Guidelines for performance evaluation of treatment technologies for water reuse systems

This document provides guidelines for performance evaluation methods of UV disinfection for full scale water reuse systems. It deals with the methods of measurement of typical parameters which indicate performance of UV disinfection systems.

Lignes directrices pour l’évaluation des performances des techniques de traitement des systèmes de réutilisation de l’eau

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Status
Published
Publication Date
17-May-2021
Current Stage
5060 - Close of voting Proof returned by Secretariat
Start Date
24-Apr-2021
Completion Date
23-Apr-2021
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INTERNATIONAL ISO
STANDARD 20468-4
First edition
2021-05
Guidelines for performance evaluation
of treatment technologies for water
reuse systems —
Part 4:
UV Disinfection
Lignes directrices pour l’évaluation des performances des techniques
de traitement des systèmes de réutilisation de l’eau —
Partie 4: Désinfection aux UV
Reference number
ISO 20468-4:2021(E)
ISO 2021
---------------------- Page: 1 ----------------------
ISO 20468-4:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2021

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
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2021 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 20468-4:2021(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms, definitions and abbreviated terms ................................................................................................................................ 1

3.1 Terms and definitions ....................................................................................................................................................................... 1

3.2 List of abbreviated terms ............................................................................................................................................................... 3

4 Purpose and function of UV disinfection ..................................................................................................................................... 3

4.1 Purpose .......................................................................................................................................................................................................... 3

4.2 Function ........................................................................................................................................................................................................ 3

5 System configuration ....................................................................................................................................................................................... 3

5.1 General ........................................................................................................................................................................................................... 3

5.2 UV unit ............................................................................................................................................................................................................ 4

5.3 Influent water quality monitoring devices ..................................................................................................................... 4

5.4 Flow meter .................................................................................................................................................................................................. 4

5.5 Power control panel ........................................................................................................................................................................... 4

6 Functional requirements ............................................................................................................................................................................. 5

6.1 General ........................................................................................................................................................................................................... 5

6.2 Evaluation of the UV unit performance ............................................................................................................................. 5

6.3 Method of monitoring UV treatment system performance .............................................................................. 5

6.3.1 Monitoring of influent water flow [M1] ....................................................................................................... 6

6.3.2 Quality control of influent water [M2] .......................................................................................................... 6

6.3.3 Monitoring of UV irradiation [M3] ................................................................................................................... 6

6.3.4 Monitoring of treated water quality [M4] .................................................................................................. 7

6.4 Diagnosis of causes for system failure ................................................................................................................................ 8

7 Non-Functional requirements ................................................................................................................................................................ 8

7.1 Environmental performance ....................................................................................................................................................... 8

7.1.1 Energy efficiency.............................................................................................................................................................. 8

7.1.2 Chemical consumption ............................................................................................................................................... 8

7.2 Safety ............................................................................................................................................................................................................... 8

7.3 Cost effectiveness of systems — Economic evaluation by LCC...................................................................... 9

7.4 Reliability and resilience ................................................................................................................................................................ 9

Annex A (informative) Main treatment technologies and target constituents for water reuse ...........10

Annex B (informative) Experimental evaluation method for UV units ..........................................................................11

Annex C (informative) Experimental evaluation method in combination with CFD-I simulations ..12

Bibliography .............................................................................................................................................................................................................................18

© ISO 2021 – All rights reserved iii
---------------------- Page: 3 ----------------------
ISO 20468-4:2021(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.

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 2021 – All rights reserved
---------------------- Page: 4 ----------------------
ISO 20468-4:2021(E)
Introduction

The rapidly growing global market for water reuse technologies inevitably demands standards which

are applicable on a world-wide basis. Many regions in the world are facing water shortages, and there

is great interest in the use of technologies that can treat wastewater and make the reclaimed water

available for a wide range of reuse applications that can satisfy non-potable water demands, thereby

conserving precious potable water supplies. Simultaneously, the implementation of water reuse

schemes is raising public and regulatory concerns regarding potential human health, environmental

and societal impacts. This has led to an increasing need to specify various aspects of water reuse

projects and there is a growing need on behalf of regulators, reuse technology suppliers, and users

of those technologies for international standardization. Without ISO water reuse standards, a great

number of opportunities for sustainable development based on water reuse will be lost.

Standardization needs 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 most appropriate technologies in an unbiased way to achieve the objectives of the

water reuse project. 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 water reuse 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 from multitude of applications.

Based on the discussion in the meetings of ISO/TC 282/SC 3, ISO 20468-1 titled “Guidelines for

performance evaluation of treatment technologies for water reuse systems – Part 1: General” has

been developed to establish the standard of generic aspects for performance evaluation which can be

applied to a variety of wastewater treatment technologies and their combinations, while descriptions

specific to the representative technologies should be included in individual standards being submitted

subsequently to ISO 20468-1. In this context, this document stipulating specific ways of performance

evaluation of UV treatment technology for water reuse systems, based on ISO 20468-1 as the generic

standard is established herein.

In non-potable water reuse systems, UV technology is used mainly for disinfection as indicated in

Table A.1 and works well with secondary or tertiary treated water as shown in ISO 20468-1:2018,

Figure 1.

This guideline is intended as an integrated part of a framework for UV systems, consistent with other

items in the work of TC 282. This framework includes several important aspects such as design,

validation and verification (ISO 9000) and evaluation.

Guidelines focused on UV System Design, Validation and Evaluation are found in ISO 16075-5:2021,

Clause 7.

Guidelines focused on UV system Design, Verification and Evaluation are found in ISO 20468-4.

© ISO 2021 – All rights reserved v
---------------------- Page: 5 ----------------------
INTERNATIONAL STANDARD ISO 20468-4:2021(E)
Guidelines for performance evaluation of treatment
technologies for water reuse systems —
Part 4:
UV Disinfection
1 Scope

This document provides guidelines for performance evaluation methods of UV disinfection for full scale

water reuse systems. It deals with the methods of measurement of typical parameters which indicate

performance of UV disinfection systems.
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
biodosimetry

procedure of measuring the UV reduction equivalent dose (3.1.7) of a specific microorganism in a UV unit

and a comparing the results to the known UV dose-response curve of this microorganism determined

by bioassay (typically collimated beam methods)
3.1.2
challenge microorganism
microorganism used for a biodosimetry (3.1.1)

Note 1 to entry: Common challenge microorganisms include Bacteriophages MS2, Qβ and T1UV as well as Bacillus

subtilis spores
3.1.3
computational fluid dynamics-intensity

simulation method to model a UV unit by performing a combination of computational fluid dynamics

(CFD) and optical analysis
© ISO 2021 – All rights reserved 1
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ISO 20468-4:2021(E)
3.1.4
lamp protection component

apparatus for protecting the light source, including a lamp protection sleeve, tube or other component

Note 1 to entry: Lamp protection sleeve – the quartz tube or thimble that surrounds and protects the UV lamp.

The exterior is in direct contact with the water being treated
3.1.5
low pressure lamp

mercury-vapour lamp that operates at an internal pressure of 0,13 Pa to 1,3 Pa (2 × 10 psi to

2 × 10 psi) and electrical input of 0,5 watts per centimetre (W/cm)

Note 1 to entry: This results in essentially monochromatic light output at 253,7 nm.

3.1.6
medium pressure lamp

mercury-vapour lamp that operate at an internal pressure of 13 kPa to 1,300 kPa (2 psi to 200 psi) and

electrical output of 50 W/cm to 300 W/cm

Note 1 to entry: This results in a polychromatic (or broad spectrum) light output at multiple wavelengths,

generally between 200 nm to 400 nm.
3.1.7
reduction equivalent dose
dose of UV in a given device which is determined by biodosimetry (3.1.1)
Note 1 to entry: See “UV dose” and “biodosimetry”.

Note 2 to entry: This UV dose is determined by measuring the inactivation of a challenge microorganism after

exposure to UV light in a UV unit and comparing the results to the known UV dose response curve of the same

challenge organism determined via Bench scale collimated beam testing.
3.1.8
UV dose
UV fluence

amount of UV energy given as the time integral of the fluence rate or irradiance (W/m )

2 2
Note 1 to entry: This is given in units of mJ/cm or J/m .
3.1.9
UV irradiance
UV fluence rate
UV intensity

UV output emitted from a given light source and entering a unit area of the irradiated surface. The

2 2
value is typically given in W/m or mW/cm

Note 1 to entry: The terms UV irradiance, fluence rate or intensity are often used to mean the same thing.

Note 2 to entry: For details, refer to Bolton and Linden 2003.
3.1.10
UV intensity sensor

UV irradiance (3.1.9) meter or radiometer instrument to measure UV irradiance (3.1.9)

3.1.11
UV transmittance

fraction of photons in the UV spectrum transmitted through a material such as water or quartz

Note 1 to entry: It is preferable that an online UVT sensor be installed and used to verify UVT.

Note 2 to entry: The wavelength of the UVT (unit %) should be specified, often using a path-length of 1 cm. The

measurement is calibrated compared to ultra-pure water (ISO 3696 grade 1 or equivalent).

2 © ISO 2021 – All rights reserved
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ISO 20468-4:2021(E)

Note 3 to entry: UVT is related to the UV absorbance (A) by the following equation (for a 1- cm path length):

% UVT = 100 × 10 .
3.2 List of abbreviated terms
AOPs advanced oxidation processes
BOD biochemical oxygen demand
CFD-I computational fluid dynamics-intensity
E. coli Escherichia coli
LCC life cycle cost
PCD pitch circle diameter
POPs persistent organic pollutants
RED reduction equivalent dose
TDS total dissolved solids
TSS total suspended solids
UV ultraviolet
UVT ultraviolet transmittance
4 Purpose and function of UV disinfection
4.1 Purpose

To conduct water reuse, secondary or tertiary treated wastewater requires disinfection and sometimes

further treatment by more advanced processes. The treated and disinfected wastewater is then used

for various applications such as, urban, agricultural, industrial recreational and environmental uses.

4.2 Function

UV light has been proven effective against microorganisms including bacteria, protozoa and viruses

(see Annex A). UV disinfection is achieved mostly by the absorption of photons by the genome of

microorganisms, resulting in the formation of damage such as pyrimidine dimers on DNA or RNA. Such

lesions hinder the self-replication in the microorganisms and thus deprives the infectivity. Accordingly,

UV disinfection does not require chemical addition and results in limited by-product formation.

5 System configuration
5.1 General

A UV disinfection system for water reuse can consist of the following components and systems may

have several of each component based on the disinfection application requirements.

— UV unit;
— influent water quality monitoring devices;
— flow meter;
© ISO 2021 – All rights reserved 3
---------------------- Page: 8 ----------------------
ISO 20468-4:2021(E)
— power control panel.
Each component will be explained in 5.2 to 5.5.
5.2 UV unit

A UV unit has simple components including irradiation chamber, a light source, an automatic cleaning

system and a UV intensity sensor. A specific UV unit may need one or more UV intensity sensor and

one or more irradiation chamber and light source, depending on the specifics of the application. UV

units may be categorized into closed and open systems, based on the configuration of UV units in the

irradiation chamber. The closed system has a UV unit, comprised of UV lamps and their sleeves, placed

in the closed vessel flow chamber. Meanwhile, the open system has a UV unit immersed in an open

channel or chamber with gravity flow and water level control device. UV systems can also consist of

non-contact unit designs with UV lamps suspended outside a transparent conduit that carries the

wastewater.
— light source

A light source for UV disinfection should have a germicidal emission at wavelengths appropriate to

the task, often at the wavelength of 253,7 nm or a combination of wavelengths between 200-385 nm.

Options include low-pressure mercury lamps, medium-pressure mercury lamps, excimer lamps,

pulsed-Xenon lamps, and ultraviolet light emitting diodes. The light source should be housed in a lamp

protection component.
— cleaning system

A cleaning system is the device having a wiper driven by electric power supply, hydraulic power supply

or pressurized air, or ultrasonic wave, etc. Options include a mechanical wiper consisting of a brush,

ring or a mechanical chemical wiper consisting of a chamber with rings filled with a washing liquid.

— UV intensity sensor

A UV intensity sensor is installed to measure the UV irradiance in the irradiation chamber so that the

irradiance can be tracked and it can be determined whether the required dose has been provided.

— ballast

A ballast is installed when using a UV lamp as a light source. Ballasts provide the power that the lamp

converts to UV photons (energy).
5.3 Influent water quality monitoring devices

A UV transmittance monitor can be used to feed data to the system controller to adjust the power of

the lamp to assure that the required dose is provided. To check whether or not the water quality of the

influent has changed from the design conditions, water quality monitors including a UV transmittance

monitor, a turbidity meter (optional) etc. are used.
5.4 Flow meter

Generally, each UV unit should have a dedicated flow meter for several reasons, including to confirm

that the unit is operating within the validated flow rate range. The measured flow rate data may be sent

to control panel and may be utilized for light-source controlling, monitoring and operating in order to

achieve system performance. The method of flow rate measurement should be selected according to the

variability in plant flow rate and installation conditions.
5.5 Power control panel

The control panel has the following functions: power receiving, power supplying, controlling,

monitoring and operating, and other functions for the light source and other apparatuses.

4 © ISO 2021 – All rights reserved
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ISO 20468-4:2021(E)
6 Functional requirements
6.1 General

Functional requirements for treatment technologies address the transformation of influent water

quality constituents to produce reclaimed water and include both water quality and water quantity

parameters.

One of the functional requirements of a given UV treatment system is to secure, at all times, enough

UV dose to obtain a target quality of the reclaimed water that is appropriate for application of such

water. The UV dose is the time integral of the fluence rate or irradiance. What is necessary to this end

includes: use of a UV light source with appropriate irradiance; and retaining the reclaimed water in a

UV irradiation chamber for a predetermined time period.

In actual equipment, the irradiation time and UV irradiance in the UV irradiation chamber vary from

one portion to another due to the shape of the chamber, as well as the location and number of the light

sources, and other similar factors. Water quality determined by, for example, suspended matter and

UV absorbing components also reduces UV transmittance, and thereby affects UV dose distribution. By

taking these influences into consideration, a predetermined UV dose, or higher dose that is sufficient

for the water flow passing through the UV irradiation chamber, shall be secured at all times.

Methods for evaluating the performance of the UV unit in the design stage and for subsequently

monitoring the performance of the UV disinfection system in operation are provided below.

6.2 Evaluation of the UV unit performance

Evaluation of the UV unit performance should be done; a number of experimental methods may be used

including those described in Annex B, while the method in Annex C is accepted as a second option.

NOTE The amount of upscaling varies from no upscaling permitted to a specific level of upscaling permitted

depending on country regulations.
Method I: Annex B (Experimental evaluation method)
I-1: Experimental testing using a challenge microorganism
I-1-1: Preliminary testing
I-1-2: Full-scale unit testing
I-2: Determine the RED

Method II: Annex C (Experimental evaluation method in combination with CFD-I simulations)

II-1: Experimental testing using a challenge organism for reference unit
II-2: Intensity measurement test on UV light source
II-3: Development of the CFD-I simulation models
II-4: Determine the RED in the unit of interest
6.3 Method of monitoring UV treatment system performance

The UV treatment system can be run automatically, so that its usual operation is generally simple

compared to other disinfection processes. What is important for routine maintenance includes:

monitoring the amount and the quality of UV treatment target water; and monitoring the UV dose.

Figure 1 shows the water flow through the UV treatment system and the monitoring points situated in

the system.
© ISO 2021 – All rights reserved 5
---------------------- Page: 10 ----------------------
ISO 20468-4:2021(E)

Figure 1 — Typical configuration of UV disinfection system and monitoring points in UV

disinfection system
6.3.1 Monitoring of influent water flow [M1]

To check the water flow rate through the UV unit for deviation from the design flow rate, a flow meter

is required as ancillary equipment. To check whether the flow meter is functioning problem-free, it is

recommended to perform calibration within a period specified by the manufacturer.

EXAMPLE Manufacturer's recommendations: once a year.
6.3.2 Quality control of influent water [M2]

Colloidal solids, suspended solids, colour and dissolved solids (particularly dissolved organic

compounds) can absorb UV radiation, reduce UV transmission and decrease UV disinfection. If, in

addition, UV absorbing substances such as iron, manganese, sulphurous acid, nitrous acid, and phenol

exist, they reduce UV transmittance and thereby affect the treatment effect. Furthermore, constituents

such as iron, calcium and magnesium can cause scaling and interfere with UV irradiation and intensity.

Consequently, the presence and potential of these constituents to adversely impact disinfection shall be

addressed during the design stage and appropriate O&M cleaning procedures implemented to reduce

or eliminate their impact on disinfection.

Accordingly, these water quality parameters need to be measured and monitored on a regular basis.

If the water quality of the treatment target water does not satisfy the conditions for UV application, a

possible halt in the treatment shall be taken into consideration.

NOTE Generally, when these water quality parameters are well controlled by pre-treatment, fluctuations

are small but could be significant depending on capacity and performance of the pre-treatment.

6.3.3 Monitoring of UV irradiation [M3]

In the course of the evaluation of the UV unit, the minimum UV irradiance for a maximum flow at a

minimum UVT of the water is defined.

Monitoring UV irradiation cannot be performed by biodosimetry in routine operation and maintenance.

Instead, the UV system is operated in a way that the UV irradiance is kept within the designed range,

which is monitored by one or more online UV intensity sensors mounted on the UV irradiation chamber.

To keep the appropriate UV irradiance, the following items shall be monitored, and maintenance work

shall be conducted if necessary.
— UV light sources
6 © ISO 2021 – All rights reserved
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ISO 20468-4:2021(E)

Check the cumulative use time of the UV light source. Replace the light source according to its service

life (operating time) or performance parameters presented by the manufacturer.
— Lamp protection component

When fouling substances adhere to the surface of the lamp protection component, the amount of UV that

can enter the water decreases. The extent of sleeve fouling can be monitored based on the UV intensity

sensor signal. Most UV systems have low intensity alarms that trigger when too much fouling builds

up on the lamp protection component. However, relying on the UV intensity sensor signal to assess the

extent of fouling is not always sufficient. Visually, check the degree of fouling on the surface regularly.

Make sure the UV light sources are turned off before looking at the sleeves. In addition, cleaning of the

lamp protection component should be conducted. Possible cleaning methods include physical cleaning

using automatic cleaner onlin
...

FINAL
INTERNATIONAL ISO/FDIS
DRAFT
STANDARD 20468-4
ISO/TC 282/SC 3
Guidelines for performance evaluation
Secretariat: JISC
of treatment technologies for water
Voting begins on:
2021-02-26 reuse systems —
Voting terminates on:
Part 4:
2021-04-23
UV Disinfection
Lignes directrices pour l’évaluation des performances des techniques
de traitement des systèmes de réutilisation de l’eau —
Partie 4: Désinfection aux UV
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
Reference number
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
ISO/FDIS 20468-4:2021(E)
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. ISO 2021
---------------------- Page: 1 ----------------------
ISO/FDIS 20468-4:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2021

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
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2021 – All rights reserved
---------------------- Page: 2 ----------------------
ISO/FDIS 20468-4:2021(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms, definitions and abbreviated terms ................................................................................................................................ 1

3.1 Terms and definitions ....................................................................................................................................................................... 1

3.2 List of abbreviated terms ............................................................................................................................................................... 3

4 Purpose and function of UV disinfection ..................................................................................................................................... 3

4.1 Purpose .......................................................................................................................................................................................................... 3

4.2 Function ........................................................................................................................................................................................................ 3

5 System configuration ....................................................................................................................................................................................... 3

5.1 General ........................................................................................................................................................................................................... 3

5.2 UV unit ............................................................................................................................................................................................................ 4

5.3 Influent water quality monitoring devices ..................................................................................................................... 4

5.4 Flow meter .................................................................................................................................................................................................. 4

5.5 Power control panel ........................................................................................................................................................................... 4

6 Functional requirements ............................................................................................................................................................................. 5

6.1 General ........................................................................................................................................................................................................... 5

6.2 Evaluation of the UV unit performance ............................................................................................................................. 5

6.3 Method of monitoring UV treatment system performance .............................................................................. 5

6.3.1 Monitoring of influent water flow [M1] ....................................................................................................... 6

6.3.2 Quality control of influent water [M2] .......................................................................................................... 6

6.3.3 Monitoring of UV irradiation [M3] ................................................................................................................... 6

6.3.4 Monitoring of treated water quality [M4] .................................................................................................. 7

6.4 Diagnosis of causes for system failure ................................................................................................................................ 8

7 Non-Functional requirements ................................................................................................................................................................ 8

7.1 Environmental performance ....................................................................................................................................................... 8

7.1.1 Energy efficiency.............................................................................................................................................................. 8

7.1.2 Chemical consumption ............................................................................................................................................... 8

7.2 Safety ............................................................................................................................................................................................................... 8

7.3 Cost effectiveness of systems — Economic evaluation by LCC...................................................................... 9

7.4 Reliability and resilience ................................................................................................................................................................ 9

Annex A (informative) Main treatment technologies and target constituents for water reuse ...........10

Annex B (informative) Experimental evaluation method for UV units ..........................................................................11

Annex C (informative) Experimental evaluation method in combination with CFD-I simulations ..12

Bibliography .............................................................................................................................................................................................................................18

© ISO 2021 – All rights reserved iii
---------------------- Page: 3 ----------------------
ISO/FDIS 20468-4:2021(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.

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 2021 – All rights reserved
---------------------- Page: 4 ----------------------
ISO/FDIS 20468-4:2021(E)
Introduction

The rapidly growing global market for water reuse technologies inevitably demands standards which

are applicable on a world-wide basis. Many regions in the world are facing water shortages, and there

is great interest in the use of technologies that can treat wastewater and make the reclaimed water

available for a wide range of reuse applications that can satisfy non-potable water demands, thereby

conserving precious potable water supplies. Simultaneously, the implementation of water reuse

schemes is raising public and regulatory concerns regarding potential human health, environmental

and societal impacts. This has led to an increasing need to specify various aspects of water reuse

projects and there is a growing need on behalf of regulators, reuse technology suppliers, and users

of those technologies for international standardization. Without ISO water reuse standards, a great

number of opportunities for sustainable development based on water reuse will be lost.

Standardization needs 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 most appropriate technologies in an unbiased way to achieve the objectives of the

water reuse project. 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 water reuse 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 from multitude of applications.

Based on the discussion in the meetings of ISO/TC 282/SC 3, ISO 20468-1 titled “Guidelines for

performance evaluation of treatment technologies for water reuse systems – Part 1: General” has

been developed to establish the standard of generic aspects for performance evaluation which can be

applied to a variety of wastewater treatment technologies and their combinations, while descriptions

specific to the representative technologies should be included in individual standards being submitted

subsequently to ISO 20468-1. In this context, this document stipulating specific ways of performance

evaluation of UV treatment technology for water reuse systems, based on ISO 20468-1 as the generic

standard is established herein.

In non-potable water reuse systems, UV technology is used mainly for disinfection as indicated in

Table A.1 and works well with secondary or tertiary treated water as shown in ISO 20468-1:2018,

Figure 1.

This guideline is intended as an integrated part of a framework for UV systems, consistent with other

items in the work of TC 282. This framework includes several important aspects such as design,

validation and verification (ISO 9000) and evaluation.

Guidelines focused on UV System Design, Validation and Evaluation are found in ISO 16075-5:—,

Clause 7.

Guidelines focused on UV system Design, Verification and Evaluation are found in ISO 20468-4.

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FINAL DRAFT INTERNATIONAL STANDARD ISO/FDIS 20468-4:2021(E)
Guidelines for performance evaluation of treatment
technologies for water reuse systems —
Part 4:
UV Disinfection
1 Scope

This document provides guidelines for performance evaluation methods of UV disinfection for full scale

water reuse systems. It deals with the methods of measurement of typical parameters which indicate

performance of UV disinfection systems.
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
biodosimetry

procedure of measuring the UV reduction equivalent dose (3.1.7) of a specific microorganism in a UV unit

and a comparing the results to the known UV dose-response curve of this microorganism determine by

bioassay (typically collimated beam methods)
3.1.2
challenge microorganism
microorganism used for a biodosimetry (3.1.1)

Note 1 to entry: Common challenge microorganisms include Bacteriophages MS2, Qβ and T1UV as well as Bacillus

subtilis spores
3.1.3
computational fluid dynamics-intensity

simulation method to model a UV unit by performing a combination of computational fluid dynamics

(CFD) and optical analysis
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3.1.4
lamp protection component

apparatus for protecting the light source, including a lamp protection sleeve, tube or other component

Note 1 to entry: Lamp protection sleeve – the quartz tube or thimble that surrounds and protects the UV lamp.

The exterior is in direct contact with the water being treated
3.1.5
low pressure lamp

mercury-vapour lamp that operates at an internal pressure of 0,13 Pa to 13,0 Pa (2 × 10 psi to 2 ×

10 psi) and electrical input of 0,5 watts per centimetre (W/cm)

Note 1 to entry: This results in essentially monochromatic light output at 253,7 nm.

3.1.6
medium pressure lamp

mercury-vapour lamp that operate at an internal pressure of 13 kPa to 1,300 kPa (2 psi to 200 psi) and

electrical output of 50 W/cm to 300 W/cm

Note 1 to entry: This results in a polychromatic (or broad spectrum) light output at multiple wavelengths,

generally between 200 nm to 400 nm.
3.1.7
reduction equivalent dose
dose of UV in a given device which is determined by biodosimetry (3.1.1)
Note 1 to entry: See “UV dose” and “biodosimetry”.

Note 2 to entry: This UV dose is determined by measuring the inactivation of a challenge microorganism after

exposure to UV light in a UV unit and comparing the results to the known UV dose response curve of the same

challenge organism determined via Bench scale collimated beam testing.
3.1.8
UV dose
UV fluence

amount of UV energy given as the time integral of the fluence rate or irradiance (W/m )

2 2
Note 1 to entry: This is given in units of mJ/cm or J/m .
3.1.9
UV irradiance
UV fluence rate
UV intensity

UV output emitted from a given light source and entering a unit area of the irradiated surface. The

2 2
value is typically given in W/m or mW/cm

Note 1 to entry: The terms UV irradiance, fluence rate or intensity are often used to mean the same thing.

Note 2 to entry: For details, refer to Bolton and Linden 2003.
3.1.10
UV intensity sensor

UV irradiance (3.1.9) meter or radiometer instrument to measure UV irradiance (3.1.9)

3.1.11
UV transmittance

fraction of photons in the UV spectrum transmitted through a material such as water or quartz

Note 1 to entry: It is preferable that an online UVT sensor be installed and used to verify UVT.

Note 2 to entry: The wavelength of the UVT (unit %) should be specified, often using a path-length of 1 cm. The

measurement is calibrated compared to ultra-pure water (ISO 3696 grade 1 or equivalent).

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Note 3 to entry: UVT is related to the UV absorbance (A) by the following equation (for a 1- cm path length): %

UVT = 100 × 10 .
3.2 List of abbreviated terms
AOPs advanced oxidation processes
BOD biochemical oxygen demand
CFD-I computational fluid dynamics-intensity
E. coli Escherichia coli
LCC life cycle cost
PCD pitch circle diameter
POPs persistent organic pollutants
RED reduction equivalent dose
TDS total dissolved solid
TSS total suspended solid
UVT ultraviolet transmittance
4 Purpose and function of UV disinfection
4.1 Purpose

To conduct water reuse, secondary or tertiary treated wastewater requires disinfection and sometimes

further treatment by more advanced processes. The advanced treated wastewater is then used for

various applications such as, urban, agricultural, industrial recreational and environmental uses.

4.2 Function

UV light has been proven effective against microorganisms including bacteria, protozoa and viruses

(see Annex A). UV disinfection is performed mostly by the absorption of photons by the genome of

microorganisms, resulting in the formation of damage such as pyrimidine dimers on DNA or RNA. Such

lesions hinder the self-replication in the microorganism and thus deprive the infectivity. Accordingly,

UV disinfection does not require chemical addition and results in limited by-product formation.

5 System configuration
5.1 General

A UV disinfection system for water reuse can consist of these and systems may have several of each

component based on the disinfection application requirements.
— UV unit;
— influent water quality monitoring devices;
— flow meter;
— power control panel.
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Each component will be explained in 5.2 to 5.5.
5.2 UV unit

A UV unit has simple components including irradiation chamber, a light source, a cleaning system and

a UV intensity sensor. A specific UV unit may need one or more UV intensity sensor and one or more

irradiation chamber and light source, depending on the specifics of the application. UV units may be

categorized into closed and open systems, based on the configuration of UV units in the irradiation

chamber. The closed system has a UV unit, comprised of UV lamps and their sleeves, placed in the

closed vessel flow chamber. Meanwhile, the open system has a UV unit immersed in an open channel or

chamber with gravity flow and water level control device. UV systems can also consist of non-contact

unit designs with UV lamps suspended outside a transparent conduit that carries the wastewater.

— light source

A light source for UV disinfection should have a germicidal emission at wavelengths appropriate to

the task, often at the wavelength of 253,7 nm or a combination of wavelengths between 200-385 nm.

Options include low-pressure mercury lamps, medium-pressure mercury lamps, excimer lamps,

pulsed-Xenon lamps, and ultraviolet light emitting diodes. The light source should be housed in a lamp

protection component.
— cleaning system

A cleaning system is the device having a wiper driven by electric power supply, hydraulic power supply

or pressurized air, or ultrasonic wave, etc. Options include a mechanical wiper consisting of a brush,

ring or a mechanical chemical wiper consisting of a chamber with rings filled with a washing liquid.

— UV intensity sensor

A UV intensity sensor is installed to measure the UV irradiance in the irradiation chamber so that the

irradiance can be tracked and it can be determined whether the required dose has been provided.

— ballast

A ballast is installed when using a UV lamp as a light source. Ballasts provide the power that the lamp

converts to UV photons (energy).
5.3 Influent water quality monitoring devices

A UV transmittance monitor can be used to feed data to the system controller to adjust the power of

the lamp to assure that the required dose is provided. To check whether or not the water quality of the

influent has changed from the design conditions, water quality monitors including a UV transmittance

monitor, a turbidity meter (optional) etc. are used.
5.4 Flow meter

Generally, each UV unit should have a dedicated flow meter for several reasons, including to confirm

that the unit is operating within the validated flow rate range. The measured flow rate data may be sent

to control panel and may be utilized for light-source controlling, monitoring and operating in order to

achieve system performance. The method of flow rate measurement should be selected according to the

variability in plant flow rate and installation conditions.
5.5 Power control panel

The control panel has the following functions: power receiving, power supplying, controlling,

monitoring and operating, and other functions for the light source and other apparatuses.

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6 Functional requirements
6.1 General

Functional requirements for treatment technologies address the transformation of influent water

quality constituents to produce reclaimed water and include both water quality and water quantity

parameters.

One of the functional requirements of a given UV treatment system is to secure, at all times, enough

UV dose to obtain a target quality of the reclaimed water that is appropriate for application of such

water. The UV dose is the time integral of the fluence rate or irradiance. What is necessary to this end

includes: use of a UV light source with appropriate irradiance; and retaining the reclaimed water in a

UV irradiation chamber for a predetermined time period.

In actual equipment, the irradiation time and UV irradiance in the UV irradiation chamber vary from

one portion to another due to the shape of the chamber, as well as the location and number of the light

sources, and other similar factors. Water quality determined by, for example, suspended matter and

UV absorbing components also reduces UV transmittance, and thereby affects UV dose distribution. By

taking these influences into consideration, a predetermined UV dose, or higher dose that is sufficient

for the water flow passing through the UV irradiation chamber, shall be secured at all times.

Methods for evaluating the performance of the UV unit in the design stage and for subsequently

monitoring the performance of the UV disinfection system in operation are provided below.

6.2 Evaluation of the UV unit performance

Evaluation of the UV unit performance should be done; a number of experimental methods may be used

including those described in Annex B, while the method in Annex C is accepted as a second option.

NOTE 1 The amount of upscaling varies from no upscaling permitted to a specific level of upscaling permitted

depending on country regulations.
Method I: Annex B (Experimental evaluation method)
I-1: Experimental testing using a challenge microorganism
I-1-1: Preliminary testing
I-1-2: Full-scale unit testing
I-2: Determine the RED

Method II: Annex C (Experimental evaluation method in combination with CFD-I simulations)

II-1: Experimental testing using a challenge organism for reference unit
II-2: Intensity measurement test on UV light source
II-3: Development of the CFD-I simulation models
II-4: Determine the RED in the unit of interest
6.3 Method of monitoring UV treatment system performance

The UV treatment system can be run automatically, so that its usual operation is generally simple

compared to other disinfection processes. What is important for routine maintenance includes:

monitoring the amount and the quality of UV treatment target water; and monitoring the UV dose.

Figure 1 shows the water flow through the UV treatment system and the monitoring points situated in

the system.
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ISO/FDIS 20468-4:2021(E)

Figure 1 — Typical configuration of UV disinfection system and monitoring points in UV

disinfection system
6.3.1 Monitoring of influent water flow [M1]

To check the water flow rate through the UV unit for deviation from the design flow rate, a flow meter

is required as ancillary equipment. To check whether the flow meter is functioning problem-free, it is

recommended to perform calibration within a period specified by the manufacturer.

EXAMPLE Manufacturer's recommendations: once a year.
6.3.2 Quality control of influent water [M2]

Colloidal solids, suspended solids, colour and dissolved solids (particularly dissolved organic

compounds) can absorb UV radiation, reduce UV transmission and decrease UV disinfection. If, in

addition, UV absorbing substances such as iron, manganese, sulphurous acid, nitrous acid, and phenol

exist, they reduce UV transmittance and thereby affect the treatment effect. Furthermore, constituents

such as iron, calcium and magnesium can cause scaling and interfere with UV irradiation and intensity.

Consequently, the presence and potential of these constituents to adversely impact disinfection shall be

addressed during the design stage and appropriate O&M cleaning procedures implemented to reduce

or eliminate their impact on disinfection.

Accordingly, these water quality parameters need to be measured and monitored on a regular basis.

If the water quality of the treatment target water does not satisfy the conditions for UV application, a

possible halt in the treatment shall be taken into consideration.

NOTE Generally, when these water quality parameters are well controlled by pre-treatment, fluctuations

are small but could be significant depending on capacity and performance of the pre-treatment.

6.3.3 Monitoring of UV irradiation [M3]

In the course of the evaluation of the UV unit, the minimum UV irradiance for a maximum flow at a

minimum UVT of the water is defined.

Monitoring UV irradiation cannot be performed by biodosimetry in routine operation and maintenance.

Instead, the UV system is operated in a way that the UV irradiance is kept within the designed range,

which is monitored by one or more online UV intensity sensors mounted on the UV irradiation chamber.

To keep the appropriate UV irradiance, the following items shall be monitored, and maintenance work

shall be conducted if necessary.
— UV light sources
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Check the cumulative use time of the UV light source. Replace the light source according to its service

life (operating time) or performance parameters presented by the manufacturer.
— Lamp protection component

When fouling substances adhere to the surface of the lamp protection component, the amount of UV that

can enter the water decreases. The extent of sleeve fouling can
...

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