ISO 4240-4

• Abstract:

  This document describes a test method and procedure for the remediation of oil-contaminated soil using fine bubble technology. It details the process of washing the soil with fine bubbles and measuring the oil content before and after the washing process. The scope of this document includes the necessary steps and considerations for conducting effective soil washing using fine bubbles, as well as the methodologies for quantifying the efficiency of oil removal from the soil.

• Status: Not Published
• ICS: 07.030 - Physics. Chemistry
• Technical Committee: ISO/TC 281 - Fine bubble technology
• Drafting Committee: ISO/TC 281 - Fine bubble technology
• Current Stage: 6000 - International Standard under publication
• Start Date: 22-Aug-2026
• Completion Date: 29-Aug-2026

Overview

ISO 4240-4: Fine bubble technology - Environmental applications - Part 4: Test method for the removal of oil from soil by washing using fine bubbles provides a standardized test method for evaluating the performance of soil washing processes using fine bubble technology to remove petroleum-based oil contaminants from soil. This standard details key steps in the preparation, execution, and assessment of fine bubble soil washing, and outlines procedures for determining total petroleum hydrocarbon (TPH) concentration before and after treatment to quantify oil removal efficiency.

The method is designed for both pilot-scale and full-scale soil washing systems and is applicable in controlled environments with various system layouts. The document emphasizes procedures that help ensure the accuracy, reproducibility, and comparability of results when assessing the efficiency of fine bubble technology in remediating oil-contaminated soils.

Key Topics

• Fine Bubble Technology: Utilizes micro- and nano-sized gas bubbles to improve contaminant removal in soil washing processes. The document defines the principle mechanisms by which fine bubbles interact with and facilitate the detachment of oil from soil particles.
• Test Methodology: Describes preparation of a representative test-bed, selection of soil samples, operation of washing equipment, control of environmental variables, and detailed procedures for soil sampling and analysis.
• Measurement of TPH: Outlines the use of internationally recognized analytical methods (such as ISO 16703, ISO 15009, and ISO 22155) to determine volatile and non-volatile petroleum hydrocarbons.
• Efficiency Assessment: Provides calculation formulas for determining removal efficiency, evaluating both volatile and non-volatile TPH fractions, as well as the total TPH removed from soil.
• Reporting Requirements: Specifies comprehensive data reporting, including environmental conditions, operating parameters, sample analysis, and removal efficiencies.

Applications

• Environmental Remediation: The primary application of ISO 4240-4 is in the remediation of soils contaminated with petroleum hydrocarbons. Fine bubble technology offers a less invasive and potentially more sustainable alternative to conventional chemical, mechanical, or thermal soil cleaning methods.
• Industrial Spill Cleanup: The standard is relevant for industries dealing with accidental oil spills or chronic soil contamination from fuel storage, transportation, or processing activities.
• Pilot and Full-Scale Soil Treatment Facilities: Soil cleaning contractors, environmental engineers, and research facilities can use this standard to validate and optimize fine bubble washing systems.
• Regulatory Compliance and Site Assessment: Supports environmental professionals in providing methodical, data-driven evidence of oil removal effectiveness for compliance with local and international remediation standards.

Related Standards

To ensure a comprehensive and consistent approach, ISO 4240-4 references and aligns with several other international standards, including:

• ISO 16703: Soil quality – Determination of content of hydrocarbon in the range C10 to C40 by gas chromatography (standard method for non-volatile petroleum hydrocarbons).
• ISO 15009: Soil quality – Gas chromatographic determination of volatile aromatic hydrocarbons by purge-and-trap method (addresses volatile petroleum hydrocarbon analysis).
• ISO 22155: Soil quality – Determination of volatile organic compounds by static headspace gas chromatography (alternative method for volatile petroleum hydrocarbons).
• ISO 20480-3: Fine bubble technology – General method for the characterization and test procedure of fine bubbles (provides technical background for bubble generation systems).

ISO 4240-4 plays a pivotal role in advancing sustainable, effective, and standardized practices for remediating contaminated soils using innovative fine bubble technology. By following this standard, organizations can enhance the efficiency and environmental compatibility of oil removal processes, support regulatory compliance, and contribute to land rehabilitation efforts.

FINAL DRAFT
International
Standard
ISO/FDIS 4240-4
ISO/TC 281
Fine bubble technology —
Secretariat: JISC
Environmental applications —
Voting begins on:
2026-06-26
Part 4:
Test method for the removal of oil
Voting terminates on:
2026-08-21
from soil by washing using fine
bubbles
Technologie 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
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
Reference number
ISO/FDIS 4240-4:2026(en) © ISO 2026

FINAL DRAFT
ISO/FDIS 4240-4:2026(en)
International
Standard
ISO/FDIS 4240-4
ISO/TC 281
Fine bubble technology —
Secretariat: JISC
Environmental applications —
Voting begins on:
Part 4:
Test method for the removal of oil
Voting terminates on:
from soil by washing using fine
bubbles
Technologie 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
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
© ISO 2026
IN ADDITION TO THEIR EVALUATION AS
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
or ISO’s member body in the country of the requester.
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland Reference number
ISO/FDIS 4240-4:2026(en) © ISO 2026

ii
ISO/FDIS 4240-4:2026(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Test equipment . 2
6 Test-bed preparation . 3
7 Procedure . 4
7.1 Environmental conditions for soil washing test.4
7.2 Procedure of the test .4
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 . 14
Annex C (informative) Example of integrated soil washing system including wastewater
treatment options . 19
Bibliography .22

iii
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
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
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 document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 281, Fine bubble technology.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
ISO/FDIS 4240-4:2026(en)
Introduction
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  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  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  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 can introduce secondary contamination risks,
while thermal desorption, though effective, is energy-intensive and expensive, making it impractical for
large-scale applications.
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  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  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
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  Challenges and Future Development

v
ISO/FDIS 4240-4:2026(en)
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  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.
vi
FINAL DRAFT International Standard ISO/FDIS 4240-4:2026(en)
Fine bubble technology — Environmental 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 can 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 B and Annex 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
ISO 15009, Soil quality — Gas chromatographic determination of the content of volatile aromatic hydrocarbons,
naphthalene and volatile halogenated hydrocarbons — Purge-and-trap method with thermal desorption
ISO 22155, Soil quality — Gas chromatographic determination of volatile aromatic and halogenated
hydrocarbons and selected ethers — Static headspace method
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/ obp
— 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.
ISO/FDIS 4240-4:2026(en)
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
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
soil washing setting with fine bubbles
facility designed for the remediation of oil-contaminated soil using fine bubble technology
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.
Further explanatory and illustrative information on the mechanisms of oil removal using fine bubble
technology is provided in Annex A for supplementary purposes.
5 Test equipment
The following equipment shall be used for conducting soil washing using fine bubbles:
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.
ISO/FDIS 4240-4:2026(en)
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) 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) 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) 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) Soil Sampler: a tool designed for obtaining soil samples from the site without altering the soil's
composition or injection of contaminants.
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.
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) 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) 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.

ISO/FDIS 4240-4:2026(en)
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) Average processing capacity
The average processing capacity shall be more than 1 ton/hour to ensure stable pilot-scale operation.
d) Temperature
The test temperature shall be maintained within the range of 15 °C to 25 °C
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 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.
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) 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 6.
Subsequently, the test equipment and the soil washing apparatus shall be prepared for operation.
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.

ISO/FDIS 4240-4:2026(en)
Three replicate subsamples shall be taken from the mixed sample and analysed 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) 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 so
...

© 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)
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication
may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying,
or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO
at the address below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: + 41 22 749 01 11
Fax: [phone]
EmailE-mail: [e-mail]
Website: www.iso.orgwww.iso.org
Published in Switzerland
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
ISO technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
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
document may beinvolve the subjectuse of (a) patent(s). ISO takes no position concerning the evidence,
validity or applicability of any claimed patent rights in respect thereof. As of the date of publication of this
document, ISO had not received notice of (a) patent(s) which may be required to implement this document.
However, implementers are cautioned that this may not represent the latest information, which may be
obtained from the patent database available at www.iso.org/patents. ISO shall not be held responsible for
identifying any or all such patent rights. Details of any patent rights identified during the development of the
document will be in the Introduction and/or on the ISO list of patent declarations received (see ).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee [or Project Committee] ISO/TC [or ISO/PC] ###, [name
of committee], Subcommittee SC ##, [name of subcommittee].
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
complete listing of these bodies can be found at www.iso.org/members.html.
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
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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.
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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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