ISO 20468-2:2019
(Main)Guidelines for performance evaluation of treatment technologies for water reuse systems — Part 2: Methodology to evaluate performance of treatment systems on the basis of greenhouse gas emissions
Guidelines for performance evaluation of treatment technologies for water reuse systems — Part 2: Methodology to evaluate performance of treatment systems on the basis of greenhouse gas emissions
This document provides guidelines for evaluating the performance of treatment systems on the basis of greenhouse gas (GHG) emissions. In order to estimate greenhouse gas emissions from a treatment system, this document covers the estimate, types of GHG emission and sources, emission factor for each GHG, and global warming potential. The weight of greenhouse gases to be used in an evaluation is equivalent to emissions during operation of a treatment system. This document also defines a method for calculating carbon dioxide equivalent (CO2eq) emission intensity, in which GHG emissions are divided by the volume of reclaimed water. It also includes a method for evaluating the performance of a treatment system using CO2eq emission intensity.
Lignes directrices pour l’évaluation des performances des techniques de traitement des systèmes de réutilisation de l’eau — Partie 2: Titre manque
General Information
Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 20468-2
First edition
2019-07
Guidelines for performance evaluation
of treatment technologies for water
reuse systems —
Part 2:
Methodology to evaluate performance
of treatment systems on the basis of
greenhouse gas emissions
Reference number
ISO 20468-2:2019(E)
©
ISO 2019
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ISO 20468-2:2019(E)
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© ISO 2019
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ISO 20468-2:2019(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms, definitions, and abbreviated terms . 1
3.2 Abbreviated terms . 2
4 Symbols . 3
5 Principles . 4
5.1 General . 4
5.2 Relevance . 4
5.3 Completeness . 4
5.4 Consistency . 4
5.5 Accuracy . 4
5.6 Transparency . 4
6 Boundary conditions . 5
6.1 General . 5
6.2 Treatment system . 6
6.3 Residue management system . 6
6.4 Auxiliary system . 6
7 Calculation . 6
7.1 Calculation procedure . 6
7.2 Step 1: Establish boundary conditions of evaluation . 7
7.3 Step 2: Calculate annual amount of reclaimed water . 8
7.4 General descriptions of methodological issues when calculating GHG emissions for
Step 3 to Step 6 . 9
7.4.1 Choice of method to determine GHG emissions . 9
7.4.2 Choice of activity data . 9
7.4.3 Choice of emission factors . 9
7.5 Step 3: Calculate GHG emissions resulting from energy consumption . 9
7.5.1 Data acquisition . 9
7.5.2 Calculate GHG emissions .10
7.6 Step 4: Calculate GHG emissions resulting from biological treatment processes .10
7.6.1 Data acquisition .10
7.6.2 Calculate GHG emissions .11
7.7 Step 5: Calculate GHG emissions resulting from consumables and generation of wastes .11
7.7.1 Data acquisition .11
7.7.2 Calculate GHG emissions .12
7.8 Step 6: Calculate GHG emissions reduced through the effective utilization of
resources resulting from the production of reclaimed water .12
7.9 Step 7: Calculate total GHG emissions.17
7.10 Step 8: Calculate CO emission intensity .18
2eq
8 Application of CO emission intensity in evaluating the environmental
2eq
performance of a treatment system .18
Annex A (informative) Examples of emission factors .19
Annex B (informative) Example of a worksheet for calculating total GHG emissions .21
Annex C (informative) Example of CO emission intensity calculation .22
2eq
Bibliography .27
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ISO 20468-2:2019(E)
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 documents 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 drawn to the possibility that some of the elements of this document may be the subject of
patent rights. 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 www .iso .org/patents).
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 282, Water reuse, Subcommittee SC 3,
Risk and performance evaluation of water reuse systems.
A list of all parts in the ISO 20468 series can be found on the ISO website.
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.
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ISO 20468-2:2019(E)
Introduction
The purpose of this document is to define a methodology more specifically for evaluating the
environmental performance of treatment systems among treatment technologies for water reuse
systems, which is covered in Clause 7 “Non-functional requirements” of ISO 20468-1:2018, Guidelines
for performance evaluation of treatment technologies for water reuse systems Part 1 General.
Water reuse has been drawing attention for contributing to environmental protection, as well as
providing solutions for water scarcity. For example, a water reclamation plant plays the additional
role of removing pollutants such as emerging pollutants, pathogens, and toxic elements. Otherwise,
water discharged into the environment can increase health risks and/or have negative impacts on
ecosystems. Compared to conventional water supply systems, including waterworks consisting of dams
and water conveyance facilities, water reuse systems can save operational energies and resources of
constructions. In addition, water reuse can minimize environmental destruction during development.
In order to establish sustainable water reuse services, while protecting the environment, appropriate
evaluation methods are needed. However, in the international community, there is no common approach
to using parameters concerning the environment in evaluations of treatment technologies for water
reuse systems. Although rules may be established for each region where water reuse systems are to be
installed, having specialists work out rules and standardizing them through the ISO is more economical
and convenient.
When discussing evaluations of environmental aspects, first of all, two aspects should be defined. One
comprises boundary conditions that determine which areas are evaluated. The other is the evaluation
parameter concerned.
Typical boundary conditions concerning environmental aspects in water reuse projects consist
of intake, conveyance, treatment, reservoir, distribution, end-use, and final discharge into the
environment. Taking into consideration the scope defined in Part 1, this document addresses treatment
systems.
On the other hand, evaluation parameters concerning the environment attributable to treatment systems
vary widely. For example, reclaimed water quality having adverse effects on a regional ecosystem and
ground water can be one parameter for evaluation. Another can be the level of soil contamination
caused by using reclaimed water. Moreover, the degree of noise and vibration from treatment systems
can be utilized for evaluations because of the impacts on the environment. Greenhouse gas emissions
in the course of plant operation should also be taken into consideration with more attention given to
preventing global warming. Naturally, a treatment system should be evaluated by taking into account
all of these parameters. However, an evaluation with so many parameters involves a great burden in
terms of time and costs, and therefore lacks practicality at the moment.
In view of the conditions described above, this document provides guidelines for evaluating the
performance of a treatment system using, as a parameter, greenhouse gas emissions in the course
of system operation with the amount of reclaimed water produced. The reason why greenhouse
gas emissions have been selected as a parameter is that it is a practical parameter on which many
greenhouse-gas related standards have been established, such as ISO 14064-1. It is, however, important
to note that this document is not intended to prevent evaluating other environmental parameters of
treatment systems, including those described above, in water reuse projects. If such evaluations are
necessary, other guidelines and/or expert judges should be referred.
The evaluation is also limited to the period during which the treatment system is being operated. This
is because the systems are expected to operate for 20 years or more after construction, during which
greenhouse gas emissions in the course of operation tend to be greater than the level at construction or
when the system is being discontinued.
This document takes a simple and standard approach that can be applied anywhere. Therefore, this
document includes how to estimate greenhouse gas emissions using typical activities, such as energy
consumption or amount of consumables used in operations. In addition, CO emission intensity is
2eq
defined to evaluate the environmental performance of a treatment system expressed as a value of the
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ISO 20468-2:2019(E)
weight of greenhouse gas emissions divided by the amount of reclaimed water produced. As a result,
there is no need to substantially change existing engineering duties. This will alleviate the burden on
engineers.
It is expected that this document will contribute to the development of environmentally responsible
treatment systems.
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INTERNATIONAL STANDARD ISO 20468-2:2019(E)
Guidelines for performance evaluation of treatment
technologies for water reuse systems —
Part 2:
Methodology to evaluate performance of treatment
systems on the basis of greenhouse gas emissions
1 Scope
This document provides guidelines for evaluating the performance of treatment systems on the basis of
greenhouse gas (GHG) emissions.
In order to estimate greenhouse gas emissions from a treatment system, this document covers the
estimate, types of GHG emission and sources, emission factor for each GHG, and global warming
potential. The weight of greenhouse gases to be used in an evaluation is equivalent to emissions during
operation of a treatment system.
This document also defines a method for calculating carbon dioxide equivalent (CO ) emission
2eq
intensity, in which GHG emissions are divided by the volume of reclaimed water. It also includes a
method for evaluating the performance of a treatment system using CO emission intensity.
2eq
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 20670, Water reuse — Vocabulary
3 Terms, definitions, and abbreviated terms
For the purposes of this document, the terms and definitions given in ISO 20670 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https: //www .iso .org/obp
— IEC Electropedia: available at http: //www .electropedia .org/
3.1 Terms and definitions
3.1.1
activity data
quantitative measure of activity that results in a GHG emission or removal
EXAMPLE The amount of imported electricity consumed, biologically treated sewage or water treatment
chemicals consumed.
Note 1 to entry: See Reference [1].
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ISO 20468-2:2019(E)
3.1.2
anaerobic-aerobic activated sludge process
AO process
biological sewage treatment process with a sequence of anaerobic and aerobic (oxic) zones
3.1.3
anaerobic-anoxic-oxic activated process
A2O process
biological sewage treatment process with a sequence of anaerobic, anoxic and aerobic (oxic) zones
3.1.4
carbon dioxide equivalent
CO
2eq
conversion of individual GHG emissions or removals into climate impact, identified as tons equivalent of
carbon dioxide (CO )
2eq
Note 1 to entry: See Reference [2].
3.1.5
carbon dioxide equivalent (CO ) emission intensity
2eq
value determined by dividing GHG emissions by amount of reclaimed water
3.1.6
emission factor
coefficient which quantifies emissions or removals per unit activity
Note 1 to entry: See Reference [2].
3.1.7
environmental performance
measurable results of treatment technologies in environmental aspects
3.1.8
greenhouse gas
GHG
carbon dioxide (CO ), methane (CH ), and nitrous oxide (N O)
2 4 2
Note 1 to entry: See Reference [1].
3.1.9
membrane bioreactor
MBR
treatment method in which bioreactor and membrane process are combined
3.1.10
recycled nitrification-denitrification process
RND process
biological nitrogen removal process utilizing nitrate recycle
3.2 Abbreviated terms
For the purposes of this document, the following abbreviated terms apply.
CO carbon dioxide
2
CO carbon dioxide equivalent
2eq
CH methane
4
N O nitrous oxide
2
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ISO 20468-2:2019(E)
GHG greenhouse gas
AO process anaerobic-aerobic activated sludge process
A2O process anaerobic-anoxic-oxic activated process
MBR membrane bioreactor
RND process recycled nitrification-denitrification process
N/A not applicable
ds dry solid
RO reverse osmosis
GWP global warming potential
STP sewage treatment plant
ID No. identification number
4 Symbols
The symbols used in this document are shown in Table 1.
Table 1 — Symbols
Symbol Unit Description
CO emissions resulting from consumption of energy, includ-
2
E tons of CO per year
E,CO2,annual 2
ing electricity, fuels, etc.
CH emissions resulting from consumption of energy, includ-
4
E tons of CH per year
E,CH4,annual 4
ing electricity, fuels, etc.
N O emissions resulting from consumption of energy, in-
2
E tons of N O per year
E,N2O,annual 2
cluding electricity, fuels, etc.
CH emissions resulting from each biological treatment
4
E tons of CH per year
P,CH4,annual 4
process
N O emissions resulting from each biological treatment
2
E tons of N O per year
P,N2O,annual 2
process
CO emissions resulting from consumables and generation
2
E tons of CO per year
C,CO2,annual 2
of waste
CH emissions resulting from consumables and generation
4
E tons of CH per year
C,CH4,annual 4
of waste
N O emissions resulting from consumables and generation
2
E tons of N O per year
C,N2O,annual 2
of waste
Reduction of GHG emissions through the effective utilization
E tons of CO per year of resources resulting from the production of reclaimed
R,CO2eq,annual 2eq
water (CO equivalent)
2
E tons of CO per year Total greenhouse gas emissions (CO equivalent)
T,CO2eq,annual 2eq 2
3
kg CO per m -reclaimed
2eq
I Carbon dioxide equivalent (CO ) emission intensity
CO2eq 2eq
water
3
thousand m -reclaimed water Annual volume of reclaimed water produced in a relevant
Q
annual
per year water reclamation plant
Amount of energy consumption, including electricity,
a
Q unit
E,t
fuels, etc.
a
The unit varies according to the substance concerned. Definitions are given in Clause 7.
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ISO 20468-2:2019(E)
Table 1 (continued)
Symbol Unit Description
a
Q unit Amount of treatment in each biological treatment process
P,t
a
Q unit Amount of consumables and the weight of waste generated
C,t
CO emission factor resulting from consumed energy, includ-
2
a
K tons of CO per unit
E,CO2,t 2
ing electricity, fuels, etc.
CH emission factor resulting from consumed energy, in-
a 4
K tons of CH per unit
E,CH4,t 4
cluding electricity, fuels, etc.
N O emission factor resulting from consumed energy, in-
a 2
K tons of N O per unit
E,N2O,t 2
cluding electricity, fuels, etc.
CH emission factor resulting from the biological treat-
a 4
K tons of CH per unit
P,CH4,t 4
ment process
N O emission factor resulting from the biological treat-
a 2
K tons of N O per unit
P,N2O,t 2
ment process
a
K tons of CO per unit CO emission factor resulting from consumables and waste
C,CO2,t 2 2
a
K tons of CH per unit CH emission factor resulting from consumables and waste
C,CH4,t 4 4
a
K tons of N O per unit N O emission factor resulting from consumables and waste
C,N2O,t 2 2
K Global warming potential (GWP)
GWP,t
a
The unit varies according to the substance concerned. Definitions are given in Clause 7.
5 Principles
5.1 General
The following principles apply to evaluations of treatment systems using CO emission intensity.
2eq
5.2 Relevance
The activities of treatment systems, which are related to greenhouse gas emissions, should be extracted
in a relevant manner and appropriately quantified.
5.3 Completeness
GHG emissions during production of reclaimed water should be calculated under conditions in which
other environmental requirements (reclaimed water quality, noise and vibration, etc.) of the system
comply with project requirements.
5.4 Consistency
In order to ensure an effective comparison, as much as possible, data should be acquired according to
the same method from year to year. The method to be used should be established at the beginning of an
evaluation for the same water reclamation plant.
5.5 Accuracy
Data acquisition should be free from bias, as much as possible, while minimizing uncertainty. For
specified methods, refer to Clauses 6 and 7.
5.6 Transparency
The process for calculating the CO emission intensity and parameters used, such as emission factors
2eq
and efficiency of equipment applied to a system, should be recorded and made available for clarification
when requested.
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ISO 20468-2:2019(E)
6 Boundary conditions
6.1 General
When using this document in an evaluation of the environmental performance of a treatment system,
the boundary conditions of the evaluation should be established according to the relevant project
requirements. To facilitate a comparison of treatment systems, it is essential to define the boundary
conditions of a performance evaluation, taking into consideration the processes of transforming raw
water into reclaimed water and, if necessary, associated facilities inside the water reclamation plant.
Unless otherwise specified, the boundary conditions should be defined referring to the example in
Figure 1. To prevent the performance evaluation of the treatment system from being influenced by
the location of a raw water intake point or distribution of reclaimed water, the boundary conditions of
the performance evaluation should be limited to part of the treatment system and associated facilities
inside the water reclamation plant. Then, tangible minimum boundary conditions should be established
between the facility that receives the raw water to produce reclaimed water and the prescribed
interface point to hand over reclaimed water produced through treatment processes. In addition, the
relevant system, such as a sludge treatment system, may be included in the evaluation, taking into
consideration project characteristics.
Figure 1 — Example of the boundary conditions of evaluation
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ISO 20468-2:2019(E)
6.2 Treatment system
An example of treatment system refers to a set of water treatment processes inside a water reclamation
plant, in which raw water, such as raw sewage, preliminary, primary, or secondary treated wastewater,
is transformed into reclaimed water. Normally, the treatment system consists of multiple treatment
processes using physical, biological and/or chemical means. Because this document is not intended to
specify the type and order of treatment processes such as A, B, and C in Figure 1, they are to be replaced
with adequate treatment processes according to the relevant project requirements. When evaluating
the environmental performance of the treatment system by applying this document, a treatment
system should at least be included in the boundary conditions.
6.3 Residue management system
Generally, treatment systems generate wastewater or sludge. The following facilities are needed to
handle them:
— Wastewater treatment facility(s);
— Sludge treatment facility(s).
These facilities may be provided as a part of the project, or treatment work may be assigned to nearby
plants already in service. GHG emissions from a residue management system may be included in the
boundary conditions of an evaluation as required. It is essential to specify clearly whether or not such
GHG emissions are included.
6.4 Auxiliary system
Systems not included in the treatment system or the residue management system, but relate to
producing reclaimed water are taken as an auxiliary system. The example is an odor control system.
They may be included in the boundary conditions of the evaluation as required.
In principle, however, power consumed for lighting, air conditioning, etc. not directly connected to the
production of reclaimed water is not counted in the performance evaluation of this document.
7 Calculation
7.1 Calculation procedure
This clause describes how to calculate CO emission intensity. The steps are as follows (see Figure 2):
2eq
— Step 1: Establish boundary conditions of evaluation (see 7.2);
— Step 2: Calculate annual amount of reclaimed water (see 7.3);
— Step 3: Calculate GHG emissions resulting from energy consumption, including electricity, fuels, etc.
(see 7.5);
— Step 4: Calculate GHG emissions resulting from biological treatment processes (see 7.6);
— Step 5: Calculate GHG emissions resulting from consumables and generation of wastes (see 7.7);
— Step 6: Calculate GHG emissions reduced through the effective utilization of resources resulting
from the production of reclaimed water (see 7.8);
— Step 7: Calculate total GHG emissions (see 7.9);
— Step 8: Calculate CO emission intensity (see 7.10).
2eq
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ISO 20468-2:2019(E)
Figure 2 — Calculation procedure
7.2 Step 1: Establish boundary conditions of evaluation
Step 1 is to est
...
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