ISO 20468-1:2018

INTERNATIONAL ISO
STANDARD 20468-1
First edition
2018-11
Guidelines for performance evaluation
of treatment technologies for water
reuse systems —
Part 1:
General
Lignes directrices pour l’évaluation des performances des techniques
de traitement des systèmes de réutilisation de l’eau —
Partie 1: Généralités
Reference number
©
ISO 2018
© ISO 2018
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ii © ISO 2018 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms, definitions and list of abbreviated terms . 1
3.1 Terms and definitions . 1
3.2 List of abbreviated terms . 4
4 Concepts of treatment technology for water reuse systems . 4
4.1 General . 4
4.2 Treatment objective . 5
4.3 Treatment technologies used in fit-for-purpose water reuse . 6
5 Principles and general guidelines for performance evaluation . 8
5.1 General . 8
5.2 Performance requirements . 9
5.2.1 Treatment technology functional requirements . 9
5.2.2 Treatment technology non-functional requirements . 9
5.2.3 Characteristics of functional and non-functional requirements in
performance evaluation .10
5.3 P erformance evaluation and meeting requirements .10
5.3.1 General.10
5.3.2 Monitoring plan .11
5.4 Application of the guidelines to treatment systems .11
5.4.1 Treatment system design .11
5.4.2 Treatment system configuration .11
6 Functional requirements .12
6.1 General .12
6.2 P erformance evaluation procedures .12
7 Non-functional requirements .14
7.1 Examples of performance indicators .14
7.2 E valuation method of environmental performance .14
7.2.1 Energy consumption .14
7.2.2 Chemical consumption .15
7.2.3 Amount of solid and liquid waste generated and requiring disposal .15
7.2.4 Performance indicators — Integrated considerations.16
7.3 E valuation method of economic performance.16
Annex A (informative) Dependability of treatment technology.17
Annex B (informative) Dependability evaluation .19
Bibliography .21
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.
iv © ISO 2018 – All rights reserved

Introduction
The rapidly growing global market for water reuse technologies inevitably demands standards
which are applicable on a world-wide basis be developed. Many regions in the world are facing water
shortages, and there is great interest in fit-for-purpose water reuse technologies that can treat and
reclaim wastewater to a water quality level that is suitable for a wide range of reuse applications that
can satisfy non-potable water demands, thereby conserving precious potable water resources. The
implementation of water reuse programs raises public and regulatory concern regarding potential
human health, environmental and societal impacts. This has led to an increasing need to specify
various aspects of water reuse projects, and regulators, reuse technology suppliers, and users of those
technologies have a growing need for international standardization. A great number of opportunities
for sustainable water use and development based on water reclamation can be lost without ISO water
reuse standards.
Standardization needs to include objective specification and evaluation of levels of service and water
reuse system performance dependability including safety, environmental protection, resilience and
cost-effectiveness considerations. Hence, appropriate methods are needed to evaluate the performance
of treatment technologies for water reuse systems.
The performance of treatment technologies for water reuse, inter alia, should be evaluated properly
in order to select the most appropriate technologies in an unbiased way to achieve the objectives of
water reuse projects. Despite considerable research and development on treatment technologies,
such scientific knowledge is largely held within commercial interests. Performance evaluations are
also useful for assessing the efficiency of existing wastewater reclamation systems and operations,
including the identification of continuous improvement opportunities. To address these challenges, this
document provides methods and tools, which can be accepted by most stakeholders, to evaluate the
performance of treatment technologies for water reuse systems for a multitude of applications. This
document provides treatment technology functional requirements and non-functional requirements,
the former based on water quality parameter concentration or removal efficiency and the latter based
on performance indicators. A step-by-step procedure for evaluating the functional requirements and
examples of non-functional key performance indicators and evaluation methods are provided.
This document is intended for use by planners and managers of water reuse projects, technical advisors,
designers, operators of the treatment systems, those involved in monitoring, assessing, regulating and
other activities of third-party organizations or relevant authorities, as well as treatment technology
manufacturers.
The application of the guidelines for performance evaluation at the stages of procurement, designing
and operation of treatment systems can enable, for example:
— designers to identify and evaluate an optimal treatment system design which will meet regulatory
performance requirements;
— manufacturers to determine technology performance expectations;
— operators to evaluate and improve the operating efficiency and performance of water reuse
treatment systems.
This document is not intended to address the design and integration of specific unit treatment processes
or overall treatment system design.
This document can be useful for the application of management system standards, such as ISO 9001,
ISO 14001, ISO 22301, ISO 50001, and ISO 55001.
INTERNATIONAL STANDARD ISO 20468-1:2018(E)
Guidelines for performance evaluation of treatment
technologies for water reuse systems —
Part 1:
General
1 Scope
This document gives guidelines on performance evaluation of treatment technologies for water reuse
systems. It provides typical parameters of water quality and treatment efficiency that are associated
with the performances of treatment technologies. It also includes a comparison of measured and target
values, and provides treatment technology functional requirements and non-functional requirements.
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 reference, 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 list of 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
availability
ability of a treatment technology to be in a state to perform a required function under
given conditions at a given instant of time or over a given time interval, assuming that the required
external resources are provided
Note 1 to entry: This ability depends on the combined aspects of the reliability performance, the maintainability
performance, and the maintenance support performance.
Note 2 to entry: Required external resources, other than maintenance resources, do not affect the availability
performance of the treatment technologies.
[SOURCE: IEC 60050-191:1990, 191-02-05]
3.1.2
benchmarking
tool for performance improvement through systematic search and adaptation of leading practices
[SOURCE: Benchmarking Water Services - Guiding water utilities to excellence (2011)]
3.1.3
correction
action to eliminate a detected nonconformity
[SOURCE: ISO 9000:2015, 3.12.3, modified — Notes 1 and 2 to entry have been deleted.]
3.1.4
corrective action
action to eliminate the cause of a nonconformity and to prevent recurrence
[SOURCE: ISO 9000:2015, 3.12.2, modified — Notes 1 to 3 to entry have been deleted.]
3.1.5
dependability
collective term used to describe the availability performance and its influencing factors
EXAMPLE Reliability performance, maintainability performance and maintenance support performance.
[SOURCE: IEC 60050-191:1990, 191-02-03]
3.1.6
downtime
amount of time that a system or a component is not able to operate or meet required functions
3.1.7
failure
state in which a treatment technology does not meet a functional or a non-functional requirement
3.1.8
functional requirement
requirement related to the transformation of water quality by a treatment technology
3.1.9
maintainability
ability of a treatment technology under given conditions of use, to be retained in, or
restored to, a state in which it can perform a required function, when maintenance is performed under
given conditions and using stated procedures and resources
[SOURCE: IEC 60050-191:1990, 191-02-07, modified — Notes 1 to entry has been deleted.]
3.1.10
maintenance support performance
ability of a maintenance organisation, under given conditions and maintenance policy, to provide, upon
demand, the resources required to maintain the treatment technology
Note 1 to entry: The given conditions are related to the treatment technology and to the conditions under which
the treatment technology is used and maintained.
Note 2 to entry: When evaluating the treatment technologies, required maintenance support performance can be
used as a given condition to evaluate the maintainability.
[SOURCE: IEC 60050-191:1990, 191-02-08, modified — Note 2 to entry has been added.]
3.1.11
nonconformity
non-fulfilment of a requirement
[SOURCE: ISO 30000:2009, 3.8]
3.1.12
non-functional requirement
requirement that specifies criteria or constraints on the design or implementation of a treatment
technology
2 © ISO 2018 – All rights reserved

3.1.13
performance evaluation
overall process to judge whether, or to measure the extent to which the outputs or state of a system, or
a component, fulfill the requirements
Note 1 to entry: See ISO 9001:2015, Clause 9.
3.1.14
performance indicator
parameter, or a value derived from parameters, which provides information about the performance of
a subject matter with a significance extending beyond that directly associated with a parameter value
Note 1 to entry: See ISO 24511:2007, 2.16.
3.1.15
predictive analysis
practice of extracting information from existing data sets in order to determine patterns and predict
future outcomes and trends
3.1.16
removal efficiency
efficiency of removal of a constituent
Note 1 to entry: Removal efficiency and log removal value for some specific constituent are defined by the
following Formula (1) and Formula (2):
C
()
e
RE =−1 (1)
()
C
()
i
 
C
()
e
loglRV =− og 1−=RE  −log (2)
() ()
 
10 10
 
C
()
 
i
 
where
RE is the removal efficiency;
C is the effluent constituent concentration;
e
C is the influent constituent concentration;
i
RV is the removal value.
Note 2 to entry: Removal efficiency is often expressed as a percentage. A value of indicator for the constituent can
be used in place of concentration of the constituent. Log removal value is often used for microbial constituents.
3.1.17
requirement
need or expectation that is stated, generally implied or obligatory
[SOURCE: ISO 9000:2015, 3.6.4, modified — Notes 1 to 6 to entry have been deleted.]
3.1.18
robustness
ability of a structure to withstand adverse and unforeseen events or consequences of human errors
without being damaged to an extent disproportionate to the original cause
[SOURCE: ISO 2394:2015, 2.1.46, modified.]
3.1.19
safety
freedom from risk which is not tolerable
[SOURCE: ISO/IEC GUIDE 51:2014, 3.14]
3.2 List of abbreviated terms
BOD biochemical oxygen demand
COD chemical oxygen demand
E. coli Escherichia coli
LCA life cycle assessment
LCC life cycle cost
LRV log removal value
MBR membrane bioreactor
PAA peracetic acid
QA quality assurance
QC quality control
RO reverse osmosis
TDS total dissolved solids
TSS total suspended solids
UV ultraviolet
4 Concepts of treatment technology for water reuse systems
4.1 General
Clause 4 outlines information on treatment technologies including treatment systems and processes.
The constituents found in untreated wastewater are derived from the substances that come into
contact with water used for various domestic, commercial, and industrial uses; as well as those carried
by stormwater which flows into sanitary system. The focus of this document is on the performance of
the processes and systems with respect to constituents of concern for water reuse applications that
include suspended solids, colloidal turbidity, dissolved constituents (i.e. dissolved organic and inorganic
substances such as sugars and fats, heavy metals, nutrients, etc.), and pathogens (disease causing
viruses, bacteria, protozoa and helminths) assessed by indicator microorganisms. Various treatment
processes can be used individually or combined to remove a target constituent.
The water quality requirements of a given reuse application governs the type of treatment needed and
the degree of treatment reliability. Because health and environmental concerns are primary issues in
implementing water reuse, attention should be focused on developing treatment systems to ensure
whether water quality requirements are consistently met. With respect to performance of disinfection
technologies, a multi-barrier approach is recommended (i.e. two or more different processes including
at least one form of disinfection and additional barriers with accepted levels of pathogen reduction).
4 © ISO 2018 – All rights reserved

4.2 Treatment objective
Because of the importance of water quality in water reuse applications, different technologies are
often combined to achieve desired levels of constituent removal. Figure 1 shows progressive stages of
wastewater treatment processes.
NOTE Post-chlorination is applied depending on the end use.
[20]
Figure 1 — Wastewater treatment stages as per reuse applications
One of the primary objectives of treatment technologies for water reuse is to reduce the pathogen
content to reduce public health risk associated with exposure to reuse water. While disinfection
requirements can vary depending on the specific water reuse application, disinfection is most
commonly accomplished by the use of chemical oxidants (e.g. chlorine based oxidants, and ozone),
UV, membrane filtration and (more recently) PAA. Disinfection can include treatment strategies that
incorporate multiple disinfection technologies or ultrafiltration/reverse osmosis treatments in series
as necessary – referred to as a multi-barrier approach to disinfection. The purpose of the multi-barrier
approach is, in part, to provide a back-up disinfection mechanism in the event one of the technologies
relied upon for disinfection should underperform because of design or equipment failure; however, it is
also carried out in recognition that not all pathogens are equally affected by a particular disinfection
technology, and that combinations of disinfection/treatment technologies can achieve a more effective
and broader range of pathogen reduction. A multi-barrier approach can also include the maintenance of
a residual level of disinfectant (e.g. post-chlorination) in water to prevent recontamination.
[20]
The general categories of treatment technologies in this document are shown below .
— Preliminary treatment
Preliminary treatment is to remove from the wastewater any constituents which can clog or damage
pumps or other equipment, or interfere with the operation or maintenance of the subsequent
treatment processes. It consists of removal of large size, suspended or floating materials and also
heavy settleble solids such as rags, sticks, grit, and grease.
— Primary treatment
Primary treatment targets the removal of settleable organic and inorganic solids by sedimentation,
and the removal of materials that will float (scum) by skimming. Enhanced removal of suspended
solids and organic matter from the wastewater can be accomplished by chemical addition or
filtration (e.g. fine mesh filtration).
— Secondary treatment
In secondary treatment, biological, chemical and physical processes are used to reduce most of
the soluble organic matter and organic and inorganic particulates, measured as BOD or COD and
TSS. There is a very wide range of biological processes used for secondary treatment including
those that incorporate suspended bacteria, fixed film and hybrid (i.e. suspended and fixed film
bacteria) followed by a solid-liquid separation step, typically by sedimentation (e.g. clarifier).
Typical biological processes used for secondary treatment include activated sludge, trickling
filters, rotating biological contactors and non-conventional treatment processes such as lagoons,
wetlands that are capable of achieving secondary treatment water quality criteria. Secondary
biological treatment can also remove nutrients. MBR is an alternative biological treatment process
for secondary treatment.
— Tertiary treatment
Tertiary treatment follows the secondary treatment of wastewater, and aims at producing higher
quality treated wastewater. Effluent from secondary treatment plants typically contains residual
dissolved organic constituents, suspended solids and colloidal particulate matter that, in certain
jurisdictions, and/or depending on the particular reuse application, can require further reduction.
Their removal can be achieved by filtration. Color and odor can also be constituents targeted for
removal by tertiary treatment. Tertiary treatment can include additional removal of nitrogen and
phosphorus.
— Advanced treatment
Advanced treatment targets the removal of TDS and/or trace constituents as required for
specific water reuse applications. This can include, for example, complex and/or toxic organic
compounds, heavy metals, color, odor compounds remaining after tertiary treatment and emerging
contaminants (e.g. pharmaceuticals, nanotechnology byproducts, etc.). Technologies to achieve
advanced treatment can include chemical or physical processes such as ozonation, advanced
oxidation, adsorption, or ion exchange, either singly or in combination with membrane technologies.
— Disinfection
Disinfection is enhanced by the upstream removal of particulate matter that often shields
pathogenic organisms from the disinfecting agent, and this is especially critical for UV disinfection.
Technologies used to remove particulates (e.g. filtration) not only improve the efficacy of
disinfection technologies, but can also reduce the number of pathogens present prior to disinfection
and form part of a multi-barrier approach to disinfection to ensure public health protection and
maximize process reliability. Disinfection can be used after secondary, tertiary, or advanced
treatment as necessary (see Figure 1).
— Post-chlorination
Post-chlorination is a method of adding and maintaining a minimum level of chlorine within the
reuse water distribution system. It provides the control of chlorine residual for the prevention
of regrowth of microorganisms or recontamination in distribution systems. Post-chlorination is
typically performed before reuse water is delivered to end users.
4.3 Treatment technologies used in fit-for-purpose water reuse
The required water quality for reuse water depends on the intended non-potable reuse application
and the degree of health and environmental risks associated with that application. As a rule, domestic,
6 © ISO 2018 – All rights reserved

commercial and irrigation water demands can be met using reclaimed water with a water quality lower
than drinking water, with the primary consideration being the degree of disinfection required to protect
public health. As a result, many jurisdictions have multiple reuse water quality standards, or treatment
objectives, that reflect the public health and environmental risks associated with specific categories of
water application. Treatment to remove the risks of clogging, biofilms, etc. is also necessary for some
industrial, urban or irrigation (for example, drip, sprinkler etc.) reuse applications. This framework
can be called “fit-for-purpose water reuse”, which achieves beneficial, safe and sustainable water reuse
with minimum energy and cost while protecting human health and the environment. The primary goal
to the success of this framework is to reclaim water to the water quality level that is acceptable for its
intended use, while ensuring the economic viability of water reuse projects, especially in the case of
decentralized small wastewater treatment systems, without significant impact on the environment.
Examples of types of treatment levels and technologies appropriate for various reuse applications are
provided in Table 1. Municipal wastewater treated to the level of primary treatment is generally not
considered suitable for water reuse applications. The level of secondary treatment with a degree of
disinfection suited to the associated potential risk of human contact is generally required for most
reuse applications. The degree of health risk is generally determined by the likelihood or ability for the
public to come into direct contact with the reuse water, as well as the concentration of health hazardous
constituents. Consequently, a lower level of disinfection can be acceptable for water reuse applications
where the public is restricted from, or has limited, access, such as for remote silviculture or agricultural
irrigation, and industrial water uses. Generally secondary or tertiary treatment incorporating
disinfection technologies to reduce pathogens is suitable for most non-potable water applications.
Table 1 — Examples of types of treatment levels and technologies
[20][24]
appropriate for various reuse applications
Increasing levels of treatment ―――――――――――――――――――→
Treatment
level
Preliminary/Primary Secondary Tertiary Advanced
Process Screening, grit and Biological oxidation fol- Chemical coagula- Activated carbon adsorp-
grease removal lowed by a solid-liquid tion, biological or tion/biofiltration, ion
separation chemical nutrient re- exchange, membrane
Sedimentation
moval, and filtration technologies, advanced
oxidation processes,
ozonation, soil aquifer
treatment.
End use No uses recommended — surface irriga-— landscape — surface water
tion of orchards and and golf course ir- reservoir augmentation
vineyards rigation
— direct aquifer
— non-food crop — toilet flush- recharge (e.g. seawater
irrigation ing intrusion barrier)
— restricted land-— vehicle — industrial sys-
cape impoundments washing tem, e.g. boiler
— wetlands, — food crop
wildlife habitat, stream irrigation
augmentation
— unrestricted
— industrial recreational im-
processes poundment
— industrial
systems, e.g.cooling
— ground
water recharge of
non-potable aquifer
NOTE  Disinfection can be used after secondary, tertiary, or advanced treatment as necessary.
Performance evaluation is required in selecting a “fit-for-purpose” water reuse treatment system.
5 Principles and general guidelines for performance evaluation
5.1 General
The purpose of performance evaluation is to determine whether individual treatment processes or
treatment systems can reliably and consistently meet specified water quality requirements. Depending
on the scale of the technology and application, performance evaluation testing may require a highly
specified testing protocol that includes:
— influent and effluent water quality and quantity criteria;
— testing conditions and duration;
— statistical criteria for use in data analysis.
There are two kinds of performance requirements: functional and non-functional. Functional
requirements are usually written in the form of “system shall do ”, and are related
to the ability of the technology to transform the influent water quality constituents. Non-functional
requirements are written in the form of “system shall be ”, and are related to the quality
of the equipment being tested (e.g. water tightness of tanks, noise generation, labelling, etc.)
8 © ISO 2018 – All rights reserved

Performance evaluation is generally achieved by following specified testing protocols and data
gathering procedures that include real-time online monitoring, sampling and testing, ancillary data
collection, documentation and scientifically valid data analysis procedures.
Performance evaluation also assists in developing an understanding of the treatment system
performance over a sufficient period of time to determine the dependability of the technology and risk
of failure. Combined with failure mode analysis, the analysis of long-term process performance provides
a relevant basis to develop adequate preventive and corrective measures to consistently achieve the
required water quality criteria, and to reduce the financial, health and environment risks associated
with such failure. See Annex A and B for additional information.
Performance requirements for water reuse systems or processes depend on stakeholders as well as
water reuse applications. Stakeholders can include regulators, manufacturers, designers, installers,
operators and end users. The performance evaluation requirements to fulfil the needs of these
stakeholder groups are expected to include both functional and non-functional criteria as well as
quantitative and qualitative parameters.
5.2 Performance requirements
5.2.1 Treatment technology functional requirements
Functional requirements for treatment technologies address the transformation of influent water
quality constituents to produce reuse water, and include both water quality and water quantity
parameters. Functional requirements are associated with safety objectives. Performance of treatment
technologies can be expressed as the concentration of constituents in the reclaimed water or by the
degree of constituent removal expressed as a percentage or logarithmic removal value. The functional
requirement for water quantity is generally expressed as the minimum, average, and maximum volume
of water that can be reclaimed, expressed as a daily flow and a maximum instantaneous flow rate, while
consistently meeting water quality requirements.
Functional requirements are generally expressed as statistical parameters including maximums,
minimums, arithmetic or logarithmic averages (means), medians or percentiles.
When performance evaluation is conducted based on a test, functional requirements generally involve
specifying the analytical methods of monitoring water quality parameters as well as specifying the
reference values which are used to judge whether the treatment technology fulfils the requirements.
The functional requirements focus on the following treatment technology effects:
— treated effluent characteristics (i.e. concentration of residual constituents);
— removal of constituents [e.g. removal efficiency or log removal value (LRV)];
— changes in other water quality indicators (e.g. temperature, toxicity, colour).
5.2.2 Treatment technology non-functional requirements
There can be a variety of non-functional requirements related to wastewater treatment technologies
including:
— dependability (e.g. duration of operation without operator intervention; long-term, trouble-free
operation);
— efficiency (e.g. water recovery ratio, energy consumption, chemicals use and plant operation);
— sustainability (i.e. economic, social and environmental factors and values);
— resilience (e.g. stress testing for over and under-loaded operating conditions, power failure, etc.);
— residual and byproduct generation (e.g. biosolids generation, odours, noise, disinfection byproducts);
— materials (e.g. structural integrity).
5.2.3 Characteristics of functional and non-functional requirements in performance evaluation
Characteristics of functional and non-functional requirements in performance evaluation are described
in Table 2. Each country or local government may apply some items of this table appropriately depending
on the type of water reuse application and local regulation.
The explanations of functional and non-functional requirements are provided in Clauses 6 and 7,
respectively.
Table 2 — Characteristics of functional and non-functional requirements in performance
evaluation of water reuse systems
Technology performance evaluation
Functional requirement Non-functional requirement
Characteristics Absoluteness Relativeness
(compliance/non-compliance) (comparison, improvement)
Water quality parameters and removal Performance indicators associated with
efficiency associated with the following: followings:
Public health target Environmental performance
— health risk target — energy consumption
— water quality target — chemical consumption
Environmental target
— waste generated and requiring
disposal
— water quality target
— greenhouse gas emission
Representative param-
Economic performance
eters or indicators for
evaluation
— capital cost
— operating cost
— life cycle cost
Dependability
— availability
— reliability (failure frequency)
Alarms
— audible, visual, remote
Representative application Evaluation methods
— qualitative risk control ap- — benchmarking, comparison with
proach and/or quantitative risk control best practices
approach (see ISO 20426)
Possible methods for
— comparison with past trend
evaluation and manage-
Evaluation methods Management methods
ment
— comparison with target value — continuous improvement
Management methods
— preventive and corrective actions
5.3 P erformance evaluation and meeting requirements
5.3.1 General
There are two approaches to evaluate whether performance requirements are being achieved or not.
One is to monitor and record the water quality parameters measured onsite during operation of the
facilities and compare the recorded data with the target performance criteria. The other is to measure
10 © ISO 2018 – All rights reserved

water quality parameters and calculate the removal efficiency based on the monitoring data and
compare the results with prediced values.
Appropriate water quality parameters should be selected or identified to quantifiably describe the
treatment technology performance requirements.
5.3.2 Monitoring plan
A monitoring plan should be established to collect the necessary data to obtain the variables and other
parameters related to the treatment system operation and performance. The monitoring plan should
specify the treatment system operating conditions during data collection, with the expectation that
these conditions are representative of those the process will experience over its operational life-span,
and over a sufficient duration to be deemed representative of those conditions. These conditions include
both expected normal routine operation as well as conditions reflecting abnormal operation such as
extended periods without use or loading (e.g. family vacations), extended periods of power failure, and
overloading.
The frequency of sampling and the amount of data collected should be determined taking into
consideration the expected variation in constituent concentrations and other monitored parameters
to ensure the data collected is representative and, as needed, to establish statistical characteristics
of the values of water quality parameters and removal efficiency. For package plant or pilot test
facility performance evaluation, the entire test plan should be specified and clearly formulated before
conducting the test.
Where the constituents of interest are present at extremely low concentrations that are close to
the analytical detection limits, or where standardized analytical methods are not available and it is
impossible or too expensive to measure the constituents of interest, surrogate parameter(s) that are
directly associated or correlate well with the target parameter(s), can be used. Use of online monitoring
(for target constituents and surrogates) is very important to assess the treatment reliability.
5.4 Application of the guidelines to treatment systems
5.4.1 Treatment system design
The raw wastewater quality and quantity characteristics should be determined based on reasonable
population projections combined with the collection and analysis of flow and water quality monitoring
data to predict the range in constituent concentrations and flows that can be experienced over the
expected operating life-span of the system. Similarly, the functional performance requirements of
potential reuse applications to satisfy non-potable applications, and offset potable water demands,
should take into consideration the water quality and quantity requirements of those reuse applications.
For a single treatment system application, the design should be based on fulfilling the functional and
non-functional requirements of the highest-risk reuse application under consideration, taking into
account the source wastewater characteristics. However, opportunities should also be considered for
the application of point-of-entry and/or point-of-use advanced water treatment, rather than necessarily
treating all of the reuse water to the same standard.
In addition to meeting both functional and non-functional performance requirements for the selected
highest risk reuse application, the treatment system design should consider what combination of
treatment processes is most suited to meet more stringent requirements: such as multi-barrier options
and point-of-use additional treatment, which are mentioned in ISO 20760-1 and ISO 20760-2.
5.4.2 Treatment system configuration
Treatment system configuration refers to the arrangement of the treatment system components and
includes the treatment system, water storage for flow equalization and operational stability, and
pumps, pipes and fittings that connect treatment system elements. The configuration also includes
electrical, instrumentation and control system elements for the purpose of ensuring the stable and
reliable performance of the treatment facility as a whole. Redundancy of some critical elements (e.g.
power supply, stand-by pumps and blowers, etc.) should be also taken into consideration.
Although the boundary condition for carrying out performance evaluations is usually the treatment
system being evaluated, it can extend from the wastewater source through to the site of reuse
applications.
6 Functional requirements
6.1 General
Functional performance evaluation addresses whether the unit treatment process(es) and/or treatment
system(s) meet predetermined treatment specifications and water quality requirements. Depending on
the scale of application, this evaluation may be carried out under highly-controlled and prescriptive
testing conditions, or it may follow an established data collection and analysis protocol intended to
ensure reasonable replicability and costs. In addition to establishing equipment and system treatment
performance capacities it may also be used for
— identifying process limitations and required modifications to improve reuse water quality at
existing water reclamation facilities,
— est
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