analytical
sensitivity and reproducibility are ensured.
b) b) Test bed area
No fixed minimum test-bed area shall be specified. The test-bed area shall be sufficient to allow
representative sampling and stable operation under defined test conditions.
The test-bed area is not required to correspond to the footprint or physical dimensions of the soil washing
plant and may be achieved through continuous operation, repeated processing, or equivalent configurations
that ensure representative evaluation
c) c) Average processing capacity
The average processing capacity shall be more than 1 ton/hour to ensure stable pilot-scale operation.
d) d) Temperature
The test temperature shall be maintained within the range of 15 °C to 25 °C
e) e) Flow rate
The flow velocity at the outlet of the fine bubble generator shall be maintained within a range of 0.,1 m/s
to 0.,2 m/s.
The flow shall be continuous rather than stationary, as continuous movement is essential to maintain
consistent fine bubble distribution and effective soil washing.
A design drawing of a representative soil washing system used for test-bed operation is provided in
Annex CAnnex C for illustrative purposes only and does not imply dimensional or layout requirements.
7 Procedure
7.1 Environmental conditions for soil washing test
The soil washing test using fine bubbles shall be conducted under controlled environmental conditions to
ensure the accuracy and reproducibility of the test results. The test may be performed in indoor, outdoor, or
semi-enclosed facilities, provided that the environmental conditions are appropriately managed and recorded.
ISO/FDIS 4240-4:2026(en)
a) a) Precipitation and external environmental influence
The test shall be conducted under conditions where external environmental influences, such as precipitation,
do not affect the soil moisture content, washing operation, or sampling. Direct exposure to rainfall or
uncontrolled water input shall be prevented during the test.
b) b) Temperature
The ambient temperature during the test shall be maintained within the range of 15 °C to 25 °C. The
temperature shall be sufficiently stable so as not to influence the volatility of petroleum hydrocarbons or the
behaviour of fine bubbles during the washing process.
7.2 Procedure of the test
To conduct the soil washing test method, the test bed shall first be prepared in accordance with Clause 6Clause
6.
Subsequently, the test equipment and the soil washing apparatus shall be prepared for operation.
a) a) Soil sampling and sample consistency:
Representative soil samples shall be collected before and after washing. This shall involve the removal of
foreign materials from a 5 cm to 10 cm radius around the target soil centre, followed by the collection of
samples from 5 to 10 points. To achieve representative sampling, the mass of the sample at each sampling
point shall be recorded, and the sampling procedure shall aim to maintain roughly consistent mass at each
point. The collected samples shall be evenly distributed by mass and mixed uniformly to prepare an on-site
mixed sample weighing approximately 1 kg for final analysis. The samples shall be immediately sealed and
stored to prevent contamination.
Three replicate subsamples shall be taken from the mixed sample and analyzedanalysed for TPH. The
sampling results shall be considered valid if the relative standard deviation (RSD) of the TPH concentrations
obtained from the three replicate subsamples does not exceed ±20 %.
If the RSD exceeds this criterion, the sampling results shall be considered invalid, and re-sampling shall be
conducted.
b) b) Operation of Soil Washing Equipment:
The soil washing equipment shall be used to clean the contaminated soil using fine bubbles. The operation of
the soil washing equipment shall be conducted according to the following step-wise procedure to ensure
reproducibility.
First, the contaminated soil shall be continuously fed into the soil washing equipment, and the washing
medium shall be prepared in accordance with the system configuration. The device operates continuously,
similar to a Continuous Flow Device (CFD), where soil is fed into the system and processed.
Second, the fine bubble generator shall be activated and operated under defined conditions. The operating
conditions of the fine bubble generator, including gas flow rate, liquid-to-gas ratio, and operating pressure,
shall be set prior to operation and recorded.
Third, the treatment time (residence time) of the soil within the washing system shall be controlled and
maintained at 60 ± ± 5 minutes. The residence time shall be determined based on the time required for the
soil to enter and exit the washing unit.
ISO/FDIS 4240-4:2026(en)
Fourth, if recirculation of the washing liquid is applied, the recirculation mode and frequency shall be specified
and recorded.
Finally, the soil washing operation shall be terminated by switching off the fine bubble generator, and the
treated soil shall be collected for subsequent sampling and analysis.
c) c) Pos
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